HI,
Quite interesting re painting satellites black. If you look at some of the photos of the recent 'wideband gapfiller satellite', the satellite bus is mostly black. http://www.boeing.com/ids/news/2006/q3/060926b_pr.html has a picture of the satellite in a frame prior to testing. If you look at it, you can see all the communications antennas are black. I'm not sure is this is painted for stealth reasons, or the antennas are made of carbon fiber. I'm sure this is only one example of many recent satellites that have been painted black.Either way, painting a satellite would only solve a small amount of the problem, since pretty much all satellites carry an RF payload which transmits data back to earth, they can be detected this way if they cannot be seen.
The article mentions the 'seesat' group which does visual obs, but a parallel group 'hearsat' works with the RF downlinks, identifying satellites purely by their RF fingerprints. In fact several satellites have been detected at RF, orbits computed which were then passed on to the 'seesat' folks for visual confirmation.
There are a few sites that you can check out if you are interested in the RF Aspects of satellite detection, www.hearsat.org, www.satellitenwelt.de and www.uhf-satcom.com being just a few.
Hi, yes looking at the spacecraft over a few frames would give you the opportunity to work out the orbit of the s/c. Once the rough orbit is known, the doppler shift can be worked out, and therefore the frequency. MGS has also been heard by radio hams, so its possible that some could watch for a signal. http://www.uhf-satcom.com/mgs/ has some info on the signals detected from MGS earlier this year.
Lets hope NASA manages to either image this s/c, or chat to it with one of the rovers.
Hi Voltageaav, you have misread the context of the article, I built the receiver and have no connection with nasa at all - it was done out of technical curiosity just to see if it was possible with simple equipment to hear anything, the answer turns out to be a "yes".
Yep its probably a victory for ham radio - since I'm licensed and operate >1GHz only, its experience with building ham transmitters / receivers etc that gave me knowledge etc, to build an 8.4GHz rx. The whole project was done to see if it was technically possible to build a receiver - I've not really got the time / interest to delve into the telemetry formats or to work out how to decode the tt&c data.
Next, I'm waiting for the 'New Horizons' mission to pluto, that will provide an interesting signal to track for a number of years.....
Hi,
re the bpf, its only a 2 cavity filter made in wg16, cf=8420 with about 50MHz bandwidth, and RF coupled in and out via the standard probed with appropriate matching screws. Using that dish, the signal isnt that strong, its detectable though on an FFT as per the article. There is a nice page on x-band space probe reception with some example audio at http://www.setileague.org/photos/probes.htm The next plan is to try to hear the orbiters that are currently at Mars, but that will need the 3.7m dish.
regards,
Paul (uhf-satcom.com contributor)
Slashdot Mirror
HI, Quite interesting re painting satellites black. If you look at some of the photos of the recent 'wideband gapfiller satellite', the satellite bus is mostly black. http://www.boeing.com/ids/news/2006/q3/060926b_pr.html has a picture of the satellite in a frame prior to testing. If you look at it, you can see all the communications antennas are black. I'm not sure is this is painted for stealth reasons, or the antennas are made of carbon fiber. I'm sure this is only one example of many recent satellites that have been painted black.Either way, painting a satellite would only solve a small amount of the problem, since pretty much all satellites carry an RF payload which transmits data back to earth, they can be detected this way if they cannot be seen. The article mentions the 'seesat' group which does visual obs, but a parallel group 'hearsat' works with the RF downlinks, identifying satellites purely by their RF fingerprints. In fact several satellites have been detected at RF, orbits computed which were then passed on to the 'seesat' folks for visual confirmation. There are a few sites that you can check out if you are interested in the RF Aspects of satellite detection, www.hearsat.org, www.satellitenwelt.de and www.uhf-satcom.com being just a few.
Hi, yes looking at the spacecraft over a few frames would give you the opportunity to work out the orbit of the s/c. Once the rough orbit is known, the doppler shift can be worked out, and therefore the frequency. MGS has also been heard by radio hams, so its possible that some could watch for a signal. http://www.uhf-satcom.com/mgs/ has some info on the signals detected from MGS earlier this year. Lets hope NASA manages to either image this s/c, or chat to it with one of the rovers.
Hi Voltageaav, you have misread the context of the article, I built the receiver and have no connection with nasa at all - it was done out of technical curiosity just to see if it was possible with simple equipment to hear anything, the answer turns out to be a "yes".
regards
Paul (www.uhf-satcom.com contributor)
HI,
Yep its probably a victory for ham radio - since I'm licensed and operate >1GHz only, its experience with building ham transmitters / receivers etc that gave me knowledge etc, to build an 8.4GHz rx. The whole project was done to see if it was technically possible to build a receiver - I've not really got the time / interest to delve into the telemetry formats or to work out how to decode the tt&c data.
Next, I'm waiting for the 'New Horizons' mission to pluto, that will provide an interesting signal to track for a number of years.....
regards,
Paul (uhf-satcom.com contributor)
Hi, re the bpf, its only a 2 cavity filter made in wg16, cf=8420 with about 50MHz bandwidth, and RF coupled in and out via the standard probed with appropriate matching screws. Using that dish, the signal isnt that strong, its detectable though on an FFT as per the article. There is a nice page on x-band space probe reception with some example audio at http://www.setileague.org/photos/probes.htm
The next plan is to try to hear the orbiters that are currently at Mars, but that will need the 3.7m dish.
regards,
Paul (uhf-satcom.com contributor)