Michal, SQ5KTM, has been successful in receiving reflections of the french GRAVES radar from the International Space Station.
The radar system is used for space surveillance tasks, located in JN27SI and operating on 143.050 MHz. Karl, DK5EC, has written a very informative article about monitoring GRAVES.
At present the HamTV transmitter, installed at the International Space Station is switched on. As the camera is not connected, only blank transmissions can be received, just to test the equipment.
As can be seen, everything is working fine, so I am waiting for the pictures now.
Jan, PA3FXB, and I skeduled a very special ISCAT test on 23 cm for today. The CAMRAS team had planned to operate PI9CAM with the 25 m radiotelescope in Dwingeloo for some astronomical experiments this afternoon. Before starting with that, we used an ISS pass with low elevation to try ISS bounce with the big dish. Such a pass ensures slow variation of azimuth end elevation angles, which is essential to track moving object like the ISS (or other spacecrafts in low orbits) with an antenna of a weight of 120 tons.
We had very strong reflections right from the beginning, but no decodes. Maybe the signal level was to high? This has to be investigated. Then we changed to aircraft scatter, although the dish had to be kept elevated at 10° by safety reasons, I got strong reflections from airplanes quite close to PI9CAM. Not as strong as from the ISS, but decodable now and it was possible to work in CW too.
Despite the fact, we had no QSO via ISS bounce, we learnt, that it is possible to track objects in low orbits with the 25 m radiotelescope, as long as the elevation keeps low. This opens up a perspective to make use of other spacecrafts as reflectors.
Jan, PA3FXB, and I were discussing the use of digimodes on ISS bounce for quite a while. Today we tried it with ISCAT-B and were successful with the first shot. As in the tests with Ronald, ON7FLY, on AS, we used 15 seconds periods.
From the moment on, traces could be seen in the waterfall diagram, decodes were possible.
When the ISS culmiated and the variation of the dopplershift was fastest, the frequency correction came to its limits. But while I am used to ISCAT in the meantime, I needed no decodes to hear, that Jan was transmitting RRRRs.
At least I decoded a 73 from him. The experiences with ISCAT in ISS bounce are very promising, although the 15 seconds periods are too long. So we have to discuss it and try with shorter ones.
At present the HAM TV transmitter aboard the International Space Station performs blank transmissons until August 6th, 2014. No camera is attatched, so only signal levels can me measured.
This was an opportunity for me to check out the FSTV-equipment, I set up during the last months. So my very first attempt last night was successful. I used the pass at 23:50 UTC on July 30th, 2014.
I am looking forward to see some pictures in near future.
After getting familiar in working us in CW via ISS Bounce, Jan, PA3FXB and I were looking for a new challenge. So we decided to try it in SSB. After some tests in the last days and finding a workaround for a bug in my PowerSDR, we completed a two way contact in SSB on a center frequency of 1296.300 MHz tonight. The doppler compensation worked well on both sides. Just minor corrections with the RIT were neccessary. The signals weren´t as strong as they were in the days before, but strong enough to copy even some 73s at the end. It seems to be the first SSB QSO via reflections on a spacecraft at all.
The audio recording starts with my recording of PA3FXB on one channel synchronized with Jans recording of my signal on the other channel.
Tonight I had a sked with Jan to try ISS Bounce once again. We agreed in trying SSB after getting in contact in CW. Jan appeared shortly after rise of the ISS and it was no problem to exchange reports and confirmation with strong signals. Then we switched to SSB and I could hear Jan clearly, but my tracking software refused to stay in SSB mode. So I have to fix this bug for our next test.
Later we tried to detect reflections from Iridium 4. We expected to see something about -19 dB, but nothing was to be seen in the waterfall diagram. Maybe that the choosen pass wasn´t too high in elevation and we will try again. When Jan was operating PI9CAM on February 2nd, faint traces of reflections on COSMOS 1823 could be detected by Hannes, OE5JFL, Dan, HB9Q and myself. As it is quite time-consuming, to find reasonable passes of satellites, I wrote a small Excel tool get an overview over satellites, passes and elevations. It can be found for free download here: Visibility
Macros have to be enabled in your Excel. Just enter the date, time, period and the locators of the two stations in the approriate cells, click “Calculate” in the “ADDINS/Satellite Overview” menu and the worksheet will be updated. Don´t forget to fill the TLE worksheet with the latest data of your choice.
Once the news about our QSO were spread out over the internet, Jan and I had an overwhelming feedback from all over the world. Many sent just congratulations, but a number of hams supported us with additional information. Domenico, I8CVS did calculations using the radar equation. His results concerning the expected signal levels correlate very well with our recordings.
