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Old 11th August 2011, 08:47 AM   #47
Join Date: Jul 2011
Posts: 3,039
Matt, this is from Reed's essay on his 07/21/1969 work as FIDO;

"After Apollo XI landed, as the World celebrated and sipped champagne, I slept in preparation for my shift prior to lunar launch. I would work with SELECT and DYNAMICS to get all the relative geometry down and work out the correct ignition time for return to the CSM. Piece of cake really. All we needed were landing site coordinates and a solid ephemeris on the CSM.

"I sat down at the console for that prelaunch shift and was debriefed by the previous team to complete hand-off. I probably had my second cup of coffee by then and got on the loop to SELECT to get the best landing site. I remember asking SELECT what he had for landing site coordinates. I’ll never forget his answer when he said, “take your pick FIDO!” I also remember not reacting too positively to his offer. He explained that we had five different sites. He said “we have MSFN(tracking radars), PNGS (primary LM guidance computer), AGS(backup LM guidance computer), the targeted landing site and, oh yes, the geologist have determined yet another site based upon the crew’s description of the landscape and correlating that with orbiter photos”. No two of these were even close to each other."

" It was the DYNAMICS computer controller, Pete Williams who catalyzed the solution. He said that if we only had rendezvous radar tracking data from the LM on the CSM we could work the problem backward. After all, we knew where the CSM was and the problem was a relative one between the CSM and the LM, not actually requiring latitude and longitude. To do this we would need to have the rendezvous radar (RR) turned on in the LM one revolution earlier than planned. Only two more passes of the CSM remained before Ascent ignition, before we had to have a solution to this problem! I remember taking my headset off and walking up to the Flight Director, Milt Windler to explain the situation. We only used that kind of face to face communication when we had a serious problem such as this. I detailed the problem as best we knew it and the process that we’d have to follow to get the data we needed, and why we had to start a rev early to finish the calculations and then find the critical lift-off time for lunar launch. I recall the CapCom instructing Buzz Aldrin that we needed him to perform the RR check early but I don’t believe that CapCom explained why, just another check was all. Shaft & trunnion angles were passed up to aid acquisition. Right on time as the CSM cleared the horizon we began seeing data. We counted the agonizing minutes as the telemetry came flowing in until the CSM was receding. Now we had the data we needed to run the problem (a rendezvous problem in reverse) and get the correct liftoff time*. And that’s what we used. Later we would find out just where were we on the surface. We were actually over 25,000 feet from the nearest of the other five choices we had! At 5,000-fps orbital velocity of the CSM that could have been up to a ten second error in liftoff. That would have meant we’d need a LOT of RCS (reaction control system fuel) to play catch up or slow down in a rather abnormal (I don’t recall training for this one) rendezvous situation."

So many hours before all of this goes on with Reed, the scientists at Lick Observatory are given Tranquility Base's exact coordinates Matt. Armstrong is actually on the moon! and they get they coordinates, way way way before Reed figures them out.

Not just any coordinates Matt, the Lick scientists get 00 41 15 north and 23 26 00 east. Getting interested in this angle Matt? Bet you are!

Last edited by Patrick1000; 11th August 2011 at 08:50 AM. Reason: read> Reed
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