Abstract
The Institute of Geodesy and Geoinformatics (GGI) of the University of
Latvia (UL) is focused now on configuring of the recently designed
optical tracking system and launching of a test program for positional
astrometric observations. The instrument is eventually intended for both
positional and laser ranging observations of near-Earth objects. The
tracking system has Alt-Alt mount and optical scheme with three optical
channels: transmitter equipped with laser collimator and two 16″ F/10
receiving optical tube assemblies (OTAs). The laser collimator has
manual/computer control capability. One of the twin optical systems is
fitted with a CCD camera and used for astrometric and positioning
purposes: orientation of the instrument in star-defined coordinate
system and observations of natural or artificial space objects. The
other may be fitted with a reflected light pulse detector and used for
SLR pulse processing or configured for other purposes. The drive has
stepper motors with worm-wheel reductors and incremental encoders
(resolution up to 0.36″); it is controlled by a FPGA under computer
control. Control software runs on a Windows PC and consists of 4
semi-autonomous modules: positioning, ephemeris, laser and astrometry.
Preliminary tests indicated that due to the field rotation, which
elongates star images in the periphery of the frame, the effective
exposure duration is limited to about one minute. At such exposure,
stars of magnitude up to 17-18 can be recognized by the software. Frame
stacking is proposed to increase this limit by several magnitudes.
Theoretically, using frame stacking, it should be possible to reach
maximum magnitude of about 22. Mount error model, implemented by the
control software, will be used to introduce the necessary pointing
corrections. After adjustment of mount mechanics and optimization of
mount error model structure the positioning accuracy of up to 5″-10″ is
expected. Project No: 1.1.1.2/VIAA/4/20/619.