431-SPEC-000112
Revision Effective Date: To be added upon Release
Expiration Date: To be added upon Release
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Robotic Lunar Exploration Program
Lunar Reconnaissance Orbiter Project
Technical Resource Allocations Specification
Date Document Generated (06/22/2005)
Goddard Space Flight Center
Greenbelt, Maryland
National Aeronautics and
Space Administration
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CM FOREWORD
This document is a Lunar Reconnaissance Orbiter (LRO) Project Configuration Management
(CM)-controlled document. Changes to this document require prior approval of the applicable
Configuration Control Board (CCB) Chairperson or designee. Proposed changes shall be
submitted to the LRO CM Office (CMO), along with supportive material justifying the proposed
change. Changes to this document will be made by complete revision.
Questions or comments concerning this document should be addressed to:
LRO Configuration Management Office
Mail Stop 431
Goddard Space Flight Center
Greenbelt, Maryland 20771
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Signature Page
Prepared by:
Michael Pryzby
Spacecraft Systems Engineer
Swales / 431
_________
Date
Reviewed by:
Martin Houghton
Mission Systems Engineer
GSFC / 599
_________
Date
Approved by:
Craig Tooley
LRO Project Manager
GSFC / 431
_________
Date
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LUNAR RECONNAISSANCE ORBITER PROJECT
DOCUMENT CHANGE RECORD
REV
LEVEL
DESCRIPTION OF CHANGE
Sheet: 1 of 1
APPROVED
BY
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List of TBDs/TBRs
Item
No.
Location
Summary
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TABLE OF CONTENTS
Page
1.0
Introduction .................................................................................................................... 1-1
1.1
Purpose................................................................................................................. 1-1
1.2
Applicable Documents ......................................................................................... 1-1
2.0
Technical Resource and Budget Tracking ................................................................... 2-1
2.1
Definitions............................................................................................................ 2-1
2.1.1 Current Best Estimate .............................................................................. 2-1
2.1.2 Contingency ............................................................................................. 2-1
2.1.3 Allocation ................................................................................................. 2-1
2.1.4 System Margin ......................................................................................... 2-1
2.1.5 Specification ............................................................................................ 2-2
2.2
Margin Progression .............................................................................................. 2-2
2.3
Allocation Approach ............................................................................................ 2-3
2.3.1 Overall Approach ..................................................................................... 2-3
2.3.2 Initial Allocations..................................................................................... 2-4
2.3.3 Reallocations ............................................................................................ 2-6
3.0
Mass Allocation .............................................................................................................. 3-1
4.0
Power allocation ............................................................................................................. 4-3
4.1
Un-switched power allocations ............................................................................ 4-3
4.2
heater power allocations ...................................................................................... 4-4
4.3
switched power allocations .................................................................................. 4-5
5.0
Delta V / Fuel Mass Allocation ..................................................................................... 5-6
6.0
Data Capture Budget ..................................................................................................... 6-7
Appendix A. Abbreviations and Acronyms ................................................................................1
ii
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LIST OF FIGURES
Figure
Page
Figure 2-1 – Resource Budget Nomenclature .............................................................................. 2-1
Figure 2-2 – Example from MEL Allocation Spreadsheet .......................................................... 2-5
LIST OF TABLES
Table
Page
Table 2-1 - LRO Resource Margin Progression .......................................................................... 2-2
Table 2-2 - LRO Software Margin Progression ........................................................................... 2-3
Table 2-3 - LRO Resource Design Maturity Factors ................................................................... 2-4
Table 3-1 - Spacecraft Mass Allocation - Wet............................................................................. 3-1
Table 3-2 - Spacecraft Wet Mass Allocation - Consumables ...................................................... 3-1
Table 3-3- Spacecraft Dry Mass Allocation ................................................................................ 3-2
Table 4-1- Un-Switched Power Allocations ................................................................................ 4-3
Table 4-2 – Instrument Heater Power Allocations ...................................................................... 4-4
Table 4-3 - Switched Power Allocations ..................................................................................... 4-5
Table 5-1 – Delta V / Fuel Mass Allocation ................................................................................ 5-6
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1.0
INTRODUCTION
1.1
PURPOSE
431-SPEC-000112
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This document will be used to set and trace technical resources for the Lunar Reconnaissance
Orbiter. This document will detail the process in which the technical resources are to be
managed and controlled. It is expected this document will be a living document over the course
of the mission.
