March 29, 1999
At 16:30 on March 22, 1999, all 5 PCUs on board RXTE were commanded to a lower high voltage setting, marking the dawn of Gain Epoch 4. The change was made after PCU 2 began to suffer breakdown events, similar to those seen in PCUs 4 and 5.
Calibration observations were performed after the gain change, and preliminary Epoch 4 response matrices will be made available shortly. From this point on, PCU 2 will regularly be 'rested', following the practice already established for PCUs 4 and 5.
Between March 23-25, a few intervals exist during which PCUs 4 and 5 were operated at the 'old' Epoch 3 voltages, leading to 'mixed gain' data files. Details of these intervals can be found on the XTE Big Events List. Affected PIs wil l be notified directly.
If you have further questions about these developments, contact the RXTE GOF at xtehelp@athena.gsfc.n asa.gov.