NASA’s Goddard Space Flight Center Flight Software Charlie Wildermann Mike Blau Code Code 582 August 16-17, 2005

NASA’s Goddard Space Flight Center FSW Requirement Flow-down Mission Requirements Document 431-SPEC FD 431-SPEC ACS Analysis 431-SPEC ACS Hardware GN&C C&DH FSW GN&C Hardware GN&C H/W ICD GN&C FSW Req C&DH FSW Req Level 3 Level 4 Level 2 HiFiAlgorithms GN&C FSW C&DH FSW API 431-RQMT C&DH Hardware C&DH H/W ICD 431-ICD …109 Instrument Data ICDs 431-RQMT C&DHInstruments

NASA’s Goddard Space Flight Center Level 2 Req.Level 3: RequirementsConcept/Compliance ParagraphRequirement MRD-58FSWR-1The development of flight software for the LRO mission shall adhere to the LRO Mission Assurance Requirements (MAR) document (TBD number) and NPR Code 582 FSW development processes will meet these requirements MRD-127FSWR-5The flight software shall provide a capability to effect a cold reset of the flight software. The FSW shall initialize the C&DH hardware on cold reset. This initialization shall include the RAD750 microprocessor, the uplink and downlink hardware, the 1553 data bus, and the SpaceWire data links. Errors detected on startup shall be handled as defined in the LRO FDC ICD. Mostly heritage FSW from SDO and JWST MRD-127FSWR-85Upon time-out of the watchdog timer, the flight software shall effect a cold reset. HW registers allow FSW to detect reset type MRD-127FSWR-7The flight software shall provide default values for proper initialization of all key operating parameters following a power on or cold reset. Default contents for all data tables are stored in non-volatile memory MRD-127FSWR-9The PROM based boot loader shall provide a capability to validate the contents of the two EEPROM banks and run the code in the bank that passes validation. Redundant EEPROM banks are used to mitigate soft-bit problems MRD-122FSWR-12The flight software shall support an uplink rate of 4 kbpsThis rate is very easy with the RAD750 processor MRD-110FSWR-11The flight software command link shall utilize the CCSDS command path service protocol; both COP-1 and bypass modes shall be supported Heritage FSW from many missions (SDO most recently) MRD-110FSWR-32The flight software shall format the housekeeping downlink telemetry as recommended by the CCSDS AOS protocol Heritage FSW from many missions (SDO most recently) Lunar Reconnaissance Orbiter (LRO) FSW System Level 2 Flow Down Key Requirements

NASA’s Goddard Space Flight Center Level 2 Req.Level 3: RequirementsConcept/Compliance ParagraphRequirement MRD-131 MRD-132 FSWR-22The flight software shall provide a stored command capability to receive, store, and later execute sequences of commands Heritage FSW from many missions (SDO most recently) MRD-50 MRD-134 FSWR-31The flight software shall downlink sufficient housekeeping engineering data to the ground to allow nominal spacecraft operation and performance evaluation, as well as anomaly investigation and resolution HK packet contents will be documented early, then reviewed by Ops and FSWM MRD-123 MRD-124 MRD-50 FSWR-36The flight software shall support downlink rates specified in the LRO Mission Operations Concept Document (431-OPS ) section TBD. S-band rates will be easy to support. 100Mb Ka-band rate is facilitated by SSR hardware DMA MRD-118FSWR-50The flight software shall store 2 hours of housekeeping data in local SBC memory for later transmission to the ground station. Data packets stored in files. Code has Triana heritage MRD-50FSWR-51The flight software shall have the capability to record housekeeping telemetry at a sampling rate of up to 32kb/sec Recording rate for each HK packet is table driven MRD-110FSWR-57The flight software shall transmit stored data files to the ground using the CFDP protocol (class 2 service). CFDP code has been tested in FSW tech lab. Lunar Reconnaissance Orbiter (LRO) FSW System Level 2 Flow Down Key Requirements