The document will allocate mass and power.
1.2
APPLICABLE DOCUMENTS
The following documents (or latest revisions available) are applicable to the development and
execution of this plan:
430-PLAN-000008,
431-PLAN-000005,
430-PG-1410.2.1,
GSFC-STD-1000,
LRO Program Plan,
LRO Systems Engineering Management Plan
LRO Configuration Management Plan
GSFC Rules for the Design, Development, Verification, and Operation of
Flight Systems
431-SPEC-0000091, LRO General Thermal Systems Specification Document
1-1
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2.0
TECHNICAL RESOURCE AND BUDGET TRACKING
2.1
DEFINITIONS
Figure 2-1 shows graphically the definitions that will be used in this document.
Specification
Limit
System Margin
Project Control
Spec
Contingency
More
Current Best Estimate
(CBE)
Allocation
Prediction/measurement
(bottoms up estimate)
Subsystem /
Instrument
Control
Figure 2-1 – Resource Budget Nomenclature
2.1.1 Current Best Estimate
CBE is the current prediction or measurement of the resource. If it is a prediction, then it is a
bottoms-up estimate.
2.1.2 Contingency
Contingency is the reserve amount of resource under the control of the subsystem and is kept as
part of the allocation.
2.1.3 Allocation
Allocation is the amount of resource assigned to a subsystem that the subsystem is allowed to
manage. It equals the CBE plus contingency.
2.1.4 System Margin
Margin the resource reserve managed at the system level. It is the difference between the overall
resource specification and the assigned allocations. Margin shall be calculated as follows:
Margin (%) = (Available resource–Estimated Value of Resource)/Estimated Resource X 100
2-1
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2.1.5 Specification
Specification is the maximum amount of resources available.
2.2
MARGIN PROGRESSION
The Systems Engineering team is responsible to identify the mission resources to be allocated
and tracked at the project level, as well as to define acceptable resource margins and set up a
margin management philosophy based on the various stages of the mission lifecycle phases.
Table 2-1 shows the LRO System Engineering resource allocation margin progression as the
project development lifecycle proceeds through the various phases of mission development. The
resource margins required decrease as the system development progresses to further levels of
definition and maturity. The resource margins are taken from GSFC-STD-1000.
Resource margin requirements from GSFC-STD-1000 will be calculated by adding the margin
plus contingency for any given system or subsystem.
Total Margin Progression
Pre Phase A
Phase A
Phase B
Phase C
Phase D
Mass
30%
25%
20%
15%
0
Power (wrt EOL capacity)
30%
25%
15%
15%
10%*
Propellant
3
Margin detailed w/ Prop Budget
Telemetry and Commands
25%
20%
15%
10%
0
RF Link
3dB
3dB
3dB
3dB
3dB
*At launch there shall be 10% predicted power margin for mission critical, cruise and safing operating modes as
well as to accommodate in –flight operational uncertainties.
Table 2-1 - LRO Resource Margin Progression
Table 2-2 shows the LRO System Engineering software margin approach.
Mission Phase
FSW SRR
FSW PDR
FSW CDR
Ship/Flight
Est.
Anal.
Anal./ Measured
Measured
Average CPU
50%
50%
40%
30%
CPU Deadlines
50%
50%
40%
30%
PROM
50%
30%
20%
0
EEPROM
50%
50%
40%
30%
RAM
50%
50%
40%
30%
1553 Bus
30%
25%
15%
10%
SpaceWire (1355)
TBD
TBD
TBD
TBD
UART/ Serial I/F
50%
50%
40%
30%
Method
2-2
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Table 2-2 - LRO Software Margin Progression
Per the Systems Engineering Management Plan, 431-PLAN-000005, the technical resources
should be in draft form by SRR. Therefore, the initial allocations set in this document will be
with the margins from Phase A in Table 2-1. At PDR, the margin progression will be at the
levels for Phase B. At CDR, the margin progression will be the levels for Phase C. At launch,
the margins will be at the levels specified for Phase D.
