posted 02-03-2009 11:25 AM               

On January 29, NASA's On-Orbit Status noted the following:

Reboost Oscillations Update: As structures specialists continue in-depth loads analysis of the 1/14 reboost anomaly, the call for the next reboost on 2/4 with the SM twin main engines is awaiting a Go/No-Go decision, to be made by the joint IMMT (ISS Mission Management Team) on Monday (2/2). [As of now, evaluation of the external video survey conducted over the last weekend and a review of subsystem data have not shown any off-nominal results.]

The station was built with extra structural strength, [NASA spokesman Kelly] Humphries said, and the current analysis is "just making sure we haven't eaten into that margin."

With the reboost canceled, the launch of Soyuz TMA-14 will be delayed by one day to March 26.

posted 02-03-2009 02:13 PM               

A faulty rocket command sequence aboard the international space station caused the 300-ton structure to shake back and forth vigorously for two minutes last month, during what was supposed to be a routine, gentle orbital adjustment. Space experts in Houston and Moscow have spent the last two weeks searching for the cause of the shaking and doing a damage assessment.

Under the worst-case scenario, such vibrations could rattle the station so much over the long term that the structure might begin to crack and leak. One of the solar arrays might bend out of position, affecting the station’s power-generating system. Experts cautioned that it was too early to determine how likely or unlikely these scenarios might be.

Partly as a result of last month's anomaly, a second rocket burn originally scheduled for Wednesday has been canceled. Since the maneuvers had been intended to line up the station’s path to receive future visiting spacecraft, the dates of those missions are now in doubt. A Russian Soyuz visit in late March already has been postponed a day.

posted 02-03-2009 04:42 PM               

The ISS Mission Management Team determined Tuesday that the station was not structurally damaged by the oscillations that were experienced during a Jan. 14 reboost. A reboost that had been scheduled Wednesday will not be performed while Russian flight controllers review procedures and techniques.

Undocking of the ISS Progress 31 cargo craft is scheduled for Thursday, and the launch and docking of Progress 32 remains on track for next week. Future reboosts will be timed with other planned activities to maximize rendezvous options for the various spacecraft scheduled to visit the station.

ISS Reboost Update: The IMMT (ISS Mission Management Team) agreed this morning to a Russian proposal to postpone the reboosts that were planned for tomorrow (2/4) and Saturday (2/7). Additional reboost may not be necessary if the Soyuz launch is delayed by one day (landing would be delayed by 2 days & Soyuz docked operations increased by 1 day). May need a reboost in the March timeframe. In the meantime, SM jets (not ME engines) will be used in the case of a DAM (Debris Avoidance Maneuver) if necessary.