NASA’s Goddard Space Flight Center Level 2 Req.Level 3: RequirementsConcept/Compliance ParagraphRequirement MRD-36FSWR-64The flight software shall communicate with the SSR over the Spacewire Bus as specified in the SSR User's Guide (doc name and number TBD) I/F is similar to the NFS standard. SSR is treated like a network file server. MRD-37FSWR-63The flight software shall copy local housekeeping data files to the SSR.Local storage is only for emergencies. SSR can hold many days worth of HK data. MRD-37FSWR-65The flight software shall store science data in files on the SSR, formatted as specified in the instrument data ICDs. File formats are unique to each inst. Facilitates data analysis at SOCs MRD-35FSWR-68The flight software shall use the 1553 bus to communicate with the relevant Observatory subsystems as specified in the LRO Electrical ICD (number TBD). Heritage FSW from many missions (SDO most recently) MRD-114 MRD-43 FSWR-72The flight software shall maintain an onboard spacecraft time driven from the hardware mission elapsed timer (MET). Heritage FSW from many missions (SDO most recently) MRD-42 MRD-43 FSWR-73The flight software shall support the ability to synchronize the spacecraft time clock to ground-based UTC. FSW maintains an adjustable S/C time correction factor (SCTF) MRD-20 MRD-133 FSWR-79The flight software shall possess sufficient onboard autonomy to allow basic fault detection and correction. Telemetry monitoring/response is a standard FSW feature MRD-128FSWR-95The flight software shall provide the capability to load code and data from the ground to RAM Allows checkout of FSW changes before making them permanent MRD-128FSWR-96The flight software shall provide the capability to load code and data from the ground to non-volatile memory. Allows FSW changes to be made permanent after checkout Lunar Reconnaissance Orbiter (LRO) FSW System Level 2 Flow Down Key Requirements

NASA’s Goddard Space Flight Center Level 2 Req.Level 3: RequirementsConcept/Compliance ParagraphRequirement MRD-20 MRD-133 FSWR-113The GN&C flight software shall monitor the health of each sensor and actuator and provide status telemetry that can be monitored by the C&DH flight software. Manage GN&C Suite of Electronics MRD-41FSWR-115The GN&C flight software shall accept and validate spacecraft ephemeris tables. Validating critical ephemeris uplinks is standard FSW practice. MRD-41FSWR-116The GN&C flight software shall interpolate between spacecraft ephemeris tables entries to compute the ephemeris for a specific time Recent missions have used propagators, however we have access to a heritage interpolator. MRD-41FSWR-117The GN&C flight software shall accept and validate Lunar ephemeris tables Validating critical ephemeris uplinks is standard FSW practice. MRD-41FSWR-118The GN&C flight software shall interpolate between Lunar ephemeris tables entries to compute the ephemeris for a specific time. Recent missions have used analytic models, however the heritage s/c interpolator can be used for lunar ephemeris. MRD-49FSWR-120The GN&C flight software shall compute ground station position vectors in J2000 GCI coordinates. Similar to the problem of computing a TDRSS vector. MRD-49FSWR-122The GN&C flight software shall maintain an estimate of the 3 axis attitude of the observatory with respect to the J2000 GCI coordinates. Heritage FSW from many missions (SDO most recently) MRD-49 MRD-84 FSWR-126The GN&C flight software shall support use of an uplinked target quaternion table. Heritage FSW from MAP. MRD-14 MRD-49 MRD-84 FSWR-127The GN&C flight software shall compute a Lunar Nadir Positive-X Velocity (LNPXV) target quaternion. Similar to the Earth-pointing missions. Lunar Reconnaissance Orbiter (LRO) FSW System Level 2 Flow Down Key Requirements

