Environmental Testing Campaign: Thermal Week 2

And we’re back!

Following a weekend catching up on work and exploring the Ardennes – La Roche-en-Ardenne in the sun on Saturday and Grottes De Hotton and Liège on a slightly damp and foggy Sunday, we return to thermal testing of Pathfinder.

Figure 1: La Roche-En-Ardenne in the sun.
Figure 3: A cloudy Liege.
Figure 2: Stalactites and stalagmites in Hotton.

You may remember, over the weekend we left the payload powered off and pumping down to a high vacuum, with the chamber walls set to 30 degrees Celsius. In fact, on Sunday evening, with Pathfinder settled to 30 degrees, the wall temperatures were raised to 52.5 degrees, our max non-operational temperature. Overnight, this temperature was reached, and our non-operational maximum dwell began.

And so this was the state of the payload when we returned to Galaxia on Monday morning. After ‘suiting up’ and entering the clean room, the chamber temperature was changed to our minimum non-operational temperature, and we monitored the temperature of the key components. On the descending limb, when the temperature reached our max operational temperature, we switched the payload on (and back off again!). We, of course, filmed this critical moment:

Video 1: A Very Relieving Switch On After Hot Non-Op.

And we were delighted when both cameras responded!

Once PROVE reached its cold non-operational temperature limit, a dwell was begun. The decision was made to make all dwells shorter than originally planned to give us more time for thermal cycling and debugging the issues noted in the first week. In practise, this meant that we did the post cold non-operational switch on (and off) before lunch. We were much less concerned by this one – but nonetheless glad when both cameras responded.

Over lunch, we returned to ambient temperature, and upon returning, we switched Pathfinder on and started the operational cycling. The first cycle was hot operational – and this was the most critical test!

We watched as the temperatures rose, and once the temperature reference point reached 38 degrees, we ran our first hot operational test. As we had come to expect from the previous week of testing, the very reduced function test (VRFT) was partially successful – with the visual camera only returning the reference image, indicating it was overtemperature.

This became the story of the following days, with our cold operational VRFTs passing completely and the hot ones being partially successful. This is summarized in the following graph, created for the purposes of our final test report.

Figure 4: Summary of operational and non-operational cycles.

To further diagnose the issues with the camera, an investigation into the Basler sensor temperature (external to the camera) was conducted between hot operational 3 and cold operational 3. This involved recording temperatures and trying to ‘ping’ the camera until it passed or failed due to overheating (allowing for the no-ping errors that we were still observing).

The final testing day of the campaign saw us conduct an overnight thermal balance at the hot operational temperature, with PROVE Pathfinder in its idle state, with another partially successful VRFT at the end of this dwell. We then made the decision to vent the chamber and try another hot non-operational test, this time on the Teflon adapter plate, without the power and data umbilical cable. This allowed for an investigation into unusual behaviour observed a few days prior – despite dwelling overnight, there was a difference observed between temperature sensors on the fixture and the DUT (with every sensor on the DUT being lower).

With that, our 2-week stay in Belgium and our 3-week testing campaign was concluded. We packed PROVE up, had our thermal post-test review and said a very grateful farewell to Loris and Gilberto – who have been utterly invaluable to us and our team.

Figure 5: TVAC Team with PROVE Pathfinder and Paxi.