461-SYS-SPEC-0115
Revision C
MMS PROJECT
Signature Controlled Document
T. Thomas – July 22, 2014
Magnetospheric Multiscale (MMS)
Project
Alignment and Coordinate System
Document
461-SYS-SPEC-0115
Revision C
Effective Date: July 22, 2014
Prepared by:
Oscar Hsu/Code 591 and Jessica Mccarthy/Code 599
Goddard Space Flight Center
Greenbelt, Maryland
National Aeronautics and
Space Administration
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461-SYS-SPEC-0115
Revision C
CM FOREWORD
This document is a Magnetospheric Multiscale (MMS) Project signature-controlled document.
Changes to this document require prior approval of the applicable Product Design Lead (PDL)
or designee. Proposed changes shall be submitted in the MMS Management Information
System (MIS) via a Signature Controlled Request (SCoRe), along with supportive material
justifying the proposed change.
In this document, a requirement is identified by “shall,” a good practice by “should,” permission
by “may” or “can,” expectation by “will,” and descriptive material by “is.”
Questions or comments concerning this document should be addressed to:
MMS Configuration Management Office
Mail Stop 461
Goddard Space Flight Center
Greenbelt, Maryland 20771
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Revision C
Review/Approval Page
K. Bromund
E. Cardiff
G. Davis
I. Dors
K. Harris
O. Hsu
K. McCaughey
W. Morgenstern
S. Placanica
S. Pope
C. Powell
S. Queen
A. Rodriguez-Arroyo
C. Schiff
*** Signatures are available on-line at: https://mmsmis.gsfc.nasa.gov ***
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Revision C
CHANGE HISTORY LOG
Revision
Level
DESCRIPTION OF CHANGE
Approved
By
Date
Approved
Revision -
Initial release of document as per MMS-SCoRe-0815.
J. McCarthy
07/26/2011
Revision A
-
O. Hsu
12/08/2011
O. Hsu
07/09/2012
-
Revision B
-
-
Updated Thruster Locations Table 4.1-3
Removed Reference to Cube on the bench in Section
3.1.1
Updated Figure 3.1-1
Released as per MMS-SCoRe-1407
Added five new coordinate systems:
o De-spun body Coordinate System
o Geocentric Solar Magnetospheric
o De-spun Spin-axis Coordinate System
o De-spun Spacecraft L-Vector Coordinate System
o Spinning Spacecraft L-Vector Coordinate System
Added a variation to Az-El called Az-Ze
Fixed Definition for the Instrument Deck Coordinate
Systems
Replaced Instrument Suite Coordinate System with
Instrument Deck Coordinate System to be consistent
Incorporated MMS-CCR-0471 (AMS Isolator)
Updated Alignment of DSS
Updated Appendix A with new acronyms based on the
additional coordinate systems.
Released as per MMS-SCoRe-1897.
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461-SYS-SPEC-0115
Revision C
Revision C
-
-
-
-
-
-
Added Section 1.1.4 (Applicable Documents)
Moved GSM Section (Old Section 2.15) so it follows
after the GSE Section (Section 2.9)
o As a result the old sections 2.10-2.13 have
moved section number
Added a new Section 2.15 MPA-aligned coordinate
system with sub sections for SMPA and DMPA
Added sections 7.2.2.4, 7.2.2.5
Updated Acronym List
Updated Section 2.1 – added standard definitions for
o Earth to Sun Vector
o Earth Dusk
Section 2.10 GSM Coordinate System
o Updated Y-axis definition
Section 2.14 (DBCS)
o Updated description
o Updated Y-axis definition
Section 2.15.2 (DMPA)
o Updated description
o Updated Y-axis definition
Section 2.17 (DMPA)
o Updated description
o Updated Y-axis definition
Added new Section 2.19
Released as per MMS-SCoRe-2883.
O. Hsu
07/22/2014
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Revision C
LIST OF TBDs/TBRs
Item
No.
Location
Summary
Ind./Org.
Due Date
None
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Revision C
Table of Contents
1.0
SCOPE AND PURPOSE OF DOCUMENT .......................................................................................................... 1
1.1 DOCUMENTS .......................................................................................................................................................1
1.1.1
Governing Documents............................................................................................................................1
1.1.2
Reference Documents ............................................................................................................................1
1.1.3
Applicable Drawings ..............................................................................................................................1
1.1.4
Applicable Document .............................................................................................................................2
1.2 DEFINITIONS........................................................................................................................................................2
2.0
COORDINATE SYSTEM DEFINITIONS ............................................................................................................. 3
2.1 OBSERVATORY COORDINATE SYSTEM (OCS) .............................................................................................................3
2.2 BODY COORDINATE SYSTEM (BCS) ..........................................................................................................................5
2.3 LAUNCH VEHICLE COORDINATE SYSTEM (LVCS) .........................................................................................................6
2.4 STACK COORDINATE SYSTEM (SCS) .........................................................................................................................7
2.5 MINI-STACK COORDINATE SYSTEM (MSCS) ..............................................................................................................8
2.6 EARTH-CENTERED INERTIAL MEAN OF YEAR 2000 (J2000) COORDINATE SYSTEM ...........................................................9
2.7 EARTH-CENTERED, EARTH-FIXED (ECEF) COORDINATE SYSTEM ..................................................................................10
2.8 RADIAL, INTRACK, CROSSTRACK (RIC) COORDINATE SYSTEM ......................................................................................10
2.9 GEOCENTRIC SOLAR ECLIPTIC (GSE) COORDINATE SYSTEM.........................................................................................11
2.10
GEOCENTRIC SOLAR MAGNETOSPHERIC (GSM) COORDINATE SYSTEM ....................................................................12
2.11
VELOCITY, BINORMAL, NORMAL (VBN) COORDINATE SYSTEM ...............................................................................12
2.12
PERIFOCAL (PQW) COORDINATE SYSTEM ..........................................................................................................13
2.13
AZIMUTH-ELEVATION (AZ-EL)/ AZIMUTH-ZENITH (AZ-ZE) COORDINATE SYSTEM ......................................................14
2.14 .........................................................................................................................................................................14
2.15
DE-SPUN BODY COORDINATE SYSTEM (DBCS)....................................................................................................15
2.16
MPA-ALIGNED COORDINATE SYSTEMS ..............................................................................................................15
2.16.1
Spinning MPA-aligned Coordinate System (SMPA) .........................................................................16
2.16.2
De-spun MPA-aligned Coordinate System (DMPA) .........................................................................16
2.17
DE-SPUN SPIN-AXIS COORDINATE SYSTEM (DSCS) ..............................................................................................17
2.18
DE-SPUN SPACECRAFT L-VECTOR (DSL) COORDINATE SYSTEM...............................................................................17
2.19
SPINNING SPACECRAFT L-VECTOR (SSL) COORDINATE SYSTEM ..............................................................................17
2.20
‘NEAR GSM’ COORDINATE SYSTEMS (E.G. GSM-DMPA) ....................................................................................18
3.0
ATTITUDE CONTROL SYSTEMS (ACS) HARDWARE ....................................................................................... 19
3.1 ACS SENSORS....................................................................................................................................................19
3.1.1
Star Sensor (micro Autonomous Star Camera ( ASC)).........................................................................19
3.1.2
Acceleration Measurement System (AMS) ..........................................................................................25
3.1.3
Digital Sun Sensor ................................................................................................................................29
3.2 ACS ACTUATORS ...............................................................................................................................................33
3.3 DEPLOYABLES ....................................................................................................................................................33
4.0
PROPULSION .............................................................................................................................................. 34
4.1 THRUSTERS .......................................................................................................................................................34
4.1.1
Thruster Naming Convention ...............................................................................................................34
4.1.2
Thruster Force and Torque Polarities ...................................................................................................35
4.1.3
Thruster Locations and Plume Direction Vectors .................................................................................36
4.2 FUEL TANK ........................................................................................................................................................36
5.0
NAVIGATOR ................................................................................................................................................ 37
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5.1 GPS ANTENNA ..................................................................................................................................................37
5.1.1
GPS Antenna Reference Designators ...................................................................................................37
5.1.2
Navigator Component Locations .........................................................................................................37
5.1.3
GPS Antenna Alignments .....................................................................................................................38
6.0
RF COMMUNICATIONS ............................................................................................................................... 40
6.1 RF COMMUNICATIONS ANTENNA ..........................................................................................................................40
6.1.1
Communications Antenna Locations and Fields of View......................................................................40
6.1.2
Communications Antenna Coordinate System and Transformations ..................................................41
7.0
INSTRUMENT COORDINATE SYSTEM DEFINITIONS ..................................................................................... 43
7.1 INSTRUMENT DECK CS, TRANSFORMATIONS, AND INSTRUMENT COMPONENTS ..............................................................43
7.1.1
Active Spacecraft Potential Control (ASPOC) .......................................................................................45
7.1.2
Axial Double Probe (ADP) .....................................................................................................................46
7.1.3
Electron Drift Instrument/ Gun Detector Unit (EDI/GDU) ....................................................................49
7.1.4
Energetic Ion Spectrometer (EIS) .........................................................................................................50
7.1.5
Fly’s Eye Energetic Particle Sensors (FEEPS) .........................................................................................51
7.1.6
Fast Plasma Investigation (FPI) ............................................................................................................52
7.1.7
Hot Plasma Composition Analyzer (HPCA) ...........................................................................................55
7.1.8
Spin-Plane Double Probe (SDP) ............................................................................................................56
7.2 SPACECRAFT DECK CS, TRANSFORMATIONS, AND INSTRUMENT COMPONENTS...............................................................58
7.2.1
Fly’s Eye Energetic Particle Sensors (FEEPS) .........................................................................................59
7.2.2
Magnetometers ...................................................................................................................................60
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List of Figures
Figure
Page
Figure 2.1-1 MMS Observatory Coordinate System ...................................................................... 3
Figure 2.1-2 MMS Thrust Tube ...................................................................................................... 4
Figure 2.1-3 MMS Spacecraft Layout - Top View ......................................................................... 4
Figure 2.1-4 MMS Spacecraft Layout - Bottom View ................................................................... 5
Figure 2.1-5 MMS Spacecraft with OCS Origin ............................................................................ 5
Figure 2.3-1 Launch Vehicle Coordinate System (Clocking is with respect to the LVCS). .......... 6
Figure 2.4-1 Stack Coordinate System ........................................................................................... 8
Figure 2.5-1 Mini-Stack Coordinate System .................................................................................. 9
Figure 3.1-1 Optical Bench Assembly .......................................................................................... 20
Figure 3.1-2 CHU Picture and CHU Reference Frame ................................................................ 21
Figure 3.1-3 CHU Glint-Free Field of View and ADP Keep Out Zone ....................................... 22
Figure 3.1-4 AMS Mechanical Reference Frame ......................................................................... 26
Figure 3.1-5 Accelerometer Locations in OCS Frame ................................................................. 27
Figure 3.1-6 DSS Graphic with DSS Mechanical Reference Frame Definition........................... 30
Figure 3.1-7 DSS1 and DSS2 mounted to the DSS bracket ......................................................... 30
Figure 3.1-8 DSS Optical Reference Frame ................................................................................. 31
Figure 4.1-1 Graphical Depiction of Thruster Locations.............................................................. 35
Figure 5.1-1 Navigator Component Locations ............................................................................. 38
Figure 5.1-2 GPS Antenna Coordinate Definition ........................................................................ 39
Figure 6.1-1 Aft Omni on S/C Deck and Forward Omni on IS Deck .......................................... 40
Figure 6.1-2 Communications Antenna Coordinate System ........................................................ 41
Figure 7.1-1 Instrument Deck Coordinate System - Top and Side Views.................................... 43
Figure 7.1-2 Instrument Deck Coordinate System - Bottom View .............................................. 44
Figure 7.1-3 ASPOC Coordinate System ..................................................................................... 45
Figure 7.1-4 ADP Coordinate System .......................................................................................... 46
Figure 7.1-5 ADP Longeron Clocking.......................................................................................... 47
Figure 7.1-6 ADP #1 ..................................................................................................................... 47
Figure 7.1-7 ADP #2 ..................................................................................................................... 48
Figure 7.1-8 EDI Coordinate System............................................................................................ 49
Figure 7.1-9 EIS Coordinate System ............................................................................................ 50
Figure 7.1-10 FEEPS Coordinate System ..................................................................................... 51
Figure 7.1-11 DES Coordinate System ......................................................................................... 52
Figure 7.1-12 DIS Coordinate System .......................................................................................... 54
Figure 7.1-13 HPCA Coordinate System...................................................................................... 55
Figure 7.1-14 SDP Coordinate System ......................................................................................... 56
Figure 7.2-1 S/C Deck Coordinate System - Bottom View .......................................................... 59
Figure 7.2-2 FEEPS Coordinate System ....................................................................................... 60
Figure 7.2-3 Magnetometer Boom Coordinate System ................................................................ 61
Figure 7.2-4 AFG Coordinate System .......................................................................................... 62
Figure 7.2-5 DFG Coordinate System .......................................................................................... 63
Figure 7.2-6 SCM Coordinate System .......................................................................................... 64
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Figure 7.2-7 Nominal Orientation of magnetometers with respect to the spacecraft, as
represented in AFG/DFG/SCM XYZ coordinates (left) versus AFG123/DFG123/SCM123
coordinates (right). ................................................................................................................ 65
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List of Tables
Table
Page
Table 1.1-1 Governing Documents ................................................................................................. 1
Table 1.1-2 Reference Documents .................................................................................................. 1
Table 1.1-3 Applicable Drawings ................................................................................................... 1
Table 1.1-4 Applicable Documents ................................................................................................ 2
Table 2.1-1 OCS Definition ............................................................................................................ 3
Table 2.2-1 BCS Definition ............................................................................................................ 6
Table 2.3-1 LVCS Definition ......................................................................................................... 6
Table 2.4-1 SCS Definition............................................................................................................. 7
Table 2.5-1 MSCS Definition ......................................................................................................... 8
Table 2.6-1 ECI Definition ............................................................................................................. 9
Table 2.7-1 ECEF Definition ........................................................................................................ 10
Table 2.8-1 RIC Definition ........................................................................................................... 10
Table 2.9-1 GSE Definition .......................................................................................................... 11
Table 2.10-1 Geocentric Solar Magnetospheric Coordinate System Definition .......................... 12
Table 2.10-2 Geomagnetic Pole Location (IGRF Epoch 2000) ................................................... 12
Table 2.11-1 VBN Definition ....................................................................................................... 13
Table 2.12-1 PQW Definition ....................................................................................................... 13
Table 2.13-1 Azimuth Angle Definition ....................................................................................... 14
Table 2.14-1 De-spun Body Coordinate System Definition ......................................................... 15
Table 2.15-1 SMPA Definition ..................................................................................................... 16
Table 2.15-2 DMPA Definition .................................................................................................... 16
Table 2.16-1 De-spun Spin-axis Coordinate System Definition .................................................. 17
Table 2.17-1 De-spun Spacecraft L-Vector Coordinate System Definition ................................. 17
Table 2.18-1 Spinning Spacecraft L-Vector Coordinate System Definition ................................ 17
Table 3.1-1 Optical Bench Assembly Mechanical Reference Frame Definition.......................... 20
Table 3.1-2 Camera Head Unit Reference Frame Definition ....................................................... 21
Table 3.1-3 CHU Boresights in OBA Frame ................................................................................ 21
Table 3.1-4 CHU Boresights in OCS Frame ................................................................................ 22
Table 3.1-5 ASC Transformations (Quaternions) ...................................................................... 24
Table 3.1-6 ASC Transformations (Euler Angles) ..................................................................... 24
Table 3.1-7 Camera Head Unit Designation Mapping ................................................................. 24
Table 3.1-8 DSS Boresights in CHU Frame ax X, Y, Z components .......................................... 25
Table 3.1-9 DSS Boresights in CHU Frame as Azimuth-Elevation Angles (degrees) ................. 25
Table 3.1-10 AMS Mechanical Reference Frame Definition ....................................................... 25
Table 3.1-11 AMS Strap-Down Reference Frame Definition ...................................................... 26
Table 3.1-12 Accelerometer Locations in AMS Mechanical Frame ............................................ 27
Table 3.1-13 AMS Mechanical Frame Origin in OCS Frame ...................................................... 27
Table 3.1-14 Accelerometer Locations in OCS Frame ................................................................. 28
Table 3.1-15 Sensing Direction in AMS Mechanical Frame ........................................................ 28
Table 3.1-16 AMS Transformation............................................................................................... 28
Table 3.1-17 DSS Mechanical Reference Frame Definition ........................................................ 29
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Table 3.1-18 DSS Optical Reference Frame Definition ............................................................... 31
Table 3.1-19 DSS Locations in OCS Frame ................................................................................. 31
Table 3.1-20 DSS Boresights in the DSS Mechanical Reference Frame ..................................... 32
Table 3.1-21 DSS Boresights in the OCS Frame .......................................................................... 32
Table 3.1-22 DSS Transformations .............................................................................................. 32
Table 4.1-1 MMS Thruster Names ............................................................................................... 34
Table 4.1-2 Thruster Force and Torque Polarity in OCS Frame .................................................. 35
Table 4.1-3 Thruster Locations and Plume Direction Vectors in OCS Frame ............................. 36
Table 4.2-1 Dry Tank Geometric Center Locations in OCS Frame ............................................. 36
Table 5.1-1 GPS Antenna Reference Designators ........................................................................ 37
Table 5.1-2 GPS Antenna Coordinate System .............................................................................. 38
Table 5.1-3 GPS Antenna Boresight in OCS ................................................................................ 39
Table 6.1-1 Comm Antenna Reference Designators .................................................................... 40
Table 6.1-2 Comm Antenna Mechanical Frame Origin in OCS Frame ....................................... 41
Table 7.1-1 IDCS Definition......................................................................................................... 44
Table 7.1-2 Instrument Deck Coordinate System Origin in OCS Frame ..................................... 44
Table 7.1-3 ASPOC Mechanical Frame Origin in OCS Frame .................................................... 45
Table 7.1-4 ADP Mechanical Frame Origin in OCS Frame ......................................................... 48
Table 7.1-5 EDI Mechanical Frame Origin in OCS Frame .......................................................... 49
Table 7.1-6 EIS Mechanical Frame Origin in OCS Frame ........................................................... 50
Table 7.1-7 FEEPS Mechanical Frame Origin in OCS Frame ..................................................... 51
Table 7.1-8 DES Mechanical Frame Origin in OCS Frame ......................................................... 52
Table 7.1-9 DIS Mechanical Frame Origin in OCS Frame .......................................................... 54
Table 7.1-10 HPCA Mechanical Frame Origin in OCS Frame .................................................... 56
Table 7.1-11 SDP Mechanical Frame Origin in OCS Frame ....................................................... 57
Table 7.2-1 FEEPS Mechanical Frame Origin in OCS Frame ..................................................... 60
Table 7.2-2 Magnetometer Boom Mechanical Frame Origin in OCS Frame ............................... 61
Table 7.2-3 AFG Mechanical Frame Origin in Boom CS Frame ................................................. 62
Table 7.2-4 DFG Mechanical Frame Origin in Boom CS Frame ................................................. 63
Table 7.2-5 SCM Mechanical Frame Origin in Boom CS Frame ................................................ 64
Table 7.2-6 OMB Coordinate System Definition ......................................................................... 66
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1.0
Scope and Purpose of Document
This document will define the coordinate reference frames used by the Magnetospheric Multiscale
(MMS) Project and their relationships (alignments) to the Observatory Coordinate System (OCS). In
addition, this document will define the coordinate transformations between the MMS components and the
Observatory Coordinate System where appropriate and also establish naming conventions for both the
hardware and coordinate systems.
1.1
Documents
1.1.1 Governing Documents
The following are other higher-level documents. These documents are subject to revision. In cases of
conflict between this document and the reference documents listed in Table 1.1-1, the higher-level
document will take precedence.
Table 1.1-1 Governing Documents
Document Title
MMS Mission Requirements Document
MMS Project Flight Dynamics Subsystem
Specification
MMS Atlas V 421 Early Definition Document
MMS Project Separation System Specification
Document Number
461-SYS-RQMT-0019
461-GS-SPEC-0049
Revision
Rev. F
Rev. C
Date
06/30/2011
06/20/2011
461-LV-ICD-0046
461-MECH-SPEC-0030
08/10/2011
01/05/2012
MMS Mechanical Requirements Document
MMS Spacecraft to Instrument Suite
Mechanical/Thermal Interface Control
Document
MMS Star Sensor System User Manual
DSS Mechanical ICD
461-MECH-RQMT-0036
461-MECH-ICD-0006
Rev. A
Rev. D w
Waiver
Rev. C
Rev. B
461-ACS-HDBK-0022
461-ACS-ICD-0058
Rev 2.1
Rev. D
02/15/2011
01/03/2012
02/16/2012
03/11/2011
1.1.2 Reference Documents
The following documents are referenced in this document. These documents are subject to revision. In
cases of conflict between this document and the reference documents listed in Table 1.1-2 , this document
will take precedence.
Table 1.1-2 Reference Documents
Document Title
Thruster Naming Convention
Propulsion Naming Convention
Document Number
461-ACS-REF-0099
461-PS-REF-0143
Revision
Rev. C
Rev. B
Date
04/15/2010
02/17/2011
1.1.3 Applicable Drawings
The following drawings in Table 1.1-3 form a part of this document to the extent specified herein. The
latest revision applies.
Table 1.1-3 Applicable Drawings
DRAWING NO.
101600011
DRAWING TITLE
ADP MICD/TICD
RESPONSIBILITY
SwRI
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101600012
101600013
101600014
101600015
101600018
101600019
101600020
101600021
101600022
101600023
101600025
2102170
2102174
2102857
2102850
2102258
2102871
2102295
SDP MICD/TICD
EDI MICD/TICD
AFG MICD/TICD
DFG MICD/TICD
DES MICD/TICD
DIS MICD/TICD
EIS MICD/TICD
FEEPS MICD/TICD
HPCA MICD/TICD
ASPOC MICD/TICD
SCM MICD/TICD
Substrate, Des/Dis Platform, Assembly
Platform, FEEPS, Instrument Deck, MMS
Instrument Deck MICD
Magnetometer Boom ICD
Spacecraft Deck Assembly Drawing
AMS Accelerometer Locations
Optical Bench, Assembly
SwRI
SwRI
SwRI
SwRI
SwRI
SwRI
SwRI
SwRI
SwRI
SwRI
SwRI
GSFC
GSFC
GSFC
GSFC
GSFC
GSFC
GSFC
1.1.4 Applicable Document
The following documents in Table 1.1-4 form a part of this document to the extent specified herein. The
latest revision applies.
Table 1.1-4 Applicable Documents
Document Number
461-GS-ICD-0013
1.2
Document Title
MMS MOC-FDOA ICD
RESPONSIBILITY
GSFC
Definitions
All transformations defined in this document are passive rotations. The quaternion definition used in this
document is:
q1  e1 sin
 ,

