14/12/2000 12:00:29 Subject: STRV-1c/d status update 13 Dec 00 STRV 1c&d Status Report Wednesday 13 December 2000 As you know, we set the middle of this week as the target date for the next status report. I appreciate and understand the considerable frustration, which you all feel about the current situation and I would like to repeat my thanks for the many offers of help. At this stage we have still not identified what has caused the problem but we have made good progress in eliminating possibilities and focussing the investigation. At the same time we have been monitoring the two spacecraft daily and both appear to be in a stable and safe condition. From the data on housekeeping which we are receiving, there is no evidence of faults other than those associated with the receivers. As I explained during my last report, the absence of an obvious cause of the problem has directed us into a systematic investigation of the design of the affected areas in the receiver/antenna and power systems. This is being followed by a component to component check to try to identify a possible failure mechanism. In parallel, we initiated a review of the operations to date, the performance of the software on both spacecraft and the environmental conditions experienced. Together, this is a very substantial amount of information to collate, analyse and assess. Although we are still waiting for a few remaining items of information from external sources, this process is now mostly complete and I hope to finalise this phase over the next few days. The current results of this process are: Receiver and antenna system design and component check - no likely single failure mechanism has been identified so far; checking the actual components in the flight spare against the specification and delivery documentation is the only aspect remaining to be completed. Power system - no likely single failure mechanism has been identified so far. Operations - all commands sent to the spacecraft since launch have been through initial review; none have been found which appear likely to initiate the fault condition. Software - all the evidence we have so far is that the software is operating exactly as it was designed to do. Environment : a) Temperature monitoring indicates that no extra-ordinary environmental conditions occurred and there does not appear to be any indication that any other spacecraft system has suffered from adverse temperature effects. b) Data from other spacecraft indicates that no extra-ordinary radiation environment conditions have occurred during the mission and there does not appear to be any indication that any other spacecraft system has suffered from adverse radiation effects. Once we have completed the design and component checking phase, our next step is to start conducting tests on first components and then, if necessary sub-systems, using flight spares. This phase will need careful planning to ensure that testing does not destroy evidence before we have fully investigated a possible failure mechanism. The test planning will start before Christmas and we will try to get the programme underway as soon after as possible. In summary therefore, the design should not have permitted the fault condition to occur unless a number of components failed. Although we have yet to complete the checking, so far the relevant components appear to be correctly specified for the operating conditions and the specified components were fitted. This leaves the possibility that components did not perform to specification, which can only be investigated by testing. No other contributory factors have been detected from operations, software and the environment. Until we make further progress in identifying the cause of the fault, any attempt at developing a recovery strategy remains speculative and I am therefore devoting our energies to identifying the cause first. All I can ask you to do is to continue to be patient and rest assured that we will keep you informed of progress regularly. My next target date for a progress report is 21 December. In the meantime, please understand that time spent answering your many questions will only slow down the progress which we can make. For progress with the investigation, can I therefore ask you to wait for the progress reports. To enable the investigation team to focus their efforts on finding the cause, please direct any important questions or issues, not directly concerned with the progress of the investigation, to me on rjblott@mail.dera.gov.uk.