Altitude of UWE-4 since launch on December 27, 2018

The University Wuerzburg Experimental Satellite 4 (UWE-4) successfully used its propulsion system in order to conduct orbit control. The 1U CubeSat, developed and built at the Chair for Robotics and Telematics, is equipped with the electric propulsion system NanoFEEP which has been developed by TU Dresden.

Several manoeuvres have been performed within 11 days between June 23rd – July 3rd 2020 such that the altitude of the CubeSat was reduced by more than 100 m, compared to an average of 21 m with natural decay. This marks the first time in CubeSat history that a 1U CubeSat changed its orbit using an on-board propulsion system.

As chance would have it, the team of UWE-4 received a conjunction data message (CDM) in the morning of July 2nd 2020 from the United Air Force’s 18th Space Control Squadron. A conjunction of UWE-4 with a non-operational Iridium satellite (ID: 34147) in the morning of July 5th 2020 with a minimum range of about 800 m was a threat to the safety of UWE-4. An analysis has shown that the altitude of UWE-4 would already be below the Iridium satellite at the time of conjunction. Thus the on-going altitude lowering manoeuvre could only improve the situation and can be considered as a collision avoidance manoeuvre. No further CDMs have been issued regarding this possible conjunction. An analysis of the orbit of the two spacecraft after July 5th 2020 results in a closest approach of more than 6000 m.

Lowering the altitude of a spacecraft in low earth orbit (LEO) is equivalent to a reduction of its lifetime, since satellites in LEO usually burn up during re-entry due to the friction with the Earth’s atmosphere. Thus, this experiment is a concept demonstration of a de-orbiting manoeuvre shown at the smallest class of spacecraft in LEO. Today, there is no commitment to carry a propulsion system for spacecraft. However, due to the vastly increasing number of satellites in mega constellations such obligations are being discussed in the space agencies of several space faring countries. The experiment of UWE-4 presents a de-orbiting solution for the fraction of space debris of operational but unused satellites of today and for the mega constellations of tomorrow.

Stay tuned for more updates on UWE-4 and the upcoming launch of NetSat – a formation flying nano-satellite mission from our partner institute Center for Telematics which is expected to be launched September 2020!

Kind regards,

The UWE‑4 Team

UWE-4: First NanoFEEP thruster ignition
https://amsat-uk.org/2019/03/04/uwe-4-first-nanofeep-thruster-ignition/

UWE-4 435.600 MHz
http://www7.informatik.uni-wuerzburg.de/forschung/space-exploration/projects/uwe-4/

After two weeks in orbit, UWE-4 is in very good shape. The batteries are fully charged, the temperatures of the batteries, the outside panels and the MCU are all lying in the expected range.

The temperatures of the outside Panels of UWE‑4 on the first day after launch

UWE-4 battery temperatures and State-of-charge on the first day after launch

It can be seen, that the battery temperatures are slightly rising around 8:45 am, when the downlink of this measurement took place.

After the early orbit phase, we are looking forward to some interesting experiments with the attitude determination sensors and the propulsion system.

Unfortunately, our uplink success rate is very poor, which currently prevents these experiments. In the precursor mission UWE-3, it was found that the reason for this is very likely a substantial noise floor at the used frequency range. For this reason, we filed a request for the change of our radio frequency to 435.600 MHz with IARU, which has already been approved.

Today, we will start the procedure to change the frequency of UWE‑4. So if you want to track UWE-4, please adjust your center frequency accordingly. We already started the procedure to change the frequency on UWE‑4, so during the next days it may happen that you can also still receive a signal on our old frequency. Additionally, we have been assigned NORAD ID 43880 in the meantime.

A tool in order to upload the received UWE-4 telemetry directly into our groundstation database is at the moment work in progress and will be shared with you as soon as we have tested it thoroughly. Until then, we would be very grateful, if you’d forward your UWE-4 telemetry files to uwe4@informatik.uni-wuerzburg.de.

Kind regards,

The UWE‑4 Team

UWE-4 in the launch deployer

Last week our Team returned from the Vostochny Launch Site (Russia) where we performed the last check out tests of UWE-4 before launch on December 27, 2018.

The satellite will be launched through the German integrator ECM Space on a Soyuz-2 mission using a Fregat upper stage on December 27, 2018 at 02:07:18 UTC.

UWE-4 transportation to Far East of Russia was very smooth, so only a last software update and recharging of the batteries needed to be performed. By now, UWE-4 has been successfully integrated into the launch deployer followed by the integration with the upper stage, the fairing encapsulation will occur Thursday December 20.

In the meantime we updated our website to provide more detailed information about the orbit and the communication parameter including the beacon decoding information.

You can find all these and some more details here:
http://www7.informatik.uni-wuerzburg.de/forschung/space-exploration/projects/uwe-4/

As soon as we can provide the TLE, you will find them also on our website.

Kind regards,

The UWE‑4 Team