Voyager 1 continues to be crossing interstellar area with six computer systems holding about 68 kilobytes of reminiscence between them — much less storage than a single compressed {photograph} on a contemporary telephone

Voyager 1 carries six flight-computer items designed within the early Nineteen Seventies, and NASA’s personal accounting places their mixed reminiscence at about 68 kilobytes. That is much less knowledge than many single pictures compressed by a contemporary telephone.

The comparability is correct solely after one essential qualification. Those 68 kilobytes are usually not a shared storage drive. They are divided amongst three specialised pc techniques, with two items of every kind, and the machines organise reminiscence in 16-bit and 18-bit phrases quite than the eight-bit bytes used to explain telephone storage.

Nearly 49 years after launch, Voyager 1 is travelling by interstellar area. It crossed the heliopause, the outer boundary of the Sun’s particle-and-magnetic-field bubble, in August 2012. Its unique pc structure nonetheless accepts directions from Earth, though some redundant {hardware} has failed and many of the probe’s science devices have been switched off.

Six items make three totally different pc techniques

NASA’s Voyager frequently asked questions lists three pc sorts aboard every spacecraft, with two items of each kind. The Computer Command System, or CCS, interprets instructions, runs saved sequences and handles fault safety. The Flight Data System, or FDS, codecs science and engineering info for transmission. The Attitude and Articulation Control System, or AACS, manages orientation and helps hold the high-gain antenna directed in the direction of Earth.

That is the supply of the six-computer description: two CCS items, two FDS items and two AACS items. They had been paired partly for redundancy, however they had been by no means six interchangeable variations of 1 machine.

An FDS couldn’t assume the AACS’s antenna-pointing work as if it had been a spare laptop computer. Each system had an outlined function, its personal design and its personal reminiscence. The SETI Institute’s Voyager spacecraft guide describes them extra aptly as interconnected digital brains, capable of settle for precoded sequences containing 1000’s of directions for autonomous operation.

The phrase “six” additionally describes the {hardware} Voyager 1 carried, not six totally accessible computer systems immediately. The backup FDS failed in 1981, Voyager venture supervisor Suzanne Dodd informed Ars Technica in reporting republished by Wired. The surviving FDS subsequently has no equal standby unit.

How six separate reminiscences add as much as 68 kilobytes

NASA describes every CCS processor as an 18-bit machine with 4,096 phrases of non-volatile plated-wire reminiscence. Each AACS unit additionally has 4,096 phrases of 18-bit reminiscence. The two FDS machines use 16-bit phrases and modular reminiscences of roughly 8,200 phrases apiece.

Add all six capacities and the result’s roughly 69,600 eight-bit bytes. Divide by 1,024, the conference behind a binary kibibyte, and it involves about 68 KiB. NASA makes use of the extra acquainted label “68KB” for the rounded whole.

The arithmetic is sound, but it surely doesn’t create one addressable pool. Code operating within the CCS couldn’t declare unused AACS reminiscence as additional room. Adding the figures is like totalling the cabinets in a number of locked workshops: each cabinet holds one thing, however every belongs to a special room.

“Storage” could cause a second misunderstanding. The 68-kilobyte determine refers to reminiscence used straight by the flight computer systems for directions and dealing knowledge. Voyager additionally carries an eight-track digital tape recorder. A NASA backgrounder prepared for the 1981 Saturn encounter gave that recorder a reusable capability of about 536 million bits, equal to roughly 67 megabytes. It buffered observations after they couldn’t be transmitted instantly.

A telephone {photograph} stays a good illustration of scale. A one-megabyte compressed picture incorporates about 15 instances as many bytes because the six-computer whole, and telephone pictures are sometimes bigger than that. File sizes range with decision, picture format and compression, so it is a comparability with a typical file, not a hard and fast rule about each telephone picture.

Why so little reminiscence may run a planetary mission

Voyager’s computer systems weren’t general-purpose client machines anticipated to run a show, apps, wi-fi networking and a computational-photography pipeline. They carried out a slender set of spacecraft features outlined earlier than launch.

The CCS acquired instructions and saved sequences. The FDS collected, formatted and encoded telemetry. The AACS learn sensors and issued directions to thrusters and mechanisms. Navigation calculations and most scientific evaluation may stay on Earth, the place floor computer systems and mission groups had far higher assets.

That division of labour explains greater than the reminiscence quantity. A telephone retains software program and knowledge for 1000’s of attainable duties as a result of its proprietor could ask it to do nearly something. Voyager had fewer jobs, no graphical interface and no want to hold a library of client software program.

Its slender function didn’t make it rigid. The flight crew may add new sequences and alter elements of the software program, permitting each Voyagers to adapt after their planetary encounters and reply to failures the unique designers couldn’t specify upfront.

A failed chip uncovered the bounds of the surviving reminiscence

That skill was examined in November 2023, when Voyager 1 stopped returning readable science and engineering knowledge. The probe continued to obtain instructions and transmit a radio provider, however its FDS produced an unusable repeating sample as an alternative of correctly packaged telemetry.

In April 2024, NASA’s Jet Propulsion Laboratory reported that one chip holding a part of the FDS reminiscence, together with flight code, was now not working. Engineers couldn’t restore the chip. They divided the affected code into sections, moved the items into separate surviving areas and revised references elsewhere within the software program so the fragments would nonetheless function collectively.

No single free area was massive sufficient to carry the whole block.

IEEE Spectrum’s reconstruction of the repair reported that the broken area held 256 bits. Engineers looked for area occupied by processes the probe now not required, together with knowledge modes created for the a lot sooner transmissions attainable in the course of the planetary encounters.

The first rearranged part was transmitted on 18 April 2024. At the time, a radio command wanted about 22.5 hours to achieve Voyager 1, adopted by one other 22.5-hour look ahead to the response. JPL acquired readable engineering knowledge on 20 April for the primary time in 5 months.

The restore added no reminiscence and restored no failed {hardware}. It fitted important code round a useless part of the one remaining FDS through the use of small areas that had been nonetheless reachable.

Only two science devices stay on

Computing capability is now not Voyager 1’s solely tight constraint. Its radioisotope thermoelectric turbines produce much less electrical energy as their plutonium gas decays, requiring controllers to change off heaters and devices in a deliberate sequence.

NASA’s instrument-status table, updated on 17 April 2026, lists solely the magnetometer and plasma-wave subsystem as switched on aboard Voyager 1. The cosmic-ray subsystem was turned off in February 2025, and the low-energy charged-particle experiment adopted in April 2026.

The surviving computer systems should nonetheless settle for directions, keep angle, handle fault safety and bundle the restricted observations that proceed to achieve Earth. The {hardware} doing that work was constructed earlier than the primary mass-market private computer systems appeared.

The 68-kilobyte comparability is greatest learn as an outline of deliberate engineering, not a contest between Voyager and a telephone. The whole is tiny by current client requirements, but it surely was divided amongst machines constructed for a brief listing of particular jobs. Nearly 5 a long time later, the open query is now not whether or not that structure was adequate. It is how lengthy declining electrical energy and ageing parts will let the remaining techniques hold doing these jobs.