EXP-TESS-RQMT-0001
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Mission Requirements Document
Transiting Exoplanet Survey Satellite (TESS)
Mission Requirements Document (MRD)
Effective Date: 1/15/2014
Expiration Date: N/A
Goddard Space Flight Center
Greenbelt, Maryland
National Aeronautics and
Space Administration
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Mission Requirements Document
CM FOREWORD
This document is a TESS controlled document. Changes to this document require prior approval
from the TESS Program Office. Proposed changes shall be submitted to the TESS Configuration
Management Office (CMO), along with supportive material justifying the proposed change.
Questions or comments concerning this document should be addressed to:
EHPD Configuration Management Office
Mail Stop 460
Goddard Space Flight Center
Greenbelt, Maryland 20771
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REVIEW/APPROVAL PAGE
Prepared by:
/electronic signature on file/
Benjamin Cichy
TESS Systems Engineer
Code 599
_______
Date
Reviewed by:
/electronic signature on file/
George Ricker
TESS Principle Investigator
MKI
_______
Date
/electronic signature on file/
Stephen Rinehart
TESS Project Scientist
Code 665
/electronic signature on file/
Teresa James
TESS Chief S&MA Officer
Code 323
_______
Date
/electronic signature on file/
_______
Andrew Carson
Date
Deputy Project Manager / Spacecraft
TBD
/electronic signature on file/
_______
Nicholas Jedrich
Date
Deputy Project Manager / Instrument
Code 432
/electronic signature on file/
Shane Hynes
TESS Mission System Engineer
Code 599
Approved by:
/electronic signature on file/
Jeff Volosin
TESS Project Manager
Code 460
_______
Date
All reviews and approvals are electronic via the TESS MIS at:
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Mission Requirements Document
DOCUMENT CHANGE RECORD
Rev/Version
Level
Description of Change
Approved By
Baseline
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Approved
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LIST OF TBDs AND TBRs
REQ ID
MRD_15,
MRD_16,
MRD_17
MRD_49,
MRD_53
Description
Science timing requirements. Evaluate timing
required by science for data analysis.
Owner
Vanderspek
Due Date
4/15/13
Orbital Debris. TBD as to whether TESS must
comply with GEO orbital debris requirements.
Hynes
4/15/13
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TABLE OF CONTENTS
1. Introduction .................................................................................................................................... 1
1.1
1.2
Mission Overview................................................................................................................................... 1
Requirements Architecture ............................................................................................................... 2
2.0
Project Architecture .................................................................................................................. 1
3.0
Requirements .............................................................................................................................. 2
3.1 Mission Architecture ............................................................................................................................ 2
3.2 Science Requirements .......................................................................................................................... 2
3.3 Mission Phase Requirements ............................................................................................................ 2
3.3.1 Prelaunch .......................................................................................................................................................... 2
3.3.2 Launch ................................................................................................................................................................ 2
3.3.3 Ascent and Commissioning........................................................................................................................ 2
3.3.4 Decommissioning .......................................................................................................................................... 1
3.4 Mission Design and Navigation Requirements ........................................................................... 1
3.5 Mission Operations Requirements .................................................................................................. 2
3.6 Fault Management and Autonomy................................................................................................... 1
3.7 Data Handling, Processing, and Archiving .................................................................................... 1
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1. Introduction
This document contains the mission-level requirements for the Transiting Expolanet
Survey Satellite (TESS).
1.1
Mission Overview
The Transiting Exoplanet Survey Satellite (TESS) will discover thousands of exoplanets
in orbit around the brightest stars in the sky. In a two-year survey, TESS will monitor at least
200,000 stars for temporary drops in brightness caused by planetary transits. This first-ever space
borne all-sky transit survey will identify planets ranging from Earth-sized to gas giants, around a
wide range of stellar types and orbital distances. No ground-based survey can achieve this feat.
TESS stars will be 30-100 times brighter than those in the relatively narrow field-of-view of the
Kepler satellite, and therefore TESS planets will be orders-of-magnitude easier to characterize
with follow-up observations. At last it will be possible to study the masses, sizes, densities,
orbits, and atmospheres of a large cohort of small planets, including a sample of rocky worlds in
the habitable zones of their host stars. TESS will provide prime targets for observation with the
James Webb Space Telescope (JWST), as well as other large ground-based and space-based
telescopes of the future. TESS data will be made public 6 months after downlink, inviting
immediate community-wide efforts to study the new planets. The TESS legacy will be a catalog
of the nearest and brightest main-sequence stars hosting transiting exoplanets, which will forever
be among the most favorable targets for detailed investigations.
