On tuesday, January 29 a month passed from the deorbit sail deployment and the beginning of the PW-Sat2 satellite’s main experiment. The deployment technology test turned out to be a great success. Maintaining the communication after the deployment was a nice surprise. Now, it’s high time to sum up the communication activities and thank the Radio Amateurs, who supported us from the very beginning of the mission.

First signal from orbit

The Falcon 9 rocket with the PW-Sat2 satellite was launched on December 3, 2018 at 19:34 CET. The satellite was released from the deployer a few hours later, at 00:00:59 on the next day. The first radio signals were sent by PW-Sat2 around 1:30. In that time the satellite was far from the range of our ground stations in Warsaw (EiTi PW) and Gliwice (Future Processing). In the early morning, the first traverse over Poland happened.

The first confirmation of the satellite turning on properly, deploying the antennas and sending signals came even earlier. Radio Amateur K4KDR received the first telemetry frame from PW-Sat2 and sent it to radio.pw-sat.pl service at 6:10, during one of the first flights over the USA.

First frame received from PW-Sat2 by radio amateur K4KDR

This information encouraged us during the wait and preparation for the first traverse in the range of our ground stations. We would like to thank you very much, K4KDR!

First received frame
K4KDR

Gain from many antennas

Signals from the PW-Sat2 satellite have been received by 50 people or Radio Clubs. Most of them are placed in Poland, but some of them were representing other countries: Slovakia, Spain, Denmark, Hungary, Russia, USA, Japan and Australia.

Locations of ground stations which received signals from the PW-Sat2 satellite during its mission

PW-Sat2 sends its telemetry data (beacon) once a minute, so that Radio Amateurs from all around the world could try to receive the signal from the orbit. Telemetry data gathered from distant places let us know the state of the satellite outside the range of our ground stations (traverses over Poland happen every day in the morning and evening).

The list below shows the ranking of Radio Amateurs who could only receive auto-generated frames, because of their geographical location:

  1. N6RFM, USA, 77
  2. VK5EI, Australia, 57
  3. K4KDR, USA, 51
  4. Carlos Picoto, USA, 7
  5. YB3MBN, Indonesia, 6
  6. EA4GPZ, Spain, 5
  7. W2RTV, USA, 1
  8. JA0CAW, Japan, 1

Largest number of received frames outside the uplink zone

N6RFM

Bigger amounts of data – old telemetry, experiment results and pictures – are sent exclusively on the operator’s request, which can only happen in the range of our ground stations (Warsaw and Gliwice). Depending on the current capabilities related to the power budget and the amount of data generated by the experiments, hundreds to thousands of data frames were sent every day. Unfortunately, radio connection with a satellite hundreds or even thousands kilometers away from the receiving antennas can be easily disturbed by signals from other transmitters, or by unfavorable relative orientation of the satellite’s antenna and the ground station.  The ground station network spread all over Poland, which exists thanks to the Radio Amateurs society, let us minimize the data loss issue. If one of the ground stations did not manage to collect the data package, one of the other stations probably received it in different location. All the collected frames are sent to radio.pw-sat.pl in real time, which enabled us to have the complete data package after every communication session.

The number of frames received and sent to radio.pw-sat.pl every day is presented in the plot below:

These numbers are really impressive. In summary, more than 260 000 frames were sent to us! Below, the list of all active Radio Amateurs is presented. Each one of you will get a memorial QLS card confirming the radio connection!

