Comment Articles

Space age planning brings problems down to earth

Rupert Goodwins ZDNet.co.uk

Published: 27 Jan 2004 17:25 GMT

On a rocky plateau 300 million miles from here, The Mars Exploration Rover A – known to its friends and PR operatives as Spirit – sits quietly, conserving its strength after a near-fatal computer breakdown. As it was not named the Mars Static Nervous Wreck A, you may assume that things are not going exactly to plan.

Much closer to home, gaggles of geeks sit with furrowed brows as they work out exactly why the machine went mad just a third of the way through its mission, when everything was looking spotless. Instead of preparing to drill into a large and tempting rock, the robot had the silicon equivalent of a prolonged and devastating epileptic fit: when HQ tried to tune in, all they heard was binary gibberish.

You will not be surprised to learn that the number one suspect for the space probe's misery is buggy software, nor that Spirit's twin, Opportunity, is being handled with the kiddest of gloves as it too unfurls its sensors on the other side of the planet.

It's happened before: same planet, same people, same problem. Five years ago, the Mars Pathfinder mission was also busy scurrying across the Martian surface -- not doing so much science, but testing out many of the techniques used by the Rovers. Just as with the Rovers, a mysterious problem caused the machinery to reset itself continually, never getting to the point where it could do its programmed tasks or return information. And as with the Rovers, the engineers running the mission were presented with a mystery: the local replica of the robot wasn't repeating the problem and you can't slap a logic analyser on a chip from the best part of half a billion miles away.

You might think, reasonably, that a NASA-developed space mission would fly with as many redundant, hand-crafted ultra-reliable systems as man has ever seen. It doesn't work like that, especially with robotic craft where lives aren't at stake. One of the most important factors is obtaining as much science per dollar as possible -- which means keeping launch costs down and active payload up. Redundant systems are dead weight. And far from automatically improving safety, back-up systems increase complexity and can even reduce reliability -- just ask anyone with experience of uninterruptable power supplies.