In Mainz-Ebersheim haben sich die Weltraum-Kinder der Katholischen Kindertagesstätte St. Laurentius intensiv auf den Raumflug Ihres Astro-Alex vorbereitet. Auftakt war ein Blick auf den Mond an der Paul-Baumann-Sternwarte der Astronomischen Arbeitsgemeinschaft Mainz e.V., der Appetit auf mehr machte. Aktivitäten, wie ein Raumfahrer-Training, das Herstellen von Astronauten-Nahrung oder Experimente zum Einfluss des Horizonts auf Funkverbindungen mit Walkie Talkies, machte kleine Experten aus ihnen.
Heute besuchten sie dann meine Amateurfunk-Station, um gegen 12:32 Uhr Ortszeit zuzuhören, wie sich die Stimme Alexander Gersts aus dem Rauschen schälte, als die ISS sich im Westen über den Horizont erhob. Mit einem Blick aus dem Dachfenster vergewisserten sie sich, dass die Antenne auch brav die Bahn der Raumstation am Himmel verfolgte. Klar und deutlich hörten sie die Antworten auf die Fragen der Schüler, die ihnen von ihrer Erzieherin vorgelesen wurden, da die Schulen hinter dem Horizont nicht zu hören waren. Nach 10 Minuten verabschiedete sich Astro-Alex und seine Stimme verschwand wieder im Rauschen.
Frequenz: 145,800 MHz FM
Empfänger: YAESU FT-897
– 17 Element Yagi F9FT für ISS in Horizontnähe bei Auf- und Untergang
– 3 m Parabolspiegel mit 145 MHz Feed in AZ/EL-Montierung für den Überflug
Tonight ESA astronaut Paolo Nespoli, IZ0JPA, aboard the International Space Station tested the amateur radio equipment in the Columbus Module.
Signal quality was better than expected, as it was a pass with quite low culmination at 48° elevation only. He could be heard well on 145.8 MHz FM as well.
Groundtrack of the ISS
The following pass at 20:44 UTC was more convenient and culminated at 62° elevation in the north. But Paolo could only be seen in the very first seconds, before he switched HamTV to blank transmission.
Another ARISS contact with an YOTA event in England was scheduled. HAMTV should be operated by Paolo Nespoli, IZ0JPA. As some nice video sequences could be received on 13 cm, nothing was heard on the 2 m downlink on 145.800 MHz in FM.
Today another ARISS contact has been established between Thomas Pesquet, FX0ISS aboard the Intenational Space Station and Collège André Malraux, Chatelaillon-Plage, France. As expected, the onboard DATV transmitter (HamTV) was in operation.
Blank transmissions have been received earlier, but today I could receive the TV pictures for my very first time. There was a lot of fading, but I managed to record a couple of sequences.
As the pass went overhead, I lost the signal, when the ISS approached the zenith, because the rotor had to turn 180° and it is too slow to catch up the bird again (full length video here best quality from 2:50 to 4:50).
The frequency used was 2.395 GHz. The equipment installed for reception is a 3 m dish with linear polarisation, a Kuhne MKU LNC 23 converter and a TT S2-3200 DVB-S receiver card in my PC with Tutioune3200 DVB-S software by F6DZP.
Today PI9CAM´s QSL for the first Satellite Bounce QSO via an unmanned spacecraft done by radio amateurs arrived by mail. As we know, there have been previous commercial attempts for Satellite Bounce in the early 60s using ECHO 1 and ECHO 2 which were inflated balloons with diameters of 30 and 41 m. The initial orbits were at heights of 1500 km and 1200 km.
The theoretical radar cross section (RCS) of ECHO 1 was 700 m², but measurements by military radar stations resulted in 900 to 1000 m² in the beginning. Later, the satellite deformed and shrunk. OKEAN-O, the one we used, has a radar cross section of 18 to 20 m² but is in a much lower orbit at a height of 650 km. This leads to quite similar unit power budgets, regardless the difference in size,
Enjoy the movie “The Big Bounce” about our predecessors 55 years ago!
Following Jan´s (PA3FXB) suggestion, we tried the new experimental WSJT-X software. The mode, we chose was JT9 H. Also we agreed in trying full doppler compensation to be used on my side. Everything worked fine, as can be seen in the screenshot below.
Back from our holidays Jan, PA3FXB, and I had another test via ISS Bounce on 23 cm today. As I located a bug in my Doppler correction software, causing unwanted steps, it could be fixed by finding a workaround for the malfunction in compilers NOW() routine, for returning the correct time in milliseconds. So the improved Doppler correction is working smoothly as can be seen and heard in the signals received.
PA3FXB in JTMS received by DJ5AR via ISS Bounce. Center frequency was 1296.300 MHz.
We even had some kind of conversation at the end 😉
As further tests showed, the full doppler correction on my side is working very well now. This enables potential sked partners to work on a fixed frequency by just tracking the International Space Station with the antenna.
Sked requests are welcome: dj5ar (at) darc.de
Modes, successfully being used so far: CW, SSB, ISCAT, JTMS
While yesterdays try for an ISS Bounce QSO failed by Ronny, SM7FWZ, missing my rogers, we tried again this morning. As this orbit culminated near the zenith for me, I decided to catch up the ISS on the descending part of the pass.
So I could avoid the singularity in the azimuth angle and we heard us right from the beginning with strong signals. As Ronny couldn´t copy any rogers yesterday, we had plenty of them today, as well as 73s!
Ground Track of the ISS versus the direct path between SM7FWZ and DJ5AR
It is remarkable, that Ronnys signal was audible on backscatter off the ISS, even when my elevation became less than 2 degrees. The slantranges to the ISS were about 2100 km for me and 1700 km for Ronny: A total distance of 3800 km!
This is the result of many tests and discussion before. Ronny transmitted and received on 1296.300 MHz during the whole pass and automatic Doppler compensation was done on my side for both of us.
It is funny, that we had a Moon Bounce QSO a couple of days ago, just to compensate some frustrating tests. EME is sooo easy!
Thank you, Ronny, for this fast and efficient QSO and enjoy your very special day!
After many previous attempts Ronny, SM7FWZ and Jan, PA3FXB, managed to complete an ISS Bounce QSO on 23 cm today. The rigs used, were a 3 m mesh dish with 375 W on the dutch and a 4 m solid dish with 300 W on the swedish side.
Ground track of the ISS versus the direct path between SM7FWZ and PA3FXB
The window opened from 2015-07-13 08:07 to 08:17 UTC. While the antenna tracking was done automatically by both stations, only Jan could perform Doppler compensation. So they used a kind of mixed mode in tracking the frequencies.
Ronny transmitted on 1296.300 MHz and tried to catch Jans signal manually. So I monitored the frequency, Ronny should be heard on my side. It is nice to see in the video, how Jan appeared on the very left, getting closer and closer to the frequency, Ronny could be heard.