Accession Number : ADA130740

Title :   LIDAR (Light Detection and Ranging) Measurements for Astronomical Refraction. Feasibility and System Definition Study.

Descriptive Note : Final contractor rept. 1 Apr-30 Sep 81,

Corporate Author : SRI INTERNATIONAL MENLO PARK CA

Personal Author(s) : DeLateur,Stephen A

PDF Url : ADA130740

Report Date : Feb 1983

Pagination or Media Count : 46

Abstract : Recent improvements in mechanical and optical instrumentation precision have occurred. Therefore, the removal of meteorologically caused systematic errors is now a major consideration in stellar position accuracy and in the repeatability of arrangement in positions taken during nightly observations. The two problems singled out in this report are absolute water vapor content and temperature structure measurements. The study revealed that (1) estimates of water vapor distribution with an accuracy of approximately 20% would routinely correct position errors of 0.01 of angle and (2) that knowledge of the temperature structure with an accuracy of 0.5K would remove the systematic errors caused by isopycnic tilts, which range from 0.01 up to 0.1 of angle at extreme zenith viewing angles. The study showed that a remote-sensing solution to the measurement problems of the U.S. Naval Observatory in Washington, DC, is provided by LIDAR (Light Detection and Ranging). Two major LIDAR systems that fulfill the Observatory's needs are based on Raman and DIAL (Differential Absorption Lidar) techniques. A study and review of experimental system using the DIAL and Raman techniques indicate tht a DIAL system is the recommended approach for simultaneous measurement of water vapor density and temperature. A DIAL system should be constructed to obtain ground-based vertical water vapor and temperature measurements. Further, alexandrite should be used as the lasing medium for the LIDAR system.

Descriptors :   *STAR TRACKERS, *OPTICAL RADAR, WATER VAPOR, ASTRONOMICAL INSTRUMENTS, ACCURACY, PRECISION, ABSORPTION SPECTRA, TRANSMISSION LOSS

Subject Categories : Astrophysics
      Active & Passive Radar Detection & Equipment
      Optics

Distribution Statement : APPROVED FOR PUBLIC RELEASE