The transportable optical ground station (TOGS) is a versatile modular instrument that can be used for a variety of experimental optical downlink and uplink scenarios as well as for assessing the atmospheric optical channel.
The Transportable Optical Groundstation – a versatile instrument for optical data links and channel measurements
The TOGS was designed and built by the Institute in the years 2010 and 2011. One major design goal was a small and lightweight construction, which can be easily transported to sites all over the world. The structure had to be stiff enough to reach the accuracy needed for optical communications.
The main component of the TOGS is a 60cm aluminum Ritchie-Chrétien Telescope, which can be deployed to a height of 3.5m by a foldable mast construction. A special requirement for the telescope in a mobile system was to maximize the mirror diameter while having a short overall length. Therefore, a special design of a Ritchie-Chrétien-Telescope was developed. To shield the telescope from dirt and shocks during transportation, it is stowed in a compartment made of carbon fiber, which is damped by shock-absorbing mount elements.
One major challenge for a transportable ground station is the rapid determination of its position and attitude. Both are needed for rapid target pointing. An advanced system based on satellite navigation and attitude sensors is used for automatic identification of these parameters and allows a quick installation of the ground station. In addition, a GPS-positioned laser reflector has been developed to allow a rapid and precise alignment.
Possible mission scenarios for the ground station include links to and from aircraft, UAVs, and satellites. Another field of operation is the evaluation of new sites for fixed ground stations in terms of cloud coverage and weather statistics.
One further application is downlinks from observation platforms after a disaster. Pictures of the disaster site may be taken by an aircraft and directly transmitted to the disaster area by an optical link. The real-time information is a fundamental requisite to coordinate emergency units.