2
q2  e2 sin
 ,

2
q3  e3 sin
 ,

2
q4  cos

Equation 1.2-1

2
where e1, e2, e3 represents the rotation axis and  represents the rotation angle.
The standard for the definition of the vector from the Earth to the Sun is given by the JPL DE4.21
ephemerides.
For the purposes of this document, the term “Earth dusk” is defined to be the direction in the Earth’s orbit
plan that points essentially at 18:00 in GSE.
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2.0
Coordinate System Definitions
2.1
Observatory Coordinate System (OCS)
Section 3.1.2 of the MMS Mission Requirements Document (MRD) defines the primary MMS
Observatory Coordinate System (OCS). The definition provided in the MRD is:
The origin of the observatory coordinate system is at the center of the launch vehicle
adaptor ring on the separation interface plane. The +Z axis originates from the origin and
runs through the observatory structure along the center line of the thrust tube. The
positive X-axis will be along a line projecting from the origin along the separation plane
and intersecting the plane of Bay 1 and the positive Y axis completes a right-handed
coordinate frame. Positive observatory roll is defined as a right-hand rotation about the
+Z-axis, positive pitch is defined as a right-hand rotation about the +X-axis, and positive
yaw is defined as a right-hand rotation about the +Y-axis. The launch stack coordinate
frame will be documented in the ICD with the Launch Vehicle.
The OCS Frame definition from the MRD repackaged into a table format is shown below as Table 2.1-1.
A graphical depiction of the OCS Frame is shown in Figure 2.1-1.
Table 2.1-1 OCS Definition
Component
Origin
Fundamental Plane
X Axis
Y-Axis
Z-Axis
Definition
Center of the launch vehicle adaptor ring on the separation interface plane
Separation Plane
line projecting from the origin along the separation plane and intersecting the
plane of Bay 1
completes the right hand system
extends through the S/C structure along the center line of the thrust tube
Figure 2.1-1 MMS Observatory Coordinate System
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The thrust tube centerline is defined as the vector originating at the center of the Passive Ring
Interface flange on the thrust tube (established using template drilled holes) and normal to the
plane defined by the interface flange. See Figure 2.1-2 below.
Figure 2.1-2 MMS Thrust Tube
Figure 2.1-3 and Figure 2.1-4 respectively show the top and bottom views of the overall
spacecraft layout. The sensors and actuators are depicted with respect to the corresponding
spacecraft bay. This image corresponds with MMS Drawing Number 2102258.
Figure 2.1-3 MMS Spacecraft Layout - Top View
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Figure 2.1-4 MMS Spacecraft Layout - Bottom View
Figure 2.1-5 defines the OCS Frame with respect to the separation plane for each observatory.
Each individual observatory uses the same local coordinate system. Bay 7 is on the –Y face in
this figure.
Figure 2.1-5 MMS Spacecraft with OCS Origin
2.2
Body Coordinate System (BCS)
The Body Coordinate System is aligned with the OCS Frame with the exception of the origin, defined by
the center of mass, and the definition is provided in Table 2.2-1.
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Table 2.2-1 BCS Definition
Component
Origin
Fundamental Plane
X-Axis
Y-Axis
Z-Axis
Definition
Center of mass
X-Y Plane
Aligned with the OCS X-Axis
Aligned with the OCS Y-Axis
Aligned with the OCS Z-Axis
2.3
Launch Vehicle Coordinate System (LVCS)
The Launch Vehicle Coordinate System definition is provided in Table 2.3-1. The launch vehicle
coordinate system will be subscripted with LV or CENTAUR in MMS documents.
Table 2.3-1 LVCS Definition
Component
Origin
Fundamental Plane
X-Axis
Y-Axis
Z-Axis
Definition
SIP Station (STA) 0 [0.00]
Standard Interface Plane (SIP)
line projecting from origin along Standard Interface Plane
completes the right hand system
extends down along the centerline (longitudinal axis) of the centaur
Figure 2.3-1 was taken directly from the MMS Atlas V 421 Early Definition Document, 461-LV-ICD0046. This figure defines the dimensions, locations, and tolerances for the SC/LV Clocking, Coordinate
Systems, and Separation Plane. LVCS definition data is shown within a green box for clarity.
Figure 2.3-1 Launch Vehicle Coordinate System (Clocking is with respect to the LVCS).
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A 180-degree rotation about the X-axis aligns the MMS Stack coordinate system (SCS) along the
LV coordinate system. The MMS Stack to LV frame coordinate transformation consists of an
axis 1 Euler angle rotation of = +180 degrees. As a direction cosine matrix, this transformation
can be expressed as:
Equation 2.3-1
X 
 Y  LVCS 
 