TESS is a low risk, high-value Explorer class planet finder, directly in line with U.S.
National Space policy and NASA science goals related to the “...search for planetary bodies and
Earth-like planets in orbit around other stars” (2010 NASA Science Plan), as well as the highest
priorities defined by the NRC Astro2010 Decadal Survey.
TESS will be ready for launch in August, 2017. TESS science objectives are achieved by
flying the observatory in a High Earth Orbit (HEO). A 13.7 day, elliptical HEO optimizes the
capability of the available Launch Vehicle performance, minimizes the requirements for the
observatory such as propulsion, telecommunications capacity and power, and provides for a
benign thermal and attitude disturbance environment, all while satisfying the requirement for a
low radiation environment.
TESS is a Principal Investigator (PI)-led mission. The PI, George Ricker, is from MIT.
He has delegated project management to Goddard Space Flight Center. GSFC also provides the
systems engineering, technical authority, flight dynamics analysis, and safety and mission
assurance for the project. MIT/LL is responsible for the payload and is home to the TESS
Science Center. Orbital Sciences Corporation is responsible for building the spacecraft,
integration and test of the flight system, and operating it. NASA ARC is responsible for the data
pipeline.
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1.2
Requirements Architecture
The TESS requirements flow-down is shown in Figure 1. This Mission Requirements
Document (MRD) sits at Level-2 in response to the Level-1 requirements from the Explorers
Program. Requirements from the MRD flow to the System element requirement documents at
L3.
Figure 1 TESS Requirements Architecture
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2.0
Project Architecture
The TESS project is organized into three major segments – the Observatory which
includes the Spacecraft and the Instrument, the Ground Segment, and the Launch Segment. The
overall Project architecture and elements are depicted in Figure 2.
Figure 2 TESS Project Architecture
The Observatory uses the reference coordinate frame illustrated in Figure 3.
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Figure 3 Observatory Coordinate Frame
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3.0
Requirements
3.1
Mission Architecture
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MRD_2 Mission Life
The TESS Project shall be designed to operate for a 2 year mission after a 2 month postlaunch commissioning phase.
Rationale: Programmatic constrains from HQ.
Allocation: SC, INSTR, MOC, FD, SOC, TSO
MRD_102 Extended Mission Consumables
The TESS Project shall launch with sufficient propellant to operate for 4 years in the
science orbit.
Rationale: Enables the possibility of an extended mission.
Allocation: SC
MRD_3 Environmental Requirements
The TESS Project shall meet the requirements in the Environmental Requirements
Document (ERD).
Rationale: Levy requirements from LV environments and on-orbit environments. ERD
will include LV and transportation mechanical & thermal environments, as well as
radiation on-orbit thermal requirements
Allocation: SC, INSTR
MRD_4 Contamination Control
The TESS Project shall deliver an Observatory on orbit with contamination level on the
front optical element of 750E per MIL-STD-1246C.
Rationale: Parent for contamination requirements at L3 and L4. The TESS Project
Contamination Control Plan outlines the processes that will be followed to achieve these
requirements.
Allocation: SC, INSTR
MRD_5 Orbital Debris
The TESS Project shall prevent the release of any orbital debris during nominal
Observatory deployment, operations, and disposal.
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Rationale: Elminates need for TESS to demonstrate mitigations to released debris per
NASA Standard Process for Limiting Orbital Debris (NASA-STD-8719.14).
Allocation: SC, INSTR, LV
MRD_6 Probability of Accidental Explosion
The TESS Project shall have an integrated probability of explosion for all credible failure
modes of the Observatory and Launch Vehicle less than 0.001 (excluding small particle
impacts).
Rationale: Required per NASA Standard Process for Limiting Orbital Debris (NASASTD-8719.14). Requirement 4.4.2.1.1.
Allocation: SC, LV
MRD_7 Common Reference Frames
The TESS Project shall comply with the reference frames in Figure 3.
Rationale: Good practice that all elements use the same reference frames
Allocation: SC, INSTR, MOC, FD, SOC, TSO
MRD_100 Inertial Reference Frame
The TESS Project shall use J2000 as the inertial reference frame for all interfaces.
