Design
| Enviro |
Astro | Propulsion
| Power | Thermal
| Structures | AD&C
| CDHS |
Test
Spacecraft
computer components
are hardened against radiation from the space environment.
They also have high fault tolerances and redundancy
due to their inaccessibility for repair.
Data
Processing
Assembly
language
programming is often used to code embedded microprocessor
systems common to spacecraft. This language enables
the programmer to produce highly-efficient execution
coding mandatory in space systems. Code is written
in well-structured modular blocks for developmental
trouble shooting and later fault tolerance on orbit.
Radiation
hardening
incorporated into integrated circuit (IC) design
protects computer chips against gamma rays and charged
particle radiation exposure, which may induce failures
such as single-event upsets.
SEU
(Single-Event Upset) failures result from excessive
radiation exposure. A high-energy particle passing
through an IC has the energy to switch a binary
value and toggle a random access memory (RAM) bit.
When the central processing unit (CPU) runs this
altered program, anything could happen from a software
crash to inadvertent instructions that fire rockets
and burn all available propellant. SEUs are identified
and corrected with software parity checks, error
detection/correction methods like the Hamming code
and by having more than one processor simultaneously
execute a critical task.
VLSI
(Very Large-Scale Integration) technology puts millions
of transistors on a single silicon chip. Spacecraft
design engineers use this high number of transistors
to build redundancy, fast parallel processing architectures
that gracefully degrade in case of unexpected failures
or memory banks to replace bulky mass storage devices
like magnetic tape recorders.
