BEXUS Projects of Kiel University
SETH – CHAOS – FaNS – TANOS – ADAM – PING – FRED
We’re excited to announce that Nicolas, our team lead, has officially submitted his Bachelor’s thesis titled “Implementation of the Attitude Determination System (ADS) of the Scintillation Event Triggering Hodoscope (SETH).”
His work on the ADS will play a crucial role in advancing the SETH project. Congratulations from the whole team, Nicolas — we’re proud of your dedication and hard work!
Yesterday, on May 15th 2025, we had our Critical Design Review. After 20 minutes of information packed presentation by us we had a discussion about our design, requirements and general SED content.
During the presentation we showed around our preamplifier, ADC and NMRENA boards which represent the signal flow from the detector to the SD Card. We also presented the wrapped BGO scintillation crystal in its holder, complete with the mounting mechanism of the photodiodes that go on top and below the BGO holder. Here, the board gave some input on possible design improvements for easier and more light-weight fabication and mounting. After the review the experts said that they were happy to see the progress we made in real life instead of just pictures on a slide.
The board critisised our thermal design requesting more information and more calculations. However the overall progress of the project seemed to be satisfactory for the reviewers and we get to go ahead with finishing up fabrication and moving on to sub-system wise integrating and testing of our parts.
Today it’s time to say “Goodbye, CDR!” and head home. We are set to arrive in Kiel at 17:22 after traveling via Amsterdam and Osnabrück.
Today is the day that team SETH is set to join up in Leiden, near ESA’s ESTEC facility in Nordwijk!
The route from Kiel to Leiden should only take about 7h20 by train. However with a signal failure and damage to the overhead line in Hamburg and a cancelled train from Osnabrück to Amsterdam, the journey is all but straight forward. After getting off in Osnabrück HBF at short notice, we caught a local train to Hengelo. The Netherlands welcomed us by canceling the next few stops of our newly made up route due to an broken train on the track.
After checking the next options, we chose an Intercity train going to Amsterdam and connecting to an IC heading to Vlissingen via Leiden Centraal! We arrived in Amsterdam with a delay of about 25 minutes, missing this train.
Thankfuly there was another train departing for Rotterdam over Leiden. With a total travel time of 10 hours and 10 minutes we will finally make it to our destination at 19:13.
The next Review on our journey is the Critical Design Review, or CDR for short, from 14th May to 17th May. There, the reviewers will critically review the proposed design. After the Preliminary Design Review (PDR) in February, this is the second and last of the two design reviews.
We have submitted the second version of the Student Experiment Documentation (SED) for the review and will give a 20-minute presentation on the changes we have made since the last review.
Once this review is approved (fingers crossed), we will receive the official go-ahead to begin manufacturing all parts. We will start with single-part testing before gradually integrating and building more complex sub-groups and sub-functions. Each will be tested until the Integration Progress Review (IPR), where the initial functionality will be assessed by the reviewers visiting our institute.
The next extraterrestrial BEXUS project SETH shall include a new module called SETHAT, to measure the magnetic and gravity field vectors. Of course, this needs to be tested on a weatherballoon mission. The launch was scheduled on Tuesday, April 1st, 11 o’clock, after we watched the forecasts for weeks, while the landing was firmly predicted in the baltic sea between Gdańsk and Malmö. Now, it would land between Rendsburg and Hohenwestedt, safely right in middle of Schleswig-Holstein, with a clear blue sky.
Prediction for a launch on 11:00 CEST from Kiel: Red dot: launch position, green dot Landing, balloon pops at 40km: explosion.
At 10 o’clock the press arrived to follow the launch preparations. The reporters were underwhelmed by the crowd of three students and one graybeard. But then, unexpectedly, Matti and his Nawi class came along, from the Ricarda-Huch-Schule. The crowd was there, and the class was immediately put to work. Inflating the balloon, calculating and watching the Helium pressure, giding the payload gondola. But the graybeard (me) immediately recognized the bad omen, that Matti’s arrivals induced: all three of Matti’s own Balloons landed off shore.
Matti’s students did a good job, though, the liftoff on 10:42 was prefect.
The Helium bottle went back into storage, we had a quick lunch, and soon where on the road to Schachtholm airport, close to the Breiholz ferry. We got a coffee and some icecream, waiting for the balloon to land on the runway in front of us. In any case, we could quickly get to either side of the canal.
The satellite tracker provides positions of our balloon every five minutes. It went to Wischhafen, a little further south than expected, but quickly came back north and turned west heading straight to the airport where we were sitting, almost exactly as expected. Even after the balloon popped, the satellite tracker was still providing positions, from heights up to 40km. Usually, there are no GPS solutions above a height of 20km from those surface trackers.
And those positions were rapidly going south, much faster than the forcasts predicted. Soon, we realized that it would land south of the river. Overhead of the Elbe, our box was still four kilometers high in the sky, … and then it turned west. It came down right in the water, close to Neufeld.
We were on the way to the ferry in Glückstadt, when we turned around towards Brunsbüttel and Neufeld. There was only one boat in the harbour, belonging to Hafenmeister Hein Claußen. We got on bord, heading towards the last coordinates submitted by the satellite tracker.
In the beautifull weather it was no problem at all to spot the payload of our mission.
The parachute was full of sand, serving as an anchor. The box was very slowly drifting towards Hamburg with the tide. The anchor kept the box upside down, the custom payload electronics on the bottom of the box was held high above the water line. It turned out that is it still fully functional.
