¡We've listened to an ARISS Contact!

28/03/2021

On March 22, an ARISS contact was celebrated between the ISS and the Oakwood School, in California, United States. NASA Astronaut Shannon Walker participated in the contact. The contact was made via telebridge with a ground station in Italy, so at Alcaraz, we were able to pick up the signal.

To do it, we set up three different receivers in our area, to ensure signal reception in at least one of the receivers. The temporary station network we set up consisted of:

• Castle-A Station: Located at our town’s highest point, the Castle Ruins, it consisted of a computer with a software defined radio connected over USB. We used the RTL-SDR Blog V3 Kit, with its V-Dipole Antenna. The antenna was configured to match the ISS’ frequency wavelength: both antennas were extended to a length of 49cm, and the angle between the antennas was 120 degrees. Computer had specific software to control the SDR (SDRSharp), to track the ISS (Gpredict), and to record the screen and computer audio while we were receiving signals.

• Castle-B Station: Located at the same place, it consisted of two Baofeng GT-3 handheld radios, lent by a local radio amateur. Each radio was assigned to an operator, which recorded the audio coming from the radio with his smartphone.

• Town Station: Located at a lower altitude, it’s a permanent station used by a local radio amateur. It consists of a fixed antenna connected to a Kenwood radio. As this station is located at a lower altitude, an early LOS was expected. You can find pictures of the fixed antenna at the video below.

Setting Up Castle-A/B Stations

At 19:00 PM Local time (18:00 UTC), the equipment was already set up at the selected zone by two project team members. At the same time, another two project team members gathered up to control their assigned handheld radios. In total, 4 project team members were at Castle-A/B Stations. We decided not to gather more people there to avoid any health risk.

Setting Up Town Station

At 18:30 PM Local time (17:30 UTC), approximately one hour before AOS, the Kenwood radio was already turned on and listening to 145.800 MHz frequency and the smartphone next to it was recording the audio. Both the station owner and a member of our team were supervising the radio and recording system to ensure there wasn’t any problem.

AOS occurred a few minutes after the ISS pass began. Specifically, it occurred at 19:27 Local time or 18:27 UTC. We received the majority of the contact on all three stations, so we determined that the experiment was a total success. Castle-A recorded almost all the contact, followed by Castle-B, which recorded a bit less. Town Station received ½ of the contact, due to being rounded by mountains. In all three stations, the signal was clear and understandable, allowing us to transcribe everything received.

We’ve published in our YouTube channel a documentary. In it, you can listen to what we received on each of the stations. It’s completely transcribed to English and translated to Spanish. We have also included pictures of the stations and how we set up them. We hope you like it!