News

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SFZ Trittau flies high, gets lost and found

The launch was at 11o’clock on Wednesday, July 9. But where did this weatherballoon go? After the balloon burst, there were no more signals coming from the SPOT satellite radio GPS tracker.

Until the the next morning (Thursday), when both GPS trackers of the probe sent coordinates, in agreement. That is the last, southernmost point of the track above. The predicted landing sites is way further south, near Munster.

Stay tuned for the news when the young scientists from Trittau retrieve the probe from the trees near Hanstedt on Friday. The red marker in the aerial map below marks the landing site.

My guess: The balloon popped but did not separate from the probe. The lump of latex dragged the probe downwards like a stone. The trackers were tumbling upside down, not able to transmit to the satellite network. The probe crashed into the trees and came to rest in an unfavorable location and/or orientation.

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SPOT cleared the Elbe

Our satellite radio GPS tracker again flew on a weather balloon mission. This time, it crossed the river Elbe and landed on a tree close to the highway A1. The students from Holstenschule Neumünster managed to reclain the payload. And then, the SPOT tracker got stuck in a traffic jam, on the way back north on A7 before the tunnel underneath the river.

Bottom: Flight path prediction, GPX track, color code is elevation. Top: SPOT map and Aerial of the landing site, elevation and horizontal speed versus time.

The GPS in the tracker is made for use on ground level. Above a height of 10km the algorithms were working only by chance. The elevation data in the exported GPX track is missing the most significant digits above 9999km. Those values were fixed with a text editor, for the images above.

After recovery of the probe, we analyse the data stored on SD-cards. The STROTO-MINI datalogger provides GPS, including heights up to 50km, and the temperature inside the probe.

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Made in Kiel #4

Last Monday, we had the opportunity to give a talk as part of the “Made in Kiel” lecture series, organized by the Hermann Ehlers Akademie. Ava and Hannes talked about CHAOS and its journey through the BEXUS student programme. Together with Pierre, they engaged in an insightful discussion with the audience after the talk. The conversation went beyond our scientific work, touching also on the political dimensions of conducting research in today’s challenging times.

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IPR-day with ZARM

Today we had two special visitors from ZARM (Center of Applied Space Technology and Microgravity) in Bremen – Dr. Merle Cornelius and Florian Leu – since it was time for our IPR (Integrational Progress Review).

Once they arrived, we quickly introduced ourselves and then headed straight to the lab. Since the ground station is finally set-up to communicate with SETH and receive data, we jumped right into a measurement with SETH – thus we demonstrated that SETH does measurements autonomously and automatic.

After that, it was time for our presentation. We talked about time management, gave a quick recap on mechanics and electronics, shared some updates on the software, and walked through our verification tests. And also: it was the debut of our outreach team (YAY!).

Next, we got some helpful feedback on our SED and discussed a few changes. Then we went back to the lab to take a closer look at the experiment (and took the photo above!). Since we had our guests with us, we also showed off our 3D printer – doing its printing – which was cool because several of our components are 3D-printed.

To wrap things up, we disassembled SETH as planned anyway. We’ve had a bit of noise in the data, so it needs fixing – nothing too dramatic, but still important.

After a full day at the University in Kiel, we said goodbye to our guests and are now looking ahead to the EAR in Bremen this September.
(But first… we have to make it through exam period. Wish us luck!)

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SETH slice 1 First Light

The first slices of the SETH sensor head is fully integrated and operational.

One of two big BGO scintillators is mounted. Below the BGO is the HET-AB double SSD stack. On the top is one layer of trigger SSDs, 20 Hamamatsu photodiodes, 1×2cm² each. The electronics for the other slice is connected and operational, but kept outside the box without sensors, for now.

Energy deposition spectra of all slice 1 channels.

The first night of data is in, cosmic muons penetrating the sensor, and a pulser generating a calibration charge pulse (200fC) into the preamplifiers once per second.

On the left you see the energy loss spectra of the cosmic muons. The muons loose about 100keV energy with a path length of 300µm in silicon. The resulting charge signal is around 4fC, or 25000 electrons.

The BGO is 20mm thick, resulting in minimally ionizing energy loss of 19MeV. The emitted scintillation photons are collected by six photodiodes, connected to three preamplifiers, giving larger peak height, due to the enormous size of the BGO.

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Congrats, Nicolas!!!

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!

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Frog’s First Fitting

After the CDR, we decided to revise the design of the photodiode holder so that it could be 3D-printed as a single piece. This change simplified the assembly process and improved the structural integrity.

We completed the first assembly and fit check of the sensor head – a big milestone for the team! The 3D-printed parts fit together nicely overall. May we present the SETH frog 🐸

However, we did have to slightly enlarge the holes on the “front feet” to make it work properly.

Next up: we’ll need to reopen the shells (the silver parts that hold our crystals) to solder the coaxial cables to the photodiodes, which are glued onto the BGO crytals. Step by step, it’s all coming together!

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CHAOS at CERN!

Some impressions from CHAOS’s trip to CERN. We got the chance to perform measurements in the CERF radiation field which is supposed to recreate the radiation environment at commercial flight altitudes. Although there were some problems with the particle beam which is used to create the radiation field, we were finally able to take our measurements during the final night of our stay. Now, we are looking forward to evaluate the data.

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Goodbye, CDR!

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.

Nicolas, Milan and Niklas posing outside the review room

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.

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CHAOS haunts SETH on their way to CDR

Spirits are high in the last train of the day (symbolic picture)

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.