 Z 
1 0 0 
0 1 0 


0 0 1
X 
 Y  SCS
 
 Z 
2.4
Stack Coordinate System (SCS)
MMS consists of four nearly identical spacecraft stacked on top of each other for launch. The
bottom spacecraft will be mounted to the launch vehicle separation system at the SC/Centaur
separation plane, SIP station 889.0 [35.00], according to Figure 2.3-1. The remaining three (3)
MMS spacecraft will be secured to each other for launch using Spacecraft Separation System
assemblies. The observatories are clocked at 180 degrees from each other. The coordinate
system of MMS #1 (bottom observatory) is used with the launch vehicle as the stack coordinate
system. MMS #2 and #4 are clocked 180 degrees relative to MMS #1. The Stack Coordinate
System definition is provided in Table 2.4-1. Figure 2.4-1 shows an image of the stack coordinate
system.
Table 2.4-1 SCS Definition
Component
Origin
Fundamental Plane
X-Axis
Y-Axis
Z-Axis
Definition
Center of the launch vehicle adaptor ring for MMS #1 (bottom observatory) on
the separation interface plane
Separation Plane
line projecting from the origin along the separation plane and intersecting the
plane of Bay 1 on MMS #1
completes the right hand system on MMS #1
extends through the S/C structure along the center line of the thrust tube
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Figure 2.4-1 Stack Coordinate System
2.5
Mini-Stack Coordinate System (MSCS)
The mini-stack is defined as any two observatories in a stacked configuration. The coordinate system is
identical to the stack coordinate system. The Mini-Stack Coordinate System definition is provided in
Table 2.5-1. The mini-stack coordinate system is shown below in Figure 2.5-1. The bottom observatory
is clocked at 0 deg and the top observatory is clocked at 180 deg.
Table 2.5-1 MSCS Definition
Component
Origin
Fundamental Plane
X-Axis
Y-Axis
Z-Axis
Definition
Center of the launch vehicle adaptor ring for bottom observatory on the
separation interface plane
Separation Plane
line projecting from the origin along the separation plane and intersecting the
plane of Bay 1 on bottom observatory
completes the right hand system
extends through the S/C structure along the center line of the thrust tube
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Figure 2.5-1 Mini-Stack Coordinate System
2.6
Earth-Centered Inertial Mean of Year 2000 (J2000) Coordinate System
The Earth-Centered Inertial Frame (ECI) is defined according to Table 2.6-1. The reference time for the
mean vernal equinox and the Earth’s mean spin axis is January 1, 2000 12:00:00 Terrestrial Time (TT):
Table 2.6-1 ECI Definition
Component
Origin
Fundamental Plane
X Axis
Y-Axis
Z-Axis
Definition
Center of the Earth
Earth’s Equator
points to the mean vernal equinox
completes the right hand system
extends through the North Pole, parallel to the Earth’s mean Spin Axis
The ECI Frame should be a realization of the International Celestial Reference Frame (ICRF) or
the Fifth Fundamental Catalogue (FK5) extension (1991). Ideally, the ICRF should be used but
given that GSFC software has not universally switched to this standard, the FK5 extension is also
allowed since the two agree to within the lower precision of the FK5 extension.
References
[1] – Vallado, D. A. and McClain, W.D., Fundamentals of Astrodynamics and Applications, 2nd
ed., Microcosm Press, El Segundo, CA, 2001, Sec. 3.7
[2] – http://en.wikipedia.org/wiki/International_Celestial_Reference_Frame
[3] – The International Celestial Reference Frame,
http://www.iers.org/IERS/EN/DataProducts/ICRF/ICRF/icrf.html
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2.7
Earth-Centered, Earth-Fixed (ECEF) Coordinate System
The Earth-Centered, Earth-Fixed (ECEF) frame is defined according to Table 2.7-1.
Table 2.7-1 ECEF Definition
Component
Origin
Fundamental Plane
X Axis
Y-Axis
Z-Axis
Definition
Center of the Earth
Earth’s Equator
points to the Greenwich meridian
completes the right hand system
extends through the North Pole, parallel to the Earth’s mean Spin Axis
2.8
Radial, Intrack, Crosstrack (RIC) Coordinate System
The Radial, Intrack, and Crosstrack (RIC) coordinate system is defined according to Table 2.8-1
Table 2.8-1 RIC Definition
Component
Origin
Fundamental Plane
 
Y Axis  Iˆ 
Z Axis  Ĉ 
X Axis R̂
Definition
Spacecraft’s current position
The instantaneous orbital plane (i.e. the plane at any instant that is
perpendicular to the unit vector in the crosstrack direction (same as the normal
direction in Section2.10).
Points along the line from the center of the Earth to the spacecraft (Equation
2.8-1)
Completes the right-handed coordinate system and points towards (but not
parallel to) the spacecraft’s velocity vector (Equation 2.8-3)
Points along orbital angular momentum (Equation 2.8-2)


and the following equations define the Rˆ , Iˆ, Cˆ coordinate frame unit vectors
Equation 2.8-1
r
Rˆ 
r
Equation 2.8-2
r v
Cˆ 
r v
Equation 2.8-3
Iˆ  Cˆ  Rˆ 
where r and v are the position and velocity vectors, respectively, of the spacecraft with respect to the
Earth.
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2.9
Geocentric Solar Ecliptic (GSE) Coordinate System
The Geocentric Solar Ecliptic (GSE) coordinate system is used extensively to describe the MMS
reference orbit and its relationship with the science requirements. The GSE Coordinate System is defined
in Table 2.9-1.
Table 2.9-1 GSE Definition
Component
Origin
Fundamental Plane
X Axis
Y-Axis
Z-Axis
Definition
Center of the Earth
Ecliptic Plane
vector from the center of the Earth to the Sun (Equation 2.9-1)
vector normal to the plane created by the ecliptic pole at J2000 and the vector
from the center of the Earth to the Sun (Equation 2.9-2)
completes the right hand system (Equation 2.9-3)
The ecliptic pole, P̂ , at the J2000 epoch is the vector normal to the mean plane of the Earth’s
motion about the Sun [ref. 1]. The mean obliquity of the pole at epoch J2000 is 23 deg, 26 min,
21.448 sec = 23.4392911 deg [ref. 2]. From the definition of the vernal equinox, the right
ascension, , of the ecliptic pole is 270 deg. The declination, , is 90 minus the obliquity. So,
the ecliptic pole at epoch J2000 in the MJ2000 ECI frame is
0
cos( ) cos( )  




ˆ
P   cos( )sin( )    0.39777715575399 .
 sin( )
  0.917482062146321



From the ecliptic pole, the Xˆ , Yˆ , Zˆ coordinate frame unit vectors
Equation 2.9-1
r
Xˆ 
r
Equation 2.9-2
Pˆ  r
Yˆ 
Pˆ  r
Equation 2.9-3
Zˆ  Xˆ  Yˆ
where r is the instantaneous vector from the Earth to the Sun.
References
[1] – Seidelmann, P. K, Supplement to the Astronomical Almanac, University Science Books,
U.S.A., 2006, p. 11
[2] – Seidelmann, P. K, Supplement to the Astronomical Almanac, University Science Books,
U.S.A., 2006, Eq 3.222-1
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2.10
Geocentric Solar Magnetospheric (GSM) Coordinate System
The Geocentric Solar Magnetospheric (GSM) is defined according to Table 2.10-1Error! Reference
source not found..
Table 2.10-1 Geocentric Solar Magnetospheric Coordinate System Definition
Component
Origin
Fundamental Plane
X Axis
Y-Axis
Z-Axis
Definition
Center of the Earth
X-Y Plane
vector from the center of the Earth to the Sun
perpendicular to the geomagnetic pole (IGRF Epoch 2000), and perpendicular
to the X-Axis, positive in the direction from Earth dawn to Earth dusk
Completes the right-handed coordinate system
and the following equations define the GSM coordinate frame unit vectors
Equation 2.10-1
S - vector from the center of the Earth to the Sun
Equation 2.10-2
P - geomagnetic pole (IGRF Epoch 2000) where positive P is toward ecliptic south
The geographic location of the geomagnetic pole from the IGRF model, Epoch 2000, i.e. the
latitude and longitude of the intersection of Earth’s dipole with the surface can be from World
Data Center for Geomagnetism, Kyoto (http://wdc.kugi.kyoto-u.ac.jp/poles/polesexp.html#MN)
and the values are shown in Table 2.10-2 Error! Reference source not found.
Table 2.10-2 Geomagnetic Pole Location (IGRF Epoch 2000)
North Geomagnetic Pole
South Geomagnetic Pole
Latitude (Deg)
79.5 N
79.5 S
Longitude (Deg)
71.6 W
108.4E
Equation 2.10-3
xˆ 
S
S
Equation 2.10-4
yˆ 
xP
xP
Equation 2.10-5
ẑ  xˆ  yˆ
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2.11
Velocity, Binormal, Normal (VBN) Coordinate System
The Velocity, Binormal, and Normal (VBN) coordinate system is defined according to Table 2.11-1
Table 2.11-1 VBN Definition
Component
Origin
Fundamental Plane
X Axis Vˆ 
Y-Axis  B̂ 
Z-Axis  N̂ 
Definition
Spacecraft’s current position
The instantaneous orbital plane (i.e. the plane at any instant that is
perpendicular to the unit vector in the normal direction (same as the crosstrack
direction in 2.8).
Points along the spacecraft’s velocity vector (Equation 2.11-1)
Completes the right-handed coordinate system and points towards (but not
parallel to) the spacecraft’s position vector (Equation 2.11-3)
Points along orbital angular momentum (Equation 2.11-2)


and the following equations define the Vˆ , Bˆ , Nˆ coordinate frame unit vectors
Equation 2.11-1
v
Vˆ 
v
Equation 2.11-2
r v
Nˆ 
r v
Equation 2.11-3
Bˆ  Nˆ Vˆ
where r and v are the position and velocity vectors, respectively, of the spacecraft with respect to the
Earth.
2.12
Perifocal (PQW) Coordinate System
The perifocal coordinate system (PQW) is defined according to Table 2.12-1.
Table 2.12-1 PQW Definition
Component
Origin
Fundamental Plane
X Axis  P̂ 
Definition
Center of the Earth
Instantaneous orbital plane
Instantaneous direction of periapsis (Equation 2.12-2)
Y-Axis  Q̂ 
Completes the right-handed coordinate system (Equation 2.12-4)
Z-Axis Ŵ 
Points along orbital angular momentum (Equation 2.12-3)
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

and the following equations define the Pˆ , Qˆ ,Wˆ coordinate frame unit vectors
Equation 2.12-1
P
v r  v 


