Thursday, May 17, 2007

Limited Technology + Limited Personell = Limited Accountability

Only a handful of people worked on the CSM and LM computer guidance systems, which in total memory, according Don Eyles - one of the MIT developers - amounted to 152Kb - less than 12% of the capacity of a common 1.4MB floppy disk.

Yes, it could have been simulated - and it was.

LM telemetry monitor
yaTelemetry would be a computer program that provides a monitor or terminal capable of displaying telemetry information downlinked from the Apollo Guidance Computer (AGC). The AGC periodically transmitted telemetry information, which was displayed on monitors in Mission Control. Similarly, the virtual yaAGC periodically transmits telemetry data, using virtual radio waves consisting of a communication channel (socket), and yaTelemetry would be capable of receiving this information. The characteristics of the digital uplink and downlink can be explored by reading section 2 of the Guidance System Operations Plan (GSOP) for the LM or the CM.

The accompanying photo [not pictured on this blog] is actually a screen capture from the "Apollo 11" episode of the great HBO mini-series From the Earth to the Moon. I have so far been unable to find actual photographs or specifications of the telemetry displays.
In addition to telemetry downlinks---i.e., reception by ground control of data from the AGC---digital uplinks also possible. Uplinks were (and are) handled by the simple expedient of transmitting DSKY keycodes, encoded in a triply-redundant format to allow detection of errors. The AGC flight software treats DSKY and uplink keycodes in a very similar fashion, so ground control could remotely perform any task which the astronaut could perform at the DSKY keypad, including data entry, entry of short program patches into memory, and activation of programs.

Flight Simulator LM
DSKY Simulator

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