A board of officials from Rocket Space Corporation Energia, which designed the spacecraft and is tasked with investigating the incident, said a glitch in one of the instruments of the descent control system sent the spacecraft along that ballistic trajectory, according to Energias May 14 press release.
The board initially planned to release its preliminary findings May 13, but then decided to carry on with its research since it is not required to present an official report until May 25, a senior Russian space industry official told Space News.
Analysis of data from flight recorders installed aboard the Soyuz-TMA-1 indicated that that the descent control system might have failed to react quickly enough when a gyroscope began to shift to an extreme position after the spacecraft experienced a dynamic disturbance during the initial stage of the descent, the senior official said.
The control system was to have fired the spacecrafts engines to prevent the further shifting of the gyroscope, but it did not, according to the official, who noted that the system reacted "only milliseconds late."
Energia engineers placed the Soyuz-TMA-1 spacecraft in a special facility to simulate the descent. However, the engineers managed to register an identical abnormality in the functioning of the spacecrafts descent control system during only one of several simulation attempts that took place at the corporations Control and Test Center, the senior space official said in a separate May 16 interview.
Having seen the simulations fail to pinpoint to the glitch, Energia engineers now are "taking apart the instruments to examine them one by one" in what will hopefully reveal which one of them and why malfunctioned during the May 4 descent, the official said. He said identical instruments of the descent control system have functioned flawlessly since they were first installed in a Soyuz spacecraft in 1978.
The boards probe should be completed and the results presented May 25, the senior official said.
Energia engineers "will hopefully be able to determine what the problem was and whether it was a one-time (phenomena) or whether we need to modify something" in Soyuz-TMA-3, which is set to fly to the international space station sometime in August or September, according to the official.
Once the cause of the glitch is determined, the crew of Russian cosmonaut Yuri Malenchenko and U.S. astronaut Edward Lu who are presently aboard the international space station will receive instructions to help them avoid a similar problem when they use Soyuz-TMA-2 to leave orbit in August or September.
Obviously, "nothing can be done" to fix any instruments on board of Soyuz-TMA-2 which is presently docked to the station, the official said.
However, the crew may receive instructions for a manual override of the descent control system should it fail. "The crew should be able to take over if needed," he said.
Soyuz-TMA-1s crew denied having entered any wrong commands during the descent. However, Energia officials, including the corporations president, Yuri Semyonov, publicly insisted that one of the two Americans did press a wrong button while the spacecraft was still in orbit. This alleged mistake was corrected by the ground control and could not have had any impact on the descent, according to first deputy general designer of Energia Nikolai Zelenshchikov who heads the investigative board.
Zelenshchikov met with NASA officials May 14 to brief them on the progress of the investigation by the board, a NASA official told Space News in a May 16 telephone interview. The NASA official said the U.S. space agency cannot comment on the investigation because it is a Russian-made spacecraft, but expressed hope that the incident was caused by a "one-time glitch."
Energia designed and manufactured Soyuz-TMA, which features a more advanced onboard computer and new components in the control system than its predecessor Soyuz-TM. The Soyuz-TMA-1 mission was the first full-fledged flight test for the new equipment.
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