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to the passenger names you selected on the I/I document.
Useful entries
Designate itinerary/invoice printer DSIV(printer address)
Undesignate I/I printer DSNO(printer address)
Print itinerary/invoice DIN ‡DP
Print multiple itinerary/invoice copies DIN ‡DP2 (number of copies)
Print I/I with accounting line select DIN ‡A2 ‡DP
Print I/I with name and accounting line
select DIN ‡N1.1 ‡A2 ‡ DP
Display accounting data *PAC
Delete accounting line AC¤ (line number) eg AC¤1
Fault Tolerant
Architectures
For Space and
Avionics Applications
Dan Siewiorek
Priya Narasimhan
Electrical &Computer
ENGINEERING
Fault Tolerant
Architectures
For Space and
Avionics Architecture
Dan Siewiorek
Priya Narasimhan
Electrical &Computer
ENGINEERING
3
Comparison of Commercial, Space, Avionics
Medium
After mission
Minimal
None
Unlimited
Unlimited
Resources
- Power
- Spare parts
Outage response time Hours Days (Cruise phase) Milliseconds
Maintenance Manual Remote After mission
Intervention
Mission duration Years Years Hours
Operational Commercial Space Avionics
Environment
4
Comparison of Commercial, Space, Avionics
Software patches Software reload
Firewalls Firewalls
Retry Retry
Multi-computer Multi-computer Multi-computer
Subsystem-level
redundancy
Subsystem-level
redundancy
Component-level
redundancy
Fault tolerance
Safe system
Design diversity Design diversity
Radiation-hardened Shake, rattle, roll
components
Fault avoidance and Burn-in
fault intolerance
Fault-Tolerant Commercial Space Avionics
Approach
5
Basic Steps in Fault Handling
Fault Confinement - limits spread of faults
Fault Detection - recognizes something unexpected
happened
Diagnosis - identify location of fault
Reconfiguration - replace or isolate faulty component
Recovery - eliminate effect of fault
• Fault Masking - redundant information
• Retry - second attempt at operation
Restart - resume after correcting state (hot, warm, cold)
Repair - replace component (on-line, off-line)
Reintegration - repaired module returned to operation
6
MTBF -- MTTD -- MTTR
7
Components of a Generic Spacecraft
Propulsion - controls stability and orientation of
spacecraft. Passive spin control or active thruster control
Power - generation and storage of electrical power,
typically solar cells for generation and batteries for
storage
Data Communications - uplink for commands from the
ground, downlinks for data and telemetry (temperature,
power supply, thruster events)
Attitude Control - dedicated computer to sensing and
controlling orientation and stability of spacecraft
Command/Control/Payload - spacecraft control and
error recovery
8
Generic Spacecraft Fault Handling Approaches
Self-Tests - Subsystems perform self-tests, such as checksums on
computer memories
Cross-Checking Between Units - Either physical or functional
redundancy may be used. When a unit is physically duplicated, one is
designated as an on-line unit and the other as a monitor. The monitor
checks all the outputs of the on-line unit. Alternatively, there may be
disjoint units capable of performing the same function. The less
precise calculation can be used as a sanity check on the more precise
units.
Safe Mode – Upon error detection, enter “safe” mode shedding all
nonessential electrical loads, stop mission sequencing, orient solar
panels to obtain maximum solar power, await commands from the
ground
Ground-Initiated Special Tests - These tests are used to diagnose and
isolate failures
Ground-Trend Analysis -Routine processing and analysis or
telemetry detect long-term trends in units that degrade or wear out.
9
Defense Meteorological Satellite Program
Sensor
payload
Attitude
determination
and control
Communicati
ons
Command
control
Electric
Power and
distribution
Equipment
status
telemetry
10
Spacecraft Trends
Move from centralized to distributed computer
architecture utilizing microprocessors and networking
For deep space probes and planetary rovers, move to
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