spacetoday.net: Computer glitch may have caused Soyuz landing error

Posted: Tue, May 6, 2003, 5:37 PM ET (2137 GMT)
A bug in guidance software may have led to the nearly 500-kilometer landing error of the Soyuz TMA-1 spacecraft on Sunday. MSNBC reported Monday night that NASA officials familiar with the investigation believe that a problem with the capsule’s guidance computer may have caused it to abandon a "lifting" reentry, where the capsule generates a small amount of lift to reduce the deceleration forces of reentry, falling back on an unguided "ballistic" reentry. The MSNBC report suggested that the capsule's autopilot lost its orientation and abandoned the lifting reentry for the ballistic reentry, causing the capsule to miss its landing site by several hundred kilometers. AFP reported that Soyuz commander Nikolai Budarin said that the capsule switched to docking mode during reentry. This was the first reentry for the Soyuz TMA spacecraft, the latest version of the tried-and-true Soyuz design. The three members of the Expedition Six crew who endured the high-g reentry also denied claims by Yuri Semenov, head of Energia, the company that builds Soyuz spacecraft, that they caused the landing error by pushing the wrong button during reentry.