Rationale: Standardize inertial reference frame across the project
Allocation: SC, MOC, FD, SOC, TSO
MRD_92 Launch Vehicle Interface
The Observatory shall comply with the LV Interface Requirements Document (LVIRD).
Rationale: LV IRD creates requirements on the interface between the LV & spacecraft
Allocation: SC, MOC, LV
MRD_93 DSN S-Band Uplink and Downlink
The TESS Project shall use S-band through the Deep Space Network for nominal
command and telemetry.
Rationale: Need large dishes to communicate efficiently with TESS
Allocation: SC, MOC
MRD_94 DSN Ka-Band Science Downlink
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The TESS Project shall use Ka-band through the Deep Space Network for nominal
Instrument Data transmission.
Rationale: Bandwidth is too large for X-band, rate is too high for S-band hence Ka-band
Allocation: SC, SOC
MRD_95 Space Network S-Band Uplink and Downlink
The TESS Project shall use S-band through the Space Network TDRS constellation for
contingency commanding and telemetry.
Rationale: TDRS provides contact for phasing orbits at perigee and for critical burns.
Critical operations may not match DSN coverage.
Allocation: SC, MOC
MRD_96 Mission Data Archive
The TESS Project shall use the Mikulski Archive for Space Telescopes (MAST) as the
project archive.
Rationale:
Allocation: SOC, TSO
3.2
Science Requirements
MRD_9 Instrument Accommodation
The TESS Project shall accommodate a wide field imaging photometer (the Instrument).
Rationale: Parent for L3 accommodation requirements including power and thermal.
Allocation: SC, INSTR
MRD_10 Observation Period
The TESS Project shall have a High Altitude Science Observation (HASO) period of at
least 13.5 days per orbit.
Rationale: Requirement on orbit so that instrument has the opportunity to observe target
stars for a minimum of 27 days over two orbits.
Allocation: FD, LV
MRD_11 Instrument FOV
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The TESS Project Instrument field of view (FOV) shall be 24 deg +/- 0.2 deg x 96 +/- 0.8
deg oriented from ecliptic plane to ecliptic pole.
Rationale: L1-BSR1 requires distribution of targets over celestial sphere. This
requirement ensures that during the 2 year mission TESS will be able to observe a large
fraction of the sky by observing 26 sectors each for 2 orbits. L1-BSR2 requires the FOV
to cover the ecliptic poles.
Allocation: INSTR
MRD_12 Targets per Observation Period
The TESS Project shall be capable of observing 15000 target stars per orbit distributed
over the Instrument FOV.
Rationale: Level 1 BSR1 requires 200,000 stars over the course of the mission. In order
to account for variation in stellar density this number is scaled by a factor of sqrt(3).
Dividing the scaled number by the 26 observation periods of the mission and rounding
and adding some margin yields 15000 target stars per period.
Allocation: INSTR
MRD_13 Instrument Availability
The TESS Instrument shall collect data from each target star for at least 22 days during
each 27 day observing session.
Rationale: This accounts for loss due to Earth/Moon interference, thermal transients
coming out of LAHO and eclipses, etc… Does not include bookeeping for hours spent in
LAHO or Eclipses.
Allocation: INSTR
MRD_15 Postage Stamp Photometric Measurements
The TESS Project shall generate a series of continuous "Postage Stamp" photometric
measurements centered on each target star with a collection time of 64 seconds +/- [10
TBR] ms.
Rationale: Primary science product with sufficient resolution to detect planetary transits
and perform astroseismology.
Allocation: INSTR
MRD_16 Measurement Time Precision
The TESS Project shall align Postage Stamps made of a target star on adjacent orbits with
a relative precision of +/- [5 TBR] sec.
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Rationale: Driven by ground processing and correlation of transits on adjacent orbits.
Allocation: SC, INSTR
MRD_17 Measurement Time Tag Accuracy
The TESS Project shall timetag Postage Stamps with an accuracy of +/- [1 TBR] sec
relative to UTC.
Rationale: Driven by ground processing and correlation of transits on adjacent orbits.
Allocation: SC, INSTR, MOC
MRD_18 Full Frame Images
The TESS Project shall be capable of generating and collecting Full Frame Images from
the Instrument every 2 hours.
Rationale: Primarily for diagnostic purposes. CSR specifies 12 per day, however
frequency will be specified in operations.
