There are couple of things on my bucket list in regards to weather probes. One entry is the hunt of a night probe. The prediction did not look bad and placed the landing zone of the night probe near Besigheim about 50 km North of Stuttgart. I teamed up with Claus, a colleague of mine.
We meet at around 2 AM near the train station of Bietigheim-Bissingen and readied the gear. At 2:25 h the balloon burst and the probe came down with close to 360 km/h. The first prediction estimated the landing position north of Bietigheim-Bissingen in Hofen. We entered “Hofen” into the navigator and Claus started driving while I kept an eye on the electronics. About 10 Minutes later, we realized that we were going into the wrong direction. By now, the prediction had shifted to Metterzimmern. We turn around. Once we were back in Bietigheim-Bissingen, we lost the signal of the probe. The last telemetry indicated a final descent speed of 20 m/s which is pretty high even if the parachute has not opened. Also the initial speed directly after the burst of the balloon had be unusually high with close to 100 m/s. The descent had taken only around 15 minutes — normally it takes about 30 minutes for the probe to plunge through the atmosphere. Somewhat pessimistic that the probe would have survived the impact we drove the Metterzimmern.
Telemetry short before the parachute burst:
[ 7557] (N3430076) Sa 2018-04-21 00:25:09.000 lat: 48.93757 lon: 9.09270 alt: 33665.07 vH: 8.6 D: 70.1° vV: 6.1 # [00000]
Last Telemetry:
[ 8394] (N3430076) Sa 2018-04-21 00:39:06.000 lat: 48.96407 lon: 9.10132 alt: 1822.34 vH: 4.5 D: 71.6° vV: -20.3 # [00000]
10 minutes later, we arrived in Metterzimmern. To our astonishment, we received the signal again. I first saw it on the waterfall diagram before we could hear it. Decoding the telemetry, we knew the current whereabouts.
[ 9200] (N3430076) Sa 2018-04-21 00:52:32.001 lat: 48.96344 lon: 9.10418 alt: 260.29 vH: 0.0 D: 167.8° vV: -0.1 # [00000]
Purple: Estimated landing sector based on last telemetry.
Yellow: The car track .
Red: Ground track of probe.
Blue: GPS positions of probe.
Sprangerstrasse. We rushed to the landing zone, overshot a bit, backed up, and then, there was nothing that could have kept Claus in car. He jumped out of the car and seconds later, I heard him happily shouting: “Here it is. I have found it”.
The probe had impacted near a blooming apple or cherry tree. The coil had broken and the parachute had detached. It was nowhere to be seen. This explained the high impact speed.
We recovered the probe and coiled up the thread. After a short but well deserved breakfast at McDonalds in Bietigheim-Bissingen, we returned home.
During post flight analysis, we wondered about the broken coil. As the ascent went normal and the initial descent velocity was already very high, the coil can only have broken at the beginning of the descent in 33km (109000 feet) altitude. If one is susceptible to conspiracy theories, one could like to believe that the balloon has collided with a secret spy plane. Civil planes do not fly above 35000 feet (The SR-71 could fly in excess of 85000 feet) and transponder data available in the Internet does not show any other flying object in the vicinity at this point in time.
It is more likely however that the coil was already weakened when the probe was placed into the starting carousel before launch. The acceleration jerk resulting from the balloon burst might have led to the complete detachment of the hook and the connected balloon nozzle with the parachute.
The second mystery is easy to explain: We went into the wrong direction as there are 2 villages with the name of Hofen in the vicinity of Bietigheim-Bissingen. Sure enough, we had picked the wrong one.
