End of Life of the Nayif-1
At DopTrack, we listen to the radio transmission of many cube-sats. One in particular, The Nayif-1 (NORADID: 42017) had captured our attention. The onboard radio was claimed to be very stable and its transmission frequency could be used for tracking purposes. So, we decided to track that satellite and recorded its transmission every time it flew over Delft, since 2019. The transmission seems to be very consistent and strong and it gave use a great dataset to assess the quality of DopTrack.
 |
Recorded transmission frequency of the Nayif-1 satellite using the DopTrack station.
The onboard frequency of the satellite showed a small linear drift over the years. In the 3.5 years we tracked it, the transmission frequency increased 40 Hz. Furthermore it showed some seasonal change and morning and evening passes showed slightly different transmission frequencies, but the stability was much better compared to other cube-sats we tracked.
After the summer holiday, we noticed that the signal was not recorded anymore. Checking the ground station hardware and software for any mistakes. No, it seemed Nayif did not send anymore. From the NORAD, we have a rough estimation of the orbital elements of the satellite. For example we can track the average height and drag parameters. So, I plotted all TLE’s and looked at the orbital postion over time. NAYIF REENTRED! Due to the high solar activity, reflected in the BSTAR parameter of the TLE, Nayif-1 experienced a lot of atmospheric drag reducing the altitude of the orbit. This resulted in a reentry on the 18th of July 2023.
 |
TLE-based height and Bstar values of the Nayif-1 satellite over its entire lifetime. |
Quick search on the internet, we found out that it had reentered in the evening, roughly over North America. It seemed that the Nayif completely burned up in the atmosphere, because we could not find any posts on the location of reentry. We found the following post:
- On the AMSAT-UK website (https://amsat-uk.org/2023/07/19/eo-88-nayif-1-re-enters/): “The last frame of data was captured by David WB0IZO in New Mexico at 18:18:54 UTC showing the antenna temperatures operating about 40 degrees above normal.”
- The SatNOGS website (https://db.satnogs.org/satellite/SVPP-9764-1942-2462-5319#data) reports an even later recording by:
o CA-USA Fixed VHF-DM13kl | 2023-07-18 18:31:44 UTC |
o KK6OAK Oakwood School-CM97ec | 2023-07-18 18:31:00 UTC |
o KJ6DZB Ppi4 Ketchup-CM87uv | 2023-07-18 18:30:08 UTC |
o KK7NBH - Scottsdale, Arizona, USA-DM43an | 2023-07-18 18:30:07 UTC |
o ai6yr-skyscanner-DM04me | 2023-07-18 18:30:00 UTC |
Our last data of the satellite initially seemed to be on the 17th of July 21:30 UTC. The recording showed that Nayif was 57.9 seconds earlier than the TLE data predicted. After some more inspection of our database, we found that we had an even later recording of the pass on the 18th of July 11:04 UTC. The satellite then was 97.3 seconds earlier than the TLE predicted. Nayif would fly over Delft again at 21:04 UTC, but in that recording no signal was seen anymore. Nayif-1 reentered.
 |
Our last reception of the Nayif-1 Satellite over Delft |
It seems counter intuitive that the satellite would seem to fly faster than predicted while experiencing more drag. However, this is how cool the physics are and the astrodynamics. With a lower orbit, the orbital velocity increases and predictions will always underestimate the time of arrival. From our data it seemed that the mismatch between the TLE system started after the 16th of July:
- 16th of July 21:54 UTC: 5.0 seconds later than TLE
- 17th of July 10:04 UTC: 10.0 seconds earlier than TLE
- 17th of July 11:32 UTC: 13.3 seconds earlier than TLE
- 17th of July 21:34 UTC: 57.9 seconds earlier than TLE
- 18th of July 11:07 UTC: 97.3 seconds earlier than TLE
So, at around 18:00-19:00 UTC, the Nayif-1 satellite would have been flying several minutes ahead of the TLE orbit.
Close inspection of the received power of the transmitted signal of the Nayif-1 shows something interesting. The transmission signal seemed to have 20 seconds burst. Withing these 20 seconds power would go up to a maximum and then lower again to zero, and this would repeat over the whole signal. This was not seen in data around May. First we believed this was related to any type of data transmission, but in the last few days we saw the period of this characteristic transmission signal become smaller.
- 16th of July 21:54 UTC: period was 9 burst in 100 seconds
- 17th of July 10:04 UTC: period was 10 burst in 100 seconds
- 17th of July 11:32 UTC: period was 18 burst in 100 seconds
- 17th of July 21:34 UTC: period was 22 burst in 100 seconds
- 18th of July 11:07 UTC: period was 43 burst in 100 seconds
We now think that we were observing the satellite to be tumbling and due to the increased atmospheric drag by lowering the orbital altitude, the tumbling became more vigorous. The bursts of the transmission signal were because of the orientation of the antennas of the satellite. This is an idea we had, and would really like to see some independent data on this.
Has this rotation also been seen with other cube-sats? Would the Delfi-C3, which is going to reenter within a few weeks, also show something similar? Or would its elongated size (3U-sat), keep it from vigorous tumbling. We will keep track the cube-sats and learn more about their dynamic behaviour in space.
Reacties
Een reactie posten