I have a ground based backscatter lidar, operating at vertical (90 degree zenith) everyday during day time. The Lidar manufacturer advise us not to operate it when the sun disc enter our Lidar's field of view. However, I found many programs that calculate the sun position at a certain latitude during a certain time. But the problem is, I cannot determine whether or not the sun disc will enter my Lidar field of view. So is there anybody who can suggest a method or program or software that can do so? Thank you.
If you know viewing angle of your Lidar (A) and the angular size of the sun disc (B) then you can use lidar when a condition (h < 90-A/2-B/2) is met.
If the lidar is switched on/off manually (I mean, if your software can't do that) and if it's crucial for the detector not to be solar blinded, you may consider an additional safety measure - install a vertical tube with a photoelement, which will turn the detector off when the sun is overhead. Varying the tube's diameter/length, you can change the FOV.
One of the most precise tools for Solar Position is SPA available at NREL
http://rredc.nrel.gov/solar/codesandalgorithms/spa/
Other faster but less accurate algorithms exist such as the one we published:
P. Blanc, L. Wald, The SG2 algorithm for a fast and accurate computation of the position of the Sun for multi-decadal time period, Solar Energy. 86 (2012) 3072–3083.
(see http://hal.archives-ouvertes.fr/docs/00/72/59/87/PDF/Solar_Energy-SG2_Article_accepted-version.pdf)
Easiest is that download solar position from the site that Dr. Blanc mentioned (http://rredc.nrel.gov/solar/codesandalgorithms/spa/). Get the solar zenith angle information with time (for your latitude-longiude and season). Put a limit to the operation in operating software of lidar using criteria of operation only if solar zenith angle is +/- 10 degrees.
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