Satellite telescope

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A satellite telescope is a device used to observe earth satellites, primarily to determine their precise orbits . Are common lens telescopes or Schmidt telescopes and radio telescopes .

Observation of earth satellites in visible light

The flight path of artificial earth satellites can be determined in various ways:

  • Visually through angle measurement with measuring telescopes equipped with pitch circles. They are (or were) mostly theodolite- like measuring instruments, especially the Kinetheodolite developed in the 1960s or swiveling telescopes like the Moonwatch telescope (USA 1956-75) or similar telescopes developed in the USSR . They are directed to pre-calculated positions in the sky and then follow the satellite.
  • Visually by observing the star background , which requires a telescope with a large field of view. A simple pair of binoculars is sufficient for this , supplemented by a good stopwatch and a suitable star atlas .
  • Photographically through special satellite cameras . During the measurement they can either be set up permanently ( ballistic camera ), tracked to the stars (see equatorial mount ) or follow the satellite. The latter method requires three-axis instruments such as the Baker-Nunn camera , and the path elements must be entered into the control computer.
  • With active laser telescopes . They send a highly focused, monochromatic beam to the satellite, which reflects it. The received light triggers the measurement of a time interval counter that was started when the laser beam was emitted. This transit time measurement basically determines the current distance to the satellite (i.e. after subtracting some corrective variables).
  • Photographically by measuring the light echo in front of the starry sky.
  • Passive by receiving or reflecting a laser beam emitted by the satellite . This method was used sporadically in the 1970s to 1990s.

Observation of earth satellites using radio waves

The devices based on radio signals are mainly to be assigned to electrical engineering or electronics and not to telescope technology. But there are some methods in which radio telescopes are used - especially for very high satellites and distant space probes on the flight to other planets.

These radio telescopes have i. A. a metallic parabolic mirror (more rarely a cylindrical mirror) and are smaller than about 50 meters due to the necessary rapid movement (exception: Deep Space Network ). In addition to high-precision control, they are usually also equipped with a directional analysis, so that they can then measure both the exact distance and a (less precise) direction to the missile.

Other methods of radio measurement technology for satellite observation use the Doppler effect , interferometry and the time of flight measurement of microwaves . However, their antenna shapes are not comparable to telescopes.

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