OMC: An optical monitoring camera for INTEGRAL

The INTEGRAL payload has been designed to study simultaneously gamma-ray so urces in a wide field of view over many decades in energy (around 2 eV + 4 keV - 20 MeV) and thus make a major contribution to short time-scale high-e nergy astrophysics. The OMC will observe the optical emission from the prim e targets of the gamma-ray instruments with the support of the X-ray monito r. This capability will provide invaluable diagnostic information on the na ture and the physics of the sources over a broad wavelength range. The main scientific objectives will be: (1)to monitor the optical emission from the sources observed by the gamma- and X-ray instruments, measuring th e time and intensity structure of the optical emission for comparison with variability at high energies, and (2) to provide the brightness and positio n of the optical counterpart of any gamma- or X-ray transient taking place within its field of view. The OMC will be based on a refractive optics with an aperture of 50 mm focu sed onto a large format CCD (1024 x 2048 pixels) working in frame transfer mode (1024 x 1024 pixels imaging area). With a field of view of 5 x 5- it w ill be able to monitor sources down to V = 19 mag. Typical exposures will c onsist of 10 integrations of 100 seconds each.