Apollo transponder first light
Added 2021-08-30 06:37:20 +0000 UTCAt least first light for us! The Apollo transponder turns on after almost 50 years and transmits its beacon 2.28 GHz signal to earth. In return, we send it a rubidium-controlled signal at a exactly 2106.40625 MHz. The transponder precisely locks on this frequency, and re-transmits it back after a 240/221 frequency ratio shift, sending it at approximately 2287.5 MHz. I say approximately, because the returned signal will have a two-way doppler shift, which is then measured on the earth receiving station to know the speed of the spacecraft. This is so complicated, it is going to be quite a challenge to explain how it works. While I am mulling on how to do that and find enough time, here is a little cut of one of the high points so far.
