Session 48 - Gamma Rays & X-ray Instrumentation.
Display session, Thursday, January 08
Exhibit Hall,

## [48.15] The ROTSE Project

S. Marshall (LLNL), C. Akerlof, R. Kehoe, B. Lee, T. McKay (U.Mich), J. Bloch, D. Casperson, S. Fletcher, G. Gisler, G. Partridge, W. Priedhorsky, D. Roussel-Dupre, J. Szymanski (LANL)

The ROTSE (Robotic Optical Transient Search Experiment) collaboration is constructing two independent detector systems to search for gamma-ray burst optical counterparts immediately following a trigger signal from satellite instruments such as BATSE. ROTSE-I is a four-fold array of telephoto lenses imaging to large format, cooled CCDs. The angular coverage is 16.4^\circ \times 16.4^\circ with a limiting magnitude of m_v \simeq 15 for a 5-second exposure. This system is installed at the Los Alamos National Laboratory at a temporary site east of the LAMPF accelerator. Automated operation will begin in early 1998. A more ambitious system is called ROTSE-II. It consists of two 0.45 m aperture telescopes with f ratios of 1.9. Each telescope covers a field of view of 1.9^\circ \times 1.9^\circ and is expected to achieve a limiting magnitude of m_v \simeq 18 for a 10-second exposure. By scanning around the most probable burst location, a 16^\circ \times 16^\circ error box can be searched in 16 minutes. More accurate initial coordinates will permit faster scans or deeper images. Delivery of the first ROTSE-II telescope is scheduled for November, 1997. By co-adding frames, both ROTSE-I and ROTSE-II will be able to detect objects considerably fainter than the limits quoted above. In particular, ROTSE-II should be able to find optical transients at the levels discovered for GRB 970228 and GRB 970508. The status of observations will be discussed.