CloudSat supervision by the operator
The CloudSat is a satellite launched for meteorological studies, with a powerful radar emitting toward the nadir direction. See the article "The 30m and the CloudSat" in the IRAM Newsletter of June 2006 (http://www.iram.es/IRAMFR/ARN/jun06/node8.html) for more details.
The risk of receivers damage due to the strong radar pulses is solved with the automatic close of the antenna vertex at the zenith position.
The risk of interference during the observation must be controlled by the permanent running of the program clsat30m.
clsat30m calculates every 5 seconds the coordinates of CloudSat and in case that the following three conditions occurs:
a) The CloudSat is above the horizon
b) The 30m antenna points to elevation higher than 10o
c) The separation between the CloudSat and the 30m antenna pointing is less than 25o
the alarm CLOUDSAT of the 30M ALARM SYSTEM will be triggered. The alarm condition will continue while the three previous points remain and typically will last no more than a few minutes. Monitor the separation between the antenna and the Cloudsat positions and inform to the astronomer of the possible corruption of the data during the alarm time, considering the possible convenience of throwing away those data. Special care must be taken in case that the Cloudsat frequency band (94.0 to 94.1 GHz) is observed or covered by the image band.
Steps to be followed by the operator:
In the machine vcdesk, directory /home/penalver/CLOUDSAT run the program ./clsat30m
The program starts showing the orbital elements read from the file tle.txt and then, every five seconds, the actual time and CloudSat position is shown in the consecutive lines. In case the CloudSat is above the horizon, the 30m antenna position and separation of the CloudSat is shown. Resuming, the information by columns is the following:
6 columns with the year, month, day, hour, minute and second (in UT)
1 column with the CloudSat azimuth (in degrees)
1 column with the CloudSat elevation (in degrees)
1 column with the CloudSat range (distance in Km) to the 30m antenna
in case the CloudSat is above the horizon, the following additional columns will appear:
1 column with the 30m antenna azimuth (in degrees)
1 column with the 30m antenna elevation (in degrees)
1 column with the separation between the CloudSat and the 30m antenna (in degrees)
In case the program clsat30m is not running, the corresponding notifying alarm bit will be produced in the superv utility.
Finally, in order to have the most updated orbital element of the CloudSat, the file tle.txt must be updated once per week (operator shift).
In the web page
http://cswww.cira.colostate.edu/data_dist/TLEs/CloudSat_Current_TLE.txt (updated April 2016)
or this one:
Another TLE data source (the two lines at the bottom of the linked page, updated April 2019):
the most recent TLE (Two Line orbital Elements) can be obtained and written in the file tle.txt with the correct format (add ‘ at the first and last character of each line). A model can be checked in tle_model.txt
After that the program clsat30m must be restarted.
If the tle.txt is not updated during the last 10 days and the program clsat30m restarted, the program clsat30m will stop producing the alarm.
In case of doubt, ask J.L.Santaren or J. Peñalver.
14-June-2006, J. Peñalver and M. Ruiz