r
r
Equation 2.12-2
P
Pˆ 
P
Equation 2.12-3
r v
Wˆ 
r v
Equation 2.12-4
Qˆ  Wˆ  Pˆ
where r and v are the position and velocity vectors, respectively, of the spacecraft with respect to the
Earth.
2.13
Azimuth-Elevation (Az-El)/ Azimuth-Zenith (Az-Ze) Coordinate System
Azimuth-Elevation Coordinates are measured relative to a fundamental plane. The Azimuth angle is
measured in the fundamental plane with positive rotation and zero azimuth defined by Table 2.13-1. The
elevation angle is measured from the fundamental plane and positive towards the axis not in the
fundamental plane. The Zenith angle is measured as Ze = 90 deg – Elevation.
Table 2.13-1 Azimuth Angle Definition
Axes in Fundamental Plane
X-Y
X-Z
Y-Z
Positive Rotation
From X-axis to Y-axis
From Z-axis to X-axis
From Y-axis to Z-axis
Zero Azimuth Angle
X-Axis
Z-Axis
Y-Axis
2.14
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2.15
De-spun Body Coordinate System (DBCS)
The De-spun Body coordinate system (DBCS) is defined according to Table 2.15-1. Due to the fact that
MMS will maintain the positive spin axis ~3 degrees away from ecliptic normal during science operations
(RMRD_0185), DBCS may nominally be considered 'near GSE'.
Table 2.15-1 De-spun Body Coordinate System Definition
Component
Origin
Fundamental Plane
X Axis
Y-Axis
Z-Axis
Definition
Center of mass
X-Y Plane
Completes the right-handed coordinate system
Perpendicular to the Z-axis, and perpendicular to the line pointing from the
spacecraft toward the sun, positive in the direction from the Earth dawn to
Earth dusk.
Aligned with the OCS Z-Axis
2.16 MPA-aligned Coordinate Systems
The Major Principal Axis (MPA) of inertia defines a fixed spin axis relative to the spacecraft
body. This is in contrast to the angular momentum vector or the instantaneous spin axis, which
are not fixed with respect to the spacecraft body when there is nutation. As nutation damps out,
these two vectors come into alignment with the MPA. Moreover, even in the presence of
nutation and boom motion, both the instantaneous spin axis and angular momentum vector
average out to the MPA when averaged over one or more periods of nutation or boom motion
(~16 sec and ~2 minutes, respectively).
Note that there are two exceptions to the statement that the MPA is fixed relative to the
spacecraft body:
 The MPA will shift over the life of the mission as fuel is expended. These shifts can be
measured and accounted for.
 The MPA will shift on time scales on the order of the spin period, due to motions of the
wire booms. It is neither practical nor useful for defining a spacecraft-fixed coordinate
system to calculate the MPA at these time scales.
For the purpose of defining MPA-aligned coordinate systems for MMS, FDOA will calculate the
new effective inertia tensor and corresponding MPA after each maneuver. The unit vector
describing the orientation of the MPA in the Body Coordinate System (BCS) is included in the
comments header of each Definitive Attitude Report (found in 461-GS-ICD-0013 as product
FDOA-5), in the following format:
COMMENT
Major principal axis of inertia in BCS = -0.00008919
0.00027234
0.99999996
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2.16.1 Spinning MPA-aligned Coordinate System (SMPA)
The Spinning MPA-aligned coordinate system is a spacecraft-fixed coordinate system, defined
according to Table 2.17-1. The Z-axis is aligned with the MPA, as defined above.
Table 2.16-1 SMPA Definition
Component
Origin
Fundamental Plane
X-Axis
Y-Axis
Z-Axis
Definition
Center of Mass
X-Y Plane (Spin Plane)
Intersection of the spin plane (MPA-normal) with the plane defined by the
MPA and the BCS X-axis. Positive in the direction of the BCS X-axis.
Normal to the plane defined by the MPA and the BCS X-axis, positive in the
direction of the BCS Y-axis.
The Major Principal Axis of the spacecraft, positive in the direction of the BCS
Z-axis.
2.16.2 De-spun MPA-aligned Coordinate System (DMPA)
The De-spun MPA-aligned Coordinate System is a quasi-inertial system defined according to Table
2.16-2. The Z-axis is aligned with the MPA, as defined above. Due to the fact that MMS will maintain
the positive spin axis ~3 degrees away from ecliptic normal during science operations (RMRD_0185),
DMPA may nominally be considered 'near GSE'.
Table 2.16-2 DMPA Definition
Component
Origin
Fundamental Plane
X-Axis
Y-Axis
Z-Axis
Definition
Center of Mass
X-Y Plane (Spin Plane)
Intersection of the spin plane (MPA-normal) with the plane defined by the
MPA and the spacecraft-sun vector. Positive towards the sun.
Normal to the plane defined by the MPA and the spacecraft-sun vector,
positive in the direction from Earth dawn to Earth dusk
The Major Principal Axis of the spacecraft, positive in the direction of the BCS
Z-axis.
Equation 2.16-1 shows how despun MPA Coordinates are related to the spinning coordinates by
the MPA-phase, φMPA, (Sun-to-body-X dihedral angle about the Major Principal Axis) (deg).
Equation 2.16-1
cos 𝜑𝑀𝑃𝐴
𝑋
[𝑌 ] 𝐷𝑀𝑃𝐴 = [ sin 𝜑𝑀𝑃𝐴
𝑍
0
−sin 𝜑𝑀𝑃𝐴
cos 𝜑𝑀𝑃𝐴
0
0 𝑋
0] [𝑌 ] 𝑆𝑀𝑃𝐴
1 𝑍
Note that there is a difference between MPA-phase, used here, and the Z-phase that should be
used to transfrom between BCS and DBCS. If we assume that the spin axis is within
requirements, but misaligned from the Body Z-axis by 1 degree, and given that the sun will be
out of the spin plane by 2.5 degrees, the difference between Z-phase and MPA-phase would be
0.04 degrees, resulting in a difference that would not be negligible for FIELDS applications.
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2.17
De-spun Spin-axis Coordinate System (DSCS)
The De-spun Spin-axis Coordinate System (DSCS) is defined according to Table 2.17-1. Due to the fact
that MMS will maintain the positive spin axis ~3 degrees away from ecliptic normal during science
operations (RMRD_0185), DSCS may nominally be considered 'near GSE'.
Table 2.17-1 De-spun Spin-axis Coordinate System Definition
Component
Origin
Fundamental Plane
X Axis
Y-Axis
Z-Axis
Definition
Center of mass
X-Y Plane
Completes the right-handed coordinate system
Perpendicular to the Z-axis, and perpendicular to the line pointing from the
spacecraft toward the sun, positive in the direction from Earth dawn to Earth
dusk
Instantaneous spin axis of the spacecraft
2.18
De-spun Spacecraft L-Vector (DSL) Coordinate System
The De-spun Spacecraft L-Vector (DSL) coordinate system is defined according to Table 2.18-1 Due to
the fact that MMS will maintain the positive spin axis ~3 degrees away from ecliptic normal during
science operations (RMRD_0185), DSL may nominally be considered 'near GSE'.
Table 2.18-1 De-spun Spacecraft L-Vector Coordinate System Definition
Component
Origin
Fundamental Plane
X Axis
Y-Axis
Z-Axis
Definition
Center of mass
X-Y Plane
Completes the right-handed coordinate system
Perpendicular to the Z-axis, and perpendicular to the line pointing from the
spacecraft toward the sun, positive in the direction from Earth dawn to Earth
dusk
Angular Momentum Vector of the spacecraft
2.19
Spinning Spacecraft L-Vector (SSL) Coordinate System
The Spinning Spacecraft L-Vector (SSL) coordinate system is defined according to Table 2.19-1.
Table 2.19-1 Spinning Spacecraft L-Vector Coordinate System Definition
Component
Origin
Fundamental Plane
X Axis
Y-Axis
Z-Axis
Definition
Center of mass
X-Y Plane
Completes the right-handed coordinate system
Perpendicular to the Z-Axis, and perpendicular to the BCS X-axis, positive in
the direction of the BCS Y-axis
Angular Momentum Vector of the spacecraft
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2.20
‘Near GSM’ Coordinate Systems (e.g. GSM-DMPA)
Noting that the difference between the GSM system and the GSE system is simply a rotation about the Xaxis, and that various despun, spacecraft-oriented systems (DMPA, DSL, DBCS, DSCS) can be
considered ‘near GSE’, it is possible to define ‘near GSM’ systems derived from any of these systems.
For example, one may rotate the DMPA system about its X-axis by the same rotation that transforms GSE
to GSM. The resulting system is dubbed GSM-DMPA, to distinguish it from true GSM coordinates and
identify the originating system. By the same method, it is possible to derive GSM-DSL, GSM-DBCS,
etc.
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3.0
Attitude Control Systems (ACS) Hardware
The ACS Hardware consists of three sensors. Their locations and alignments will be defined in this
section. A graphical depiction of the ACS, Propulsion, Navigator hardware that can be seen from this
view is shown in Figure 3.0-1.
Figure 3.0-1 MMS Spacecraft Layout
3.1
ACS Sensors
The ACS Sensors consists of Star Sensors, Accelerometers, and Digital Sun Sensors.
3.1.1 Star Sensor (micro Autonomous Star Camera (ASC))
The Star Sensor is being supplied by the Danish Technical University (DTU). It consists of a single data
processing unit (DPU) and 4 Camera Head Units (CHU). The output of the ASC is a quaternion from
each CHU that defines the attitude of the CHU with respect to J2000.0 heliocentric inertial equatorial
reference frame (xhc, yhc, zhc triad) which is equivalent to ECI except for a translation in the origin. The
ASC has 4 Camera Head Units (CHU) and each optical bench assembly will house two CHUs and a
removable “Cube on a Stick”. Alignment information that MMS will receive from the vendor will be
from the CHU Electrical frame to the ”Cube on a Stick”. The CHU Electrical frame is nominally aligned
with the CHU Reference frame and a separate transformation will not be provided from the CHU
Electrical frame to the CHU Reference frame. Therefore, a definition of the CHU Electrical frame will
not be provided in this document.
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ASC Reference Frames and Coordinate Systems
There are two references frames associated with the ASC: Optical Bench Assembly Mechanical
Reference Frame and the Camera Head Unit Frame.
3.1.1.1.1 Optical Bench Assembly (OBA) Mechanical Reference Frame
The OBA mechanical reference frame definition is provided in Table 3.1-1. Two CHUs will be mounted
to each Optical Bench.
Table 3.1-1 Optical Bench Assembly Mechanical Reference Frame Definition
Component
Origin
Fundamental Plane
X Axis
Y-Axis
Z-Axis
Definition
Center of the bench
X-Y plane
Long side of the bench, positive from the CHUs towards the cube on a stick
Completes the right-handed coordinate system
Normal to the bench surface, positive from bench away from the cube on a stick
The two optical bench assemblies are identical and a picture of the assembly is show in Figure 3.1-1.
The Bay 4 Optical Bench hosts CHU C and CHU D and the Bay 6 Optical Bench hosts CHU A and CHU
B.
Figure 3.1-1 Optical Bench Assembly
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3.1.1.1.2 Camera Head Unit (CHU) Reference Frame
The Camera Head Unit (CHU) reference frame definition is provided in Table 3.1-2. Each CHU uses the
same frame definition.
Table 3.1-2 Camera Head Unit Reference Frame Definition
Component
Origin
Fundamental Plane
X Axis
Y-Axis
Z-Axis
Definition
Intersection of the CCD plane with the optical axis of the camera
CCD Plane
In the CCD plane along the long side of the CCD pointing towards the right of
the image (towards the communication cable)
Completes the right-handed coordinate system
Boresight of the Star Sensor
A picture of a CHU with its optical cube and the reference frame definition is shown in Figure 3.1-2.
The origin has been translated from the center of the CCD in this figure.
Figure 3.1-2 CHU Picture and CHU Reference Frame
Camera Head Unit Boresight Direction
The ASC has 4 Camera Head Units. The boresight direction in the CHU frame is defined as the +Z-axis
[ 0; 0; 1]. The boresight direction provided in Table 3.1-3 represents the boresights of each CHU in the
OBA Frame. Table 3.1-4 provides the direction of each CHU boresight in the OCS Frame.
Table 3.1-3 CHU Boresights in OBA Frame
Item
CHUA
CHUB
CHUC
CHUD
CHU Boresight in OBA Frame
X
Y
Z
Optical Bench 1
-0.173648178
0
-0.984807753
0
0.173648178
-0.984807753
Optical Bench 2
0
0.173648178
-0.984807753
-0.173648178
0
-0.984807753
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Table 3.1-4 CHU Boresights in OCS Frame
Item
CHUA
CHUB
CHUC
CHUD
CHU Boresight in OCS Frame
X
Y
Z
0.059391175
-0.163175911
-0.984807753
-0.163175911
-0.059391175
-0.984807753
0.133022222
0.111618897
-0.984807753
-0.111618897
0.133022222
-0.984807753
The CHU Glint-free Field of Views and the ADP Keep Out Zone is shown in Figure 3.1-3.
Figure 3.1-3 CHU Glint-Free Field of View and ADP Keep Out Zone
ASC Transformations
The transformation from the ASC CHU Frame to the BCS is defined in Equation 3.1-1 and the
associated quaternions are shown in
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Table 3.1-5.
Equation 3.1-1
qCHUntoBCS  qCHUntoCubeX  qCubeXtoBCS
where n represents CHU identifier (A, B, C, D) and X is the OBA identifier (1, 2). The equivalent Euler
Rotation Sequence and Angles are shown in Table 3.1-6.
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Table 3.1-5 ASC Transformations (Quaternions)
Item
CHUA_to_Cube1
CHUB_to_Cube1
CHUC_to_Cube2
CHUD_to_Cube2
Cube1_to_BCS
Cube2_to_BCS
CHUA_to_BCS
CHUB_to_BCS
CHUC_to_BCS
CHUD_to_BCS
ASC Transformations
q2
q1
-0.704416026402759
0.996194698091746
0.996194698091746
-0.704416026402759
0.000000000000000
0.000000000000000
-0.981060262190407
0.571393804843270
0.902859012285174
-0.340718653421610
0.704416026402759
0.000000000000000
0.000000000000000
0.704416026402759
0.000000000000000
0.000000000000000
-0.172987393925089
0.816034923451708
-0.421010071662834
0.936116806662859
q3
0.061628416716219
0.000000000000000
0.000000000000000
0.061628416716219
-0.819152044288992
0.422618261740699
-0.015134435901339
-0.071393804843270
0.036833608500735
0.081899608319089
q4
0.061628416716219
0.087155742747658
0.087155742747658
0.061628416716219
0.573576436351046
0.906307787036650
0.085831651177431
0.049990480332730
0.078989928337166
0.029809019626209
Table 3.1-6 ASC Transformations (Euler Angles)
Item
CHUA_to_Cube1
CHUB_to_Cube1
CHUC_to_Cube2
CHUD_to_Cube2
Cube1_to_BCS
Cube2_to_BCS
CHUA_to_BCS
CHUB_to_BCS
CHUC_to_BCS
CHUD_to_BCS
ASC Transformations
1st (deg)
Order
(1,2,3)
(1,2,3)
(1,2,3)
(1,2,3)
(1,2,3)
(1,2,3)
(1,2,3)
(1,2,3)
(1,2,3)
(1,2,3)
2nd (deg)
3rd (deg)
0
0
0
0
0
0
0
0
0
0
90
0
0
90
-110
50
-20
-110
50
140
-170
170
170
-170
0
0
-170
170
170
-170
In some documents you will see a different nomenclature used for the Camera Head Unit, Table
3.1-7 shows the relationships between the different naming designations with the preferences
given to the first column.
Table 3.1-7 Camera Head Unit Designation Mapping
DTU (Preferred)
CHUA
CHUB
CHUC
CHUD
GSFC
Camera 1
Camera 2
Camera 4
Camera 3
GSFC
Bay 6 (-Y)
Bay 6 (-X)
Bay 4 (Inside)
Bay 4 (Outside)
DSS Boresights in the CHU Frame
The Star Sensor has the ability to provide a pseudo sun pulse. In order to provide an accurate
pseudo sun pulse, the star sensor needs to be provided the boresight of the DSS in each CHU
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Frame. The DSS Boresight in the CHU frame as X,Y,Z components are provided in Table 3.1-8
and as Az-El angles in Table 3.1-8
Table 3.1-8 DSS Boresights in CHU Frame ax X, Y, Z components
Item
CHUA
CHUB
CHUC
CHUD
DSS Boresight in CHU Frame
Y
X
0.559192903470747
0.829037572555042
-0.587785252292473
-0.809016994374948
-0.816442628990626
0.550697506767399
-0.796726208379082
0.578855473563864
Z
-0.143960863691598
-0.097102828651975
0.140484326774787
0.102067837920085
Table 3.1-9 DSS Boresights in CHU Frame as Azimuth-Elevation Angles (degrees)
Item
CHUA
CHUB
CHUC
CHUD
DSS Boresight in CHU Frame
Az (deg)
304.407785503165710
33.594546250842072
233.581925896079010
144.416101100390620
El (deg)
-8.277109742764814
-5.572362699291856
8.075873110658067
5.858258259153572
3.1.2 Acceleration Measurement System (AMS)
The Acceleration Measurement System (AMS) is being provided by Zin Technologies and consists of
two redundant sets of three orthogonal Honeywell accelerometers and associated electronics.
AMS Reference Frames and Coordinate Systems
There are two reference frames associated with the AMS: Mechanical Reference Frame and the AMS
Strap-Down Reference Frame
3.1.2.1.1 AMS Mechanical Reference Frame
The AMS Mechanical Reference Frame represents the frame where the Accelerometer locations are
defined. The definition of the frame is provided in Table 3.1-10 and a depiction of the frame is shown in
Figure 3.1-4.
Table 3.1-10 AMS Mechanical Reference Frame Definition
Component
Origin
Fundamental Plane
X Axis
Y-Axis
Z-Axis
Definition
Center of mounting plate
Mounting plate
Long Axis of AMS from X2 Accel to X1 Accel
Completed the right-handed coordinate system
Positive from mounting plate towards Z Accelerometers
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Figure 3.1-4 AMS Mechanical Reference Frame
3.1.2.1.2 AMS Strap-Down Reference Frame
The AMS Strap-Down Reference Frame is defined in Table 3.1-11. The Strap-Down reference frame is
the frame that corresponds with the output of the AMS data.
Table 3.1-11 AMS Strap-Down Reference Frame Definition
Component
Origin
Fundamental Plane
X Axis
Y-Axis
Z-Axis
Definition
Same as AMS Mechanical Reference Frame
Plane created by X-Axis and Y-Axis
Nominally the same as AMS Mechanical Frame X-Axis. Strap-down Frame
can be modified by an AMS Command.
Nominally the same as AMS Mechanical Frame Y-Axis. Strap-down Frame
can be modified by an AMS Command.
Nominally the same as AMS Mechanical Frame Z-Axis. Strap-down Frame
can be modified by an AMS Command.
AMS Accelerometer Locations
The AMS has 6 accelerometers per unit and an image of the accelerometer locations in the OCS frame is
shown in Figure 3.1-5. The locations provided in Table 3.1-12 represent the center of the exterior face of
each accelerometer in the AMS Frame. The location provided in Table 3.1-13 represents the location of
the AMS Frame in the OCS Frame.
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Table 3.1-14 provides the accelerometer locations in the OCS Frame.
Figure 3.1-5 Accelerometer Locations in OCS Frame
Table 3.1-12 Accelerometer Locations in AMS Mechanical Frame
Item
AMS_ACC1 (PT_AX)
AMS_ACC2 (PT_AY)
AMS_ACC3 (PT_AZ)
AMS_ACC4 (PT_BX)
AMS_ACC5 (PT_BY)
AMS_ACC6 (PT_BZ)
Location from AMS Origin (mm)
X
Y
Z
57.15
0.00
63.50
19.05
25.4
63.50
33.02
0.00
114.30
-57.15
0.00
63.50
-19.05
-25.4
63.50
-33.02
0.00
114.30
Table 3.1-13 AMS Mechanical Frame Origin in OCS Frame
Item
AMS_Box
Location from OCS Origin (mm)
X
Y
Z
-392
0
1043.96
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Table 3.1-14 Accelerometer Locations in OCS Frame
Item
AMS_ACC1
AMS_ACC2
AMS_ACC3
AMS_ACC4
AMS_ACC5
AMS_ACC6
Location from OCS Origin (mm)
X
Y
Z
-334.85
0
1107.46
-372.95
25.4
1107.46
-358.98
0
1158.26
-449.15
0
1107.46
-441.05
-25.4
1107.46
-425.02
0
1158.26
AMS Sensing Direction
The AMS has 6 accelerometers per unit. The positive sensing direction provided in Table 3.1-15
represents the sensing direction in the AMS Mechanical Frame.
Table 3.1-15 Sensing Direction in AMS Mechanical Frame
Item
AMS_ACC1
AMS_ACC2
AMS_ACC3
AMS_ACC4
AMS_ACC5
AMS_ACC6
Sensing Direction in AMS Frame
X
Y
Z
1
0
0
0
1
0
0
0
1
-1
0
0
0
-1
0
0
0
1
AMS Transformation and Alignment
The transformation from the AMS Strap-Down Frame to the BCS Frame is shown in Table 3.1-16. The
Alignment matrix from the AMS Mechanical Frame to the Strap-Down Frame for Side A and Side B is
shown in Equation 3.1-2 and Equation 3.1-3, respectively.
Table 3.1-16 AMS Transformation
Item
Strap-down_to_BCS
AMS Alignment Matrix Transformations
q1
q2
q3
0
0
0
q4
1
Equation 3.1-2
X 
1 0 0   X 
Y 
  0 1 0   Y 
 
