Friday August 25 Bruce started the REAL at 0900 PDT with a 30 minute warm up. Data collection to start at 0930.
Calm with scattered clouds and temperature around 70.
Above: MPD03 shows high levels of water vapor and possibly a light rain shower overnight about 1000 UTC (0300 PDT).
Scattered clouds looking east 0915 PDT
Scattered clouds looking west 0915 PDT
LabVIEW start 0934 PDT
The lidar return is a bit stronger today. Did not have to increase the elevation angle to 0.11 deg today to avoid ground returns. Elevation angle at 0.10.
First dust structures of the day.
Below: lots of cumulus clouds at 12:50 PM PDT:
LabVIEW display at 1536 PDT - note the increased signal levels in both channels
Today, Bruce and Shane adjusted the attitude of the REAL trailer to restore it to the pitch and roll prior to TS Hilary. Background: rain from TS Hiliary caused the east and front of the trailer to sink slightly (about 0.2-degrees in roll and about 0.03-degrees in pitch). It was just enough that that beam was intersecting the ground to the NE of the linear array. Since August 21 until this afternoon we compensated by increasing the elevation angle on the BSU to 0.10 degrees. That is relative to the platform. So, if you see 0.10-degrees in the data/images from 8/21 until about 2:20 PM PDT today (8/25), that is with a platform that is not perfectly level and it was our best effort at keeping the beam horizontal as it was before TS Hilary passed over.
From the 10-day history of platform angle data shown above, you can see that the Trans (transverse) angle had been ranging from -0.12 to -0.09 degrees with a mean of about -0.107 degrees.
The Long (longitudinal) angle had been running +0.371 to +0.397 with a mean of about 0.381 degrees. The gap in the middle was the day off when it rained all day. The step changes in angles on the far right are through the adjustments that Bruce and Shane made today on the hand-cranked leveling legs of the trailer. We found that one full clockwise crank on both of the right (east) legs decreased the Trans angle by about 0.026 degrees. In all, we made 7.75 full clockwise cranks on both of the east leveling legs to bring the trans angle (roll) back down. We gave 5 full clockwise cranks to both front legs to raise the Long angle (pitch) to about the same range where it was on the day before the rain started.
Note for the record: we use two Applied Geomechanics TuffTilt tiltmeters that are fastened to the optics table. Photos below. (They are the high-gain version and the user manual states they have a resolution of <0.0001 degrees and repeatability of <0.0002 degrees, although we take the analog out of each and run it through our signal conditioning box and into the REAL data acquisition computer to be digitized by the NI multifunction card.) The rooftop scanner sits on an x-rail tower that is bolted to the table so changing the trailer, changes the table, which changes the tower and scanner. The tiltmeter closest to the telescope is the Trans angle and the one closer to the side is the Long angle. To know for sure which angles they are sensing requires looking on the end of the sensor box where the cable feeds in and noticing the sticker that shows neg to pos range of angles and an arrow. The sticker on the Long angle sensor is hidden on the side but we know that it must be since one senses Trans and one senses Long.
At about 2:20 PM PDT we set the elevation angle on the BSU back down to 0.0 degrees.
Skies become much clearer in the later afternoon. The following eastern panorama was taken at 16:51 PDT.
View to the south at 5:12 PM PDT:
Bruce and Shane left field site around 5:30 PM PDT.
Shane shutdown system from hotel at 10:33 PM PDT.
