Tracking satellites and other space objects with RF signal reflections
Mike Coletta is a ham radio hobbyist who uses RF signals emitted by the Air Force Space Surveillance System (AFSSS), also known as the space fence, “to track near-Earth objects like satellites and space debris”: Tracking the International Space Station with metal coat hangers – gigaom.com
Coletta tracks all kind of near-Earth objects: the International Space Station, satellites, meteors. Signals picked up by the antenna, which is made of a 10-foot wooden board and metal coat hangers, are converted into tones that differ depending on the direction and location of an object. The tones, layered over a background of heavy static, grown louder and then softer as the object passes by, like a train traveling toward you and then barreling away. Listen to the sound of the ISS here.
This space fence is described in this recent article: Air Force Space Command to discontinue space surveillance system – U.S. Air Force
The AFSSS, which has been operational since 1961, is just one part of AFSPC’s global Space Surveillance Network. The system is designed to transmit a “fence” of radar energy vertically into space to detect all objects intersecting that fence. The operational advantage of the AFSSS is its ability to detect objects in an un-cued fashion, rather than tracking objects based on previous information. The disadvantage is the inherent inaccuracy of the data, based on its dated design. The new operating modes at Cavalier AFS and Eglin AFB will provide more accuracy than the AFSSS and still collect un-cued observations.
Coletta’s website SatWatch.org describes the hobby. For example, the diagrams at Orbiting Object RF Reflection 101 at SatWatch.org show the basics of how an amateur radio receiving station can pick up the reflections of the AFSSS signals when an object passes through the AFSS beams. He also shows the data displays for over 100 different objects that he has tracked.
As a money saving measure, the AF is planning to shut down the AFSSS and use a lower cost system until a new $3B “space fence” is built.
Coletta and other space fence hobbyists won’t have to hang up their receivers, though:
Now, he’ll have to turn his attention to another source of radio waves: Mexican television stations.
“Guess what: Those signals also get bounced down from satellites, meteors and what not,” Coletta said. “You use it just like a space fence.”
Check out Mike Coletta’s SPACE GAB webcast program “where we Gab about SPACE”.