LGC computer requirements to provide DPS backup of SPS


During our discussion at MIT last week, the question came up as to whether it is necessary to have trajectory integration techniques in the LGC for the trans-earth phase of the mission as well as the lunar phase. The argument is that if we are serious about using the LM descent propulsion system to back up the command module SPS during the trans-earth phase, it will be necessary to have this integration capability as a service program for such things as platform alignment and maneuver targeting. In fact, this capability would also be required for trans-lunar aborts using the DPS, I suppose. The more I think about it, the more I am convinced that this capability should be included and I am interested in your comments on the subject. Of course, if you agree I assume you will include it in the 504 LGC program requirements.

Terms & Abbreviations


see AS-504


Before the Apollo 1 fire, the mission referred to as AS-504 was originally scheduled for December 1967. AS-504 eventually launched as Apollo 9, March 3 1969.


Descent Propulsion System.


Lunar Module Guidance Computer.


Lunar Module. Earlier it was known as the Lunar Excursion Module and abbreviated “LEM.” Even after the name change, it continued to be pronounced “lem.”


Massachussets Institute of Technology. In these memos, MIT is shorthand for the MIT Instrumentation Laboratory, created and led by avionics pioneer Charles Stark Draper. It is now known as the Charles Stark Draper Laboratory and became independent of MIT in 1973.


Service Propulsion System, the large engine of the Service Module that was used to enter and exit lunar orbit, as well as make course corrections while going to and from the moon.