The CPUs of Spacecraft
Computers in Space

Many CPUs have been used in space craft, space stations and other such probes.
Such CPUs must be highly reliable, and very durable. The temperatures in space, even
with heaters, can vary widely. The radiation that a system is exposed too can be immense.
So when designing one of these systems designers don't always use the latest and greatest
microprocessor. They use a chip that has been tried and tested. That they KNOW will work.

A CPU for use in space must first be MIL-STD-883. This means it has met the over 100 tests
that the Department of Defense has developed to insure reliable operation.
These tests include: thermal, mechanicle, AC electrical and DC electrical tests as well as sampling
requirements for individual wafer inspections.

Most CPUs that pass come from the center of a wafer. This eliminates edge defects and
generally makes for a more radiation resistant device.

Also note that MANY spacecraft use many CPUs. Either for redundancy or to split tasks.
Being able to seperate control EACH component of a spacecraft is very important.
This would be impossible if one CPU controlled them all. With each sub-system powered
by its own CPU the sub-systems can be better controlled for power management and
fault tolerance. (for example if one CPU dies it only would disable one instrument, not the whole ship)

Date	Space Craft	CPU	Note:
1972	Pioneer 10 and 11	Custom CPU in TTL	Early on CPU's were implemented by many chips, basically building the gates of a CPU with a custome intructionset. This was very reliable but weighed a lot.
1976	Viking	RCA 1802	The 1802s used in spce are built using Silicon-on-Sapphire which is much more stable in a radiation environment.
1977	Voyager 1 and 2	RCA 1802 (3 of them at 6.4MHz)
1981	Space Shuttle	Intel 8086 and RCA 1802 (display controller) - Later Intel 80386	The Space shuttle uses the APA-101S computer (5 of them for redundancy). They run at about 1.2MIPS and still use a couple megs of ferrite core memory (which is impervious to radiation). The entire control software for the shuttle is less then one meg. The new glass cockpit in the shuttle runs on Intel 80386s
1989	Galileo	RCA 1802
1990	Hubble Space Telescope	Originally a DF-224 (8-bit). First service mission added a 386 coprocessor. The Hubble now runs on a 80486
1996	Pathfinder	BAE RAD6000	The RAD 6000 is a radiation hardened IBM POWER CPU made by British Aerospace Electronics.
1996	Sojourner (on Mars)	Intel 80C85
1998	International Space Station	Intel 80386SX-20 w/ Intel 80387	There are several computers on the ISS. The most important are the command computers which use the i386.
2004	Spirit and Oppurtunity Rovers	BAE RAD6000 (25MHz Max)	The RAD6000 is becoming very popular for space applications.

Other chips are as follows in lesser known space craft:

Flight Processor Usage
Mission	Processor
Cassini	1750A
Cluster (ESA)	1750A
MSTI-1,2	1750A
Rosetta (ESA)	1750A
EOS Terra	1750A (2)
EOS Aqua	1750A (4) & 8051 (2)
EOS Aura	1750A (4) & 8051 (2)
Clementine	1750A, 32 bit RISC
MSTI-3	1750A, R-3000
Pluto Express	32 bit RISC
Sampex	80386, 80387
SMEX	80386, 80387
SWAS	80386, 80387
TRACE	80386, 80387
WIRE	80386, 80387
FUSE	80386, 80387, 68000
Surrey MicroSat	80386EX (2)
UoSat-12	80386EX (3)
FAST	8085 (2)
HealthSat-II	80c186 (2), 80c188
PoSat-1	80c186, TMS320C25, TMS320C30
Galileo AACS	ATAC (bit slice) and 1802
SPOT-4	F9450
EO-1/WARP	Mongoose V
IceSat Glas	Mongoose V
MAP	Mongoose V, UTMC 69R000
CGRO	NSSC-1
Topex/Poseidon	NSSC-1
UARS	NSSC-1
EUVE	NSSC-1, 1750A
HST	NSSC-1/386, DF-224->486
Coriolis	RAD6000
Deep Space-1	RAD6000
Gravity Probe B	RAD6000
HESSI	RAD6000
MARS 98	RAD6000
SIRTF	RAD6000
SMEX-Lite	RAD6000
Swift	RAD6000
Triana	RAD6000
MightySat-II	TMS320C40 (4)

Notes:
Mongoose V is a MIPS core
TMS320 is a DSP chip
1750 is a MIL-STD 16 bit non-RISC CPU.
NSSC-1: NASA Standard Spacecraft Computer
F9450: 1750A MMU

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As you can see a WIDE variety of chips are used in space. Today most are progressing towards 32-bit CPUs with memory management. This is so that programming is easuier and a wider spread of operating systems (Java, Linux etc) are available to use.