On March 25, the team started working on mapping the network connections and instrument locations in the Ridge Lab: Petra is taking care of the IR Lab, Kevin is taking care of the UV Lab, and Darby and Pierre are mapping the rest of the connections at the Ridge Lab. After dinner, Kevin and Pierre continued the herculean task of extracting the CANDAC truck from its glacier-like snow drift at the Weather Station.

Over these three days at the Ridge Lab, Kevin performed a stray-light test on the UT-GBS and a second round of polarization tests. The stray-light test involves using a filter to block out light in a known wavelength range and ensuring that no other unwanted light enters the spectrometer. Kevin also performed resolution, stray-light, and polarization tests on the PEARL-GBS. Overnight on March 26, both GBS instruments performed dark current tests. These tests determine the background signal the detectors inside the instrument read out when no light enters the instrument. This is an important instrument property to account for when analyzing measurements throughout the year. The CANDAC truck was finally freed with the help of the Weather Station Heavy Equipment Operator and Mechanic, just in time!

On March 27, Kevin analyzed the PEARL-GBS and UT-GBS test results and found that they were both successful. Then, he started running the usual measurement sequences for each instrument. The GBS’s are operating nominally. More work was required on the FTIR data transfer and Petra with Yan Tsehtik's help (thank you, Yan!) has (hopefully!) re-established the connection, so that the 125HR data will be backed up automatically. Darby worked on network mapping at 0PAL. The Pandora operated nominally.

On the evening of March 27, Darby got to release the 00:00GMT balloon sonde with the Senior Aerological Observer; Kevin captured the joyful moment on camera.

Cheers,
Darby Bates
[on behalf of the 2025 Canadian Arctic ACE/OSIRIS Validation Campaign team]