The first space probe using distributed computing was Voyager:
Voyager employs three dual-redundant computer systems per
spacecraft. The first, the CCS, is nearly identical to that flown on
Viking, performing sequencing and spacecraft health functions along
with new ones necessitated by the addition of the other computers.
Telemetry data formatting and transmission handled by the Flight
Data System are done on Voyager with the help of a custom-built
computer. Attitude control and articulation of the scan platform are
accomplished with the third computer system. One concept from the
STAR computer proposed for the TOPS, applicable to Voyager, is
longer dormancy. if unpowered JPL's pro B
ect . Although staff believed both CCSs that equipment are always would powered,
last
rarely are both Flight Data Systems running, and both attitude control
computers are never turned on at the same time. Full bit-for-bit redun-
dancy is not maintained in the dual memories. For example,
"expended" algorithms, such as the deployment sequence executed
shortly after separation from the booster, need not be maintained5.
Both memories are accessed by the single active processor in each
system. The Flight Data System keeps a copy of its instructions in
both memories, but intermediate data and variables can be stored in
either memory. This seemingly casual attitude toward memory
duplication tightens up considerably near encounter periods, which is
one time that both CCS processors are in tandem mode.
Source: Computers in Spaceflight, p. 174
