Mars Express Reception - Latest news                                                                                          updated: (23/12/2007 22:10:58 -0000)

Update from 23rd December 2007 : MEX was easily found with the aid of the SDR-14. Very strong carrier with a little doppler.

Update from 22nd April 2006 : A strong pass of MEX, copied at 19:53GMT on 8419.926 and rising fast. Note that the FFT shows the carrier falling due to being received in CW mode.

Update from 15th April 2006

A nice pass from MEX, received on 8419.923 at 18:46GMT. FFT plot from spectran shows the nice signal strength. Mars and MEX are 165473058.6 miles away from Earth, with light taking 14.827335 minutes to get here.

Update from 23st March 2006

Extreme Doppler on Mars Express, followed by an abrupt end to the signal, either its gone behind Mars or its commanded off. The centre frequency at the time was around 8419.939 and moving up in frequency very fast, around 100Hz per second.

Watching MEX again on the FFT whilst having lunch. The signal strength is pretty good considering the range is now 145.1 million miles. That's over a 100 million miles further away than when I first copied a signal from the MRO. Interestingly, the signal stopped abruptly at 13:27:20, presume that the TX was commanded off, or the space craft went behind Mars.

Update from 21st March 2006

Finally, whilst having my lunch break, I was about to take a big bite from my sandwich, when a carrier appeared on Spectran, exhibiting a fair amount of Doppler. The frequency in question is 8419.905 which can only mean its coming from ESA's Mars Express space craft which is in orbit around Mars. I would say that its 4dB to 6dB weaker than the carrier from the MRO. The Mars Express space craft has a 1.6m diameter high gain antenna which is used for communications with Earth. The actual space craft transmit frequencies are 8420.432 MHz (telemetry/tracking) and 2296.482 MHz (telemetry/tracking). The X-band signal  is amplified by two TWT amplifiers to an  output power  of 65 W which is then fed to the 1.6m dish. The S-band transmitter is only 5 watts output to two low-gain omni directional antennas. There is an interesting paper from the ESA on the Mars Express Orbiter Radio Science - its well worth reading for some background info on the space craft RF subsystems.

Mars Express Mars Express showing the HGA antenna behind the space craft main bus.

Image above courtesy of ESA

The picture above shows the Doppler trace in Spectran. Its exhibiting around 400Hz per minute in the downwards direction, which means that the space craft is moving away from Earth, as is Mars.

This is the SDR-14 output of the MEX Doppler - its a fairly weak signal, but at audio its easy to see.

Finally, here is a WAV file recording of the carrier with Doppler. You may have to listen to it several times in order to pick out the tone, as its quite weak.