Receiving Dead Satellites with the RTL-SDR

Recently happysat, a reader of RTL-SDR.com wrote in to let us know about an unusual hobby he has found with the RTL-SDR. Happysat has been using the RTL-SDR together with a QFH antenna to detect old decommissioned satellites in the 136-138 MHz and 150-400 MHz frequency ranges. Although these satellite’s batteries have long been expired, because of some sort of chemical reaction due to thousands of failed recharge cycles the batteries begin to conduct over time and allow the satellite to be powered directly from the solar panels thus activating the transmitter. Happysat writes:

During weathersat reception of NOAA/Meteor on the 137 MHz band i did see quite often unidentified interrupting signals. After a bit of Googling around I learned that these were Dead Satellite’s that still are broadcasting given the right sunlight conditions, the signal strength is sufficient to show up in SDRSharp, not all signals are very strong some very weak and needed a good close up zoom in SDRSharp. There are many shutdown Satellite’s who apparently having a life of their own varying from Military, Navigation, Experimental, Weather, and also Amateur ones. Most are not transmitting any usable telemetry or weather images but they still use the original frequencies to sent out a unmodulated carrier, which interferes with the current operational Satellite’s in the 136/138 MHz band. Normally when a satellite goes out of service and runs almost out of fuel the last reserve is used to shift it in a graveyard orbit which resides above the normal operation orbit, it will be switched off and left on their own. But this will not always goes as planned, sometimes due solar radiation or other technical failures it will not respond again to the ground station commands, which leaves the Satellite in its current orbit. Some have a timer onboard which will be activated at end of life scheduled to end/shortcut the power feed to the transmitter so it will not broadcast again, also this can fail. Until some day they might not work at all anymore.. But that can take a while one of the oldest satellite still broadcasting are: Transit 5B-5 (Military Navigation) from 1964 – they can be heard in either CW or USB mode. An audio example of Transit is over here [link to example] (my recording – link to online stream  uploaded by commenter Jordan here) it sounds like some kind of melody song. And LES-1 from 1965 (Lincoln Experimental Satellite 1) – Audio example over here [link to example] thanks to Phil Williams. Others are just a spooky hauling sound like LES-1, NOAA’s etc due the Voltage fluctuation from the solar panels. DD1US does have a very nice collection images and orginal sounds on : [space sounds] A list of frequencies and more in depth details can be found on Mike Kenny’s excellent website: [mike kenny’s website] My TLE containing all current Deadsatellite’s is available on dropbox for anyone would like to try out – [TLE file] Updated once a week. You can use it in your favorite tracker, i prefer Gpredict for this course of the unstable frequency and Doppler effects Orbitron will not always suite on this birds.

Happysat has also provided a frequency database for SDR# containing the frequencies of all the dead satellites.

Aloutte
Aloutte
Transit 5B
Transit 5B
Transit 5B
Transit 5B
Tiros-N
Tiros-N
NOAA-9
NOAA-9
NOAA-9
NOAA-9
LES-1
LES-1
ISIS-1
ISIS-1
GPredict
GPredict
Fenyung 1D
Fenyung 1D

 

16 comments

  1. perraud

    Hello, I just want to know if Happysat is still in the area? the dropbox’s link of this articles are all broke . Can I find infos somewhere?

  2. Nicholas

    I see that AO-7 is in the dead satellites database when in reality it is partially functional! This one died in the early 1980s but was rediscovered in 2002 after the battery short became an open. Unlike the other zombie satellites listed BOTH transponders are functional but in sunlight only and they are in SSB mode. It switches modes whenever it receives enough power through its solar panels to function in two modes known as A and B. For the purposes of this I will list the downlinks in case anyone wants to try for it. The mode A downlink is 29.4 to 29.5 MHz and the mode B downlink is 145.920 to 145.980 MHz. If all else fails there are beacons which will be in CW mode and due to the unstable voltage from the solar panels there will be a chirp or pitch variation to the signal. The beacons are 29.502 MHz in the 10 meter band and 145.972 in the 2 meter band.

  3. KF5UUM

    Hello happysat,
    I’m thinking about choosing an SDR for doing satellite work and being faced with so many options (many of which with little documentation) I thought I would ask someone with a proven setup. Thanks for the help and any other feedback is appreciated!

  4. Phil

    There are also a couple of amateur radio satellites worth monitoring, in particular OSCAR-11, launched in 1984 and still running strong. It’s on 145.826 Mhz. and still sending telemetry.

    Moving satellites out of their orbits is primarily done for geosync satellites and also done for satellites in heavily populated constellations. In fact many satellites don’t have any fuel for operational purposes. Even if a weather satellite (for example) uses its thrusters to move out of the operational orbit, it’s still in an orbit with very similar characteristics. Whether a satellite’s been moved out of its operational orbit or not has no relation to its transmitter.

    When a satellite finishes its planned operational life it’s commanded to shut off its transmitter (to prevent interference with other satellites using those frequencies), drain its batteries (to prevent potential gas build up and explosion) and vent anything pressurized (also to prevent explosions). On rare occasions a satellite will accidentally turn back on because of some quirk (e.g. cosmic ray upset turns the transmitter on, battery goes from short to open).

    But in many cases a satellite fails while running for whatever reason (battery failure, solder joint goes through too many heat cycles, fried by solar storm, etc.). In those cases there’s no way to send the commands to passivate the satellite and almost anything can happen.

    In a couple of rare cases a random event turns the transmitter back on and in extremely rare cases the satellite might be usable (or partially usable) after its recovery.

    There have been a couple of cases where commands were sent to satellites which had been intentionally shut down just to see if they could be revived.

  5. Happysat

    Hello Alexander,

    No LNA is used however i have a TV-pre amp (20dB) i only use for Meteor reception, the result on other sat’s is not very good to much noise.

    I only have a very weak signal with ECS-4 currently visible in Europe.

Post a comment

You may use the following HTML:
<a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>