UWE-3 News

23.05.2016 - UWE-3 Status Report

On 21st of May UWE-3 celebrated 2.5 years in space without any significant failures. Batteries, EPS, OBC and ADCS are fine, nevertheless we were confronted with a minor problem with one of the radios UWE-3 autonomously recovered from. Since then UWE-3 is in a very stable condition again. Some weeks ago we have re-initiated operations with UWE-3 on an interim basis. The goal is to test new magnetic control algorithms in space. Therefore we operate the satellite on the 436.395200 MHz frequency and perform data downloads from time to time. In the figure below the satellite’s rotation rate is shown for one of the experiments. The goal was to establish a rotation about the satellite’s X-axis (blue) at 10 deg/s while the Y/Z-axes should be at 0 deg/s. In general the desired rotation rate could be achieved but with major deviations from the setpoint. With the intention of optimizing the relevant control laws we will continue with these experiments within the next days and weeks.

 

 

During our experiments we received an outstanding support from the radio community from all over the world we are very thankful for. The received packets were instantaneous injected into our algorithms and delivered an important contribution to our research work. We would like to express our special thanks to DK3WN, PE0SAT, DL8MCO, EU1XX, ON4HF, Rainer, JA5BLZ, JA6PL, CU2JX, LU4EOU, JA1GDE, SP7THR, G7GQW, YC3BVG, JF1EUY, JE9PEL, JE1CVL, JO1PTD, ZL4JL, EA7ADI, K4KDR, JA0CAW, JH4XSY, PA2EON, SM0TGU. THANK YOU!

12.03.2015 - Software update of all subsystems

In the beginning of February 2015 we uploaded new software images for all UWE-3 subsystems to the satellite, which comprise in total 3 images on 9 micro-controllers. This software was installed thereafter and is since then successfully operational on UWE-3. The software update targeted major improvements for the attitude control of the satellite, which was the focus of tests right after the update.

The satellite now is back to a preliminary un-operated state (switching between the on-board computers every 4 days) while we process the data and decide on future operation plans. Thanks a lot for your great support! Especially we want to thank: CX8AF, DK3WN, EU1XX, G7GQW, IW0HLG, JA0CAW, JA1GDE, JA5BLZ, JA6PL, JE1CVL, JE9PEL, JO1PTD, LU4EOU, ON4HF, PE0SAT, R4UAB, Rainer Rothe, SP7THR, VK5HI.

02.02.2015 - Preliminary continuation of operations

Since the temporary end of UWE-3 operations two months ago we received great support from the HAM community all over the world observing the health state of our satellite. For this reason and this reason alone we can say today UWE-3 is still experiencing a very good health state with fully charge batteries in a safe temperature area.

Now, UWE-3 will be temporary operated during the next days and weeks, which will presumably also involve, at times, temporary changes of frequency between 437.385000 MHz and 436.395200 MHz.

We would especially appreciate the support of the HAM community during this period and we would like to thank you very much for your helpful support!

Sincerely yours,

UWE-3 Team

10.12.2014 - UWE-3 temporary end-of-operations

Today, more than one year after launch, there will be a temporary end-of-operations caused by the end of funding. However, UWE-3 is in a very good health condition with fully charged batteries and operations may be continued depending on future research plans.

Without any reception from ground, UWE-3 will carry out a warm reset every four days and switch regularly between the redundant on-board processors and radios. Therefore, UWE-3 will switch back to its nominal frequency of 437,385 MHz.

Nevertheless we appreciate the extensive support we received from the HAM amateurs in the past and hope that also in the future the status of UWE-3 will be monitored with your support, like you did so many times in the past year. Thank you so much for the very helpful cooperation in this respect!

The UWE-3 Team

08.10.2014 - UWE-3 In-Orbit Interference Analysis

From beginning of UWE-3 operations the downlink quality from the satellite to ground was excellent, showing high signal strengths even at low elevations. However, the telecommand uplink was initially difficult showing temporarily significant transmission failure rates. From beginning of 2014 the uplink quality degraded even further.

After excluding hardware problems from the list of potential failure sources it could be revealed that the uplink quality significantly depends on the location of the groundstation and the frequency used, due to local interferences on parts of the amateur radio spectrum. A change of uplink frequency could significantly improve operations. In beginning of June 2014 a software update has been uploaded to one of the redundant onboard-computers of UWE-3. Among other features, the update included several new experiments targeting the analyzation of the link quality. In order to further analyze the spatial distribution of in-situ interference levels for the whole amateur radio spectrum, an RSSI frequency sweep experiment has been implemented. The experiment allows to monitor and log measured RSSI noise levels while automatically scanning over a specified frequency range.

