A mostly cool cloudy & calm morning in the valley. The fog/cloud lifted around midday and it was partly sunny although windy during the afternoon.
We were mostly working at ISS3 Sedgwick today. We took the profiler antenna apart, temporarily removing the clutter screen and radome to clean off the antenna, which was covered in a thick layer of dust and dirt. We had wondered if this was affecting the performance of the antenna, however as John will report elsewhere, is wasn't clear if this helped. Taking it apart did allow us to inspect the surface of the antenna and it was noticed that the panels are a little warped and cracked which may explain the problems we are having with it. We mostly reassembled the antenna this afternoon, although John is making repairs to still one of the clutter screen panels so the profiler is missing that panel for now. Liz also replaced one of the relays that had been sticking earlier.
Isabel is making good progress on the data flow and many plots are appearing on the web. The first are now available at the SWEX ISS web page with more to follow soon. Erik's wind plot visualization tool plotting up the 449 MHz profiler and the link to that was also added to the web page.
We replaced the main SSD disk drive on the wind lidar yesterday with a new drive that arrived from Vaisala. This included a software update that should improve the stability of the system. It seems to be working well so far, however the file names are misnamed ("WCS999951_" instead of the usual "WLS200s-181_") which is causing a few problems with the downstream processing for now.
Cleaning off the antenna at Sedgwick and reassembling the clutter screen afterwards.
1 Comment
John Sobtzak
When we arrived at ISS3/Sedgwick, the system was not showing the clutter signals we had been seeing in the past. As Bill mentioned, the conditions were very cool and humid (~50F, foggy) which seems to improve the antenna input return losses for each beam. The images below show the returns the system was receiving when we arrived and the lack of the clutter return at 0 m/s Doppler. Note that the images were captured at 1000-1002 local time under the weather conditions noted above.
Weather conditions at time of images.
ISS3 WA0 X-vert ISS3 WA1 Y-vert
ISS3 WA2 X+ North-West ISS3 WA4 X- South-East
ISS3 WA3 Y+ South-West ISS3 WA5 Y- North-East
I wanted to see what the IRL's were, so Liz and I took a few rounds of IRLs measurements before we removed the clutter fence and radome. The table below shows the IRL (in dB) for each beam with each beam measured multiple times, with multiple VNA calibrations and checks done.
Several of these IRL levels were better than seen in the past, with values in the mid- to high-teens versus low teens in the past. There were some values that even reached >20 dB but they were not recorded as a new VNA calibration was done. Also, several of the values would 'bounce' around during one measurement and/or show significantly different values between successive measurements with the same calibration and connection, i.e. as the beam selection would come back around. This was mostly seen on beams WA0, WA1, and WA5, as seen in the wide variation of IRLs for WA0 and WA1. WA5 numbers don't show the fluctuations as well, but the instability was noted when the measurements were taken.
The antenna's clutter fence and radome were then removed and the antenna's IRLs measured again for two beam cycles. The antenna surface was then vacuumed and wiped clean and another 3 beam cycles of IRLs were taken. Finally, the input impedence at the antenna's input SMA was recorded for each beam.
Pre-cleaning
IRL #1
Pre-cleaning
IRL #2
Post-cleaning
IRL #1
Post-cleaning
IRL #2
Post-cleaning
IRL #3
Post-cleaning
Impedance
28.2+j7.5
26.3+j18.0
Again, the IRL measurements were bouncing all over the place as measurements were taken, despite multiple checks of the VNA calibration using known loads and attenuator values. It appears that the antenna panels are not stable, which supports the theory that the substrate material has broken down in some manner.
In the afternoon, the radome and 3 of the 4 clutter fence panels were then reattached to the system. Liz replaced the relay in the X/Y polarization bank, third in from the 'X25' labeled side of the antenna array, that was found to be 'sticky' on3/14/22. The system was restarted and the following set of returns were captured from 1635-1636 under the mostly sunny skies and light wind conditions shown in the image below. The images show the return of the clutter signal at 0 m/s Doppler velocity in every beam, despite all our efforts.
Weather conditions at time of images.
ISS3 WA0 X-vert ISS3 WA1 Y-vert
ISS3 WA2 X+ North-West ISS3 WA4 X- South-East
ISS3 WA3 Y+ South-West ISS3 WA5 Y- North-East