A lot of details about earlier attempts were reported by GW4DGU (ex G4DGU), VK3UM and VA7MM. Here a summary in brief:
Chris, G4DGU and John, G4ANB performed tests with Ben, SM6CKU in 1980 on 70 cm. Ben was able to copy a SSB burst of Chris reflected on a COSMOS 3 stage launcher.
Dough, VK3UM had several QSOs with Graham, ZL3AAD on 432 MHz in the 1990s by bouncing signals off the Russian space station MIR. It seems, they were the first to complete a QSO using a space craft as reflector!
In an AMSAT forum Miles, WF1F, reports about reflections of Joe´s, W2KQ, signal bounced off the MIR on 2 m while arranging school schedules with one of the cosmonauts in 1994.
We knew that Mark, VA7MM and Cor, VE7BBG (sk) had their first tests on 23 cm on May 16th, 2004, as Mark published on his website. He now told in an email about four(!) QSOs they had on May 23rd, May 25th, May 31st and June 5th, 2004. As far as we know now, this team was the first to complete a QSO via ISS bounce at all.
In end of 2007 a lot of activities happened on 144 MHz. Rob, PE1ITR tried with Mike, DK3WN, who received reflections. Peter SM2CEW nearly completed a QSO with Håkan, SM7WSJ and tried also with Petros, SV3AAF (more). Frank, PE1NFE and Rune, SM5CUI were able to copy the signals from Sweden as well. Bernd, DF2ZC completed on 2 m with Frank, DH7FB on December 9, 2007. They had three more QSOs in 2008.
Addendum May 2016:
I found a link to the website of Philippe, F6ETI, where he described the successful experiments with F6AGR to bounce reflections off the Russian MIR space station on 144 MHz in February 2001. As he told me, they performed just a one way test and had no QSO.
To be continued ……
May 23rd, 2013
(Copyright by NASA [Public domain], via Wikimedia Commons)
After a lot of tests and improvements have been done in tracking the doppler shifted signals, Jan, PA3FXB any I had another try around 1296.300 MHz this morning. Both of us performed compensation of the own doppler component as well in receiving as in transmitting. We agreed in using the EME QSO protocol and periods of 30 seconds.
PA3FXB as received by DJ5AR
Jan appeared within my filter bandwidth as soon as the ISS became visible to both of us. His signal strength was peaking up to nearly 20 dB above noise and was easy to copy. The tracked frequency seemed to be stable until the ISS culminated. Then the variation of the doppler shift became so rapid that the compensation mechanism was not fast enough anymore. But that happened to the very last part of our QSO while we were transmitting our final 73s. So I can state that the best signal quality can be expected during the ascending and the descending parts of the pass.
In the meantime I received Jan´s recording. Listen how DJ5AR sounds on his side:
DJ5AR as received by PA3FXB
Many thanks to Jan for his cooperation and his patience in numerous tests before.
This success is dedicated to our fathers, who suffer from the same disease!
If you are interested in a try, do not hesitate to contact Jan or me. You can find us in the HB9Q 1296 MHz EME logger or in the ON4KST microwave chat, when QRV.
Today Jan, PA3FXB and I used ISS passes to improve doppler compensation.
The first pass of three was disappointing because no reflections could be detected. In the second one I found Jan shortly after his window opened. But it sounded more like a strange kind of music than CW, Jan stated after listening to the audio file, I recorded of his signal. The reason were too long steps in timing for the frequency correction. I reduced it for the last try from 100 ms to 10 ms. After some recalibration of frequency and rotor control I started the system again when the ISS rose.
I could hear Jan without any manual corrections immediately after he started transmissions. The frequency tracking worked quite smoothly and reading his CW was possible without any problems.
PA3FXB as received by DJ5AR with QRG tracking every 10 ms
The audio file contains Jan´s signal in three periods. From 0:00 to 1:00 the signal raises while being on the upper flat part of the doppler curve shown above. During the second period from 1:00 to 2:00 the signal passes the steep part and even an adjustment every 10 ms leads to a kind of jumping signal. When receiving the third period, the signal was quite stable again and faded out, while the ISS moved to the eastern horizon.
In between his TX periods Jan tried to catch my signal without doppler compensation, just playing with the RIT. He successfully got a short part of my transmission:
DJ5AR as received by PA3FXB without QRG tracking
Doppler compensation on my TX part did not work. It seems that the SDR does not accept CAT commands for frequency change while transmitting. So we will work on another strategy, where TX frequencies remain fixed and both stations will do full doppler compensation only while receiving.