From ISS On-Orbit Status Report for 30/11/2010.
Soyuz TMA-19/23S Reentry Anomaly:
During landing on 26/11 (GMT), the 23S Descent Module (SA) with the Exp. 25 crew experienced an internal pressure anomaly which is currently under investigation. [After sealing of the internal hatch between the SA and the Orbital Module (BO) by the Soyuz crew before undocking, the standard hatch leak check failed. After reopening and resealing the hatch, the leak rate stayed within allowable parameters, and 23S undocked. Upon subsequent further depressurization of the BO (by opening valve KSD-BO) prior to BO-SA separation, the crew observed the same leak signature on the hatch as before, still within limits and without violating flight rules. The crew introduced oxygen into the cabin atmosphere (by opening valve ZPK-RD). After module separation, air pressure in the Descent Module was maintained at the appropriate level with additional oxygen. Because the BO-SA hatch did not pass the initial pre-undocking leak check and the SA module pressure decreased when the BO module was evacuated during descent, the hatch remains suspect. TsUP-Moscow specialists are analyzing the anomaly and NASA engineers are awaiting further data.]
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