27/02/2001 17:21:29 Subject STRV-1c&d Anomaly Investigation update. Dear Payload Sponsor, Good progress has been made on the investigation since the last update report but the process has been very time consuming. In the absence of an obvious cause of failure at the beginning of the year, and with several potential avenues of investigation, a 'skeleton' spacecraft was built from the flight spares. Tests were conducted to check the performance of the RF units, the on-board software, the commands sent to the spacecraft and for any adverse effects from the power supply. These tests did not identify a failure mechanism but did remove the majority of candidates. Since then, effort has increasingly focussed on the performance of the RFDU and in particular the antenna- and transmitter-select relays. The decision was taken in early February to subject the flight spare RFDU to simulated operations in a temperature-controlled vacuum chamber. After 16 days of stable current consumption, it was observed to have suddenly (within one minute) drawn in excess of 500mA, which was sufficient to blow an external fuse on the power supply. This timescale matches very closely what was observed in orbit and the magnitude of the current drawn is sufficient to have caused the receiver one power supply to fuse and the receiver two current trip to trip. This event occurred on 25 February and we have set in hand some further tests to identify precisely which component has failed and determine the failure mechanism. Understanding this is essential in assessing the current state of the spacecraft, scope for recovery and why the failure occurred. It will take several more days if we are to avoid the risk of accidentally damaging the evidence. Unfortunately, this means that there will be a delay in the production of the final report of the investigation and the target is now 15 March 2001. Although small compensation for length of time taken to make this progress and the frustration at the lack of the promised report, the nature of the failure still appears very surprising. It is difficult to see how could have made the current progress without a painstaking, methodical approach. Best wishes R J Blott STRV-1c&d Project Manager.