EXITE2 detector and telescope development and initial balloon flight results

The second-generation Energetic X-ray Imaging Telescope Experiment (EXITE2) is designed to image (22 arcmin resolution) and measure spectra of cosmic X-ray sources in the 20-600 keV band from a high altitude scientific balloon. We describe the continued development of the EXITE2 imaging phoswich (NaI/CsI) detector and its pulse-shape discriminator (PSD) as well as tagged calibration source (Am-241) system. A low-gain imaging readout and event blanking system has been implemented with the PMT dynodes to minimize effects of cosmic ray saturation and afterglow. Detector and gondola housekeeping, as well as quick-look science data, can be monitored in a real-time data display system. New gondola target acquisition systems, including real-time display of coarse azimuth (/spl sim/6 arcmin) from on-board GPS and a rotating sun-sensor, have been implemented. An off-axis CCD camera plus an on-axis intensified CCD camera and overlaid predicted star field have been developed for measurement of telescope fine aspect (/spl sim/1 arcmin). An on-board flight computer system for data recording and event compression has been implemented. All systems were tested on the first EXITE2 science flight on 7-8 May 1997 from Ft. Sumner, NM. Results of the detector and gondola performance, as well as initial hard X-ray imaging results on the black hole candidate Cygnus X-1, are reported.