By Armand Budzianowski, Krzysztof Czart.

RX-SSTV software

From time to time there is an opportunity to try your hand at amateur radio and pick up images broadcast from the International Space Station (ISS) orbiting over the World. During the World Space Week 2020 with the subject “Satellites improve the life on the Earth”, amateur radio operators (HAM Ops) in ARISS in cooperation with Roscosmos prepared very unique series of 12 images with satellites. These images cosmonauts sent from the board of the ISS in the period between October 3-8, 2020. Apart of it there was underway the ARISS SSTV Award.

This article was originally published in Polish in the “Urania”, which is the largest Polish web-portal about astronomy and space (www.urania.edu.pl), owned by an astronomical magazine “Urania – Postępy Astronomii” [1]. Publishers of “Urania” are the Polish Astronomical Society and the Polish Society of Astronomy Amateurs. Here you can read the article with small modifications after its translation and adaptation to English.

Amateur Radio on the International Space Station (ARISS) is an international organization that facilitates the cooperation of amateur radio associations and space agencies [2]. The space station is “a home” for amateur radio equipment that is used for amateur radio operators in space and on the Earth including outstanding educational purposes. From time to time, images are broadcast from the ISS. On the occasion of the last activity in October 2020, an action with commemorative ARISS SSTV Award diplomas was also organized.

The task of the participants is to receive and decode the images. The subject of the 12-image collection recently broadcasted is satellites. SSTV stands for Slow Scan TV – a very old technique of transmitting still images with the help of sound that sounds like a melody. Converting sound into the image can be done with computer software, eg MM-SSTV [3], RX-SSTV [4] (using virtual cable or external cable or a microphone) or on a smartphone by e.g. the Robot36 which is easier to use using the microphone. Remember please, that when are you try to use a speaker to a microphone air way, in the room should be silence. Each noise like voices, dog barking, wind rain, passing cars, can generate an extra noise on the image. Also, wrong levels of audio signals can cause distortions of the picture or noise.

The last event began on October 3 at 14:00 UTC and finished October 8 at 19:15 UTC, with a break on October 5 for space operations related to the NG-14 spacecraft mission. Images can be received on the frequency 145.800 MHz ± 3 kHz FM, SSTV in PD 120 mode. Transmission of one image took about 2 minutes, then there was a two minutes break and broadcast of the next image. During the day, there are about five orbits of the ISS over each part of the World, with attempts to receive the images. One pass over a point on Earth allows for up to 10 minutes for radio contact between the ground station and the station in the sky. Passes you can determine by tracking software such as Polish software Orbiton [5] (available in any languages) with special modification to use for direct ARISS contact, or using online services. There are also many applications for android system, such as AmsatDroid.

Orbitron - the software for antenna system tracking and CAT radio communication. It allow to calculate predictions also for only visual pass. — *Orbitron – the software for antenna system tracking and CAT radio control. It allow to calculate predictions also for only visual pass.*

How to receive a signal?

Receiving the radio signal can be done in three different ways. Detailed descriptions are available in the articles on the Polish ARISS website [6], but also in English language on ESA/ESSERO movies. In short: you need (1) a radio or (2) a DVB-T USB TV tuner with RTL2832U chip. The TV tuner using special free software is very easy to turn into the very cheap Software Defined Radio (abr. SDR). Both receivers require antenna. Remember please words of Polish famous HAM operator and the constructor of station Błyskawica, which he built at home and which was used during the Warsaw Uprising in 1944 – Antoni Zębik SP7LA: “Young people very often forgot that antenna is always the most important element of each radio system. The antenna. Not such a big power”. Sometimes the signal form the ISS is so strong, that a simple “rubber antenna” of the handheld radio is enough to receive one image. However, in order to be able to receive more images during one pass of the ISS over the location, better use other types of antennas.

The TH-D74E radio was used to receive images transmitted from the ISS and record the received sound onto a microSD card. At the railway station (a) in Kutno, there was a presentation of receiving the "melody" broadcasted from the International Space Station (Photo by M. Baran). The sound from the speaker of the TH-D74E was picked up by the microphone of the Android phone and decoded with the Robot36 application, to show for presentation purposes only what is included in the "melody". The sound recorded on the microSD card in the TH-D74E was later copied to the computer and decoded with the MMSSTV (d) program. You cannot see the digital audio sampling mismatch in such a recorded audio file from TH-D74E, which may be seen in the decoded images as diagonal stripes or "dots" similar to those in (c). The image and description were previously published in Świat Radio 4/2019 pages 19-23 A. Budzianowski SP3QFE, D. Rosołowski SQ5JQI, S. Szymanowski SQ3OOK “Testy TH-D74A/E, część 2”. "Świat Radio" is the sole representative of Poland in the network of journals of member organizations IARU. — The TH-D74E radio was used to receive images transmitted from the ISS and record the received sound onto a microSD card. At the railway station (a) in Kutno, there was a presentation of receiving the “melody” broadcasted from the International Space Station (Photo by M. Baran). The sound from the speaker of the TH-D74E was picked up by the microphone of the Android phone and decoded with the Robot36 application, to show for presentation purposes only what is “included in the melody”. The sound recorded on the microSD card in the TH-D74E was later copied to the computer and decoded with the MMSSTV (d) program. You cannot see the digital audio sampling mismatch in such a recorded audio file from TH-D74E, which may be seen in the decoded images as diagonal stripes or “dots” similar to those in (c). The image and description were previously published in Świat Radio 4/2019 pages 19-23 A. Budzianowski SP3QFE, D. Rosołowski SQ5JQI, S. Szymanowski SQ3OOK “Testy TH-D74A/E, część 2”. “Świat Radio” is the sole representative of Poland in the network of journals of member organizations IARU.

For those who do not have hardware capabilities, there is also another solution (3) the WebSDR. User can connect via the Internet to some WebSDR amateur radio server and receive audio signal from there. Another solution is recording the audio on the WebSDR server and after the pass download the audio file and then decode it. There are many WebSDR servers in the World in the 2m band, so in this solution user is not limited only to orbiting the ISS over his home. However, user need to spend some time with patience to find WebSDRs that have antennas designed to receive radio signals from space, not from Earth.

During the ARISS SSTV event in August 2019, about 70 different images received using different WebSDR over the World. Here is shown the set of all 12 pictures for broadcasted series. Locations of WebSDR are as grid-locator notation. Type of antenna of the WebSDR is also in the description. — During the ARISS SSTV event in August 2019, about 70 different images received using different WebSDR over the World. Here is shown the set of all 12 pictures for broadcasted series, all recived via WebSDR servers only. Locations of WebSDRs are in grid-locator notation. Type of antenna of the WebSDR is also in the description.

On the base of reports received by ARISS since couples’ years, we know that this kind, of activity very often start to evoke positive emotions and curiosity in people – how to get a better effect – and this is an element of self-education and unconscious learning about the world of physics and more.

In addition, ESA and ESERO from different countries have prepared a number of instructional videos [7] about images from the ISS and how to receive them.

A commemorative award

Participants may send received images to ARISS SSTV Gallery [8]. After uploading the image, participants can receive a special award as a diploma. Details are available on the ARISS SSTV Award website [9].

Below you can see a pattern of a commemorative certificate of ARISS SSTV award, that was sent to participants who fulfilled the conditions of the award. Each diploma has its own unique number, and their list together with the information to whom it was issued is posted on the ARISS website.