By 1975 the hunt for GRB counterparts had been on for almost ten years without success. Gamma burst instruments of that day provided little or no directional data in themselves. Positions could be extracted only using the time delay technique – potentially accurate but very slow. Triggered by a japanese report of a balloon instrument for GRB studies based on a Rotation Modulation Collimator we at the Danish Space Research Institute started the development of an RMC detector for GRBs, the WATCH wide field monitor.
Four WATCH units were flown on the Soviet Granat satellites, and one on ESA’s EURECA satellite. The design and results will be summarized. Now, 35 years later, recent detector developments may allow the construction of WATCH-type instruments able to fit weight, power and data-wise into 1 kg cubesats. This could provide the basis for a true all-sky monitor with 100 percent duty cycle for rare, bright events.