Allocation: INSTR
MRD_19 Measurement Sensitivity
The TESS Instrument shall have an instrumental effictive area, defined as the product of
the geometric area of the entrance pupil, the CCD QE over the 0.6-1.0 um bandpass, the
transmissivity of the optics, and the transmissivity of the bandpass filter, of at least 50
cm^2.
Rationale: Allows for the detection of 50% of Earth-sized planets
Allocation: INSTR
MRD_26 Instrument Thermal Stability
The Observatory shall provide a stable thermal environment to maintain the Camera
CCDs at their operating temperature during nominal operations across LAHO and
HASO.
Rationale: CCDs require cold operating environment. Temperature defined in
Instrument-Spacecraft MICD. Large thermal transients during LAHO and eclipses limit
the science that can be collected during HASO. Does not apply during fault conditions.
Elaborated at L3.
Allocation: SC
MRD_27 Noise Floor
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The Observatory shall have a photometric noise floor of 60 ppm or better on a timescale
of 1 hour during High Altitude Science Operations (HASO).
Rationale: Flowdown of L1 to allow for detection of Earth sized planet transits.
Allocation to SC and INSTR at L3 tracked in ARD.
Allocation: SC, INSTR
MRD_28 Science Context Data
The TESS Project shall collect, transmit, and archive Ancillary Spacecraft data and
Instrument Housekeeping data to support science analysis.
Rationale: Ancillary data allows ground post-processing of science data.
Allocation: SC, INSTR, SOC
MRD_30 Follow-Up Direct Imaging
The TESS Project shall be capable of performing direct imaging and follow-up
observations for 5000 targets.
Rationale: Identify sufficient number of targets for spectroscopic follow-up observations
Allocation: TSO
MRD_31 Follow-Up Reconnaissance Spectroscopy
The TESS Project shall be capable of performing spectroscopic follow-up observations
for 2000 targets.
Rationale: Identify sufficient number of targets for high s/n transit photometery
Allocation: TSO
MRD_97 Follow-Up Transit Photometry
The TESS Project shall be capable of performing high S/N transit photometry follow-up
observations for 100 targets.
Rationale: Identify sufficient number of targets for radial velocity measurements
Allocation: TSO
MRD_32 Follow-Up Radial Velocity
The TESS Project shall be capable of performing radial velocity follow-up measurement
of 100 targets.
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Rationale: Peform a sufficient number of radial velocity measurements to achieve the L1
of 50 measured masses
Allocation: TSO
3.3
Mission Phase Requirements
3.3.1 Prelaunch
MRD_35 Integration, Test, and Launch Operations
The TESS Project shall be designed to support Observatory Integration, Test, and Launch
Site operations.
Rationale: The project must design for test, integration, and launch in addition to on orbit
operations. Hardware and software design must account for safe operations in all
environments.
Allocation: SC, INSTR, MOC, LV
3.3.2 Launch
MRD_105 Observatory Launch Mass
The Observatory wet mass shall not exceed 385 kg at launch.
Rationale: Allocation for Observatory not-to-exceed mass driven by required delta-v
(MRD_105), estimated maximum propellant mass capability, and Isp. Allocations to
Spacecraft and Instrument tracked in Technical Allocations Requirements Document.
Allocation: SC, INSTR
MRD_54 Launch Period
The TESS Project shall have launch opportunities on 20 days of any given Lunar cycle.
Rationale: Maximize the probability of launch within a given lunar cycle. 20 days ~=
75% of lunar cycle.
Allocation: FD, LV
MRD_55 Launch Window
The TESS Project shall provide for launch windows of at least 20 minutes during each
day of the launch period.
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Rationale: Allow for minor delays in launch countdown (e.g. weather or clearing of
range).
Allocation: FD, LV
MRD_38 Initial Acquisition
The TESS Project shall acquire telemetry from the Observatory no later than separation +
2 minutes.
Rationale: Spacecraft transmitter must be powered OFF during launch due to LV
constraints. This requirement sets the time at which first contact with the spacecraft can
be established. 2 minutes chosen to minimize telemetry outage duration around LV sep
critical event, and provide time for SC to turn on transmitter and ground to acquire signal.
Allocation: SC, MOC, FD
MRD_39 Post Launch Autonomy
The Spacecraft shall autonomously achieve a thermally stable and power positive state
after separation from the Launch Vehicle.
Rationale: Any critical deployments must happen autonomously so that the health of the
vehicle does not depend on the ability of the ground to command the vehicle.
