by Mike Cook, AF9Y
In late November of 1996, many hams and amateur SETI stations around the world participated in a NASA experiment to detect a beacon signal from the Mars Global Surveyor (MGS) satellite. The beacon was a 1 watt carrier which was activated when MGS was 5+ Million km from the Earth. This experiment was a unique opportunity to test the limit of an amateur receiving system. Key factors were:
The signal was detected immediately at beacon turn-on and was tracked for over an hour. The expected 6 dB of margin was verified as the signal dropped from -187 dBm to -193 dBm before the trace disappeared from the FFTDSP display. More spectrograms and a correlation to NASA's antenna gain plot can be seen on my webpage at http://www.webcom.com/af9y. Pictures of the helix antennas and testing techniques are also available.
Detection of the MGS carrier was a great thrill and ranks up there with my first Moonbounce (EME) ham contact. An even greater challenge lies ahead for detection of MGS while in orbit around Mars. At that time the signal will be 25 dB weaker. In addition, there will be three forms of doppler to deal with in the signal processing. While this would be a very difficult challenge, I believe it may be possible for the larger amateur SETI stations. As a group, we need to participate in more tests like this to assure that the receiving capability is at the level we expect.
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this page last updated 5 February 2005
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