The avionics (SIM trackers, datalogger, video camera) are all corroded beyond repair. Salty water and with the batteries still connected quickly destroyed those units. Only the watertight satellite tracker survived unscratched.
All three storage cards in the gondola were recovered and are readable. We have video from launch and until the battery run out at 35 km height. The card from the datalogger provides pressure, temperatures, further environmental data, and precise GPS coordinates. The later are the source of the flight track shown above. The SD-card in the Raspberry Pi bord computer faithfully recored the output of the SETH Attitude sensor, the 3Diodes cosmic ray detector and furher environmental data.
The mission is a full success.
Outside temperature got as low as -50°C. The electronics stayed above 0°C. The sensor temperature is shown here with a wrong calibration. The battery voltage was good until the end. When the pressure reached 800mbar on descent, the unit turned itself off, to protect the electronics against fatal transients on impact. The storage cards are particularly sensitive to transient power disconnections .
The comic ray count rates are highest at around 50 to 80mbar. This is called the Regener-Pfotzer maximum. (This pressure sensor is not rated for pressures below 10 mbar.) The colors denote various trigger conditions. The yellow line is the overall trigger rate.
The pulse height spectra for the whole mission. Each detector diode (A, B, and C) individually count about the same number of hits, with a broad spectrum due to variable path lengths in the sensitive volume. Coincidences for vertically aligned diodes A and B show a narrow sprectrum (blue line, purple dots), due to the contrained path lengths. Coincidences for diodes A and C (red line, green dots) detect particles from a zenith angle around 45°. The path lengths are longer, the spectrum is shifted to larger energy deposits. The projected area is smaller and the flux from that angle may be different. The dependence of the flux on the zenith angle depends on the height, which is not resolved in this picture.
Check out the press release on the offical website of Kiel University covering the upcoming launch campaign in Kiruna, Sweden:
https://www.uni-kiel.de/de/detailansicht/news/147-bexus-wetterballon
From 15th to 17th May 2024, we went to ESTEC (European Space Research and Technology Centre) in Noordwijk, Netherlands. There we had our CDR (Critical Design Review). Again, we presented progress we made on our experiment to the review board, which was made up of experts from DLR, ESA, ZARM and SSC. Even though the board had some useful comments and tips for us, we passed the review, and our experiment design was accepted. Now, we can focus all our efforts on integrating the CHAOS instrument. The next milestone will be the IPR (Integration Progress Review) at the end of July. Two experts from ZARM will visit us in Kiel and inspect the integration process.
Although it was an exhausting couple of days, we had a lot of fun in the Netherlands and used the time to explore the cities of Leiden and Amsterdam. Stay tuned for more information on CHAOS!
CHAOS has successfully started into the year 2024. The next big milestone on our journey is the Preliminary Design Review (PDR) in Kiruna, Sweden at the beginning of February. At the PDR we will present the current status of our experiment design. But first, we have to hand in our first version of the SED (Students Experiment Documentation) at the end of January. This document includes all relevant information regarding our experiment. Currently, we are finalizing the design of CHAOS to include it in the SED and present it at the PDR. It is a lot of work but also a lot of fun. We have been told that it might be cold in Kiruna, but the polar lights make up for it. Therefore, the work will be definitely worth it. Stay tuned for more information on CHAOS and our journey to Sweden.
CHAOS has been selected for the 15th cycle of the BEXUS program! The next step of our journey will be the Preliminary Design Review (PDR) in February next year in Kiruna, Sweden, where we will be presenting the current status of our experiment. The final flight will take place next fall, also in the Esrange Space Center in Kiruna.
Thank you @germanaerospacecenter for selecting our experiment, we are very excited about this opportunity!
The selection workshop is over and we are on the train back to Kiel. We had two days with lots of new impressions and experiences at DLR in Bonn.
We arrived in Bonn on late Sunday evening. On Monday morning the workshop started with a general introduction to the BEXUS program. After that the invited teams presented their proposed experiments. Each team held a presentation of about 25 minutes followed by a discussion between the presenting team, the board of experts and the other teams. There were a total of three teams proposing an experiment for BEXUS and five teams proposing an instrument for the REXUS program. Our presentation of our proposed instrument CHAOS was the second talk of the day. Even though we were a little bit nervous, our talk went very well. The board of experts had some questions about our experiment design and scientific goals but we believe we could give satisfying answers. We were especially happy about the positive feedback which we got from the other applying teams. We ended the day with the other teams going out for burgers and visiting the Christmas market. Today the last three teams presented their experiments and we got some more information on what to expect from the BEXUS program and the further schedule. The workshop ended at noon with the board of experts starting to discuss which experiments they want to accept. The final decisions will be announced until 18th December. We had some time left before we had to catch our train, so we had lunch with the team SHAMA from STAR Dresden and in Cologne we took the chance for a picture at Cologne Cathedral.
One of the cool things during the workshop was meeting the other student teams. We were introduced to many promising experiments and it was especially interesting to see students from other fields than ours proposing ideas. We as physicists were forced to think outside the box. There were two teams focussing on the behaviour of liquids in microgravity which is particularily interesting for the fuel tanks of rockets and satellites. Another experiment wants to look at the effects of the conditions in the stratosphere on oxygen producing bacteria. But these are only a few examples.
The selection workshop was a lot of fun and we hope we get the chance to take the next steps in the BEXUS program. We are looking forward to potentially meeting the other teams again (Jay, I still owe you a drink). You can find more pictures and stories covering our journey on our instagram channel. There we will keep you updated on everything related to CHAOS, just as in this blog.