Allocation: SC
3.3.3 Ascent and Commissioning
MRD_41 Commissioning
The TESS Project shall characterize the health and performance of the Observatory
within 2 months after launch.
Rationale: Enables project to evaluate end-to-end system operation, and troubleshoot any
issues early in operations.
Allocation: SC, INSTR, MOC, SOC
MRD_42 Ascent and Commissioning Duration
The TESS Project shall achieve the mission orbit within 2 months after launch.
Rationale: Allows for a full 2 year science mission
Allocation: FD, LV
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MRD_43 Science Operations
Rationale:
Allocation:
MRD_46 LAHO
The TESS Project shall be capable of performing all required Observatory housekeeping
and data downlink during Low Altitude Housekeeping Operations (LAHO) spanning
Perigee +/- 8 hours.
Rationale: Bounds the time that the observatory will be down for communication and
engineering activities each orbit. Also sets time range where s/c must be able to support
high-rate communication passes.
Allocation: SC, MOC, FD
MRD_45 HASO Telemetry
The TESS Project shall be designed to receive Observatory Houskeeping Data during
HASO.
Rationale: Allows for ground operations team to evaluate and respond to onboard
anomalies without waiting up to 13 days for the next LAHO communications
opportunity.
Allocation: SC, MOC
MRD_47 Target Specification
The Observatory shall point the Instrument at a ground specified inertial target.
Rationale: Observing strategy will be based on pointing the instrument boresight at 26
different inertial targets to define observation sectors.
Allocation: SC, SOC
MRD_20 Coarse Pointing Control
The Observatory shall point the Instrument boresight to within 120 arc-sec 3-sigma
without the use of the Instrument.
Rationale: The Instrument does not support a lost-in-space attitude solution. Coarse
pointing is required to get the instrument on to the correct guide stars. Includes thermomechanical misalignment between Instrument and Spacecraft.
Allocation: SC
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MRD_57 Observatory HASO Sun Angle
The TESS Project shall collect science data over the range +/-15° between the
Observatory z-axis projected onto the ecliptic plane and the anti-sun vector.
Rationale: Constrains science operations to allow for thermal and power limits. Mission
design requires 13.5 degrees. 15 degrees provides approximately 10 percent margin over
requirement for variations in orbital period.
Allocation: SC, INSTR, FD
MRD_58 Observatory Pitch Angle
The TESS Project shall collect science data at pitch angles from 54° to 78° measured
from the ecliptic plane
Rationale: Nominal operations will always be at 54 degrees. 78 degrees for off nominal
case where camera closest to celestial pole fails, and operations team must reorient the
Observatory in order to meet threshold coverage of long-duration targets.
Allocation: SC, INSTR, FD
3.3.4 Decommissioning
MRD_49 Decommissioning
The TESS Project shall be designed to decommission and passivate the Observatory at
the end of the mission. (TBD)
Rationale: Required per NASA Standard Process for Limiting Orbital Debris (NASASTD-8719.14). Note that there is no requirement for changing the orbit.
Allocation: SC
3.4
Mission Design and Navigation Requirements
MRD_51 Mission Orbit
The TESS Project shall achieve a mission orbit that is a 2:1 lunar resonance High Earth
Orbit that is operationally stable.
Rationale: This orbit has a period of 13.7 days, which provides long science view periods
and periods that are close to the earth for downlink. This orbit is to first order, stable with
respect to lunar perturbations.
Allocation: FD, LV
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MRD_52 Maximum Range in LAHO
The TESS Project shall operate the Observatory in orbits with perigee less than 22 Re for
the mission life.
Rationale: Allows for balance of Transmitter power, downlink rate & pass duration using
standard DSN 34m dishes. Covers all orbits during the mission, including
Ascent&Commisioning.
Allocation: SC, FD
MRD_101 Mission Maximum Range
The TESS Project shall operate the Observatory in orbits with apogee less than 90 Re for
the mission life.
Rationale: Bounds communication requirements during HASO. Covers all orbits during
the mission, including Ascent&Commisioning. The semimajor axis of the TESS science
orbit is close to 38 Re. With perigee at its lowest allowed, 7 Re, the apogee would be at
its highest possible, 2*38 – 7 = 69 Re. However these are all bounded by the post-lunar
encounter apogee which is 90 Re.
