Introduction

The Explosive Transient Camera has been developed primarily to establish the existence of optical counterparts for GRBs and is currently the most sensitive optical transient experiment in operation. It does not require a trigger from BATSE or any other experiment, but automatically searches for any rapid optical flashes of duration (1-10 s) over a wide field of view. Detection of an optical flash by the ETC in coincidence with a BATSE gamma-ray burst detection would confirm that GRB sources produce emission at optical wavelengths and would localize the burst position to ~10-20 arc seconds, as opposed to the ~2.5 degree localization possible with BATSE alone[1]. A coincident observation would allow for immediate follow-up observations by interested optical, IR, radio and satellite observatories, greatly increasing the chances of detection of long-lived non-gamma-ray emission from a GRB source and adding greatly to the understanding of cosmic gamma-ray bursts.

The ETC is also able to search for other variable sources on short time scales (1-10 s) as well as on longer time scales ranging from hours to years. This latter goal is achieved by collecting an archive of sky images in which each part of the ETC declination band is imaged on average more than 60 separate times per year.

The ETC is housed in a dedicated building on the summit ridge at Kitt Peak National Observatory, U.S.A. and is described in a number of references[2,3,4]. It is a fully automated instrument, and normally operates entirely by computer control without human intervention. Data collected each night is automatically transferred to Massachusetts Institute of Technology (MIT) for further analysis.

Hans Krimm
Thu Jun 13 14:06:17 EDT 1996