Weeks 46-49:

SwissCube is still doing well and alive. Over the last weeks, we have had several passes with lots of data and several passes with no data at all (besides the beacon). The satellite has experienced a few resets (5 since launch), which can be expected. That did not impact its functioning.

One newly involved student, Angelo, has been performing radiation tests at the Paul Scherrer Institute, in Villigen Switzerland, on the MSP 430 microcontroller. He could characterize its performance compared to ARM type controllers. Quite interesting... we are impatiently waiting for his report. We will post it as soon as possible.

Coming back to Swisscube, it is still rotating very fast, which prevents us from taking pictures. Leaving it alone, its rotation is actually decreasing, as can be seen in the attachment (thanks Anton!). The data seen in the graph comes from the analysis of the RF signal. If SwissCube keeps the same slowing rate, we should be able to start the bdot controller onboard by the end of January.

For those interested in the daily activities, you can check the live data received from the satellite on: swisscube-live.ch

9 Nov:

Over the week-end of Oct. 24-25, the satellite's attitude control system experienced a "reset" of the microcontroller. The satellite has one microcontroller per subsystem (power, communication, payload...), but only the attitude control one was reset, which leads to think that some external event happened. That behavior had never been seen during the tests.

The satellite's communication still works well, as all its subsystems. We experienced communication difficulties due to some software anomalies on the ground and also due to the spinning of the satellite. We are currently resolving the ground software anomalies (related to the uplink TNC). Both the EPFL and the Fribourg ground stations are used for uplink and downlink of the data. We are also seeing perturbations on the I2C data bus aboard the satellite, also never seen during tests. But they do not prevent us from talking to the satellite. We are investigating the reasons.

Our efforts to understand the rotation rates of the satellite are making progress. The new students working on it are improving models and getting close to making predictions. One of the students made an Antenna Deployment Test in air, which shows that we do have a residual rotation after deployment. Further testing will be done in vacuum next semester at the EPFL LCSM laboratory. You will be able to see one video of the deployment tests on the SwissCube main website. (See here) Although this does not totally explain the initial high rotation rates, and although it is very counter-physical, it is one potential explanation . We will be investigating another reason with additional tests at DTU (Denmark Technical University) with measurements of the residual magnetic dipole of the satellite.

We also had a discussion with the Radio Amateurs of Vaud to share our understanding and findings about the high rotation rates. Quite a few radio-amateurs are proposing very good explanations and solutions to this high rotation. Work is still in progress and we still have a few weeks of work before implementing a detumbling (de-spinning) procedure.

We really want to thank all the Radio-Amateurs in the world sending us very valuable data every day. They allow us to check that the satellite is still in good health, and also participate in our understanding of the behavior of the satellite when it is far away from Switzerland.

28 Oct:

The satellite is still in very good health, all subsystems send green housekeeping data. The operations still concentrate on explaining the high rotation rates seen after launch and the strategy for slowing it down (call detumbling). Most of the new students in the operations team are now analyzing the data and trying to understand the rotation from the RF signature and other housekeeping parameters (like temperatures, current in the solar cells). But this task is not easy as the rotation rates (200-400 deg/s) are higher than the sampling rates for the sensors on-board. It is a tricky problem, but this makes it even more motivating! In this matter, we are getting help from the Radio-Amateurs around the world and from other universities in Europe. As soon as the satellite is more stable, we will start taking pictures.

One student performed antenna deployment tests, which tend to confirm that it could be the cause of the high rates in the Y-axis, but we are still investigating why we experienced high rates in the X-axis as well.The ground stations are now being used daily and we are trying to improve them as we go along. Commanding and reception on satellite data is done from both ground station (HES-Fribourg and EPFL).