Allocation: SC, FD
MRD_53 Avoidance of Geosynchronous Orbit
The TESS Project shall achieve a mission orbit that does not intersect the GEO band for
the nominal mission and a period of at least 100 years after end of mission. (TBD)
Rationale: Required per NASA Standard Process for Limiting Orbital Debris (NASASTD-8719.14). Requirement 4.6.2.2 specifies disposal at EOM to be above GEO for at
least 100 years. Requirement 4.6.2.4 specifies a probability of success of 0.9 for disposal
operations. The latter is satisfied by operating the mission during nominal ops in the
desired disposal orbit (dispose in place).
Allocation: FD, LV
MRD_56 Eclipse Frequency and Duration
The TESS Project shall limit the total number of eclipses during the prime mission to 16
with 2 eclipses that have a max duration of 6 hours, and the remainder having max
durations of 4 hours.
Rationale: Allows power system sizing for reasonable battery size while providing
adequate flexibility in mission design targeting of lunar fly-by and launch day of year
constraints.
Allocation: SC, FD, LV
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MRD_98 Deleted
Rationale:
Allocation:
MRD_59 Orbit Determination during ascent
The TESS Project shall determine the orbit ephemerides during ascent to less than 3 km
(X,Y, Z J2000, 3sigma)
Rationale: Allow for pointing of DSN antennas & dV maneuver planning
Allocation: SC, FD
MRD_60 Orbit Determination during science orbits
The TESS Project shall determine the orbit ephemerides during the science orbit to less
than 3 km (X,Y, Z J2000, 3sigma)
Rationale: Allow for pointing of DSN antennas and control of orbit
Allocation: SC, FD
MRD_61 Slew Performance
The Spacecraft shall be capable of slewing >0.3°/sec with a control accuracy of ≤5° (3
sigma, per axis).
Rationale: The requirement is driven by the operations duration concept and efficiency.
Allocation: SC, FD
MRD_104 Delta-V Allocation
The TESS Project shall achieve and maintain the mission orbit with 99% probability of
success given a delta-v allocation of 215 m/s.
Rationale: Sets requirements on spacecraft propellant and mass given expected LV
capability. See Technical Allocations Document for elaboration of delta-v budget that
informed the selection of 215 m/s.
Allocation: SC, FD
MRD_62 Delta-V Attitude Accuracy
The Spacecraft shall control the Observatory thrust axis during ∆V maneuvers to within
5° of the desired target.
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Rationale: Provides proper pointing during all maneuvers.
Allocation: SC, FD
MRD_63 Delta-V Maneuver Accuracy
The Spacecraft shall perform ∆V maneuver with an accuracy of +/- 5%.
Rationale: Bounds uncertainty for maneuver design. 5% used based on rule of thumb.
Allocation: SC, FD
MRD_64 Missed Maneuver
The TESS Project shall be able to achieve the mission orbit and threshold mission in the
presence of any single missed or aborted maneuver.
Rationale: Allows the maneuvers to be handled as nominal operations rather than mission
critical events. Reduces the availability requirements on the ground and flight system.
Allocation: SC, MOC, FD
3.5
Mission Operations Requirements
MRD_66 Real time commands
The TESS Project shall generate, transmit, and execute real time commands to the
Observatory.
Rationale: Real time commands are required for testing, engineering operations, and to
diagnose and recover from anomalies on orbit.
Allocation: SC, INSTR, MOC
MRD_67 Stored commands
The TESS Project shall generate, transmit, store, and execute command sequences
constructed with either absolute or relative execution times.
Rationale: The Observatory will be out of ground contact for much of the science orbit.
Stored commands are required to manage operations during this time.
Allocation: SC, MOC, SOC
MRD_68 Telemetry
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The TESS project shall provide Observatory Housekeeping data to determine Spacecraft
and Instrument health, support science operations, and diagnose anomalies during all
mission phases.
Rationale: Telemetry required from observatory to determine spacecraft health on orbit,
readiness to launch on the pad, etc…
Allocation: SC, INSTR, MOC, SOC
MRD_69 Recorded Telemetry
The TESS Project shall be capable of downlinking real-time and recorded Observatory
Housekeeping data during all S-band contacts.
Rationale: Allows for operations team to debug spacecraft outside of LAHO, potentially
enabling recovery prior to the next LAHO and thereby minimizing lost science.
Allocation: SC
MRD_70 CCSDS Protocols
The TESS Project shall utilize Consultative Committee for Space Data Systems (CCSDS)
protocols for command and telemetry links.
Rationale: Provides interoperability for flight and ground systems.
