European Space Operations Centre

1
European Space Operations Centre
OBSM Operations Automation through On-Board
Control Procedures
SpaceOps 2004
C. Steiger, R. Furnell and J. Morales European
Space Agency (ESA) Darmstadt, Germany

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Overview

• Introduction
• The On-board control procedure (OBCP) concept
• On-board Software Maintenance (OBSM) at ESA/ESOC
• OBSM Operations with OBCPs
• General concept
• Demonstrations on the Rosetta Spacecraft
• Conclusions and further work

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The OBCP Concept (I)

• Traditional spacecraft operations
• Flight Control Procedures (FCPs)

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The OBCP Concept (II)

• OBCP Capabilities
• Send TC to and receive TM from on-board
  subsystems, send own TM to ground
• Processing capabilities similar to
  state-of-the-art PLs (ADA, C)
• OBCP start/stop/suspend/resume through dedicated
  TC

• OBCP Usage on ESA Missions
• First used on Eureca (92/93) Mars Express
  (launch 06/03) and Venus Express (launch 11/05)
  with OBCP capabilities other missions to adopt
  the concept
• Deep-space mission Rosetta (launch 03/04) makes
  operational use of OBCPs for payload operations,
  FDIR functionalities, TM link maintenance, pass
  management, power subsystem , TTC subsystem,
  OBSM support etc.
• Thorough OBCP testing and validation before
  in-flight usage mandatory
• ESA OBCP standardisation endeavour through the
  ECSS (2004/05)

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On-Board Software Maintenance
Maintain the OBS System to allow for smooth
mission operations.

• OBSM Tasks
• OBS system status checks through the dump of
  relevant areas of on-board memory or through
  advanced OBS monitoring and logging facilities
• Enhancement of OBS code or parameters through
  direct writing into on-board memory

• OBSM at ESA/ESOC
• Partial or full responsibility for Avionics OBS
  (i.e. data handling, SSMM, and AOCS systems) and
  P/L OBS in coordination with Industry (OBS
  developer)
• Increasing OBS complexity renders OBSM more and
  more important
• OBSM operations done manually with little OBS
  support OBS not developed with maintenance in
  mind

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OBCPs for OBSM Activities
Usage of dedicated OBCPs to support or
autonomously carry out OBSM activities.

• OBSM Areas suitable for OBCP support
• Dumping and patching of on-board memory
• Further areas routine system checks and
  monitoring/logging

• OBSM OBCP Demonstrators on Rosetta
• Development and full testing done by ESOC
• To be used during the mission, starting in the
  commissioning phase during spring and summer 2004

7
The ROSETTA Mission

• Interplanetary mission to rendezvous with comet
  Churyumov-Gerasimenko
• Launch 02/03/2004, main mission in 2014/15
• 4 planetary gravity assists (Earth, Mars, Earth,
  Earth)

• 1.5 years orbiting around the comet nucleus
  (estimated 2000m radius) down to 1 km from the
  surface
• Delivery of a Lander to the comet surface
• Large distances from Earth (6.2 AU) and Sun (5.2
  AU) reached during the mission
• Spacecraft powered by solar arrays

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The ROSETTA Spacecraft

• Spacecraft Mass and Dimensions
• Launch mass 3054 kg (1720kg propellant)
• Size 2.8 x 2.1 x 2.0m, solar array span 32 m
• 24 bi-propellant 10 N thrusters
• Radio Frequency Communications
• TM rates 11 bps 23 kbps
• TC rates 7 bps 2 kbps
• Solar Arrays power 850 W at 3.4 AU, 440 W at
  5.25 AU

• Rosetta On-board Software
• DMS and AOCMS S/W coded in Ada 83 (running on MA3
  1750 16bit PMs), STR/CAM and SSMM S/W coded in C
  (running on TSC21020E 32bit DSP)
• Complex due to variety of mission phases and
  autonomy requirements OBCPs a major part of the
  Rosetta Autonomy Concept

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Memory Dump Activities by OBCP

• Typical constraints on memory dump activities
• Maximum size and rate of memory dump TC
• Specific modes in which devices allow for dumps

Rosetta SSMM - 4000 words/TC,
1 TC/sec - SSMM in Init Mode
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Memory Load Activities by OBCP

• OBCP support for memory load activities
• Similar constraints as for memory dumps
• Example patching of the Star Tracker or
  Navigation Cam EEPROM

• Advantages of using OBCPs for memory load (and
  dump) activities
• Reduced overhead on the ground due to issuing
  dump/patch TC by OBCP with right size and correct
  timing
• More efficient procedure due to commanding
  activities done by OBCP (Rosetta propagation
  delay up to 50 min!)
• Reduced uplink capacity needed

BUT Use of patch OBCP considered only as a
support tool for the operator no autonomous
SW modifications foreseen out of pass visibility
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Routine Checks and Logging Activities by OBCP

• Routine hardware/software system checks
• Checking the status of on-board devices used by
  the OBS
• Autonomous switch ON/OFF non-used HW units for
  periodic Health Checks
• Example automation of routine checks on
  redundant processor modules (checking of
  processor RAM-EEPROM, commanding of self tests)

• Monitoring and logging by OBCP
• Simple standard OBS monitoring facilities in
  place
• e.g. monitoring of TM parameters and issue TC
  upon triggering of the monitor
• Monitoring by OBCP
• More powerful than current state-of-the-art
  mechanisms
• More flexible than current mechanisms

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Pros and Cons of OBCP Usage

• PROS
• Increased capability
• Procedure execution out of ground station
  coverage
• More precise commanding with additional checks

• Important for...
• missions with limited ground
  station coverage
• deep-space missions (long propagation delays,
  low data rates)

• Increased operations efficiency

• Increased safety through more autonomy
• Real-time verification by OBCP of telecommands
  issued
• Immediate reaction to on-board events

• CONS
• OBCP development overhead v.s. Flight Procedures
  generation

• Reduced ground visibility on spacecraft
  operations?

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Conclusions and Further Work

• Conclusions
• The OBCP concept is generally useful for safely
  automating (some parts of) mission operations
• OBSM tasks characterized by heavy manual
  involvement of the OBSM engineer can be done
  much more efficiently with OBCP support

• Further Work
• Refinement of OBSM OBCPs based on Rosetta
  in-flight experience
• ESA OBCP standardisation endeavour through the
  ECSS (2004/05) to prepare for OBCP usage on ESA
  missions on a broader scale
• Future ESA missions to benefit directly from
  Rosetta OBSM OBCP experience