2.3
ALLOCATION APPROACH
2.3.1 Overall Approach
Allocations, per the definition in Section 2.1, consist of the Current Best Estimate (CBE) and the
contingency. CBEs are calculated by each subsystem and presented, with any technical detail to
the Spacecraft Systems Lead. Depending upon the amount of design maturity in the subsystem,
a Design Maturity is designated to the subsystem or to the components within the subsystem.
Depending upon the level of Design Maturity, a percent contingency is assigned to the resource
and a resource value is calculated. At the Spacecraft Systems Lead’s discretion, some or all of
that contingency resource value is allocated to the subsystem. The remaining contingency
resource value is maintained as System Margin by the Spacecraft Systems Lead. The sum of the
System Margin plus the Subsystem Contingency is used to calculate the overall margin used to
meet the progression requirements from Section 2.2.
2.3.1.1 Current Best Estimate
Current Best Estimates (CBEs) are estimated or calculated by the subsystems. Estimates are to
be provided to the Spacecraft Systems Lead with any assumptions that were made. CBEs range
from guesses based on engineering judgment to tested values from flight units. As the design
matures, both the fidelity and accuracy of the estimate will increase. The assumptions and
calculations behind the CBEs are critical to an effective management of resources.
The assumptions and calculations will be documented in the Master Equipment List (MEL). The
MEL is a tracking tool used by the Spacecraft Systems Lead. The MEL will track CBEs against
allocations from concept to launch.
2.3.1.2 Design Maturity
As the maturity of the system architecture increases, the precision of the resource estimates will
improve with the method of estimating the resources required. Table 2-3 illustrates the LRO
margin factors that will be applied to the system elements as they progress through the various
levels of development maturity. These factors will be multiplied against their appropriate
estimates to determine a contingency resource value. The Spacecraft Systems Lead will allocate
that resource value between the subsystem contingency and system margin. If the CBE is
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deemed to be conservative, the Spacecraft Systems Lead may keep a portion of the contingency
resource value at the system level, reducing the subsystem allocation.
Mass Design Maturity
Contingency
Allocation %
Calculations from sketches/schematics
25
Calculations from preliminary layout
20
Calculations from detailed layout/Major
modified unit
15
Calculation from pre-released
drawing/Moderate modified unit
10
Calculation from released
drawing/Minimum modified unit
Actual weight for similar flight
hardware/Engineering model
Actual weight for flight hardware
5
Power Design Maturity
Contingency
Allocation %
New units containing new
technologies or Thermal Control
System (TCS) components
New units based on existing
technology
Major modifications to existing
units
Minor modifications to existing
units/New units with
engineering models
Off the shelf, flight qualified
units
20-25
15-20
10-15
5-10
3-5
3
0.5
Table 2-3 - LRO Resource Design Maturity Factors
2.3.1.3 System Margin
System Margin is maintained by the Project or Spacecraft Systems Lead. At first glance, the
margin would be any resources remaining after the CBE as calculated and the assigned
contingency allocation were subtracted from the resource specification. At the system level,
specifications will be generated to determine the amount of available resources exist. For mass,
it would be the maximum throw weight of the launch vehicle.
The System Margin will be distributed, as appropriate, over the design phase of the mission.
Distribution of the margin to Subsystem Allocations will require a CCR to this document. The
CCR will require formal documentation as to the reason the allocations are to be changed. Most
often, trade studies will be requested to show adequate efforts were made to maintain the
allocation. Some changes in allocation will be accepted as a trade against cost or schedule
savings.
2.3.1.4 Overall Margin
System Margin will be combined with the subsystem contingency to determine the overall
resource margin. The overall resource margin will be used to show adequate design margin as
required by GSFC-STD-1000.
2.3.2 Initial Allocations
2.3.2.1 Spacecraft
Initial specifications for the space segment were derived for the following resources.
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2.3.2.1.1 Mass
The mission traded different designs regarding a transfer to lunar orbit. The project examined
various direct lunar insertion trajectories and phasing loops. The project also traded monopropellant verses bi-propellant verses hybrid propellant systems.
Given a Level 1 requirement of using an intermediate class launch vehicle, the best solution was
for a mono-propellant system on a direct lunar insertion trajectory. Further analysis has yielded
a maximum throw mass for the launch vehicle of 1480 kgs. This mass has set the initial mass
specification.