  1. SP5ULN 61208
  2. SQ5KTM 18354
  3. SP9MOA 18347
  4. SP7K 11753
  5. HA6NAB 10252
  6. OZ7JL 7793
  7. SP2ZIE 6111
  8. SQ2ODE 4413
  9. 161BD710 1386
  10. SQ5LAB 1331
  11. SQ2DK 796
  12. SQ3PMN 781
  13. SP9UOB 466
  1. SP1ATOM 451
  2. SQ9MUP 433
  3. SQ1FYB 288
  4. SP9HSQ 249
  5. R4UAB 163
  6. SQ3RPS 94
  7. OM3KAA 93
  8. N6RFM 77
  9. VK5EI 57
  10. K4KDR 51
  11. PS 50
  12. SQ3OOK 48
  13. SP9ACQ 39
  1. SP5MG 37
  2. SQ5KVS 35
  3. JACEK 31
  4. SQ3DHO 30
  5. SP8NCG 26
  6. SP3RNZ 23
  7. HE 16
  8. JO73FJ 14
  9. TEIKS 13
  10. SQ9SAT 10
  11. SP6RYD 10
  12. INIT2 9
  13. CS 5
  1. YB3MBN 6
  2. EA4GPZ 5
  3. SQ9KFZ 2
  4. SP9WPN 2
  5. SQ8BGR 1
  6. SP7RB 1
  7. W2RTV 1
  8. SQ3MQD 1
  9. SP3OSP 1
  10. AB 1
  11. JA0CAW 1

Congratulations SP5ULN and thank you for receiving a great number of frames every day!

Most received frames

SP5ULN

Main challenge – deorbit sail deployment

Initiation of the main experiment – deorbit sail – was scheduled for December 29, 2018. Lab tests have shown that the deployment process of  a 4 m^2 sail is very dynamic and can lead to a significant rotating motion. This posed a threat to the maintaining of the radio connection during the experiment, which was the only experiment with live transmitted data. This time, once again, we could count on the Radio Amateurs society! The deorbit sail deployment data (special frames named ‘sail exp’) were received by 17 Radio Amateurs.  7 of them collected the last frame sent after the sail deployment. Lucky Radio Amateurs are listed below:

  1. HA6NAB
  2. SP5ULN
  3. 161BD710
  4. SQ5LAB
  5. SP9MOA
  6. SP7K
  7. SQ9SAT

Special Task

Borg

The On-Board Computer team prepared a special task – an easter egg – which required not only good receiving equipment, but also some cleverness and ability to decode binary data. A day before the start of broadcasting the frames with the secret message, a hint how to decode it was posted on our Twitter:

1On December 15, during an evening traverse over Poland, the transmition of the easter egg frames was initiated – a so called periodic message.

The frames were received by:

  1. SP5ULN 15
  2. OZ7JL 8
  3. SQ5KTM 7
  4. SQ2ODE 4
  5. SP9MOA 4

We did not have to wait long for the decoding! K4KDR and Łukasz SQ5RWU shared their results on Twitter:

Photos decoding

We would like to congratulate Łukasz SQ5RWU, who managed to decode pictures from sent ‘file send’ type of frames. This task was extremely difficult – one picture can consist of 180 frames! He shared his results on his Twitter:

The future of PW-Sat2

Our simulations assumed that – shaded by the deorbit sail – solar panels will not generate enough power to keep PW-Sat2 operating constantly. However, the first month after the deorbit sail deployment shows that the current power budget is slightly positive, which means that PW-Sat2 is active and fully operative. It is planned to maintain the satellite in as good conditions as possible and continue our in-orbit experiments.

The satellite is broadcasting a beacon once a minute (BPSK 9600 bps), and even more frequently during every traverse over our ground stations. Bigger packages of data – hundreds of frames – are sent everyday during high evening traverses over Poland. You are still welcome to continue your activities! Current information for the Radio Amateurs and the software for signal decoding can be found at https://pw-sat.pl/en/information-for-radio-amateurs/ and https://github.com/PW-Sat2/HAMRadio/wiki.

radio.pw-sat.pl service

The telemetry received from the PW-Sat2 satellite by Radio Amateurs can be browsed and analyzed in a web application designed by SoftwareMill at radio.pw-sat.pl. SoftwareMill not only developed the application, but also takes care of its maintenance now. In the application, you can find some information about the crucial temperatures, the batteries’ charge level, the energy received from the solar panels and the state of the on-board computer and experiments. The data is also visualized in the form of graphs. Thank you so much, SoftwareMill!

Translated by Marcin Pulik, thanks a lot!