Allocation: SC, INSTR, MOC, SOC
MRD_29 Science Data Volume
The Observatory shall process the Science, Ancillary Spacecraft data, and Instrument
Housekeeping data to limit the total data volume to 96 GB per orbit.
Rationale: Downlink constraints preclude downlinking all raw data. Data must be
reduced onboard to a volume that can be downlinked in a nominal DSN downlink pass.
96 GB selected from analysis in CSR.
Allocation: INSTR
MRD_71 Downlink Performance
The TESS Project shall be capable of downlinking 240 GB of Instrument Data and 2 GB
of Spacecraft Data in a 5 hour LAHO communication pass.
Rationale: Allows for the collection of 2 orbits of Spacecraft and Instrument data in
single DSN pass. Includes 20% margin over Instrument allocation in MRD_29.
Allocation: SC, INSTR, MOC, SOC
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MRD_72 Data Retransmit
The TESS Project shall transmit the current and prior orbit's Instrument Data in each
comm pass.
Rationale: L1 requires 95% of data collected by the spacecraft to be returned to the
ground. This approach allows for >97.5% of data to be returned in the presence of DSN
outages and weather.
Allocation: INSTR
MRD_73 Unattended operation
The TESS Project shall be capable of operating the Observatory, including collecting
science data, without ground intervention for 2 orbits.
Rationale: Communication passes may be lost due to ground station issues or weather.
Under the scenario where we are unable to communicate with the Observatory during an
individual LAHO, we do not want to sit idle for the subsequent orbit.
Allocation: SC, INSTR, MOC, SOC
MRD_74 Common Time Format
The TESS project shall utilize the CCSDS Time code format.
Rationale: Consistent time code format across elements minimizes confusion
Allocation: SC, INSTR, MOC, SOC
MRD_75 Mission Critical Telemetry and Commanding
The TESS Project shall maintain continuous telemetry and command coverage during all
mission-critical events.
Rationale: Gold Rule 1.14. Continuous telemetry coverage shall be maintained during all
mission-critical events. Mission-critical events shall be defined to include separation
from the launch vehicle; power-up of major components or subsystems; deployment of
mechanisms and/or mission-critical appendages; and all planned propulsive maneuvers
required to establish mission orbit and/or achieve safe attitude. After separation from the
launch vehicle, continuous command coverage shall be maintained during all following
mission-critical events.
With continuous telemetry and command capability, operators can prevent anomalous
events from propagating to mission loss. Also, flight data will be available for anomaly
investigations.
Allocation: SC, MOC, FD
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MRD_76 Commandability
The Observatory shall be capable of receiving and executing real-time commands at all
times after launch vehicle separation subject to RF constraints identified in the Spacecraft
to Ground ICD.
Rationale: To support anomaly recovery, the ground should always have the capability to
command the spacecraft.
Allocation: SC, INSTR
MRD_77 Modification of flight software
The TESS Project shall allow for modification of all flight computer flight software
images.
Rationale: On-orbit modification of software provides the mission some robustness to
unanticipated operational conditions and scenarios.
Allocation: SC, INSTR, MOC, SOC
MRD_84 Inadvertent Commanding
The TESS Project shall protect against the inadvertent generation, transmission, and
execution of commands that may result in damage to the Observatory or loss of mission.
Rationale: Protects against a single operations team mistake causing damage to the
spacecraft. Also satisfies Gold Rule 1.23 where In a single string Spacecraft no single
command shall result in Spacecraft "OFF."
Allocation: SC, INSTR, MOC
MRD_117 Time Correlation
The TESS Project shall correlate onboard Spacecraft time to UTC with an accuracy of +/1 sec.
Rationale: Sequences are executed in MET. Manuevers and other sequences will need to
execute relative to UTC.
Allocation: SC, MOC
3.6
Fault Management and Autonomy
MRD_79 Deleted
Deleted
Rationale:
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Allocation:
MRD_110 Critical Function Monitoring
The Observatory shall monitor the ability of the system to perform critical functions
including
-Power Generation and Management
-Uplink and Commanding
-Attitude Determination
-Attitude Control
-Thermal Control
and autonomously take steps to isolate and recover from the fault causing the failure.
Rationale: By monitoring the end-to-end ability of the system to perform critical
functions, the Observatory can detect and respond to previously unknown fault
conditions.
