After briefly losing their link to the outside world - their internet connection - shortly after 9 PM on Tuesday evening, the team woke up to a slightly slower than usual network. However, this didn't impact their work with the instruments at PEARL, so they left the Eureka Weather Station at their usual time, around 8:30 AM. The temperature at the Ridge Lab remained close to -30°C with low winds and a few clouds on the horizon. At the weather station it was considerably colder with temperatures from -37°C to -40°C. The wind occasionally picked up at the weather station, resulting in temperatures of down to -53°C with the windchill. Eureka and the Ridge Lab saw a total of almost 4.5 hours of sunlight today. After a long work day, the team left the Ridge Lab just in time to arrive at the weather station for dinner at 5 PM.

Although the day was partly cloudy Beatriz and Tyler had a brief period of thin cloud. They attempted to do solar measurements but the intensity of the solar beam was too low, so they only obtained one noisy spectrum for Filter 6. They realized that the beam was not fully centred at the aperture of the instrument. To solve this problem, they made fine adjustments to the mirror at the entrance window to improve the signal. They also verified that the solar beam was centred on the EM27/SUN detectors. They continued performing some tests with the Raspberry Pi device to ensure an error message will be transmitted in case of loss of electrical power, reboot of the Raspberry Pi or the pressure sensor, or a failure in the data transmission from the sensor to the Pi device. This will allow the operator to address problems quickly and ensure continuous measurements.

Ramina continued focusing the PEARL-GBS CCD, with guidance from Kristof. After a long morning of tests and adjustments, they arrived at a position that provides ideal resolution for UV measurements. After completing the full set of pen lamp measurements for the resolution tests, they moved on to the polarization tests. They hope to finish most of the lab testing tomorrow.

Ali started the DIAL around 6:30 PM to warmup the laser. When he checked the weather he noticed it was snowing, so he opted to wait to avoid snow on the mirror. When he checked the weather conditions again at 8 PM, it was still snowing. Ali and Alexey opened the hatch around 9:30 PM and tried to take measurements until 10:30 PM. Unfortunately, snow started to build up on the mirror, so they stoped the DIAL. Since it continued to snow, no measurements were obtained with the DIAL during the night of February 25 to February 26. Ali spent his time trying to adapt the DIAL code to read raw data using his laptop, which would allow him to remove corrupted data and analyze the data using the optimal estimation method (OEM). The CRL is now in nominal operations. Both lasers are working and things are going well. Emily will be doing some sky alignments soon, and calibrations later in the campaign. However, these are the considered routine and the CRL is generally back in full operations mode.

Tom continued to collect measurements with the SPS and analyzed yesterday's data. He also consulted the daily ozone maps and found that these were consistent with his observations. So far, the repair and re-installation of the SPS have been a great success.

Guillaume found that the laser in the E-AERI had suddently decreased in intensity, meaning that the interferometer occasionally produced bad spectra. He was able to adjust the laser fringe detection diode to return the instrument to nominal operation.

Even though ideal measurements conditions have not yet emerged, the team has plenty of things to do running tests, engaging in hands-on training and analyzing their first observations. They are looking forward to the next two weeks of the intensive phase of the campaign at this unique place.

Cheers,
Ellen Eckert
[on behalf of the 2020 Canadian Arctic ACE/OSIRIS Validation Campaign]