Flash satellite

The flash satellite technology is a method of satellite geodesy that was developed in the 1960s to facilitate photographic observations of small satellites and to reduce the influence of time errors on orbit measurement . The method became obsolete when high-precision clock systems became available around 1975 and electronic distance measurement became possible over great distances.

At the beginning of space travel, geodetic satellites were measured visually or photographically, which required the missiles to be sufficiently bright . For large-scale surveying networks, bright, high-flying balloon satellites were initially the best solution, but their low weight led to severe orbital disruptions . As an alternative, smaller, compact satellites were built and equipped with powerful xenon lamps and solar panels that could generate short series of flashes . Their brightness was sufficient for satellite cameras with highly sensitive emulsions , and the satellites could also be observed in the earth's shadow .

A second advantage was the possibility of precise simultaneous measurements through distant ground stations . The Timing of the cameras was still hardly accurate possible than some milliseconds , which would km at near-Earth line speeds 7-8 per second already tracking error of 10 to 20 feet mean. If, on the other hand, the simultaneity of the measurements is guaranteed, this influence no longer plays a role in a three-dimensional survey network defined by the flashed target points .

The first such experimental satellite in the USA was ANNA 1B , launched at the end of 1962. The flash technology was already mature in 1965 when the small - now electronic - satellite GEOS (later called Geos-1) was launched. With his younger brother GEOS 2 (1968) he brought a noticeable increase in accuracy, while Geos-3 (1975) tested other measuring methods.

In the following years, however, the importance of almost all optical measurement methods declined because they were overtaken by the rapid advances in electronic distance measurement . Only with the new observation methods with CCD and the high-precision star locations of Hipparcos and future astrometric satellites could this change in favor of directional measurements.