 Z  AMS _ Strap  down  0 0 1   Z  AMS 1_Mechanical
Equation 3.1-3
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X 
 1 0 0   X 
Y 
  0 1 0   Y 
 
 Z  AMS _ Strap  down  0 0 1   Z  AMS 2 _Mechanical
3.1.3 Digital Sun Sensor
The Digital Sun Sensor (DSS) is a photoelectric sensor device that provides an encoded discrete output
and being supplied by Adcole Corporation. This output is a digital representation of the angle between the
sun line and the normal to the sensor face when the sun is in the field of view (FOV) of the DSS. The
DSS will be used to determine


the angle between the sun line and the fundamental plane of the DSS
to indicate sun crossing within the sensor field-of-view (FOV).
The detection of the Sun Crossing is only valid with a given spin direction, i.e. it only works in one
direction. This knowledge will be used by the spacecraft's attitude control system to estimate the spin rate
of the spacecraft and the position of the spacecraft relative to the sun-to-vehicle line-of-sight.
There will be two DSSs aboard each MMS spacecraft.
DSS Reference Frames and Coordinate Systems
There are two references frames associated with the DSS: DSS Optical References Frame, and the DSS
Mechanical Reference Frame.
3.1.3.1.1 DSS Mechanical Reference Frame
The DSS coordinate system is defined such that the boresight of the sensor is perpendicular to the
spacecraft’s +Z axis. Positive measurements of the sun elevation angle shall be defined as zero in the X-Y
plane and increasing in magnitude towards the +Z axis. DSS measurements are provided with respect to
the DSS Mechanical Reference Frame. The definition of the DSS Mechanical Reference Frame is
provided in Table 3.1-17. A figure showing the DSS and the DSS Mechanical Reference Frame is shown
in Figure 3.1-6.
Table 3.1-17 DSS Mechanical Reference Frame Definition
Component
Origin
Fundamental Plane
XDSS
YDSS
ZDSS
Definition
Intersection of Reference Edge, Mounting Plane, and Surface A
XY Plane
Completes the right-handed system
Coincident with the reference edge and lies in the DSS mounting plane
Nominal Spin Axis, positive from B reticle to A reticle, lies in the DSS
mounting plane
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Figure 3.1-6 DSS Graphic with DSS Mechanical Reference Frame Definition
An image of the DSS1 and DSS2 mounted to the DSS bracket with the DSS Mechanical
Reference frame is shown in Figure 3.1-7.
Figure 3.1-7 DSS1 and DSS2 mounted to the DSS bracket
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3.1.3.1.2 DSS Optical Reference Frame
The DSS Optical Reference Frame is based on optical reference cube mounted to the DSS and used for
aligning the DSS to the OCS. The optical reference cube is a piece of ground support equipment that is
attached to the DSS only during alignment activities. The definition of the DSS Optical Reference Frame
is provided in Table 3.1-18 and an image of the frame is shown in Figure 3.1-8.
Table 3.1-18 DSS Optical Reference Frame Definition
Component
Origin
Fundamental Plane
X Axis
Y-Axis
Z-Axis
Definition
center of cube
XY Plane
Completes the right-handed system
Aligned with A and B slits
Nominal Spin Axis, positive from B reticle to A reticle
Figure 3.1-8 DSS Optical Reference Frame
DSS Reticle and Boresight Locations
Each DSS has two optical windows. The locations provided in Table 3.1-19 represent the center of the
outer surface of each optical window.
Table 3.1-19 DSS Locations in OCS Frame
Item
DSS 1 Mechanical
Reference Frame
DSS 2 Mechanical
Reference Frame
Location from OCS Origin (mm)
X
Y
Z
1017.64
1255.06
127.220
959.418
1269.57
127.220
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DSS Reticle and Sensor Boresight
The DSS Boresights as measured in the DSS Frame are provided in Table 3.1-20.
Table 3.1-20 DSS Boresights in the DSS Mechanical Reference Frame
Normalized Boresight Vector in DSS
Mechanical Reference Frame
X
Y
Z
1
0
0
0.7071
0
0.7071
-0.7071
0
-0.7071
1
0
0
0.7071
0
0.7071
-0.7071
0
-0.7071
Item
DSS 1 Boresight
DSS 1 “A” Optic
DSS 1 “B” Optic
DSS 2 Boresight
DSS 2 “A” Optic
DSS 2 “B” Optic
The DSS Sensor Boresight in the OCS Frame is provided in Table 3.1-21
Table 3.1-21 DSS Boresights in the OCS Frame
Normalized Boresight Vector in OCS
Frame
X
Y
Z
0.2419
0.9703
0
0.1711
0.6917
0.7071
0.1711
0.6917
-0.7071
0.2419
0.9703
0
0.1711
0.6917
0.7071
0.1711
0.6917
-0.7071
Item
DSS 1 Boresight
DSS 1 “A” Optic
DSS 1 “B” Optic
DSS 2 Boresight
DSS 2 “A” Optic
DSS 2 “B” Optic
DSS Transformations
The transformation from the DSS Mechanical Reference Frame to the BCS Frame is provided in Table
3.1-22. The alignment matrix from the DSS Optical Reference Frame to the DSS Mechanical Reference
Frame is shown in Equation 3.1-4 and Equation 3.1-5. The transformation matrix from the DSS Optical
Reference Frame to the BCS frame is shown in Equation 3.1-6 and Equation 3.1-7 and this is equivalent
to the information provided in Table 3.1-22.
Table 3.1-22 DSS Transformations
Item
DSS1_Mechanical_to_BCS
DSS2_Mechanical_to_BCS
q1
0
0
q2
0
0
DSS Transformations
q3
-0.615661475325658
-0.615661475325658
q4
0.788010753606722
0.788010753606722
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Equation 3.1-4
X 
1 0 0   X 
Y 
 0 1 0   Y 
 
 Z  DSS1_MechanicalReferernceFrame 0 0 1   Z  DSS1_Optical
Equation 3.1-5
X 
1 0 0   X 
Y 
 0 1 0   Y 
 
 Z  DSS2_MechanicalReferenceFrame 0 0 1   Z  DSS2_Optical
Equation 3.1-6
ADSS1_ OpticaltoBCS
 cos(76) sin(76) 0   0.241921895599668 0.970295726275996 0
   sin(76) cos(76) 0   0.970295726275996 0.241921895599668 0

0
0
1  
0
0
1 
Equation 3.1-7
ADSS 2 _ OpticaltoBCS
 cos(76) sin(76) 0  0.241921895599668 0.970295726275996 0
   sin(76) cos(76) 0   0.970295726275996 0.241921895599668 0

