The team arrived at the Ridge Lab at about 9 am after a smooth ride from Eureka and proceeded to their individual labs right away.
At this time, the outside temperature was at about -19℃ and stayed close to -21℃ throughout most of the day. It was less windy compared to Sunday and the favourable clear sky conditions persisted for yet another day. The duration of daylight increased to almost six and a half hours and the sun rise occurred shortly before 10 am. Clouds started to obscure the instruments' view of the sun at around 3:30 pm local time.
The clear skies allowed Sébastien and Erik to continue mid-infrared measurements with the Bruker 125HR. With each day, the daylight hours increase providing the opportunity for more measurements to be taken. Today, a total 66 measurements were taken, while yesterday they made 33 measurements. Sébastien and Erik also tested the instrument vacuum at the end of the day. The scroll pump, which keeps the instrument evacuated was shut off. They carefully monitored the internal pressure of the instrument and noted a fairly rapid increase in pressure. Because of this, Sébastien and Erik turned the scroll pump back on and evacuated the instrument. For now, the scroll pump will remain on overnight to keep the instrument evacuated in order to protect the beam-splitter and allow for easy start-up of measurements in the morning. Sébastien and Erik will continue mid-infrared measurements until a cloudy day and then cell test measurements will be made.
After a short session on the roof, which consisted of getting to and removing the diffuser from the PEARL-GBS telescope, Kristof spent most of the day calibrating the PEARL-GBS spectrometer. In the afternoon, he completed most of the resolution tests and hopes to finish all the lab tests tomorrow.
Ellen started operational measurements with PARIS-IR at around 10:30 am but stopped them close to 12:10 pm due to the PARIS-IR detector temperature continuously rising and the detectors getting close to being oversaturated as well. After topping up liquid nitrogen she started operational measurements again and checked back on the detector temperatures and both detector values every 30 minutes. After rising slightly again, the detector temperature dropped to the optimal value and remained at this temperature for the rest of the day. Overall, Ellen completed 35 measurements with the instrument and was able to convert the measurements taken during the first weekend at the Ridge Lab to interferograms.
The CRL ran for 23.75 hours on 28 February (UTC) with a 15 minute break to check the alignment of the laser beam to the sky. Last night (evening of 28 February), the DIAL lidar was started up at the Ridge Lab after supper, this time with some power meter tests to begin the night. Startup was quicker than yesterday as both Ghazal and Emily are now more practiced with the procedures. Regular measurements continued on into the next morning at 8 am local. Ghazal has now taken over the main operation of the DIAL lidar. Emily took some photos of the lidar beam in the clear night sky.
The first ozonesonde launch of the intensive campaign was performed today at 6:15 pm. Unfortunately, the ozonesonde only reached 5763 m.
Overall, the team was very happy with the atmospheric conditions, which were perfect for the Bruker and PARIS-IR until close to the sun set. Smoothly running measurements also allowed the team to sneak outside for a few minutes and enjoy the beautiful views.