PACS Data Flow, Instrument Modes and Operations

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PACS Data Flow, Instrument Modes and Operations

• Helmut Feuchtgruber
• MPE

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TM/TC Constraints

• Nominal TM TC constraints from IID-A and IID-B
• Raw data rate of 1.6 Mbit/s in photometry and 3.6
  Mbit/s in spectroscopy require flexible
  compressionreduction schemes
• Prime nom. 120 kbit/s pure science TM, average
  over 24 h
• Prime burst 300 kbit/s pure science TM for up to
  30 min.
• 50 bit/s TC, average over 24 hours
• PACS has a total of 170 commands and gt40 OBCPs
• The total amount of HK TM is of the order of 7000
  bits

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Data Flow

• - 5 commandable units
• 6 interfaces
• 27 Mbytes memory
• (PROM,EEPROM,PRAM,DRAM)
• Virtuoso RTOS
• 2 different detection systems
• Autonomous operation
• Uplink bandwidth limit
• Downlink bandwidth limit
• Redundant units

Data Flow
MTL

Blue arrows TC/SCI/HK Green arrows TC/HK Red
lines power Black analog lines
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Commanding Concept (1)

• The commanding concept adheres to the PS-ICD for
  the CDMU-DPU interface
• All mandatory services are implemented within the
  DPU OBSW, as well as Functions and OBCPs
• The protocol, data rates and data formats between
  the individual sub-units are described in the
  respective ICDs BOLC-DMC, DMC-DPU, DMC-SPU and
  SPU-DPU
• The sole repository for all TC and HK definitions
  is the MIB (SCOS2000) and is currently under
  completion

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Commanding Concept (2)

• Single commands correspond to service (8,4)
  requests Perform Activity of a Function
• Separate Functions are defined for each sub-unit
• For bandwidth and synchronization reasons a
  number of OBCPs are and will be defined
• DMC sequences, stored in the DPU and transferred
  on request to DMC are used to manage the required
  highly accurate synchronization of the
  mechanisms with the acquisition of detector
  readouts.

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Operating Modes
Preferred Mode for non-prime
Only used for mixed operational days
Blue boxes represent nominal modes

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Observing Modes
Observing Modes

Observing Mode
Curing
Single-Band Photometry
Prime
Parallel
Dual-Band Photometry
Calibration Measurement
Single-Band Photometry
Line Spectroscopy
Range Spectroscopy
Dual-Band Photometry
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Autonomy Concept (1)

• Operational days with only 3h ground contact
• MTL operation
• 3 hierarchical levels of autonomy
• DPU
• Spacecraft
• Ground
• DPU monitors all PACS HK parameters at a rate of
  0.5 Hz
• CDMU needs to react to events and may also need
  to monitor certain Spacecraft and/or PACS HK
  parameters

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Autonomy Concept (2)

• Reporting of anomalies by events, service 5 from
  DPU to CDMU
• Events raised by DPU may or may not trigger CDMU
  activities
• All unexpected anomalies lead to SAFE or OFF mode
  and will require ground investigations
• Expected anomalies may be cured by coordinated
  procedures between CDMU and DPU

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Autonomy Concept (3)

• Type of anomalies
• Non-health critical HK parameter OOL ?
• ? transit to SAFE mode
• Health-critical HK parameter OOL
• ? transit to OFF mode
• Health-Critical HK parameter OOL monitored by
  CDMU
• ? transit to OFF mode
• Regular non-critical failure ?
• ? execute curing procedure
• Failure related to PACS which can be detected by
  CDMU only ?
• ? transit to OFF mode
• Failures in other sub-systems of the spacecraft
• ? disable MTL for a while and continue with
  the next observation

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Non-health critical HK Parameter out of Limit
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Regular Non-Critical Failure
 
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Failures which can be detected by CDMU only