This Sunday afternoon we (namely Ava, Pierre and Hannes) started our journey to the selection workshop in Bonn. During the next two days we are going to meet the other candidates for the next BEXUS and REXUS cycles at the German Aerospace Center. It is planned that we hold a talk to present our proposed instrument CHAOS. After the selection workshop the final decision on which experiments can take part in BEXUS will be made by a board of experts and announced on 18th December. We did some last adjustments to our talk while sitting on the train and are looking forward to the selection workshop.
CHAOS has been selected to be presented at the selection workshop for the 15th BEXUS cycle from 27th November to 28th November 2023 in Bonn. We are happy about this great opportunity and will keep you updated. After the selection workshop the final decision on which experiments will have the chance to take part in BEXUS will be made.
In today’s meeting we discussed the final version of our Experiment Proposal for the upcoming BEXUS cycle. After some minor adjustments, we submitted our application to the DLR. Now, we are hoping for a positive response. If we are invited, we will attend the DLR Selection Workshop on November 27th and 28th. Stay tuned for further information on our instrument CHAOS.
The balloon flight of CHAOSjunior was a total success. We were able to recover our instrument near Neubrandenburg and recorded a lot of useful data.
After the launch of the balloon at around 11:45 am we met up at the university and started to follow the balloon by car. The predictions said our balloon would land in Mecklenburg-Western Pomerania, so we started in the direction of Rostock. Unfortunately, the tracker did not work properly. At around 02:25 pm we recieved a message from the balloon while it was already sinking with an altitude of around 10 km. But this was the only message we recieved. The tracker stopped sending and we already started worrying. After not hearing from the ballon for a while, we decided to make a short break. After some snacks we decided to wait for another 30 minutes before driving home. But then the tracker sent a sign of life at 03:20 pm. The coordinates were 53.671600, 13.448170 with an altitude of 53 m. We concluded that CHAOSjunior landed at these coordinates and continued our journey. The tracker led us to a small forest near Neubrandenburg where we did not have to search for long. After crossing a small dried-up river we found CHAOSjunior hanging in a tree. Recovering the instrument was very easy because it hang in a height of around 1.5 m. At 04:37 pm we reported the successful recovery of CHAOSjunior back to Kiel. Back at the car we saved the recorded data and started our journey back home. At around 09:00 pm we were back at the Physikzentrum.
We were already able to evaluate some of the recoreded data.
This is the route which CHAOSjunior took. It fits pretty well to the predictions. The ballon reached a height of 40 km near Tessin were it burst and started descending.
Here we can see the temperature and pressure curves of the internal (1) and external (2) sensors of the probe. The pressure decreased in higher altitudes and started rising again after the balloon burst.
Furthermore, we took a first look at the measurements of CHAOSjunior. In this fish plot muons and helium are visible. Further explanations and investigations of the data will be added to the CHAOSjunior subpage.
But one of the most stunning things are the photos which our onboard camera recorded. Just take a look at these pictures of Kiel and our earth.
The only thing left to do is to say thank you. Thanks to the Department of Extraterrestrial Physics at Kiel University and “Highlights der Physik” for the help. And thank you to all members of our CHAOS team who worked on CHAOSjunior.
Visit our Instagram channel @chaos.bexus to see more of our recovery mission. More information on CHAOSjunior and the analysis of our data will be added to the corresponding subpage.
We successfully launched a weatherballon with our instrument CHAOSjunior as part of “Highlights der Physik”, a science festival taking place in Kiel. The clear blue sky allowed a launch at around 11:45 am. Many spectators followed the launch and interesting questions were asked, especially by kids. We even had a send-off by a friend and colleague from the Department of Extraterrestrial Physics who accompanied our ballon with his plane. He took the pictures of the balloon from the air. Currently, we are on our way to Rostock to recover CHAOSjunior. Stay tuned for further information on CHAOSjunior and visit our social media channels and the channels of “Highlights der Physik”.
Es sieht hoffnungsvoll aus, daß wir am Samstag Mittag starten können. Die Wettermodelle sagen etwas blauen Himmel voraus und eine Landung zwischen Rostock und Stettin.
