  The success of the SWIFT/BAT and INTEGRAL missions has definitely opened a
new window for follow-up and deep study of the transient gamma-ray sky. This
now appears as the access key to important progresses in the area of
cosmological research and deep understanding of the physics of compact objects.
To detect in near real-time explosive events like Gamma-Ray bursts,
thermonuclear flashes from Neutron Stars and other types of X-ray outbursts we
have developed a concept for a wide-field gamma-ray coded mask instrument
working in the range 8-200 keV, having a sensitivity of 0.4 ph cm-2 s-1 in 1s
(15-150 keV) and arcmin location accuracy over a sky region as wide as 3sr.
This scientific requirement can be achieved by means of two large area, high
spatial resolution CZT detection planes made of arrays of relatively large
(~1cm2) crystals, which are in turn read out as matrices of smaller pixels. To
achieve such a wide Field-Of-View the two units can be placed at the sides of a
S/C platform serving a payload with a complex of powerful X-ray instruments, as
designed for the EDGE mission. The two units will be equipped with powerful
signal read out system and data handling electronics, providing accurate
on-board reconstruction of the source positions for fast, autonomous target
acquisition by the X-ray telescopes.