2.3.2.2 Subsystems
At approximately the time of the Instrument Accommodations Review, subsystem allocations
were set against the appropriate resource specification. The timing was chosen to freeze
allocations and show adequate Overall Margin at the start of subsystem and instrument PDRs.
The MEL contains CBE for the subsystem and an assigned Design Maturity rating. Spacecraft
Systems appropriated the resource contingency value, as appropriate, to maintain adequate
Overall Margin per GSFC-STD-1000. The contingency value assigned to each subsystem is also
shown in the MEL.
LRO MASTER CONCEPT E
EQUIPMENT
LIST
CURRENT
BEST
ESTIMATE
Subsystem
(kg)
Mechanical
148.00
Design
Maturity
Rating
7
%
25
Assigned
Margin
Contingency Allocation (Allocation - CBE)
SubSystem SubSystem
Subsystem
Mass (kg)
37.00
Mass (kg)
185.00
Mass (kg)
37.00
Figure 2-2 – Example from MEL Allocation Spreadsheet
2.3.2.3 Instruments
Initial instrument allocations were set from the instrument proposals. Most proposals included
contingency. For the initial allocations, the CBE and contingency were accepted as proposed.
For those instruments which proposed less than 15% contingency, the instrument contingency
was increased to 15% and the allocation was set.
The Spacecraft Systems felt it was important to track any variations to the proposed resources. It
was understood that the spacecraft would imposed design changes on the instruments. It is in
both parties interests to track resource growth against the true cause of it. For spacecraft induced
changes like requiring different electrical interfaces, it is important to trade the impacts with
regard to all resources (cost, mass, power). For allocation growth due to self-imposed design
changes, it is important for the Spacecraft to have insight into major changes and the trades that
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decided those changes. Design heritage and maturity was a criteria for instrument selection and
deviation from the proposed design should be scrutinized.
2.3.3 Reallocations
Changes to the allocations will be handled per the LRO CM Plan. The reallocation will be
addressed as part of a Configuration Control Board (CCB).
To expedite the process, it is required that any subsystem requesting a reallocation provide
technical documentation supporting the request. Engineering discipline should be applied to
show a good faith effort to remain within the allocation. The documentation can include results
from trades of mass against cost and schedule. There should also be detail in the new mass
estimate. Engineering rigor should be applied in determining the new resource allocation.
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MASS ALLOCATION
The overall Orbiter mass allocation is traced from the Mission Requirements Document (431REQT-000004, requirement # 1.2.10. The Wet Mass Allocation is derived from the Table 5-1,
Delta V Allocation. Section 5.0 derives the Delta V allocation and the requisite fuel to perform
those delta V maneuvers. The mass of the fuel was subtracted from the LV capability to
determine the maximum allowable dry mass. Those allocations are set below.
Subsystem
Allocation
SubSystem
Mass (kg)
Components
L/V Wet Mass Capability
1480.00
Derived Wet Mass Allocation
Max Dry Mass Allocation
715.30
764.70
Comments
MRD Req’t: 1.2.10
Propellant Budget derived
from Delta V budget
Remaining mass
Table 3-1 - Spacecraft Mass Allocation - Wet
The wet mass consumable allocation is derived from the Table 5-1 Delta V Allocation budget.
Subsystem
Components
Consumables
Allocation
SubSystem
Mass (kg)
715.30
Propellant
Pressurant
713.0
2.3
Comments
Derived from Delta V
budget - includes 3
Table 3-2 - Spacecraft Wet Mass Allocation - Consumables
The spacecraft dry mass allocation is derived from the launch vehicle “throw mass” less the Wet
Mass Allocation from Table 3-2. Any difference between the Max Dry Mass Allocation from
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Table 3-1 and the Total Dry Mass from Table 3-3 will be kept as System Margin. The Orbiter
Systems team will keep that mass and will distribute it later as justified.
