Cursory definition of Spacecraft Computer Program capabilities currently planned for AS-503 and AS-504

One of the possible actions which has been identified to help our spacecraft computer program development schedule is to fly the AS-503 mission with the AS-278 programs. I have indicated in previous memoranda that in order to do this we would probably have to add several routines to the AS-278 program to make it applicable to AS-503. However, as we have studied this matter in more detail, we have arrived at a point where only one routine is still considered a candidate – some guidance of the SIVB simulating TLI. This is a command module program. There are no additions contemplated for the LGC. Those interested in exactly what capability would be available are referred to the AS-278 GSOP.

I am sure if we proceed in this way that it will have some impact on establishment of the final mission requirements, and in turn will influence how certain of the spacecraft capabilities for the lunar mission must be tested prior to making the AS-504 flight. I would like to call your attention particularly to the fact that we shall have no navigation (orbit determination) capability other than that associated with rendezvous for the AS-278 and AS-503 missions, nor will we have the ascent or descent guidance equations in the LGC. There has been much discussion on the testing of all of these. Based on recent discussions with ASPO mission planning people, I really don’t expect that any mission requirements affected by this decision are of such a mandatory nature that we would be directed to proceed other than I have indicated above. Obviously, if this is incorrect, the sooner we find out about it the better.

Somewhat associated with this, it seems worthwhile to me to provide a list of the additions to the AS-278/503 program which will have to be made for 504. This list, presented below, is MIT’s current best estimate and is by no means final, official or definitive, but perhaps it will serve to let you know what the job we have before us is as well as giving you some idea of the capabilities we intend to provide for AS-504.


  1. Return to earth
  2. LOI guidance
  3. Direct intercept targeting routine
  4. Navigation a. SXT star/horizon and star/landmark b. Lunar landmark
  5. Boost monitor
  6. Orbit integration additions for a. Trans-lunar operations b. Lunar operations
  7. Lunar ephemeris program
  8. Lunar rotation routine
  9. Lunar landing prediction routine
  10. LGC initialization
  11. Lunar landmarks (28)


  1. Descent Holman Injection guidance
  2. Lunar landing guidance
  3. Ascent guidance
  4. Direct intercept targeting routine
  5. Orbit integration a. Remove earth orbit b. Add Lunar
  6. Lunar rotation
  7. Lunar landing time prediction
  8. LGC initialization program changes
  9. Post landing service programs such as IMU angle storage
  10. Lunar surface IMU alignment a. Normal b. AOT failure
  11. Launch time determination
  12. AGS initialization program changes

Finally, I suppose I ought to add the following remark based strictly on my own intuition – namely, we have almost certainly got a computer storage problem on the AS-504 programs again if all the above items are added to the AS-278 program, particularly with all of the special flexibilities and options which will be suggested. Therefore, the fact that your favorite processors are listed above does not necessarily mean that we will be able to get them all in.

Terms & Abbreviations


see AS-207/208


see AS-503


see AS-504


Abort Guidance System.


Alignment Optical Telescope, a "space sextant" the astronauts used to correct the alignment of their intertial guidance system.


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.


see AS-207/208


Before the Apollo 1 fire, the mission referred to as AS-503 was an unmanned Earth orbit test flight of the LM and CM scheduled for October 1967. The launch vehicle, SA-503 was used for Apollo 8, December 23 1968.


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.


Apollo Spacecraft Program Office.


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


Intertial Measurement Unit


Lunar Module Guidance Computer.


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.


The second stage of a Saturn IB or the third stage of a Saturn V.


see S-IVB