Ask Dr. SETI ®
I recently acquired an LNA and PLL LO for reception at 8.4 GHz (the NASA Deep Space network frequency band) using my 4.9m dish. How about that as a potential SETI frequency, as extraterrestrials might pick up signals from our various spacecraft?
The Doctor Responds:
Spacecraft power budgets are extremely limited, so the downlinks use the lowest possible transmitter power, with high-gain antennas pointed back toward Earth to make up the link margin. I highly doubt that these signals can be detected over interstellar distances. Thus, listening on those frequencies for extraterrestrial replies to our spacecraft would probably be an exercise in futility.
On the other hand, those same spacecraft receive uplink telecommands from Earth, and the NASA Deep Space Network uses very powerful transmitters to send those commands. Some of those uplink signals are also in X-band, in the vicinity of 8.6 GHz, and it is conceivable that they are powerful enough to be detected by advanced extraterrestrial SETI scientists. So, on the offchance that ETI might reply on the same frequency it receives, it certainly couldn't hurt to monitor the DSN uplink frequencies, at least occasionally.
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this page last updated 28 June 2008
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