SSETI ESEO OBDH

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SSETI ESEO - OBDH
On Board Data Handling
Warsaw University of Technology
Faculty of Electronics and Information Technology
Student Group of Space Engineering
Speaker Rafal Graczyk
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Points of presentation

• OBDH's role in ESEO satellite
• OBDH's environment of work during the mission
• Problems to solve
• Solution
• Questions

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OBDH's role in ESEO satellite (1)
Receiving and decoding of telecommand pac. (TC)

• immediate execution of TC, or
• inserting into scheduler

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OBDH's role in ESEO satellite (2)
Gathering status and experiment data

• collecting status information from every on
  board subsystem
• collecting data from payload (RadFET)

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OBDH's role in ESEO satellite (3)
Generation and sending of telemetry pac.(TM)

• forming of TM packets from stored data, and
• sending to COMM subsystem

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OBDH's role in ESEO satellite (4)
Buffering pictures taken by NAC

• high quality picture is 1MB size
• send using TM protocole (special class)

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OBDH's role in ESEO satellite (5)
An AOCS backup

• Ping every 5000 msec.
• Backuping some core AOCS functionality
• The same rule aplies to AOCS backuping OBDH

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OBDH's work environment (1)

• Thermal environment
• stablised by Temperature Control Subsystem
• temperature of structure -60 to 20 Celsius deg.
• Need for thermal sinks due to power dissipation
  in CPU
• No atmosphere inside spacecraft (no heat
  conduction).
• Radiation
• Low Earth Orbit doses
• Van Allen Belts doses

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OBDH's work environment (2)
TID Total Irradiation Dose Changing
parameters of materials breaking chemical
bonds, disrupting crystalline molecule
structures
TID obviously affects semiconductor devices.
Change occur i.e. in Icc, tri-state leakage
current, Vin / Vout levels, threshold voltage of
transistor
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OBDH's work environment (3)

• SEP (Single Event Phenomena)
• Source
• cosmic rays (especially heavy ions), solar
  flares
• Effects of SEP
• SEL (Single Event Latchups)
• SEU (Single Event Upsets)

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Problems to solve
Radiation hardening
cost-effectivity
?
availability
hw/sw redeundancy
mass/power budget limits
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Solution (1)
Due to OBDH's AOCS backup functionality, which
means, in practice, executing AOCS code on OBDH,
computers architecture compatibility is needed.
AOCS is i586 based.
OBDH is AOCS compatibile
Solutions from SSETI ESEO on board subsystems
must be made of COTS elements / systems. They
also are financially supported by student groups
and/or universities, so aim at cost-effectivity.
OBDH should be preferably a Pentium (costs,
compatibility) based industrial PC (COTS, env.)
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Solution (2)

• Mechanical needs of OBDH electronics
• Small PCB factor
• High PCB area utilisation
• Simple but effective mounting
• Expansion slots (shock, vibration resistant)

• Functional (electric) needs of OBDH electronics
• Small power consumption
• i586 architecture
• watchdog
• ISAbus (for easy expansion)
• RS232 (debugging purposes)

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Solution (3)
MOPS686 PC/104 industrial PC

• Pentium CPU on board
• PC/104 ISA-like expansion slot
• lt8W power consumption (avarage)
• Stackable (mounting, expansion)

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Solution (4)

• CANbus interface board
• 2 redundant interface logic and transceivers
• AN 82527 (Intel) based
• PC/104 compatibile

• AN 82527 pros
• low-cost
• very fast(no O. fr.)
• ISA compatibile
• MsgObj allowing SW redundancy
• SMT packages

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Solution (5)
Software (1)

• OBDH's general purpose requirements
• Hardware drivers
• Multi-threading
• Process menagement
• Provided by Linux kernel, 2.6 series

• OBDH's real-time requirements
• AOCS backup module
• CAN bus interface

Provided by
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Solution (6)
Software (2)
Architecture
Various Service Providers Image Acquisition
M.HK Diag. Data M. Antenna Management
M.On-Board Functions Management Module
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Questions?
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Thank You
rafal_gaczyk_at_wp.pl