Mars Global Surveyor
Update 14th April 2006 Mars Global Surveyor was a good signal when this FFT shot was taken. The frequency was 8422.744 and rising fast. It appears that the s/c only transmits carrier some of the time, presumably for Doppler measurements. The signal moved about 300Hz in 10 seconds.
Update 12th April 2006 Mars Global Surveyor has been detected. The Doppler shift was extremely fast perhaps in the order of 200Hz per second, which makes finding the signal pretty hard. It took about one hour or searching before finding the brief signal that is in the FFT below.
The signal was detected at 21:17GMT on a frequency of 8422.722 and rising rapidly. Mars global surveyor has a High Gain Antenna of 1.5m that is being fed with 25 watts of power. Its nominal frequency is 8423.177 MHz.
The telecoms subsystem on MGS is fairly complex, a block diagram can be seen below:
An excellent technical document on Mars Global Surveyor can be found here