0
0
1  
0
0
1 
3.2
ACS Actuators
MMS does not have any ACS supplied actuators. The actuators used by the ACS Control System are 12
thrusters and they are supplied by the Propulsion Subsystem and are described in section 4.1.
3.3
Deployables
The MMS Spacecraft has four radial booms, two axial booms, and two magnetic booms that deploy after
separation. There are no active deployables on the MMS spacecraft. Each of the boom coordinate
systems and transformations are discussed in Section 7.2, Spacecraft Deck Instrument Components.
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4.0
Propulsion
The propulsion system consists of thrusters, tanks, latch valves and other various components. In regards
to this document, the thrusters and tanks are the only relevant components. The thrusters are discussed in
section 4.1 and the tanks will be discussed in section 4.2. The MMS Propulsion naming convention can
be found in 461-PS-REF-0143.
4.1
Thrusters
There are a total of twelve thrusters on each MMS spacecraft consisting of eight radial 4-lbf class
thrusters supplied by Aerojet and four axial 1-lbf class thrusters supplied by AMPAC.
4.1.1 Thruster Naming Convention
The naming convention for each of the twelve MMS thrusters is a combination of number and letter
designators:
Thruster number – (1) through (12)
Thruster type – (A)xial or (R)adial
Module type – (D)ual or (S)ingle
Spacecraft X-axis polarity of thruster location – (P)ositive or (N)egative
Spacecraft Y-axis polarity of thruster location – (P)ositive or (N)egative
Thruster’s location within spacecraft’s vertical (Z-axis) orientation – (U)pper or (L)ower
This yields the following thruster nomenclature:
Table 4.1-1 MMS Thruster Names
Radial Thrusters
“4 lbf”
1RDPNL
2RSPPL
3RSNNL
4RDNPL
5RDPNU
6RSPPU
7RSNNU
8RDNPU
Axial Thrusters
“1 lbf”
9ADPNL
10ADNPL
11ADPNU
12ADNPU
A graphical representation of the twelve thrusters in the Observatory Coordinate System (OCS) is shown
in Figure 4.1-1.
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Figure 4.1-1 Graphical Depiction of Thruster Locations
4.1.2 Thruster Force and Torque Polarities
The thruster force and torque polarities are shown in Table 4.1-2. The reference frame for the polarities is
OCS.
Table 4.1-2 Thruster Force and Torque Polarity in OCS Frame
Thruster
1RDPNL
2RSPPL
3RSNNL
4RDNPL
5RDPNU
6RSPPU
7RSNNU
8RDNPU
9ADPNL
10ADNPL
11ADPNU
12ADNPU
Fx
0
0
0
0
0
0
0
0
0
0
0
0
Thruster Force Polarity
Fy
+
–
+
–
+
–
+
–
0
0
0
0
Fz
0
0
0
0
0
0
0
0
+
+
–
–
Thruster Torque Polarity
Tx
Ty
Tz
+
0
+
–
0
–
+
0
–
–
0
+
–
0
+
+
0
–
–
0
–
+
0
+
–
–
0
+
+
0
+
+
0
–
–
0
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4.1.3 Thruster Locations and Plume Direction Vectors
The thruster locations measured from the OCS origin to the center of the thruster nozzle exit plane and the
normalized plume directions are provided in Table 4.1-3. Note that the thruster force direction vectors
imparted on the spacecraft during firings shown in Table 4.1-2 are the inverse of the thruster plume
direction vectors shown in Table 4.1-3.
Table 4.1-3 Thruster Locations and Plume Direction Vectors in OCS Frame
Thruster
1RDPNL
2RSPPL
3RSNNL
4RDNPL
5RDPNU
6RSPPU
7RSNNU
8RDNPU
9ADPNL
10ADNPL
11ADPNU
12ADNPU
Thruster Location (mm)
Measured from OCS Origin
X
Y
533.40
–1709.527
533.40
1709.533
–533.40
–1709.534
–533.40
1709.527
533.40
–1709.527
533.40
1709.534
–533.40
–1709.534
–533.40
1709.527
469.901
–1677.301
–469.901
1677.301
469.893
–1677.132
–469.893
1677.132
Z
92.547
92.547
92.547
92.547
1006.195
1006.195
1006.195
1006.195
31.816
31.816
1056.926
1056.926
Thruster Plume Direction Vector
(normalized)
X
Y
Z
0
–1
0
0
1
0
0
–1
0
0
1
0
0
–1
0
0
1
0
0
–1
0
0
1
0
0
0
–1
0
0
–1
0
0
1
0
0
1
4.2
Fuel Tank
There are four fuel tanks on each MMS spacecraft. Their geometric center locations measured from the
OCS Frame Origin are provided in Table 4.2-1.
Table 4.2-1 Dry Tank Geometric Center Locations in OCS Frame
Item
Tank 1
Tank 2
Tank 3
Tank 4
Quadrant
-X/+Y
+X/+Y
+X/-Y
-X/-Y
Fuel Location
Down (-Z)
Up (+Z)
Down (-Z)
Up (+Z)
Location from OCS Origin (mm)
X
Y
Z
-331.012
331.012
598.250
331.012
331.012
598.250
331.012
-331.012
598.250
-331.012
-331.012
598.250
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5.0
Navigator
The Navigator is responsible for performing orbit determination using GPS data. The Navigator is block
redundant and being built by Code 596 of NASA Goddard Space Flight Center.
5.1
GPS Antenna
The Navigator subsystem uses 8 GPS antennas per spacecraft with 4 antennas attached to the primary side
and 4 antennas attached to the redundant side.
5.1.1 GPS Antenna Reference Designators
The designators for each antenna are based on the locations on the S/C and represent their locations
relative to the nearest bays. Each antenna is located at the apex of two S/C bays and they alternate
between primary and redundant around the circumference of the S/C. All antennas are mounted near the
instrument deck. Table 5.1-1 shows the mapping of the antennas to the Primary/Redundant side of
Navigator, and the RF Chain,
Table 5.1-1 GPS Antenna Reference Designators
Antenna
Ref. Des.
S/C
Location
Side
RF Chain
GPS 1-2
Apex of bays 1 & 2
Primary
#1A
GPS 2-3
Apex of bays 2 & 3
Redundant
#1B
GPS 3-4
Apex of bays 3 & 4
Primary
#2A
GPS 4-5
Apex of bays 4 & 5
Redundant
#2B
GPS 5-6
Apex of bays 5 & 6
Primary
#3A
GPS 6-7
Apex of bays 6 & 7
Redundant
#3B
GPS 7-8
Apex of bays 7 & 8
Primary
#4A
GPS 8-1
Apex of bays 8 & 1
Redundant
#4B
5.1.2 Navigator Component Locations
The Navigator component locations are shown in Figure 5.1-1..
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Figure 5.1-1 Navigator Component Locations
5.1.3 GPS Antenna Alignments
Each GPS Antenna has a Field of View (FOV) of ± 90 degrees in the ± Z direction (spin axis) and > 120
degrees perpendicular to the spin axis. The GPS antenna coordinate system is defined by Table 5.1-2.
The GPS Antenna is symmetrical, therefore the primary axis is the Z-axis of the antenna and the clocking
of the antenna is irrelevant.
Table 5.1-2 GPS Antenna Coordinate System
Component
Origin
Fundamental Plane
X Axis
Y-Axis
Z-Axis
Definition
Center of the antenna on the interface plane
Interface Plane
Lies in the interface plane.
Completes the Right-Handed Coordinate Systems
Normal to the interface plane
A drawing of the coordinate system is shown in Figure 5.1-2
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Figure 5.1-2 GPS Antenna Coordinate Definition
The Boresight of each GPS antenna is listed in Table 5.1-3
Table 5.1-3 GPS Antenna Boresight in OCS
GPS Antenna
X
Y
Z
GPS 1-2
0.923879532511287
0.0161240409850359
0
GPS 2-3
0.382683432365090
0.0066790362285014
0
GPS 3-4
-0.382683432365090
-0.0066790362285014
0
GPS 4-5
-0.923879532511287
-0.0161240409850359
0
GPS 5-6
-0.923879532511287
-0.0161240409850359
0
GPS 6-7
-0.382683432365090
-0.0066790362285014
0
GPS 7-8
0.382683432365090
0.0066790362285014
0
GPS 8-1
0.923879532511287
0.0161240409850359
0
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6.0
RF Communications
The RF Communications subsystem is responsible for the uplink of commands and downlink of telemetry
data. The RF Communications is block redundant and includes two transponders and two omnidirectional antennas on each observatory.
6.1
RF Communications Antenna
The RF Communications subsystem uses 2 S-Band antennas per spacecraft with 1 antenna side-mounted
to the primary side, located on the IS deck and 1 antenna side-mounted to the redundant side, located on
the S/C deck.
The reference designators for each antenna are based on the locations on the observatory and represent
their locations relative to the nearest bays. Each antenna is located near the apex of two deck bays. Table
6.1-1shows the mapping of the antennas.
Table 6.1-1 Comm Antenna Reference Designators
Antenna
Ref. Des.
Deck
Location
Side
S-band Fwd Omni
In Bay 5 on IS Deck
Primary
S-band Aft Omni
In Bay 7 on S/C Deck
Redundant
6.1.1 Communications Antenna Locations and Fields of View
Each Comm Antenna has a Primary Field of View (PFOV) of +45 to +135 degrees in elevation, measured
in the + Z direction (spin axis) by 0 to 360 degrees in azimuth. The two elements on an omni antenna are
out of phase with one another to provide a +10 degree overlap in coverage. The FOV for one element
ranges from +45 to +95 degrees and the FOV of the other element ranges from +85 to +135 degrees;
together providing the PFOV stated above.
The Comm Antenna locations are shown in Figure 6.1-1. Both antennas are viewed from the front;
the aft omni is in the –Z direction and the forward omni is in the +Z direction
Figure 6.1-1 Aft Omni on S/C Deck and Forward Omni on IS Deck
The Comm Antenna Mechanical Frame origin in the OCS frame is shown in Table 6.1-2.
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Table 6.1-2 Comm Antenna Mechanical Frame Origin in OCS Frame
Location from OCS Origin
(mm)
Description
X
MMS Fwd Omni, Antenna Axis
MMS Fwd Omni, Mast Foot
MMS Aft Omni, Antenna Axis
MMS Aft Omni, Mast Foot
Y
Z
-1675 -372.6 1707.00
-1675
-525
1167.63
-452.466 -1759.98 -443.00
-337.448 -1660
96.872
6.1.2 Communications Antenna Coordinate System and Transformations
The Communications Antenna Coordinate System is shown in Figure 6.1-2.
Figure 6.1-2 Communications Antenna Coordinate System
Communications Antenna to Instrument Deck
A –180-degree rotation about the Z-axis aligns the Fwd Omni antenna frame with the Instrument Deck
frame (Section 7.1). Thus the Fwd Omni antenna to OCS frame coordinate transformation consists of an
axis 3 Euler angle rotation of α= -180 degrees. As a direction cosine matrix, this transformation can be
expressed as:
Equation 6.1-1
X 
  1 0 0  X 
 Y  OCS   0  1 0  Y  FW D _ OMNI
 

 
 Z 
 0 0 1  Z 
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Communications Antenna to Spacecraft Deck
A +49-degree rotation about the Z-axis places the Aft Omni antenna Y-axis along the S/C Deck frame
(Section 7.2) Y-axis. A 180-degree rotation about the Y-axis then aligns the Aft Omni antenna frame
along the S/C Deck frame. Thus the Aft Omni antenna to OCS frame coordinate transformation consists
of a 3-2 Euler angle rotation sequence of (α, β) where α= +49 degrees and β = 180 degrees. As a
direction cosine matrix, this transformation can be expressed as:
Equation 6.1-2
X 
 0.656 0.755 0   X 
 Y  OCS   0.755 0.656 0   Y  AFT _ OMNI
 

 
 Z 
 0
0
1  Z 
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7.0
Instrument Coordinate System Definitions
Instruments are located on both the Instrument Deck and Spacecraft Deck.
7.1
Instrument Deck CS, Transformations, and Instrument Components
The Instrument Deck Coordinate System (IDCS) is oriented identically to the OCS but is offset from the
center of the separation plane. The offset between IDCS and OCS is shown in Table 7.1-2. The top view
and side view of the IS deck is shown in Figure 7.1-1with the orbital debris shield removed for clarity.
The z-axis is with respect to the component mounting side of the IS Deck.
Figure 7.1-1 Instrument Deck Coordinate System - Top and Side Views
The bottom view of the Instrument Suite in Figure 7.1-2 depicts the instruments relative to the bay
number. This image corresponds with Drawing 2102857, the IS Deck Assembly Drawing. The local
coordinate system for each instrument is defined in the MICD and will be shown for each instrument in
subsequent sections of this document.
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Figure 7.1-2 Instrument Deck Coordinate System - Bottom View
The Instrument Deck Coordinate System definition is provided in Table 7.1-1.
Table 7.1-1 IDCS Definition
Component
Definition
Center of the launch vehicle adaptor ring on the bottom surface of the IS Deck
(primary instrument interface plane).
Bottom Surface of IS Deck (primary instrument interface plane).
line projecting from the origin along the bottom surface of the IS deck and
intersecting the plane of Bay 1
completes the right hand system
extends through the IS structure along the center line of the thrust tube
Origin
Fundamental Plane
X-Axis
Y-Axis
Z-Axis
Table 7.1-2 Instrument Deck Coordinate System Origin in OCS Frame
Location from OCS Origin (mm)
Description
MMS Instrument Deck
X
0.0
Y
0.0
Z
1051.0
The Instrument Deck coordinate system (IDCS) is aligned with the OCS. Therefore, the direction cosine
matrix for this transformation is the identity matrix:
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Equation 7.1-1
X 
1 0 0  X 
 Y  OCS  0 1 0  Y  IDCS
 

 
 Z 
0 0 1  Z 
There are eight different types of instruments located on the Instrument Deck. Many of these instruments
have multiple instances. The coordinate system and reference hole for each will be depicted in figures in
the following sections. A table describing the instrument location from the observatory coordinate system
origin and a coordinate transformation from each instrument to the OCS is included.
7.1.1 Active Spacecraft Potential Control (ASPOC)
The ASPOC coordinate system is depicted in Figure 7.1-3. This reference view was obtained from
MMS Drawing 101600023.
Figure 7.1-3 ASPOC Coordinate System
There are two ASPOC instruments on the Instrument Deck located in Bays 2 and 6. The location of each
ASPOC Coordinate System origin in the OCS frame is shown in Table 7.1-3.
Table 7.1-3 ASPOC Mechanical Frame Origin in OCS Frame
Item
ASPOC #1
ASPOC #2
Location from OCS Origin (mm)
X
Y
Z
732.33
1319.89
898.20
-732.33
-1319.89
898.20
Bay Number
2
6
Both ASPOC instruments have their Z-axis parallel to the Instrument Deck Z-axis. A rotation about the
Z-axis aligns the ASPOC frame with the Instrument Deck frame. The ASPOC to OCS frame coordinate
transformation consists of an axis 3 Euler angle rotation of α1= +195 degrees and α2= +15 degrees for
ASPOC #1 and ASPOC#2 respectively. As a direction cosine matrix, this transformation can be
expressed as:
Equation 7.1-2
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X 
 0.966 0.259 0  X 
 Y  OCS   0.259 0.966 0  Y  ASPOC # 1
 

  
 Z 
 0
0
1   Z 
Equation 7.1-3
X 
 Y  OCS 
 
 Z 
 0.966 0.259 0  X 
 0.259 0.966 0  Y  ASPOC # 2

  
 0
0
1   Z 
7.1.2 Axial Double Probe (ADP)
The ADP coordinate system is depicted in Figure 7.1-4. This reference view was obtained from MMS
Drawing 101600011.
Figure 7.1-4 ADP Coordinate System
The longeron clocking at the base plate (z=0 mm) is shown in Figure 7.1-5.
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Figure 7.1-5 ADP Longeron Clocking
There are two ADP booms, each is located on the bulkhead panel assembly. ADP #1 deploys in the +z
direction. Figure 7.1-6 is a top view (looking –z) of the ADP base plate. The OCS frame is shown in red
and the ADP local coordinate system is shown in black, with the origin centered on the dowel pin hole.
Figure 7.1-6 ADP #1
The ADP#1 coordinate system is aligned with the OCS. Therefore, the direction cosine matrix for this
transformation is the identity matrix:
Equation 7.1-4
X 
1 0 0  X 
 Y  OCS  0 1 0  Y  ADP#1
 

 
 Z 
0 0 1  Z 
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ADP #2 deploys in the -z d+irection. Figure 7.1-7 is a top view (looking +z) of the ADP base plate. The
OCS frame is shown in red and the ADP local coordinate system is shown in black, with the origin
centered on the dowel pin hole.
Figure 7.1-7 ADP #2
A rotation about the Y-axis aligns the ADP#2 frame with the Spacecraft Deck and OCS frame. The
ADP#2 to OCS frame coordinate transformation consists of an axis 2 Euler angle rotation of β = 180
degrees. As a direction cosine matrix, this transformation can be expressed as:
Equation 7.1-5
X 
 1 0 0   X 
 Y  OCS   0 1 0   Y  ADP# 2
 

 
 Z 
 0 0  1  Z 
The location of each ADP Coordinate System origin in the OCS frame is shown in Table 7.1-4.
Table 7.1-4 ADP Mechanical Frame Origin in OCS Frame
Item
ADP #1 Stowed
ADP #1 Fully Deployed
ADP #2 Stowed
ADP #2 Fully Deployed
Location from OCS Origin (mm)
X
Y
Z
0
-161.925
945
0
-161.925
15745
0
-161.925
-385
0
-161.925
-15185
NOTE: Nominal volume of the ADP receiving element dynamic envelope referenced in the
MICD as +/- 50mm, which is not necessarily the worst case volume.
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7.1.3 Electron Drift Instrument/ Gun Detector Unit (EDI/GDU)
The EDI coordinate system is depicted in Figure 7.1-8. This reference view was obtained from MMS
Drawing 101600013.
Figure 7.1-8 EDI Coordinate System
There are two EDI instruments on the IS Deck, one in Bay 4 and one in Bay 8. The location of each EDI
Coordinate System origin in the OCS frame is shown in Table 7.1-5.
Table 7.1-5 EDI Mechanical Frame Origin in OCS Frame
Item
EDI #1
EDI #2
Location from OCS Origin (mm)
X
Y
Z
-1332.748
889.069
1051
1332.748
-889.069
1051
Bay Number
4
8
A -90-degree rotation about the Y-axis places the EDI#1 Z-axis along the Instrument Deck frame Z-axis.
A +221-degree rotation about the Z-axis then aligns the EDI#1 frame along the OCS frame. Thus the
EDI#1 to OCS frame coordinate transformation consists of a 2-3 Euler angle rotation sequence of (β,α)
where β = -90 degrees and α= +221 degrees. As a direction cosine matrix, this transformation can be
expressed as:
Equation 7.1-6
X 
 0 0.656 0.755  X 
 Y  OCS   0 0.755 0.656   Y  EDI # 1
 