Several frequency sweeps have been recorded in third quarter of 2014, each lasting several days to ensure global coverage. The results discussed in the following base on measurements recorded between 06.08.2014 and 11.08.2014 and are representative for the observations made. The recording comprises more than 100.000 data points downloaded from the satellite in a 1.5 MB compressed data file.

 

Figure 1: Extract from the raw RSSI [dBm] measurements over time [UTC]

 

Figure 2: Orbit coverage of measurement recording.

 The downloaded measurements have been mapped to their instantaneous sub-satellite points. The recorded data points show sufficient coverage of the entire globe and can be properly used as a grid for spatial interpolation to generate a global interference map for each frequency under investigation. It can be seen that the average interference levels vary significantly with location and observed frequency. Especially orbital regions connected to central Europe seem to be affected significantly on a wider frequency band between 437.000 MHz and 437.600 MHz. 

 

Figure 3: RSSI [dBm] average interference world plot between 6.8.2014 and 11.8.2014.

The results reflect our experiences when operating UWE-3 during the first six month after launch. They further underline the importance of proper frequency selection for satellites using the radio amateur bands. Moreover, the results emphasize the requirement for in-orbit frequency re-configuration to be able to react to changes of inevitable global interferences caused for example by military space surveillance radars.

These and further results are published in: Busch, S., Bangert, P., Dombrovski, S., Schilling, K., UWE-3, In-Orbit Performance and Lessons Learned of a Modular and Flexible Satellite Bus for Future Picosatellite Formations, 65th International Astronautical Congress, Toronto, Canada, Online Reference: 14.B4.6B.6

04.06.2014 - UWE-3 software update in Space (copy 1)

This week we successfully updated the flight software on the On-Board-Computer (OBC) of UWE-3. The redundant OBC of UWE-3 is capable to receive, store and flash software-updates while the satellite itself stays fully functional. After transmitting the software to UWE-3 we flashed the redundant microcontroller via the JTAG EEM cross connection and toggled the satellite to the controller running the new software.

After the software update the redundant controller seamlessly continued operations, now with new features available. Extended functionalities include support for additional measurements and experiments as well as new beacon frames. 

21.05.2014 - Six Months in Space: Attitude Determination during Pass over Würzburg

Today we’re celebrating UWE-3 “Six months in Space” with a highlight created out of the on-board ADCS data recorded.

Already in January the satellite obtained a precise attitude determination after in-orbit calibration of the magnetometers. With this, we have now compiled a graphical demonstration of its movement during a pass over Wuerzburg. 

The video shows the satellite’s rotation in 8x time lapse, based on an attitude determination recording during which every 2 seconds the current estimated quaternions have been sampled. The satellite’s rotation is mainly about the Body Z axis, which is the axis in which the antennas are deployed and in which the main magnetic dipole is located. Visible is also minor jitter due to sensor noise inherent to the attitude determination process.

Please click on the picture below to download the video.

(The Video was created by use of the STK free software from AGI.)

13.05.2014 - New UWE-3 Telemetry Online Decoder

Since launch we received great support from radio amateurs all around the world, which sent us beacon files via e-mail or uploaded them to our ftp-server. More than 6.000 Beacon frames have been collected from the radio amateur community, growing daily.

Yesterday we harmonized all the received beacon files online with support of Mike Rupprecht (DK3WN) by use of his new UWE-3 Telemetry Online Decoder software with online capabilities. As a result of the test period of the last weeks we decided to turn off our ftp-server and we would like to ask you to use the new online feature of the decoder software which can be downloaded here: www.dk3wn.info/software.shtml

Please setup your call sign and QTH in the ini-file before you use it. With this information you can see an actual statistic of the received beacons here: 213.188.119.203/query.html

As an upcoming event we will celebrate UWE-3 six months in space next week.

04.04.2014 - Transmission tests – no beacons

Beginning next week UWE-3 will not continuously transmit beacons due to transmission tests. We will inform you once the tests are completed.

17.03.2014 - UWE-3 Expected toggle of the microcontroller

Today UWE-3 switched to the redundant micro controller as a precautionary measure after 67 days without interruption. At the weekend we had a storm warning for the city of Würzburg, so the antennas have been down for several days. Without any contact to the ground segment, UWE-3 switched during the morning hours of March 17 to the redundant microcontroller purely as precautionary measure. The current weather conditions are back to normal and we have already re-established contact to UWE-3 successfully.


Antenna tower at the roof of the informatics building.

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