Line trace
In astronomy and satellite geodesy , the photographic recording or analysis of line tracks is an important method for discovering and determining the orbit of new or already identified celestial bodies .
There are essentially three methods used:
- Fixed ( Altaz -mounted) or ballistic camera : the stars are shown as short line tracks , whereas artificial earth satellites or meteors are shown as long tracks. If precise time measurement is required, time stamps are stamped on the tracks with a rotary shutter .
- parallactic or equatorial mounting - especially with astrographs : the stars become point-shaped, all other objects short to long tracks. Serves among other things for the discovery and measurement of asteroids (minor planets) and comets .
- Weak celestial bodies at the threshold of perceptibility can be more easily discovered with a blink comparator .
- Multi-axis mounted satellite cameras , for example the Baker-Nunn camera : they are approximately tracked to the searched satellite, whose orbit elements must be known. The satellite is shown as a short line track, the star background with long tracks.
In the last decade, the photographic plates that had prevailed in methods 1 and 2 were replaced by CCD or other photoelectric sensors . The complex cameras of type 3, which mostly work with films, have now largely been shut down.