 
 Z 
 1
0
0   Z 
A -90-degree rotation about the Y-axis places the EDI#2 Z-axis along the Instrument Deck frame Z-axis.
A +41-degree rotation about the Z-axis then aligns the EDI#2 frame along the OCS frame. Thus the
EDI#2 to OCS frame coordinate transformation consists of a 2-3 Euler angle rotation sequence of (β,α)
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where β = -90 degrees and α= +41 degrees. As a direction cosine matrix, this transformation can be
expressed as:
Equation 7.1-7
X 
 0 0.656 0.755   X 
 Y  OCS   0 0.755 0.656  Y  EDI # 2
 

 
 Z 
 1
0
0   Z 
7.1.4 Energetic Ion Spectrometer (EIS)
The EIS coordinate system is depicted in Figure 7.1-9. This reference view was obtained from MMS
Drawing 101600020.
Figure 7.1-9 EIS Coordinate System
The EIS instrument is located in Bay 4 on the Instrument Deck. The location of the EIS Coordinate
System origin in the OCS frame is shown in Table 7.1-6.
Table 7.1-6 EIS Mechanical Frame Origin in OCS Frame
Item
EIS
Location from OCS Origin (mm)
X
Y
Z
-1061.49
1037.224
1051
Bay Number
4
The EIS has its Z-axis parallel to the Instrument Deck Z-axis. A rotation about the Z-axis aligns the EIS
frame with the OCS frame. The EIS to OCS frame coordinate transformation consists of an axis 3 Euler
angle rotation of α= +45 degrees. As a direction cosine matrix, this transformation can be expressed as:
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Equation 7.1-8
X 
 Y  OCS 
 
 Z 
 0.707 0.707 0  X 
 0.707 0.707 0  Y  EIS

  
 0
0
1   Z 
7.1.5 Fly’s Eye Energetic Particle Sensors (FEEPS)
The FEEPS coordinate system is depicted in Figure 7.1-10. This reference view was obtained from
MMS Drawing 101600021.
Figure 7.1-10 FEEPS Coordinate System
There are two FEEPS instruments, one is located on the top side of the IS Deck in Bay 2 and one is
located on the S/C Deck in Bay 6. The S/C Deck FEEPS is discussed in Section 7.2.1. The location of the
FEEPS Coordinate System origin in the OCS frame is shown in Table 7.1-7. Note: Each FEEPS is
mounted on a bracket (see MMS Drawing 2102174).
Table 7.1-7 FEEPS Mechanical Frame Origin in OCS Frame
Item
FEEPS (IS Deck)
Location from OCS Origin (mm)
X
Y
Z
1207.015
1095.66
1109.70
Bay Number
2
The FEEPS has its Z-axis parallel to the Instrument Deck Z-axis. A rotation about the Z-axis aligns the
FEEPS frame with the OCS frame. The FEEPS to OCS frame coordinate transformation consists of an
axis 3 Euler angle rotation of α= +45 degrees. As a direction cosine matrix, this transformation can be
expressed as:
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Equation 7.1-9
X 
 Y  OCS 
 
 Z 
 0.707 0.707 0  X 
 0.707 0.707 0  Y  FEEPS _ IS

 
 0
0
1   Z 
7.1.6 Fast Plasma Investigation (FPI)
The FPI consists of two instruments, the Dual Electron Spectrometer (DES) and the Dual Ion
Spectrometer (DIS).
Dual Electron Spectrometer (DES)
The DES coordinate system is depicted in Figure 7.1-11. This reference view was obtained from MMS
Drawing 101600018.
Figure 7.1-11 DES Coordinate System
There are four DES instruments located on the IS Deck in Bays 1, 3, 5, and 7. The location of each DES
Coordinate System origin in the OCS frame is shown in Table 7.1-8. Note: Each DES instrument is
mounted on a bracket (see MMS Drawing 2102170).
Table 7.1-8 DES Mechanical Frame Origin in OCS Frame
Item
DES #1
DES #2
DES #3
DES #4
Location from OCS Origin (mm)
X
Y
Z
1454.73
-225.82
1015
225.82
1454.73
1015
-1454.73
225.82
1015
-225.82
-1454.73
1015
Bay Number
1
3
5
7
Each DES has its Z-axis parallel to the Instrument Deck Z-axis. DES#1 requires a rotation about the Zaxis to align the DES#1 frame with the OCS frame. The DES#1 to OCS frame coordinate transformation
consists of an axis 3 Euler angle rotation of α= -90 degrees. As a direction cosine matrix, this
transformation can be expressed as:
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Equation 7.1-10
X 
0 1 0  X 
 Y  OCS  1 0 0  Y  DES # 1
 

 
 Z 
0 0 1   Z 
DES#2 requires a rotation about the Z-axis to align the DES#2 frame with the OCS frame. The DES#2 to
OCS frame coordinate transformation consists of an axis 3 Euler angle rotation of α= -180 degrees. As a
direction cosine matrix, this transformation can be expressed as:
Equation 7.1-11
X 
  1 0 0  X 
 Y  OCS   0  1 0  Y  DES # 2
 

 
 Z 
 0 0 1  Z 
DES#3 requires a rotation about the Z-axis to align the DES#3 frame with the OCS frame. The DES#3 to
OCS frame coordinate transformation consists of an axis 3 Euler angle rotation of α= +90 degrees. As a
direction cosine matrix, this transformation can be expressed as:
Equation 7.1-12
X 
 Y  OCS 
 
 Z 
 0 1 0  X 
 1 0 0  Y  DES # 3

  
 0 0 1   Z 
DES#4 is aligned with the OCS frame. Therefore, the direction cosine matrix for this transformation is the
identity matrix:
Equation 7.1-13
X 
1 0 0  X 
 Y  OCS  0 1 0  Y  DES # 4
 

 
 Z 
0 0 1  Z 
Dual Ion Spectrometer (DIS)
The DIS coordinate system is depicted in Figure 7.1-12. This reference view was obtained from MMS
Drawing 101600019.
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Figure 7.1-12 DIS Coordinate System
There are four DIS instruments located on the IS Deck in Bays 1, 3, 5 and 7. The location of each DIS
Coordinate System origin in the OCS frame is shown in Table 7.1-9. Note: Each DIS instrument is
mounted on a bracket (see MMS Drawing 2102170).
Table 7.1-9 DIS Mechanical Frame Origin in OCS Frame
Item
DIS #1
DIS #2
DIS #3
DIS #4
Location from OCS Origin (mm)
X
Y
Z
1480.885
242
1015
-242
1480.885
1015
-1480.885
-242
1015
242
-1480.885
1015
Bay Number
1
3
5
7
Each DIS has its Z-axis parallel to the Instrument Deck Z-axis. DIS#1 requires a rotation about the Zaxis to align the DIS#1 frame with the OCS frame. The DIS#1 to OCS frame coordinate transformation
consists of an axis 3 Euler angle rotation of α= -90 degrees. As a direction cosine matrix, this
transformation can be expressed as:
Equation 7.1-14
X 
0 1 0  X 
 Y  OCS  1 0 0  Y  DIS # 1
 

  
 Z 
0 0 1   Z 
DIS#2 requires a rotation about the Z-axis to align the DIS#2 frame with the OCS frame. The DIS#2 to
OCS frame coordinate transformation consists of an axis 3 Euler angle rotation of α= -180 degrees. As a
direction cosine matrix, this transformation can be expressed as:
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Equation 7.1-15
X 
  1 0 0  X 
 Y  OCS   0  1 0  Y  DIS # 2
 

 
 Z 
 0 0 1  Z 
DIS#3 requires a rotation about the Z-axis to align the DIS#3 frame with the OCS frame. The DIS#3 to
OCS frame coordinate transformation consists of an axis 3 Euler angle rotation of α= +90 degrees. As a
direction cosine matrix, this transformation can be expressed as:
Equation 7.1-16
X 
 Y  OCS 
 
 Z 
 0 1 0  X 
 1 0 0  Y  DIS # 3

  
 0 0 1   Z 
DIS#4 is aligned with the OCS frame. Therefore, the direction cosine matrix for this transformation is the
identity matrix:
Equation 7.1-17
X 
1 0 0  X 
 Y  OCS  0 1 0  Y  DIS # 4
 

 
 Z 
0 0 1  Z 
7.1.7 Hot Plasma Composition Analyzer (HPCA)
The HPCA coordinate system is depicted in Figure 7.1-13. This reference view was obtained from
MMS Drawing 101600022.
Figure 7.1-13 HPCA Coordinate System
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The HPCA instrument is located on the IS Deck in Bay 6. The location of the HPCA Coordinate System
origin in the OCS frame is shown in Table 7.1-10.
Table 7.1-10 HPCA Mechanical Frame Origin in OCS Frame
Item
HPCA
Location from OCS Origin (mm)
X
Y
Z
-915.56
-1059.696
1051
Bay Number
6
The HPCA has its Z-axis parallel to the Instrument Deck Z-axis. A rotation about the Z-axis aligns the
HPCA frame with the OCS frame. The HPCA to OCS frame coordinate transformation consists of an axis
3 Euler angle rotation of α= +135 degrees. As a direction cosine matrix, this transformation can be
expressed as:
Equation 7.1-18
X 
 0.707 0.707 0  X 
 Y  OCS   0.707 0.707 0  Y  HPCA
 

  
 Z 
 0
0
1   Z 
7.1.8 Spin-Plane Double Probe (SDP)
The SDP coordinate system is depicted in Figure 7.1-14. This reference view was obtained from MMS
Drawing 101600012.
Figure 7.1-14 SDP Coordinate System
There are four SDP instruments on the IS Deck located in Bays 2, 4, 6 and 8. The location of the SDP
Coordinate System origin in the OCS frame is shown in
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Table 7.1-11.
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Table 7.1-11 SDP Mechanical Frame Origin in OCS Frame
Item
SDP #1
SDP #2
SDP #3
SDP #4
Location from OCS Origin (mm)
X
Y
Z
1342.598
865.542
1051
-1342.598
-865.542
1051
-865.542
1342.598
1051
865.542
-1342.598
1051
Bay Number
2
6
4
8
A +60-degree rotation about the Z-axis places the SDP#1 Y-axis along the Instrument Deck frame Y-axis.
A 180-degree rotation about the Y-axis then aligns the SDP#1 frame along the OCS frame. Thus the
SDP#1 to OCS frame coordinate transformation consists of a 3-2 Euler angle rotation sequence of (α, β)
where α= +60 degrees and β = 180 degrees. As a direction cosine matrix, this transformation can be
expressed as:
Equation 7.1-19
X 
 0.500 0.866 0   X 
 Y  OCS   0.866 0.500 0   Y  SDP # 1
 

 
 Z 
 0
0
1  Z 
A -120-degree rotation about the Z-axis places the SDP#2 Y-axis along the Instrument Deck frame Yaxis. A 180-degree rotation about the Y-axis then aligns the SDP#2 frame along the OCS frame. Thus the
SDP#2 to OCS frame coordinate transformation consists of a 3-2 Euler angle rotation sequence of (α, β)
where α= -120 degrees and β = 180 degrees. As a direction cosine matrix, this transformation can be
expressed as:
Equation 7.1-20
X 
0.500 0.866 0   X 
 Y  OCS  0.866 0.500 0   Y  SDP # 2
 

 
 Z 
 0
0
1  Z 
A -30-degree rotation about the Z-axis places the SDP#3 Y-axis along the Instrument Deck frame Y-axis.
A 180-degree rotation about the Y-axis then aligns the SDP#3 frame along the OCS frame. Thus the
SDP#3 to OCS frame coordinate transformation consists of a 3-2 Euler angle rotation sequence of (α, β)
where α= -30 degrees and β = 180 degrees. As a direction cosine matrix, this transformation can be
expressed as:
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Equation 7.1-21
X 
 0.866 0.500 0   X 
 Y  OCS   0.500 0.866 0   Y  SDP # 3
 

 
 Z 
 0
0
1  Z 
A -210-degree rotation about the Z-axis places the SDP#4 Y-axis along the Instrument Deck frame Yaxis. A 180-degree rotation about the Y-axis then aligns the SDP#4 frame along the OCS frame. Thus the
SDP#4 to OCS frame coordinate transformation consists of a 3-2 Euler angle rotation sequence of (α, β)
where α= -210 degrees and β = 180 degrees. As a direction cosine matrix, this transformation can be
expressed as:
Equation 7.1-22
X 
 0.866 0.500 0   X 
 Y  OCS   0.500 0.866 0   Y  SDP # 4
 

 
 Z 
 0
0
1  Z 
7.2
Spacecraft Deck CS, Transformations, and Instrument Components
Figure 7.2-1 depicts the instrument components located on the bottom of the spacecraft deck. The S/C
Deck coordinate system is identical to the OCS and is shown from the bottom view in the figure below.
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Figure 7.2-1 S/C Deck Coordinate System - Bottom View
The Spacecraft Deck coordinate system is aligned with the OCS. The Z offset of the S/C deck in the
OCS is nominally 167mm based on a nominal thickness of the thermal spacer between the S/C
deck and the propulsion thrust tube assembly. This thickness could result in a Z offset up to
170mm depending on shimming. The direction cosine matrix for this transformation is the identity
matrix:
Equation 7.2-1
X 
1 0 0  X 
 Y  OCS  0 1 0  Y  SC
 