Gezeigt sind die Landeorte je nach Startzeitpunkt. Angefangen heute um 7 Uhr, wenn die Landung noch mitten in der Ostsee passieren würde, wie während der ganzen letzten Woche. Die eingezeichneten Flugrouten sind für Starts um 12 Uhr am Samstag. Einmal links, für einen kurzen Flug, wenn der Ballon sehr früh platzen sollte, schnell aufsteigt, und der Fallschirm verheddert kaum Wirkung zeigt. Zum anderen rechts, wie die meisten Flüge bisher verlaufen sind, der Ballon platzt unerwartet spät in 40km Höhe.
Morgen, am Samstag werden um 10 Uhr die Startvorbereitungen auf dem Rathausplatz beginnen. Der Start sollte dann zwischen 12 und 13 Uhr passieren, sobald genug blauer Himmel zu sehen ist und die Flugsicherung die Starterlaubnis erteilt.
Diese Sonde mit Fallschirm sollen fliegen. Darin ist ein Instrument zur Messung primärer und sekundärer kosmischer Strahlung.
Last Wednesday, September 6, the Ricarda-Huch-Schule in Kiel launched their third Weatherballon mission.
And just as with the last two missions, this mission ended in the water as well. We filled an extra large volume of Helium into the balloon, 93bar×50l, to make sure it would rise fast and burst early, to safely land close to Oldenburg in Holstein.
That was the prediction. We reached 5m/s rise speed, but the balloon burst at 40.7km height, five kilometers higher than predicted. The real flight dropped our sensor box about six nautical miles east of Dahme.
Of course, we did not know about that at first. We spend the time waiting for the GPS trackers to come in range in an ice cream cafe in Lensahn. When the satellite radio tracker finally send the first messages descending into GPS range below 10km height, we got the first idea that the track may be way to far east. The message after touchdown confirmed that. The satellite radio tracker did not send further messages, because the box was floating at very low speed that did not trigger the motion alert. Anyhow, we went to Grömitz and hired a boat to look for it. The boat with one teacher and three pupils returned empty handed after more than five hours.
The next morning, we got a scheduled daily message from the tracker, the box drifted north over night. Shall we make a hike along the beaches from Dahme to Großenbrode? No, the next morning the box reached the Fehmarn Belt and set of to continue through the Store Belt. But here the currents were so fast, that we got new positions every five minutes. Another boat was put behind a car, went to Fehmarn, launched into the water and picked the box out of the water.
What did we find inside the box? The electronics was mostly destroyed by some salty water and the voltages still applied. The SDcards of the video camera and the primary payload, an Arduino reading the pulses from a Geiger-Müller counter, were readable. But the Arduino stopped working properly before the balloon launched. There was no data except for an hour before launch. The raw video awaits processing and compression. The STRATO3 datalogger is in very bad shape. Its SDcard is very exposed and the contacts were eroded. Two contacts were gone. But that has never been a problem in the past. We scratched the plastic a little, exposed all contacts, and soldered an adapter to the card, that could be inserted into an SDcard reader. The data was fully recovered, covering the whole flight. That is how we know where our balloon was flying. The datalogger has a specially hacked GPS chip, that works up to a height of 50km.
The pressure data shows a very remarkable feature. At a height between 20km and 30km the pressure did not fall monotonically. There were strange fluctuations. Seen here in purple, with the battery voltage in yellow, and inside (green) and outside (blue) temperatures.
Looking at the GPS data, the strange fluctuations happened while the balloon was tumbling around the Bungsberg, the highest mountain of Schleswig-Holstein, at 168m.
So, what happened to the first two missions? The first mission landed sixty nautical miles west of Rømø. The balloon did not burst at all when it arrived at 40km height. It was floating at that height for another hour before it finally burst. It was found after a month by two girls in Sweden. All SDcards were readable in the end.