Subsystem
Components
Total Dry Mass
Spin balance Weight
S/C Bus Subtotal
Mechanical
Mechanisms
Thermal
Power
ACS
PDE
Propulsion (Dry Mass)
C&DH
S Comm
Ka Comm
Electrical
Instruments Subtotal
CRaTER
Diviner
LAMP
LEND
LOLA
LROC
Mini RF
Allocation
SubSystem
Mass (kg)
710.3
25.0
595.5
155.1
52.8
32.4
76.2
63.4
16.8
105.8
19.5
12.6
18.5
40.0
89.9
6.4
11.9
5.3
23.2
15.3
19.0
12.6
Comments
Concept J
Place holder
Table 3-3- Spacecraft Dry Mass Allocation
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POWER ALLOCATION
Power consumption is highly mode dependent and can vary with orbital location, bus voltage,
and other spacecraft component configurations. Power allocations are to be calculated against a
nominal, fully operational orbit average scenario unless otherwise noted.
In assessing energy balance against the entire mission, the nominal orbits with Ka and S-Band
contacts during nominal measurement operations was the driving phase with respect to power.
Spacecraft component power allocations were set against this mission phase, except for heater
power.
Operational heater power allocations for each instrument/component are based on Beta=90° cold
case orbit average predictions plus margin.
Survival heater power allocations for each instrument/component are based on Safe-hold orbit
average predictions plus margin.
4.1
UN-SWITCHED POWER ALLOCATIONS
Subsystem
Comm
C&DH
C&DH
ACS
ACS
ACS
ACS
Thermal
Thermal
Power
Components
TT&C XPDR Stack (Rec)
COMM Card
C&DH Backplane
Reaction Wheels
Reaction Wheels
Reaction Wheels
Reaction Wheels
Essential S/C Survival HTRs Prime
Essential S/C Survival HTRs Redundant
PSE
Switched
Services
S / US
USA1
USB1
USC1
USA2
USA3
USB2
USC2
USB3
USC3
DIRECT
Table 4-1- Un-Switched Power Allocations
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Allocation
Orbit Avg
(W)
11.0
17.6
43.5
7.7
7.7
7.7
7.7
37.5
37.5
44.0
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HEATER POWER ALLOCATIONS
Heater powers are sized per the General Thermal Systems Specification Document, 431-SPEC000091.
Instrument
CRaTER
DRLE
LAMP
LEND
LOLA
LROC
Mini-RF
Switched
Services
S / US
C10
C4
C13
B12
C10
C4
C10
C4
C10
C4
C10
C4
TBD
TBD
Components
Operational Heaters
Survival Heater
Operational Heaters
Survival Heater
Operational Heaters
Survival Heater
Operational Heaters
Survival Heater
Operational Heaters
Survival Heater
Operational Heaters
Survival Heater
Operational Heaters
Survival Heater
Allocation
Orbit Avg
=90°
=0°
2.0*
2.0*
2.2
45.6
14.0
31.0
9.1
5.5
12.6
2.0*
2.0*
2.0*
42.0
15.6
45.0
12.8
8.0
43.7
TBD
TBD
TBD
* - Current analysis shows no heater power is necessary
Table 4-2 – Instrument Heater Power Allocations
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SWITCHED POWER ALLOCATIONS
Subsystem
Instrument
Instrument
Instrument
Instrument
Instrument
Instrument
Instrument
Instrument
Instrument
Instrument
Instrument
Instrument/thermal
Instrument/thermal
C&DH
S Comm
Ka Comm
ACS
ACS
ACS
Prop PDE
Prop PDE
Prop PDE
Prop PDE
Prop
Prop
Mechanisms PDE
Mechanisms PDE
Thermal
Thermal
Thermal
Thermal
Components
CRaTER
Diviner
Diviner Operational Heater (HOLD)
Diviner Survival Heater (HOLD)
LAMP PRIME
LAMP REDUNDANT
LEND
LOLA
LROC
LROC Optics Decontamination
Mini RF
System Instrument Operational Heaters
Instrument Survival Heater
SSR
TT&C XPDR Stack (xmit)
Ka Transmitter complement
Inertial Measurement Unit
Star Trackers
Star Trackers
PDE
Pressure Transducers
Prop Valve Actuator
Prop Valve CAT BED
Prop Heaters Prime
Prop Heaters Redundant
S/A & HGA Control Electronics
S/A & HGA Release & Deploy
Gimbal Heaters Prime
Gimbal Heaters Redundant
Spacecraft Operational Heaters
Deployable heaters
Switched
Services
S / US
Allocation
Orbit Avg
(W)
B8
C12
C13
B12
C14
B13
C8
B14
C15
A10
B10
C10
C4
A7
A12
C5
A13
B11
A11
B6
A15
A6
B4
B5
A5
B7
C7
C16
B15
C6
B16
5.9
19.6
0
0
4.86
4.86
13.0
39.4
27.6
98.0
7.5
37.5
37.5
48.3
15.3
61.6
33.0
10.3
10.3
37.5
3.2
24.5
16.5
84.3
84.3
44.0
40.0
25.0
25.0
62.5
25.0
Table 4-3 - Switched Power Allocations
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DELTA V / FUEL MASS ALLOCATION
The overall Orbiter mass allocation is traced from the Mission Requirements Document (431REQT-000004, requirement #1.2.10. The given allocation was determined assuming maximum
wet mass at liftoff.