 
 Z 
0 0 1  Z 
There are three different types of instruments located on the Spacecraft Deck. The coordinate system and
reference hole for each will be depicted in figures in the following sections. A table describing the
instrument location from the observatory coordinate system origin and a coordinate transformation from
each instrument to the OCS is included.
7.2.1 Fly’s Eye Energetic Particle Sensors (FEEPS)
The FEEPS coordinate system is depicted in Figure 7.2-2. This reference view was obtained from MMS
Drawing 101600021.
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Figure 7.2-2 FEEPS Coordinate System
There are two FEEPS instruments, one is located on the top side of the IS Deck in Bay 2 and one is
located on the S/C Deck in Bay 6. The Instrument Deck FEEPS is discussed in Section 7.1.5. The
location of the FEEPS Coordinate System origin in the OCS frame is shown in Table 7.2-1. Note: Each
FEEPS is mounted on a bracket (see MMS Drawing 2102174).
Table 7.2-1 FEEPS Mechanical Frame Origin in OCS Frame
Item
FEEPS (S/C Deck)
Location from OCS Origin (mm)
X
Y
Z
-724.15
-1471.52
225.7
Bay Number
6
A -45-degree rotation about the Z-axis places the FEEPS Y-axis along the Spacecraft Deck frame Y-axis.
A 180-degree rotation about the Y-axis then aligns the FEEPS frame along the OCS frame. Thus the
FEEPS to OCS frame coordinate transformation consists of a 3-2 Euler angle rotation sequence of (α, β)
where α= -45 degrees and β = 180 degrees. As a direction cosine matrix, this transformation can be
expressed as:
Equation 7.2-2
X 
 0.707 0.707 0   X 
 Y  OCS   0.707 0.707 0   Y  FEEPS _ SC
 

 
 Z 
 0
0
1  Z 
7.2.2 Magnetometers
There are three magnetometer instruments on board each MMS observatory. The Analog Flux Gate
(AFG) Magnetometer and the Search Coil Magnetometer (SCM) are both mounted on the boom located
in S/C Bay 6 when fully deployed. The Digital Flux Gate (DFG) Magnetometer is mounted on the boom
located in S/C Bay 2 when fully deployed.
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The Magnetometer Boom coordinate system is depicted in Figure 7.2-3.
Figure 7.2-3 Magnetometer Boom Coordinate System
The location of each Magnetometer Boom Coordinate System origin in the OCS frame is shown in Table
7.2-2.
Table 7.2-2 Magnetometer Boom Mechanical Frame Origin in OCS Frame
Location from OCS Origin (mm)
X
Y
Z
-991.47
-991.47
-77.1
991.47
991.47
-77.1
Item
AFG /SCM Boom
DFG Boom
Bay Number
6
2
The Magnetometer Boom’s Z-axis is parallel to the Spacecraft Deck Z-axis. A rotation about the Z-axis
aligns the AFG/SCM Boom frame with the OCS frame. The AFG/SCM Boom to OCS frame coordinate
transformation consists of an axis 3 Euler angle rotation of α= +135 degrees. As a direction cosine
matrix, this transformation can be expressed as:
Equation 7.2-3
X 
 Y  OCS 
 
 Z 
 0.707 0.707 0   X 
 0.707 0.707 0  Y  BOOM _ AFG / SCM

  
 0
0
1   Z 
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The Magnetometer Boom’s Z-axis is parallel to the Spacecraft Deck Z-axis. A rotation about the Z-axis
aligns the DFG Boom frame with the OCS frame. The DFG Boom to OCS frame coordinate
transformation consists of an axis 3 Euler angle rotation of α= -45 degrees. As a direction cosine matrix,
this transformation can be expressed as:
Equation 7.2-4
X 
 Y  OCS 
 
 Z 
0.707 0.707 0  X 
0.707 0.707 0  Y  BOOM _ DFG

  
 0
0
1   Z 
Analog Flux Gate (AFG) Magnetometer
The AFG coordinate system is depicted in Figure 7.2-4. This reference view was obtained from MMS
Drawing 101600014. Note: The AFG sensors mount to a boom adapter depicted in Drawing 2102850,
Sheet 4. The boom adapter is the same for the AFG and the DFG.
Figure 7.2-4 AFG Coordinate System
The location of the AFG Coordinate System origin in the Boom CS frame is shown in Table 7.2-3.
Table 7.2-3 AFG Mechanical Frame Origin in Boom CS Frame
Item
AFG Fully Deployed
Location from Boom CS Origin (mm)
X
Y
Z
5187.85
-8
2.1262
Bay Number
6
A -90-degree rotation about the Y-axis places the AFG sensor’s Z-axis along the AFG Magnetometer
Boom frame Z-axis. A -90-degree rotation about the Z-axis then aligns the AFG sensor frame along the
AFG Mag Boom frame. Thus the AFG sensor to AFG Mag Boom coordinate transformation consists of a
2-3 Euler angle rotation sequence of (β,α) where β = -90 degrees and α= -90 degrees. As a direction
cosine matrix, this transformation can be expressed as:
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Equation 7.2-5
X 
 0 1 0  X 
 Y  BOOM _ AFG / SCM   0 0 1   Y  AFG
 

 
 Z 
 1 0 0  Z 
Digital Flux Gate (DFG) Magnetometer
The DFG coordinate system is depicted in Figure 7.2-5. This reference view was obtained from MMS
Drawing 101600015. Note: The DFG sensors mount to a boom adapter depicted in Drawing 2102850,
Sheet 4. The boom adapter is the same for the AFG and the DFG.
Figure 7.2-5 DFG Coordinate System
The location of the DFG Coordinate System origin in the Boom CS frame is shown in Table 7.2-4.
Table 7.2-4 DFG Mechanical Frame Origin in Boom CS Frame
Item
DFG Fully Deployed
Location from Boom CS Origin (mm)
X
Y
Z
5187.85
-8
2.1262
Bay Number
2
A -90-degree rotation about the Y-axis places the DFG sensor’s Z-axis along the DFG Magnetometer
Boom frame Z-axis. A -90-degree rotation about the Z-axis then aligns the DFG sensor frame along the
DFG Mag Boom frame. Thus the DFG sensor to DFG Mag Boom coordinate transformation consists of a
2-3 Euler angle rotation sequence of (β,α) where β = -90 degrees and α= -90 degrees. As a direction
cosine matrix, this transformation can be expressed as:
Equation 7.2-6
X 
 0 1 0  X 
 Y  BOOM _ DFG   0 0 1  Y  DFG
 

 
 Z 
 1 0 0  Z 
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Search-Coil Magnetometer (SCM)
The SCM coordinate system is depicted in Figure 7.2-6 and is located on the boom with the AFG. This
reference view was obtained from MMS Drawing 101600025. Note: The SCM mounts to a bracket
depicted in Drawing 2102850, Sheet 5.
Figure 7.2-6 SCM Coordinate System
The location of the SCM Coordinate System origin in the Boom CS frame is shown in Table 7.2-5.
Table 7.2-5 SCM Mechanical Frame Origin in Boom CS Frame
Item
SCM Fully Deployed
Location from Boom CS Origin (mm)
X
Y
Z
4147.85
-4.79899
-33.2010
Bay Number
6
A +90-degree rotation about the X-axis places the SCM sensor’s Z-axis along the Magnetometer Boom
frame Z-axis. A 180-degree rotation about the Z-axis then aligns the SCM sensor frame along the Mag
Boom frame. Thus the SCM sensor to Mag Boom coordinate transformation consists of a 1-3 Euler angle
rotation sequence of (,α) where  = +90 degrees and α= 180 degrees. As a direction cosine matrix,
this transformation can be expressed as:
Equation 7.2-7
X 
 1 0 0   X 
 Y  BOOM _ AFG / SCM   0 0 1  Y  SCM
 

  
 Z 
 0 1 0   Z 
Sensor Axis 1,2,3 Coordinate Systems
Once mounted on the spacecraft, the axes of the AFG, DFG and SCM systems all point in different
directions, as shown in the left side of Figure 7.2-7. For convenience, we define AFG, DFG and SCM
‘Sensor Axis’ systems (AFG123, DFG123, SCM123), so that the 1,2,3 sensor axes all have the same
nominal orientation for all three instruments. The nominal orientation corresponds to the AFG Boom
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Coordinate System. The right hand side of Figure 7.2-7 shows the AFG, DFG, and SCM axes labeled
according to the AFG123, DFG123, and SCM123 systems.
To obtain Sensor Axis 1, 2, 3 coordinates for a given instrument, the non-orthogonal sensor triad outputs,
which are nominally aligned with the instrument chassis XYZ coordinates, are rotated using the relations
defined in Equation 7.2-8, Equation 7.2-9, and Equation 7.2-10. Thus, AFG123, DFG123 and SCM123
denote three distinct, but closely aligned, non-orthogonal systems. .
Figure 7.2-7 Nominal Orientation of magnetometers with respect to the spacecraft, as represented in
AFG/DFG/SCM XYZ coordinates (left) versus AFG123/DFG123/SCM123 coordinates (right).
The AFG Sensor Axes 1, 2 and 3 are related to AFG coordinates by Equation 7.2-8:
Equation 7.2-8
-𝐴𝐹𝐺1
0 −1 0 𝑋
𝐴𝐹𝐺
[
0 1] [𝑌 ] 𝐴𝐹𝐺
2]= [ 0
𝐴𝐹𝐺3
−1 0 0 𝑍
The DFG Sensor Axes 1, 2 and 3 are related to DFG coordinates by Equation 7.2-9:
Equation 7.2-9
-𝐷𝐹𝐺1
0 1
[ 𝐷𝐹𝐺2 ] = [ 0 0
𝐷𝐹𝐺3
−1 0
0 𝑋
−1] [𝑌 ] 𝐷𝐹𝐺
0 𝑍
The SCM Sensor Axes 1, 2, and 3 are related to the SCM coordinates by Equation 7.2-10:
Equation 7.2-10
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-𝑆𝐶𝑀1
−1 0
0 𝑋
[ 𝑆𝐶𝑀2 ] = [ 0
0 −1] [𝑌 ] 𝑆𝐶𝑀
𝑆𝐶𝑀3
0 −1 0 𝑍
Orthogonalized Magnetometer Coordinate System (OMB)
The OMB coordinate system is defined to be a fixed 225° rotation from the SMPA coordinate system,
as in Equation 7.2-11. As described in Table 7.2-6, the OMB Z-axis is aligned with the MPA, while the
OMB X-axis is closely aligned with the AFG Boom X-axis. Because the OMB X, Y, and Z-axes are
closely aligned with sensor axes 1, 2, and 3, respectively, this coordinate system is useful as an
intermediate state of calibrated, orthogonalized AFG & DFG data before rotation into body coordinates.
Table 7.2-6 OMB Coordinate System Definition
Component
Origin
Fundamental Plane
Definition
Center of Mass
X-Y Plane (Spin Plane)
Intersection of the spin plane (MPA-normal) with the plane defined by the
MPA and the Nominal AFG Boom X-axis. Positive in the direction of the
X-Axis
AFG Boom X-axis (radially outward along the nominal AFG boom
orientation).
Normal to the plane defined by the MPA and the Nominal AFG Boom X-axis,
Y-Axis
positive in the direction of the AFG Boom Y-axis.
The Major Principal Axis of the spacecraft, positive in the direction of the ZZ-Axis
axis that is common to the BCS and AFG Boom coordinate systems.
The MAG coordinates are defined to be a fixed 225° rotation from SMPA coordinates, as in Equation
7.2-11.
Equation 7.2-11
−√2/2 √2/2 0 𝑋
𝑋
[𝑌 ] 𝑆𝑀𝑃𝐴 = [−√2/2 −√2/2 0] [𝑌 ] 𝑀𝐴𝐺
𝑍
0
0
1 𝑍
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APPENDIX A: ACRONYM LIST
Abbreviation/
Acronym
ACS
ADP
AFG
AMS
ASPOC
Az
BCS
CHU
CS
DBCS
DES
DFG
DIS
DMPA
DSCS
DSS
DSL
DTU
ECEF
ECI
EDI
EIS
El
FD
FEA
FEEPS
FDOA
FK5
FPI
GDU
GNC
GPS
GSE
GSM
HPCA
ICRF
IDCS
LVCS
ASC
MAG
MMS
MOC
DEFINITION
Attitude Control System
Axial Double Probe
Analog Flux Gate
Acceleration Measurement System
Active Spacecraft Potential Probe
Azimuth
Body Coordinate System
Camera Head Unit
Coordinate System
De-spun Body Coordinate System
Dual Electron Spectrometer
Digital Flux Gate
Dual Ion Spectrometer
De-spun MPA Coordinate System
De-spun Spin-axis Coordinate System
Digital Sun Sensor
De-spun Spacecraft L-Vector Coordinate System
Danish Technical University
Earth Centered, Earth Fixed
Earth Centered Inertial
Electron Drift Instrument
Energetic Ion Spectrometer
Elevation
Flight Dynamics
Front-End Electronics Assembly
Fly’s Eye Energetic Particle Sensors
Flight Dynamics Operations Area
Fifth Fundamental Catalogue
Fast Plasma Investigation
Gun Detector Unit
Guidance, Navigation, and Control
Global Positioning System
Geocentric Solar Ecliptic
Geocentric Solar Magnetospheric
Hot Plasma Composition Analyzer
International Celestial Reference Frame
Instrument Deck Coordinate System
Launch Vehicle Coordinate System
micro Autonomous Star Sensor
Orthogonalized Magnetometer Coordinate System
Magnetospheric Multiscale
Mission Operations Center
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Abbreviation/
Acronym
MPA
MSCS
OBA
OCS
PQW
RF
RIC
SCM
SCS
SDP
SIP
SMPA
SSL
STA
TT
USO
VBN
Ze
DEFINITION
Major Principal Axis
Mini-Stack Coordinate System
Optical Bench Assembly
Observatory Coordinate System
Perifocal Coordinate System
Radio Frequency
Radial, Intrack, Crosstrack
Search-Coil Magnetometer
Stack Coordinate System
Spin-Plane Double Probe
Standard Interface Plane
Spinning MPA Coordinate System
Spinning Spacecraft L-Vector Coordinate System
Station
Terrestrial Time
Ultra Stable Oscillator
Velocity, Binormal, Normal
Zenith
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