Allen Telescope Array picks up ISEE3 Satellite

“Waterfall” plot from the Allen Telescope Array displaying frequency on the horizontal axis, and time on the vertical. The slow drift of the signal towards lower frequency is due to a changing Doppler shift caused mostly by Earth’s rotation.

By Seth Shostak, Senior Astronomer and Director of SETI Research

The ISEE3 satellite – originally launched in 1978 to study the interaction of Earth’s magnetic field with the solar wind – made a close approach to Earth yesterday, during which its transmitter was picked up by the ATA .
 
The carrier signal from the transmitter, at a frequency of about 2.2 GHz, was successfully snagged by Jon Richards, of the SETI Institute, and can be seen as the diagonal white line in the accompanying plot.
 
Tests of this type, on known transmitters in space, are important in verifying the operation and sensitivity of the Array.  They are like canaries in coal mines, and can warn when unseen equipment problems arise.  In this case, the test verifies that the Array has been successfully returned to operation after interruptions caused by recent brush fires nearby.
 

The ISEE3 satellite has been the subject of a reboot attempt by a team of seasoned space experts.  They raised $160 thousand in a RocketHub campaign, and hope to place the craft at the L1 LaGrange point where it can be used for additional science.  So far, this effort has been stymied by the failure of the thrusters to fire, apparently due to a leak of pressurizing gas on-board.