Sorry to leave you all hanging for so long. It’s been a busy past year for COSI! And it’s about time that we caught you up on what we’ve been working on.
First and foremost, COSI is just about ready to launch again! We’re launching from another Super Pressure Balloon this coming April, except this time, instead of being in the freezing cold of Antarctica, we’ll be the first science group to launch from CSBF’s new site in Wanaka, New Zealand! And we’re all looking forward to a much longer flight.
The last post in the blog was the disappointing news about the COSI’14 flight terminating early after a meager 2 days at float due to a leak in the ballon. The silver lining to the instrument coming down so early is that it landed relatively close to McMurdo Station, meaning it would be a fairly straightforward recovery. If you want to hear more about my Antarctica recovery adventures and check out all of the pictures, look my other post from today titled “COSI’14 Recovery.” I’ll pick up the story here starting with the delivery of all of the COSI instrument back to Berkeley in March 2015.
Before any decision could be made about COSI’s future timeline, we needed to check the status of our detectors. We pumped down the cryostat and turned on the cryocooler right when the we got it all back in April. And, low and behold, each of the twelve detectors came up working well; none had been damaged during the flight/landing/shipping! We had the whole readout pipeline running in our lab within a couple of weeks, so when the Balloon Program Office offered to have us fly out of Wanaka in Spring of 2016, we felt pretty confident we could be ready in time.
One major hurdle that we had to pass over was disassembling the cryostat. One of our twelve detectors had 10 bad strips, so given the opportunity, we wanted to see if it could be refabricated to be fully operational. In August (after I passed my quals!), we disassembled the cryostat and removed one of the detectors for refabrication. Everything was put back together in September and we started system tests immediately.
Chris Cork, a retired SSL engineer who used to work with the LBL Detector Group, graced us with his presence and took the lead with the cryostat integration. Here he is putting the new and improved germanium detector into the stack.
The COSI cryostat put together again! At the same time as refabricating one of the detectors, we developed a new temperature regulation system for the cryoscooler. You can see the copper tubing around the cryocooler here.
Before our flight from New Zealand we needed to pass a compatibility test with CSBF in Palestine, Texas, just like in Summer 2014. But, due to the fact that COSI’16 is almost identical to COSI’14, both teams agreed that a simple compatibility,with just the power system, flight computer, and one card cage would be sufficient. Brent, Alex, and McBride spent a leisurely 10 days working in Palestine to pass the COSI’16 compatibility test (but none of them took any pictures!).
We had another trip to Palestine this past November to use their thermal vacuum chamber. We wanted to put our cryostat and electronics through more rigorous testing before our flight. In their BEMCO chamber we are able to simulate the space environment through day and night cycles. It’s pretty anti-intuitive, but flights from New Zealand will have colder temperatures than flights from Antarctica, this is not only because we’ll be going through night cycles, but you can get some very cold storms over the ocean. The temperature in flight can reach as low as -100 C, but with foam surrounding the gondola we should be able to maintain a balmy -40 C in the electronics bay.
Clio and McBride monitoring during the BEMCO test. Clio’s written a whole new GSE (Ground Support Equipment, i.e. the program that we use to talk to and monitor the instrument) in the past few months, so this was a great opportunity to test it!
Once back in Berkeley, we had the month of December to fully integrate the gondola and do some system testing and calibrations before packing up.
Clio installing the new cryocooler cooling system. We’re pumping liquid fluorinert (environmentally friendly!) through the cryocooler and out to a radiator to keep everything a moderate temperature in flight.
Clio installing the new cryocooler cooling system. We’re pumping liquid flourinert (environmently friendly!) through the cryocooler and out to a radiator to keep everything a moderate temperature in flight.
COSI gondola fully operational in Berkeley. The California winter months are perfect for calibrations in the SSL highboy.
We shipped everything out on January 6th and we’ll be meeting the container in Wanaka on the 15th of February! We’re all so excited about the next few months! GO COSI CO!