NASA space tech: From Pioneer to Curiosity

NASA space tech: From Pioneer to Curiosity

Summary: As Voyager celebrates its 35th birthday and Curiosity starts on the most exciting Mars mission ever, we look back at the IT under the hood of six NASA projects that have made science fiction into everyday fact.

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  • The two Voyager probes launched in 1977 to study Jupiter, Saturn, Uranus and Pluto, and remain in contact with Earth as they move into interstellar space.

    The probes have identical designs, with six computers apiece in three roles. Each has a duplicate Computer Command System (CCS) — 18-bit word, interrupt-type processors with 4,096 words each of plated wire, non-volatile memory; a duplicate Flight Data System (FDS) — a 16-bit word machine with modular memories and 8,198 words each; and a duplicate Attitude and Articulation Control System (AACS) — 18-bit word machines with 4,096 words each. That's a total of around 88 Kbytes of memory.

    Each computer is a custom design by the Jet Propulsion Laboratory (JPL), which runs the project, and is built by General Electric. The CCS runs the spacecraft and reports problems back to base; the FDS manages the scientific instruments and prepares data for transmission back to Earth; while the AACS performs thruster and instrument platform manoeuvres.

    Both Voyager probes have suffered a variety of hardware failures during their lives. Most of their experiments are now turned off, following the last planetary encounters, but with reprogramming and about eight years of life left in the nuclear generators, both have some distance left to run.

    Image: NASA

  • At seven metres high and four wide, with a launch weight of 5,600kg, the Cassini mission to Saturn is the largest planetary mission to date. Blasting off in 1997, it arrived at Saturn in 2004 and continues to observe the planet, its rings and moons, with mission-end planned for 2017.

    Its 12 instrumentation packages contain many processors, but the core guidance and control is provided by dual Harris (now Intersil) RTX 2010RH processors running at six million instructions a second, 192kB of radiation-hardened static RAM (SRAM), 8 or 4kB of ROM, and 64kB radiation-hardened electrically erasable ROM (EEPROM, a precursor to flash). There's more memory on a support board — 832kB SRAM and 64kB EEPROM.

    These systems are most notable for being hardware-implemented Forth systems — Forth being an obscure programming language initially designed to control radio telescopes with a small but fanatical following among technical programmers.

    Image: NASA

  • Uniquely among unmanned spacecraft, the iconic Hubble Space Telescope has had its hardware changed several times during its mission since its launch in 1990. While most of those upgrade missions concentrated on replacing instruments, two included processor upgrades.

    The original controlling computer was the DF-224 built by Rockwell Autonetics, which has three 8-bit 1.25MHz custom CPUs and six 8K 24-bit plated-wire memory units. This was a general purpose, space-qualified unit.

    By 1992, two of the six memory units on the DF-224 memory units had failed, and a minimum of three working units are needed for spacecraft operation. A co-processor was installed on the first servicing mission in 1993. It had two sets of 80386/80387 processor/numeric processor pairs, each with 1MB of RAM and 256kB EEPROM, plus 384kB of non-alterable permanent ROM.

    The DF-224 was replaced altogether on the third servicing mission in 1999 by the Advanced Computer. This has three Intel 486 processors running at 25MHz, each with 2MB of SRAM and 1MB of EEPROM. This remains the main processor on the spacecraft, and with the retirement of the space shuttle, no further upgrades are possible.

    The Hubble is expected to remain in use until at least 2014.

    Image: NASA

Topics: Nasa / Space, After Hours

Rupert Goodwins

About Rupert Goodwins

Rupert started off as a nerdy lad expecting to be an electronics engineer, but having tried it for a while discovered that journalism was more fun. He ended up on PC Magazine in the early '90s, before that evolved into ZDNet UK - and Rupert evolved with them into an online journalist.

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  • Bits Bytes and nibbles

    "...upgrade to 1 megabit (256kB) of chip memory ..."

    How many bits were there in a Byte in 1974? :-)
    SheridanH
    • bits

      8 bits to a byte I think... 4 bits were a nibble...
      Bobdeloyd
      • Sheridan's quibble wasn't with the nibble...

        ...but with the author's erroneous math. 1 megabit does not equal 256kb. It's equal to 125kb.
        harry_dyke
        • kB, I mean

          Kilobyte. Typo.
          harry_dyke
          • Far too subtle...

            Yup, I was trying to nudge gently rather than scream abusively about a typo or mathematical inexactitute - I even added a 'smiley'. Guess I should just be direct in future but I can never resist the opportunity to use the much neglected 'nibble'.
            I don't think it's ever used as an abbreviation as it could be confused with Newtons but, just perhaps...
            1mb = 265kn = 128kB
            SheridanH
  • Byte

    Hey guys, the Intel 4004 is/was a 4-bit microprocessor. And it was not written that a byte equals 8 bits. A byte is the basic addressable element in computer architecture, not necessarily 8 bits. It is hardware dependent and there is no official standard that dictates that a byte is 8 bits. So in this instance, the author is correct. One megabit is egual to 256 KB.
    Superbiker
  • Byte, undefined?

    Hmmm... having checked the usual source, I have to agree that it isn't 'set-in-stone' that a byte is 8 bits. However, back in 1976 we were using substantial numbers of 8080s. 6800s, 6502s (and even a few Z80s) and the term byte was generally accepted as being 8 bits - as I suggest it is now.

    While the term 'word' often needs clarification it is now usually thought of as 16 bits but some of us remember the PDP8 with words of 12 bits. Interestingly, the usual source quotes the 4004 as using '4 bit data words' (not bytes). However, Intel data for the 4004 refers to one word instructions being 8 bits and two word instructions being 16 bits - but I don't see them mentioning bytes anywhere.

    So, Superbiker, I take your point regarding absolute definitions and I will even say; "Mea culpa". But... with the wide acceptance of byte meaning 8 bits, perhaps journalists could make it clear when they mean another size. I've never had to check that a hard disk or RAM that quotes the size in bytes means 8 bit per byte - and I hope I don't have to start now. (Bad enough that hard disks use powers of 10 while the rest of IT uses powers 2).

    So, officially ??? -
    bit = single binary digit (1 or zero)
    nibble = group of four bits
    octet = 8 bits or 2 nibbles
    byte = one or more bits (context dependant)
    word = one or more bits (context dependant)

    I need to go and edit/clarify a lot of my documents - and try to work out if I've bytten more or less than I can nibble!
    SheridanH
  • One small correction

    The Voyagers were sent to study Jupiter, Saturn, Uranus and Neptune, not Pluto. Pluto will be visited for the first time ever in 2015 by the New Horizons probe.
    LeonBA