Here the result of our small excursion from working on the Apollo 7+8 only NASSP 7.0 release. Lunar Landings are now possible with the Virtual AGC. I started working on this just to test the ignition algorithm of the LGC. And somehow it ended in a month long adventure, working closely with the Virtual AGC developers to find some bugs in the AGC engine and now we can perform landings with the actual AGC version flown on Apollo 11.
The landing programs in the LGC are probably the most complicated operations with the AGC, so it's no wonder that if there were any bugs in the Virtual AGC that they would cause problems. The few bugs we found and were fixed by the Virtual AGC guys were usually some special case in a rarely used AGC instruction. Ones' complement is evil. So during any other program or in the Command Module Computer these bugs would probably have never had any impact. One of the bugs was stealing a lot of machine cycles, which caused 1201 and 1202 alarms that actually were harmful and affected guidance a little bit and no DSKY inputs were possible. But these problems were Virtual AGC issues, not the problem Apollo 11 had with processing rendezvous radar data.
This video was recorded in the experimental NASSP version for Orbiter 2016. There is a lot of things working fine in Orbiter 2016, launching and staging is not among these things. But landing on the Moon apparently works fine. :lol:
You will perhaps have noticed, that the inititial altitude difference between the landing radar and the LGC is pretty high. The reason for that is that I have simply pulled over this PDI scenario from Orbiter 2010. In Orbiter 2010 all the bodies are spherical, so the landing site vector in the LGC should have the mean radius of the Moon. Tranquility Base is about one nautical mile below the mean Moon radius and so the measured altitude of the landing radar is different in Orbiter 2016.
The lunar module was distracting us from working on the Apollo 7+8 release, which isn't too far away anymore. But we will be focusing on that work again now.