I-03

Ballerina - A small Gamma Ray Burst Mission

Soren Brandt(1), Niels Lund(1), and Bernd Aschenbach(2)

(1) Danish Space Research Institute (2) MPE, Garching

The cosmological origin of gamma ray bursts has now been established with certainty. Many more bursts will need to be studied establish the typical distance scale, and to map out the large variability in properties which have been indicated by the first handful of well-studied events. We are proposing Ballerina, a small satellite to provide new data on the gamma burst phenomenon and accurate positions at a rate an order of magnitude larger than obtained from Beppo-SAX. Ballerina will be capable of detecting and studying about 70 burst per year, providing real time positions with an accuracy better than 30 arc seconds. The Ballerina payload will consist of a true all-sky monitor covering 4 pi steradian, and a unique combination of a grazing incidence X-ray telescope and a collimated telescope. By quick reorientation of the spacecraft in response to a gamma burst detection, Ballerina will provide important spectral information in the 0.2-20 keV band on the early phase of the X-ray afterglow. With a 50 all-sky coverage Ballerina will focus on the study of brighter GRBs, for which follow-up observations in all wavelength bands are likely to be particularly rewarding.