BeppoSAX is a scientific X-ray satellite programme developed by
the Italian Space Agency (ASI) with a contribution from the Netherlands agency
for Aerospace Programs (NIVR) and the Space Research Organisation
Netherlands (SRON) (Boella et al. 1996a).
Galactic and extragalactic sources will be
observed in the energy band of 
. The satellite
has been launched on April 30, 1996 and operates succesfully in a low equatorial
orbit.
SAX carries six scientific instruments, including
two identical Wide Field Cameras (WFCs),
pointing 180
away from each other, perpendicular to the sun
vector and to the other instruments (Parmar et al. 1996;
Boella et al. 1996b; Manzo et al. 1996;
Frontera et al. 1996).
The WFCs are coded mask cameras for imaging of hard X-ray sources and are part of the Dutch contribution to BeppoSAX. Three WFCs have been developed and built by SRON Utrecht, two of which were integrated in the satellite and one was used for testing purposes and as a flight spare instrument.
Other comparable coded mask type cameras that have flown or will fly are a.o. the SL2-XRT experiment onboard Spacelab-2 (Willmore et al. 1985), COMIS/TTM on KVANT/MIR (Brinkman et al. 1983), ART-P on the GRANAT mission (Sunyaev et al. 1990) and MART/LIME on Spectrum X-Gamma (Bazzano et al. 1994). An overview of X-ray astronomy missions is given by Bradt et al. (1992). The WFCs can carry out spatially-resolved simultaneous monitoring of compact X-ray sources in crowded fields with high sensitivity. This allows for systematic spectral variability studies of different types of compact X-ray sources over a large range of timescales. Surveys of selected sky regions such as the galactic centre are carried out to search for and study the characteristics of X-ray transients. The WFCs image X-ray emission of various classes of astrophysical objects, ranging from nearby stars to active galactic nuclei. In addition, the WFCs will monitor large regions of the sky for previously unknown X-ray sources, such as black hole candidates and neutron stars, for follow-up studies with the narrow field instruments onboard BeppoSAX.
Here we discuss the design and performance of the instrument as well as the principle for the image reconstruction and the analysis software.