text: See list belowAUG 29 196767-FM-T-72FM/Deputy ChiefInflight loading of the spacecraft computer erasable memory
  1. On August 25 we had a little meeting of Flight Control and Flight Software people to discuss adding a program in the RTCC to reload the spacecraft computer erasable memory in flight. This might be necessary to do when the LM computer is powered up for the first time in each manned flight or in the event of a fresh start occurring in either the LM or command module program anytime in flight.
  2. Flight Control Division has provided the capability of checking the memory of the spacecraft computer against stored values to inform the flight controllers if any of the critical erasable parameters are in error. This is pretty much a manual operation using a 1218 computer in Building 12, or some place like that, involving hand carrying the data from one place to another and manually scanning an on-line printout. A response time of between 30 and 45 minutes has been quoted from the request to initiate the check until receipt of the data.
  3. Having determined that reloading the erasable is required, the sub- sequent task becomes quite formidable at present. It is necessary for the computer controllers to type out the uplink command message word by word which takes quite a bit of time and has high risk of being in error. We concluded that an automatic RTCC program to do this job could be added fairly easily which would speed up the process a great deal while providing high confidence that the message would be formulated correctly. (It should be emphasized that neither the checking nor up- dating of the memory, even using an automatic RTCC program, is a fast response procedure.)
  4. All together only a small part of the 2048 words of erasable memory is involved in this process – certainly less than 200 words and probably no more than about 100. Charley Parker (FCD) intends to identify the actual parameters in the near future and include this list in a request for development of the new computer program to the FSD. He will also specify that it must be possible to modify these critical parameters stored in the RTCC program since many of them change as the flight progresses (i.e., accelerometer biases, spacecraft inertias and weights, etc.). Since the S/C 101 flight does not even need a computer to perform the mission or support crew safety, we certainly could not justify making this program a requirement for that mission. However, the second command module flight includes rendezvous where crew risk is involved as well as a powerdown LM ?? ???, so this will be needed on that mission. In order to reduce the number of command loads as much as possible, Tommy Keeton will request MIT to locate the critical parameters sequentially in erasable memory as often as possible in order that the Verb 71 uplink command format can be used to the maximum extent. This format, you recall, makes it necessary to only identify the address of the first word and permits loading twice as many registers per command message.
  5. Did I just hear the RTCC groan?