  Several payloads for hard X-ray (20-600 keV) imaging with coded aperture
telescopes have been developed for balloon flight observations of cosmic x-ray
sources. We briefly review the characteristics of these, particularly the
EXITE2 system. The recent NASA program to develop an extended long duration
(100d) balloon flight capability employing super-pressure balloons would allow
a qualitatively new hard x-ray imaging experiment: the Energetic X-ray Imaging
Survey Telescope-Long Integration Time Experiment (EXIST-LITE). The longer
continuous viewing times (per source) available from an LDB platform than from
low earth orbit would enable both surveys and objectives complementary to the
EXIST mission proposed for a MIDEX satellite. We summarize the scientific
objectives of EXIST-LITE, a possible instrumentation approach incorporating a
large area array of Cd-Zn-Te (CZT) detectors, and our program for the
development and balloon flight testing of relatively thick (5mm) CZT detector
arrays.
