The principle is actually very simple: a series of laser impulses are directed to satellites through the telescope. The satellite itself or prisms on the satellite reflect the light back to the telescope. The distance from the telescope to the satellite can be calculated with the time difference between the emission and reception of the laser signals. The impulses are sent at a frequency of 10 per second and the resulting distance measurements are accurate to within a centimetre. This degree of accuracy is all the more impressive when we consider that around 20 satellites are observed at distances of up to 20,000 kilometres.

In the meantime, observations can also be carried out during the day, so that satellite laser ranging can now be carried out 24 hours a day. The only disadvantage of this method versus GPS technology is that observations are not possible when there is cloud cover. For further information, please visit the University of Bern website.

Zimmerwald is a significant station of the International Laser Ranging Service ILRS. The same telescope is also used for optical observations such as the automatic detection of space junk.

Two permanent GPS / GLONASS receivers and a permanent GPS receiver operate in Zimmerwald. The data are available internationally. Zimmerwald is therefore one of the important base stations of the International GPS Service IGS which determines the global orbits of the GPS / GLONASS satellites.

An earth tide gravimeter is being operated permanently together with the Federal Institute of Technology, Zurich. It automatically measures and records daily gravity variations. By way of comparison, swisstopo and the Swiss Federal Office for Metrology (METAS) carry out absolute gravity observations once a year with a highly precise FK5 absolute gravimeter.

In Zimmerwald, sensors are used that permanently record pressure, temperature and humidity which are needed for the atmospheric reduction of the geodetic observation data.