what the signal looks like (Score 2)

Replying to a commment buried somewhere down below.. As far as I know, the signal is a UHF (400 MHz) very low power (just a few dB above the noise floor) narrow (a few Hz) tone that slowly moves about 50-100 Hz over a about a half hour time span. It could be of earth origin or from any number of other sources. In order to determine if it is from MPL, someone will need to calculate how much doppler shift would be expected from 1) the rotation of earth (this is easy, about 511 Hz, but changing), 2) the rotation of Mars (this is not so easy, because we don't know where on Mars the transmitter is, and that affects the doppler), and the relative motion of Earth and Mars (this is fairly easy) You match up the changes in the frequency of the received signal against the expected doppler changes from relative motion. If it is reasonably close, you are in good shape. If the frequency variations don't match what's expected, you have two choices: 1) It is some other source (most likely).. 2) It IS MPL, but the transmitter on Mars is drifting in frequency (it might, say due to temperature fluctuations, etc. Pathfinder's UHF transmitter frequenciess varied quite a bit over temp) Fortunately, the receiver at Stanford is locked to an atomic reference. You also need to eliminate the possibility that it is some other source (like an out of band (normally in the 300 MHz area) garage door opener that is slowly heating up in the sun, etc. etc.