Lessons from the Moon. Gotta have good documentation!

A YouTube video is circulating: How to Get to Mars. Very Cool!. It reminded me of the joy of my early years working for Ford Aerospace with satellites and satellite designers. Such fun.

Intelsat 5 Satellite
Intelsat 5

At one point in my aerospace career, I was the project lead managing the Ford Graphics CAD/CAM systems. These were big stroke graphics tubes Ford Motor used for designing cars. Ford Aerospace wanted to see if they would be as productive for the satellite designers. The Ford Graphics tubes were as precise as designer drafts. Unlike raster graphic terminals, they used unique vector graphics.

Looking at this Mars video I remember one great designer, John Giassi, who described the technical difficulty of designing the stow point hinges required in order to fold up the satellite antennas and solar arrays so they would fit inside the launch envelop in the rocket cone.

Intelsat 4A Sketch Intelsat 4A being built
Intelsat 4A being Designed and Built

The hinge had to be done correctly. Once a hinge wasn’t designed quite right so the mechanic on-site had to push it physically to get it in it’s final position. In orbit the array wouldn’t unfold, couldn’t stabilize, and it wobbled off orbit into space. Not good after 3 years and $3 million dollars investment (and that was 1980’s costs)! Using the Ford Graphics system, a stow point error in the Intelsat VA Satellite was found and resolved on the “drawing board” prior to fabrication.

Looking at the video amazes me at the design that has to go into the mechanics to unfold a system as complex as the Mars Rover!

The other story this video reminds me of is one that was told by the Ford Satellite designers about an early rover built by a competitor. Lunar Rover The rover successfully landed on the moon and carried out mission after mission. Each new mission was designed by the ground scientists based on previous tests and findings and would be uploaded into a special area of memory for missions.

Unfortunately, the concepts grew and the scientists eventually designed a mission that was too large to fit in the memory allocated. They scrambled to find a way to carry out this next important mission. The designers looked through the rover’s specifications and finally one bright engineer said “Aha! We can reuse the memory where the landing coordinates are stored. We’ve already landed so we don’t need those any longer.” Excitedly they went to work. When ready, the new program was updated and stored in memory.

At that point the lunar went dark. No transmissions. What happened? The team went into panic mode trying to find out.

The answer was simple. There was one other function the landing coordinates were used for – an undocumented function. The coordinates were used to let the lunar know where earth was, where to point it’s antenna for communication. Once the memory was overwritten, the rover pointed it’s antenna to some unknown point in space, forever awaiting its next mission.

Guess no one thought anyone would be writing to memory not allocated for missions!

If you liked this post and the video, check out No Ordinary Moments, my reflections about our trip to see the launch of a satellite and the excitement of the young entrepreneurs who were counting on it for their start-up’s future. And if you want to know how to document easily, automatically in an Agile or non-Agile software world, see Automatic Documentation – How we use Software 2020 to Build Software 2020.

1 thought on “Lessons from the Moon. Gotta have good documentation!

  1. Pingback: Can Documentation be part of the Definition of Done? « Duck Pond Software

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