Allocation: SC
MRD_80 Safe Hold Mode
The Observatory shall detect anomalous conditions that threaten the health or
consumables of the Observatory and autonomously enter a minimum safe operating state
(Safe Hold) that maintains the health, consumables, and commandability of the
Observatory.
Rationale: Gold Rule 1.17. Safe mode provides a state that requires fewer resources and
is more robust than operational mode
Allocation: SC
MRD_81 Safe Hold Duration
The Observatory shall autonomously maintain Safe Hold mode indefinitely, or until all
propellant resources have been expended.
Rationale: It may take multiple orbits for the ground to diagnose and recover the
spacecraft from an onboard anomaly. During this time commandability may be limited,
thus the spacecraft must autonomously maintain vehicle health. This includes performing
momentum management, which requires propellant.
Allocation: SC
MRD_82 Catastrophic Hazards
The TESS project shall mitigate any failure which leads to a Catastrophic Hazard with
three independent verifiable inhibits.
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Rationale: Gold Rule 1.24. Catastrophic Hazard A condition that may cause death or
permanently disabling injury, major system or facility destruction on the ground, or
vehicle during the mission.
Allocation: SC, INSTR
MRD_83 Critical Hazards
The TESS Project shall mitigate any failure which leads to a Critical Hazard with two
independent verifiable inhibits.
Rationale: Gold Rule 1.24. Critical Hazard A condition that may cause severe injury or
occupational illness, or major property damage to facilities, systems, or flight hardware.
Allocation: SC, INSTR
MRD_111 Robustness to Failed Camera
The TESS Project shall continue to collect science data in the presence of a single failed
camera.
Rationale: Threshold science requirements can be met with only 3 functioning camers.
Should a camera fail prior to launch or on orbit the Project should be able to achieve
minimum mission success.
Allocation: INSTR
MRD_85 Instrument Sun/Earth Sensitivity
The Instrument shall be capable of pointing at any target, including the Sun and the
Earth, indefinitely with no damage or permanent impact to performance.
Rationale: Allows for flexibility in mission design and spacecraft safing responses. No
expectation that the instrument will be able to collect science data when pointed at the
Sun - see requirement on Sun Angle for science operating range.
Allocation: INSTR
MRD_86 Non Volatile Science Data Storage
The Instrument hardware shall have the capability to store Science Data such that it will
persist across a power cycle of the instrument.
Rationale: In certain fault conditions the Spacecraft may remove power from the
instrument. In these cases we do not want to lose the 2 orbits of science data that has been
collected onboard.
Allocation: INSTR
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MRD_112 Instrument Power Shutdown
The Instrument shall be robust to sudden removal of powerfrom the spacecraft with no
damage or permanent impact to performance.
Rationale: During certain fault scenarios the spacecraft may remove power from the
instrument without any warning.
Allocation: INSTR
MRD_113 Software Fault Monitoring
The TESS Project shall detect software faults in health and safety critical software, and
initiate a response that will reconfigure the system into the minimum safe operating state.
Rationale: Partial robustness to software faults either caused by latent defects or
environmental effects.
Allocation: SC
MRD_114 Environmental Effect Robustnes
The TESS Project shall be robust to any single Single Event Upset (SEU) without
compromising the health or safety of the Observatory.
Rationale: Robustness to environment effects
Allocation: SC, INSTR
3.7
Data Handling, Processing, and Archiving
MRD_88 Science Data Retention
The TESS Project shall deliver >= 95% of Instrument data collected to the SOC.
Rationale: In this requirement, collected refers to data that has been successfully stored
within the Instrument onboard the spacecraft. This allocation allows for potential loss of
data in transmission and handling.
Allocation: SC, INSTR, SOC
MRD_106 Initial Science Data Archive
The TESS Project shall deliver the first 4 months of raw and calibrated Instrument Data
to the project archive 6 months after the start of nominal science operations.
Rationale:
Allocation: SOC, TSO
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MRD_89 Interim Science Data Archive
The TESS Project shall deliver the previous 6 months of raw and calibrated Instrument
Data at 4 month intervals beginning 10 months after the start of nominal science
operations.
Rationale: Allows for public access to TESS data during mission operations.
Allocation: SOC, TSO
MRD_90 Final Science Data Archive
The TESS Project shall deliver the final fully-calibrated set of science data products to
the project archive within 12 months following the end of mission.
Rationale: Allows the public access to TESS data after the mission has been completed.
Allocation: SOC, TSO
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