Apollo rendezvous navigation data edit is too complicated

In my notes of the AS-207/208 GSOP meeting with MIT, reference 66-FM1-100 of August 30, I indicated that MIT was including an automatic data edit scheme in the rendezvous navigational program for both the LM and the CSM. As you recall, this scheme was to accept radar or SXT data automatically if its effect on the spacecraft state vector is less than some pre-established amount and would reject it if its effect is greater then some other (larger) pre-established amount. Data falling between these two criteria was to be accepted but a warning light was to be turned on. Dr. Shea commented that this seems unnecessarily complicated - that really there is no apparent sense in having three conditions when two would do just as well. I must say, although I was foolish enough to argue at the time, I certainly agree now that we really should make this a simple binary decision. Use the data or don’t use the data based on some pre-established level of quality - probably light a light when the computer is rejecting the data and do away with that central region altogether. I have searched my memory and can’t recall why MIT proposed to do it that way, but unless someone can find a good reason, we should direct MIT to simplify the decision logic as noted above.

Flight Office Branch personnel please take appropriate action immediately.

Terms & Abbreviations


AS-207/208 (also known as AS-278) was to have been the first test of the LM in Earth orbit. It was also to have be a dual mission with the command and lunar modules launched on separate Saturn 1Bs. The mission was cancelled after the Apollo 1 fire and the Saturn 1Bs were used to launch Skylab 3 (AS-207) on July 28, 1973 and Skylab 4 (AS-208) on November 16, 1978. The LM was first tested by Apollo 5 in January 1968.


Command-Service Module.


see Guidance System Operations Plan

Guidance System Operations Plan

The GSOP was essentially the specification for how the guidance computer and its software where required to work for a specific mission. Many of GSOP’s are available online including the GSOP for the cancelled AS-207/208 mission


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.