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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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