Software glitch blamed for off-target Soyuz May 2003

A glitch in guidance software is thought to have caused an upgraded version of the Soyuz spacecraft to land 460 kilometres off course in Kazakhstan on Sunday.
The Russian spacecraft - bringing two astronauts and one cosmonaut back from the International Space Station (ISS) - re-entered Earth's atmosphere at a steeper angle than expected, causing the craft to decelerate at a higher rate and land 460 kilometres off course.
The steeper-than-normal re-entry angle would have caused the craft to encounter denser atmosphere and decelerate at twice the normal rate. The Soyuz touched down by parachute near the town of Turgai in south central Kazakhstan.
But the temporary loss of the spacecraft caused considerable concern among both Russian and US space officials. Although they knew the craft had landed off course and that radio contact had been lost, the crew was not known to be safe until rescue helicopters spotted them two-and-a-half hours later.
Upgraded software
James Oberg, a veteran of the US space program and now an independent space analyst, says NASA believes the craft's upgraded software may have accidentally deactivated the system that keeps it oriented correctly.
"It's looking like a software error," Oberg told New Scientist. "That's based on the crews' account of how the computer mode changed without any input from them."
The Soyuz is the only way to carry astronauts to the ISS since the loss of the space shuttle Columbia on 1 February, which led to the grounding of NASA's shuttle fleet. This was the first landing by the new Soyuz TMA craft, which has more powerful flight computers, upgraded software, new soft-landing rockets and a larger cockpit.
Back-up system
The computer system aboard each Soyuz is designed to automatically orient the craft so that it enters Earth's atmosphere at precisely the right angle. If this system should malfunction, it will switch to a less precise back-up orientation mechanism.
Yury Semenov, head of the Energia Space Corporation, which builds the Soyuz TMA, said a member of craft's three-person crew could have accidentally deactivated the orientation system. But Oberg's NASA sources did not suspect human error: "They have reviewed the accounts of what the crew did and see no incorrect actions," he says.
Shortly after the crew was picked up, Yuri Koptev, head of the Russian Space Agency, said an investigation had been launched to determine what went wrong.
Another Soyuz TMA is currently docked at the International Space Station (ISS) and is scheduled to return the current crew of two to Earth in October. But Oberg says it would be relatively simple to remotely update the software aboard this craft.