The second mission dropped down one nautical mile east of Schleimünde. We went to Maasholm, found a boat and recovered the box after a few hours. The video coverage was complete and showed how the crew of a sailing boat found the box, looked at it and put it back into the water. The big letters on the box read: “Safe Scientific Experiment”. The small print talked about recovery and phone numbers. The crew was afraid to disturb important measurements. The datalogger SDcard failed. The datalogger was later fixed. It turned out that a regulator was damaged by corrosion and put the full battery voltage to the SDcard, instead of a much lower supply voltage.
The sensor head for the CHAOS-Junior weatherballon mission was put in the styrofoam box. The area was made light tight with black ducttape. The CPU of the Raspberry Pi Zero and the FPGA of the RPiRENA DAQ board were glued to copper bands that extend through the styrofoam, where another copper foil was placed outside. The copper bands were fixed with copper tape and covered with a second surface mirror foil used for space missions. That foil emits heat radiation but reflects sunlight. Two GPS trackers and a battery box were placed in the box. One of the GPS trackers sends the NMEA messages to the serial port of the Raspberry Pi (via the FPGA), to be recorded in the data file. A STRATO3 datalogger will be added. Maybe we will find a camera to add as well. The Raspberry Pi is online.
CHAOSjunior is a reduced version of the CHOAS experiment. The sensor head consists of a scintillator of Bismuth Germate Oxide (BGO) and two silicon detectors taken from High Energy Telecope (HET-B) in front of and behind the BGO. Two photodiodes were glued on the hexagonal BGO at opposite sides. The energy deposited in the detectors is proportional to the signals from the detectors. During configuration, the calibration parameter is determined. For this purpose a radioactive source of bismuth isotope 207 Bi is used. The characteristic lines of this source are known relatively precisely and can therefore be used for the calibration. First, the calibration of the HET-B detectors was carried out without BGO. The calculation of the channel names was chosen in following way. CHAOSjunior basically consists of three detectors, one HET-B, the BGO and another HET-B. These are named A,B and C in the direction of particle pass through. The information from the BGO (B) is shared between two channels. These are designated B1 and B2. The two HET-B detectors have only one channel each, these are designated AA and CC respectively. For calibration of preampfilters the sensor units were stimulated by a radioactive source of bismuth isotope 207 Bi. This isotope was placed in front of the sensor head. The prominent emission lines were taken from NUDAT3 (https://www.nndc.bnl.gov/nudat3/ ). The Compton effect of the γ lines at 569.698 keV and 1060 keV could be well observed for both HET-B signals where the first edge is much more precise. The data recorded was adapted by three models, one for the x-ray peaks and one for each Compton-edge. The models deliver the noise s and the calibration parameters u, which allow the conversion of the signals into keV.
For a Weatherballoon mission lead by the Ricarda-Huch-Schule we prepared and tested a Geiger-Müller Counter module. The challenge is to operate the high voltage supply of the tube in the partial vacuum of the stratosphere. We may encounter a Corona discharge, which may destroy the electronics or at least impact the measurements. We are all happy to leave Corona behind us. The second issue is the internal pressure of the tube. We passed all tests. Down to 1mbar pressure the unit worked flawlessly.
First, the tube was tested individually. It survived low pressure. The HV was calibrated to 400V as prescribed in the manual. Then we removed the calibration connecter and a power connector that were too close to the HV electrode of the tube. The board was coated twice with a space grade 2-component silicone encapsulant, in particular the HV supply and the area close to the HV end of the tube. We obtained an insulation distance of about 4cm.
The Paschen Curve tells us that we should be good down to a few mbar.
First, we tested in a glas chamber, to visually observe the test. But that pump could not go below 60mbar. Then we used our regular thermal vacuum test stand for balloon missions, shown above. The test was performed at room temperature. We used only the rough vacuum pump, which took the chamber pressure down to 1mbar. The output of the module was monitored with an oscilloscope. A ²⁰⁷Bi souce was place inside the chamber to increase the counting activity. It worked well. Unfortunately, we did not take any pictures.
Vio did the coating, see the log sheet above. Ronja soldered the feedthrough harness and performed the Vaccum tests. Sönke observed radiation safety. Matti provided the counter module.
Now we are waiting for the flight forecasts to predict a landing site on land.