The Mid-Course Correction (MCC) allocation was determined from the MRD requirements,
#1.2.14 and #2.3.1. This assumes a MCC at launch + 24 hours.
The station-keeping allocation was determined from the MRD requirement # 1.1.54.
The extended mission was derived from the MRD requirement #1.1.90. The delta V for the
extended mission is a placeholder while extended mission options are traded. This allocation
could be used for contingency if the mission required it.
Mission Phase
MCC
Lunar Insertion – 1st burn
Lunar Insertion – All other
burns
Station-keeping
Extended Mission
Margin
Momentum Unloading
Other
Total
LRO Baseline dV Fuel Mass
Comments
(m/sec)
(kg)
75
52
3, MCC @ L+24 hours
1st insertion burn, finite dV, any launch date,
391
210
20% off-pulsing
535
288
All other insertion burns, finite dV
180
125
20
77
48
8
16
14
713
+/- 20 km altitude, 3 including errors
Placeholder only
1326
Ullage, De-spin, Residuals
Table 5-1 – Delta V / Fuel Mass Allocation
5-6
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https://lunarngin.gsfc.nasa.gov
TO VERIFY THAT THIS IS THE CORRECT VERSION PRIOR TO USE.
Technical Resource Allocation
6.0
431-SPEC-000112
Revision Release Status ( DRAFT)
DATA CAPTURE BUDGET
TBD
6-7
CHECK WITH RLEP DATABASE AT:
https://lunarngin.gsfc.nasa.gov
TO VERIFY THAT THIS IS THE CORRECT VERSION PRIOR TO USE.
Technical Resource Allocation
431-SPEC-000112
Revision Release Status ( DRAFT)
Appendix A. Abbreviations and Acronyms
Abbreviation/
Acronym
C&DH
CBE
CCB
CCR
CDR
CM
CMO
COMM
CPU
Delta V
EEPROM
Est.
FSW
GSFC
HGA
HTR
I/F
Kg
LRO
LV
MCC
MEL
MRD
PDE
PDR
PROM
Prop
PSE
RAM
Rec
RF
S/A
S/C
SRR
SSR
TBD
DEFINITION
Command & Data Handling
Current Best Estimate
Configuration Control Board
Configuration Change Request
Critical Design Review
Configuration Management
Configuration Management Office
Communication
Central Processing Unit
Delta Velocity
Electrically Erasable Programmable Read Only Memory
Estimate
Flight Software
Goddard Space Flight Center
High Gain Antenna
Heater
Interface
Kilogram
Lunar Reconnaissance Orbiter
Launch Vehicle
Mid-Course Correction
Master Equipment List
Mission Requirements Document
Propulsion Deployment Electronics
Preliminary Design Review
Programmable Read Only Memory
Propellant
Power System Electronics
Random Access Memory
Receive
Radio Frequency
Solar Array
Spacecraft
Systems Requirement Review
Solid State Recorder
To Be Determined
A-1
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Technical Resource Allocation
TT&C
UART
W
Xmit
XPDR
431-SPEC-000112
Revision Release Status ( DRAFT)
Tracking, Telemetry, & Commanding
Universal Asynchronous Receiver / Transmitter
Watt
Transmitter
Transponder
A-2
CHECK WITH RLEP DATABASE AT:
https://lunarngin.gsfc.nasa.gov
TO VERIFY THAT THIS IS THE CORRECT VERSION PRIOR TO USE.