Editing Voyager program (section)

=== Computers and data processing ===
There are three different computer types on the Voyager spacecraft, two of each kind, sometimes used for redundancy. They are proprietary, custom-built computers built from [[CMOS]] and [[Transistor–transistor logic|TTL]] medium-scale CMOS integrated circuits and discrete components, mostly from the [[7400-series integrated circuits|7400 series]] of [[Texas Instruments]].<ref>{{cite web | url=https://www.eejournal.com/article/voyagers-1-and-2-take-embedded-computers-into-interstellar-space/ | title=Voyagers 1 and 2 Take Embedded Computers into Interstellar Space | date=25 July 2022 | access-date=5 August 2023 | archive-date=5 August 2023 | archive-url=https://web.archive.org/web/20230805033258/https://www.eejournal.com/article/voyagers-1-and-2-take-embedded-computers-into-interstellar-space/ | url-status=live }}</ref> Total number of words among the six computers is about 32K. Voyager&nbsp;1 and Voyager&nbsp;2 have identical computer systems.<ref name="FAQ">{{cite web |url=http://voyager.jpl.nasa.gov/faq.html |title=Voyager Frequently Asked Questions |url-status=dead |archive-url=https://web.archive.org/web/20110721050617/http://voyager.jpl.nasa.gov/faq.html |archive-date=21 July 2011}}</ref><ref>{{cite web |url=https://pds-rings.seti.org/voyager/spacecraft/vg1host.html |title=Voyager 1 Instrument Host Information |publisher=seti.org |access-date=10 August 2019 |archive-date=24 July 2024 |archive-url=https://web.archive.org/web/20240724092319/https://pds-rings.seti.org/voyager/spacecraft/vg1host.html |url-status=live }}</ref>

The Computer Command System (CCS), the central controller of the spacecraft, has two 18-bit word, interrupt-type processors with 4096 words each of non-volatile [[plated-wire memory]]. During most of the Voyager mission the two CCS computers on each spacecraft were used non-redundantly to increase the command and processing capability of the spacecraft. The CCS is nearly identical to the system flown on the Viking spacecraft.<ref name="Tomayko">{{cite book
 |first         = James E.
 |last          = Tomayko
 |editor-last1  = Kent
 |editor-first1 = Allen
 |editor-last2  = Williams
 |editor-first2 = James G.
 |chapter       = Distributed Computing On Board Voyager and Galileo (chapter 6)
 |url           = https://ntrs.nasa.gov/citations/19880069935
 |title         = Computers in Spaceflight: The NASA Experience
 |series        = Encyclopedia of Computer Science and Technology
 |chapter-url   = https://history.nasa.gov/computers/Ch6-2.html
 |publisher     = NASA
 |date          = 1987-08-03
 |isbn          = 978-0-8247-2268-5
 |volume        = 18. Supplement&nbsp;3
 |via           = NASA History
 |access-date   = 26 July 2022
 |archive-date  = 18 October 2023
 |archive-url   = https://web.archive.org/web/20231018062947/https://ntrs.nasa.gov/citations/19880069935
 |url-status    = live
}}</ref>

The Flight Data System (FDS) is two 16-bit word machines with modular memories and 8198 words each.

The Attitude and Articulation Control System (AACS) is two 18-bit word machines with 4096 words each.

Unlike the other on-board instruments, the operation of the cameras for [[visible light]] is not autonomous, but rather it is controlled by an imaging parameter table contained in one of the on-board [[digital computer]]s, the Flight Data Subsystem (FDS). More recent space probes, since about 1990, usually have completely [[automaton|autonomous]] cameras.

The computer command subsystem (CCS) controls the cameras. The CCS contains fixed [[computer program]]s such as command decoding, fault detection, and correction routines, antenna-pointing routines, and spacecraft sequencing routines. This computer is an improved version of the one that was used in the [[Viking program|''Viking'' orbiter]].<ref name="Tomayko"/> The hardware in both custom-built CCS subsystems in the Voyagers is identical. There is only a minor software modification for one of them that has a scientific subsystem that the other lacks.

According to Guinness Book of Records, CCS holds record of "longest period of continual operation for a computer". It has been running continuously since 20 August 1977.<ref>{{Cite web |title=Longest period of continual operation for a computer |url=https://www.guinnessworldrecords.com/world-records/635980-longest-period-of-continual-operation-for-a-computer |access-date=2023-04-28 |website=Guinness World Records |date=20 August 1977 |language=en-gb |archive-date=28 April 2023 |archive-url=https://web.archive.org/web/20230428123751/https://www.guinnessworldrecords.com/world-records/635980-longest-period-of-continual-operation-for-a-computer |url-status=live }}</ref>

The Attitude and Articulation Control Subsystem (AACS) controls the spacecraft orientation (its attitude). It keeps the high-gain antenna pointing towards the Earth, controls attitude changes, and points the scan platform. The custom-built AACS systems on both craft are identical.

It has been erroneously reported<ref>{{cite web |last=Johnson |first=Herb |date=November 2014 |url=http://www.retrotechnology.com/memship/1802_spacecraft.html |access-date=27 July 2015 |title=COSMAC 1802 History in Space |archive-date=15 July 2015 |archive-url=https://web.archive.org/web/20150715200158/http://www.retrotechnology.com/memship/1802_spacecraft.html |url-status=live }}</ref> on the [[Internet]] that the Voyager space probes were controlled by a version of the [[RCA&nbsp;1802]] (RCA CDP1802 "COSMAC" [[microprocessor]]), but such claims are not supported by the primary design documents. The CDP1802 microprocessor was used later in the [[Galileo (spacecraft)|''Galileo'' space probe]], which was designed and built years later. The digital control electronics of the Voyagers were not based on a microprocessor integrated-circuit chip.