NASA’s Goddard Space Flight Center Level 2 Req.Level 3: RequirementsConcept/Compliance ParagraphRequirement MRD-10 MRD-97 FSWR-130The GN&C flight software shall compute the total angular momentum in the body reference frame. Heritage FSW from many missions. MRD-8 MRD-90 MRD-91 FSWR-131The GN&C flight software shall provide a CSS Sun Pointing attitude control mode. Heritage mode from many missions. FSW implements algorithms supplied by GN&C MRD-9 MRD-49 FSWR-134The GN&C flight software shall provide a science attitude control mode.Heritage mode from many missions. FSW implements algorithms supplied by GN&C MRD-10 MRD-88 MRD-97 FSWR-137The GN&C flight software shall provide a Delta-H control mode.Heritage mode from many missions. FSW implements algorithms supplied by GN&C MRD-10 MRD-87 FSWR-140The GN&C flight software shall provide a Delta-V attitude control mode.Heritage mode from many missions. FSW implements algorithms supplied by GN&C MRD-20 MRD-133 FSWR-143The GN&C flight software shall monitor the performance of each control mode and provide status telemetry that can be monitored by the C&DH flight software. Heritage GN&C and C&DH FSW relationship. MRD-10 MRD-87 FSWR-147The GN&C flight software shall send propulsion commands at the control law execution rate. Typically send actuator commands at the controller rate. Lunar Reconnaissance Orbiter (LRO) FSW System Level 2 Flow Down Key Requirements

NASA’s Goddard Space Flight Center Level 2 Req.Level 3: RequirementsConcept/Compliance ParagraphRequirement MRD-15 MRD-84 FSWR-149The GN&C flight software shall read SA orientation data at 1 Hz (TBD) and compute a solar array normal to sun angle. Standard requirement when a spacecraft has articulating arrays. MRD-15 MRD-84 FSWR-150The GN&C flight software shall command the SA gimbals at 1Hz (TBD) to orient the SA normal to the sunline. A 1Hz rate can easily be accommodated by a RAD750 processor. MRD-16 MRD-84 FSWR-153The GN&C flight software shall read HGA orientation data at 5 Hz (TBD) and compute an HGA-pointing direction vector in the spacecraft body frame. Standard requirement when a spacecraft has a gimbaled HGA. Note mechanical complexities when tracking can present challenges. MRD-16 MRD-84 FSWR-154The GN&C flight software shall command the HGA gimbals at 5Hz (TBD) to point the HGA towards a ground station. 5Hz can be accommodated. Note the rate could be much higher depending on the “intelligence” HGA controller Lunar Reconnaissance Orbiter (LRO) FSW System Level 2 Flow Down Key Requirements

NASA’s Goddard Space Flight Center LRO Flight Software Architecture New C&DH Task Inter-task Message Router (SW Bus) Event Services EDAC Memory Scrubber Stored Commanding CFDP File Transfer Software Scheduler Self Test Health & Safety Manager Executive Services Time Services File Manager Transponder Cmd (UDP COP-1) cFE Task Heritage C&DH Task Memory Dwell Real-time Telemetry (UDP) S-Band COMM (up/down) New GN&C Task Local Storage 1553 Bus Support Backup path for files (CFDP) Software Bus Instrument Manager Command Ingest Telemetry Output Checksum Summit Chip Memory Manager HK Data Storage Spacecraft Data Recorder Table Services GN&C Applications (5)

NASA’s Goddard Space Flight Center LRO FSW Verification Pre-release verification –Peer reviews of SW design –Code walkthroughs –Unit tests Post-release verification in FSW lab –Build Tests –Requirements verification matrix of L4&L5 rqmts Verification of final build –System Tests Verify L3 requirements and selected L4s Run on “FlatSat” IV&V –WVa group validates process and run code analysis –Code 300 SQA participates throughout SW development

NASA’s Goddard Space Flight Center LRO FSW Summary LRO FSW architecture defined –VxWorks, cFE forms the SW core –Heritage FSW subsystems selected from Triana and SDO FSW development process defined –Developed and documented by code 582 for CMMI compliance –LRO-specific process documents are in work FSW development labs being prepared –Lab designs baselined –Most components in house or on order FSW team members identified and ready to work FSW is ready to proceed with preliminary design