Data requirements during rendezvous sequence

See list belowAUG 5 196868-FM13-445FM/Chief, Mission Planning and Analysis DivisionData requirements during rendezvous sequence

The purpose of this memorandum is to establish a requirement for high bit rate (HBR) telemetry data during the mission “C” rendezvous sequence.

In a recent postflight analysis meeting between GCD and MPAD, it was discovered that, based on the current flight plan, the onboard recor- der was to be on a low bit rate (LBR) for the final phase of the ren- dezvous (from TPI through TPF). Since the final phase will take place largely out of sight of ground tracking stations, if only LBR recorded telemetry data is recovered, a thorough analysis of the rendezvous systems, ground as well as onboard, will be impossible.

The standard used to evaluate performance of both the RTCC and the G&N system is the Best Estimate Trajectory (BET). The BET is gener- ated postflight from a best fit of all available tracking data, aug- mented during maneuvers by velocity time histories recorded by the G&N system. When a number of maneuvers will be made between stations, as in the rendezvous sequence, the G&N data will be mandatory for valid trajectory reconstruction. In the LBR record mode, the time history of G&N velocity cannot be recovered from the data.

Therefore, it is requested that DTO 20.13 be changed to make HBR recorded telemetry data mandatory for the terminal phase of the ren- dezvous, and that the crew procedures and flight plan reflect this change. As a minimum, the DSE should be switched to HBR 10 seconds prior to each maneuver and held there until 10 seconds after the maneuver (and any residual nulling) is completed.