EXIST Free Flyer

EXIST would include 3 large area (2.7 m² each) coded aperture telescopes each with field of view 60° x 75°, for a combined total detection area of 8 m² and field of view 180° x 75°. The 180° "fan beam" is oriented perpendicular to the orbital direction so that the full sky is imaged each orbit. Any given source is observed for at least 20% of the time, with sources closer to the orbital poles having correspondingly longer exposures. The EXIST survey sensitivity is a factor of ~1000 greater than the only previous full-sky, but non-imaging survey (HEAO-A4; 1979).

Mission Study Report (Dec 2002)
White Paper for EXIST (Jan 2002)

A Few Overview Figures


Wide axis of fan beam (180° x 75°) is perpendicular to scan direction, so whole sky is swept out over one orbit.	View of 9 sub-telescopes.	Within the Delta IV shroud.

Est. BG spectra (J. Hong). Major components are cosmic diffuse, cosmic rays, and spallation. Full-array BG rate ~25000 cts/s.	Sensitivity of EXIST and other surveys.

Sensitivity vs energy for 3 telescopes. "20° x 25°" should read "180° x 75° fully coded".	Approximate 1-day coverage plotted in Galactic coordinates. Exposure is greatest at orbital poles. This is for the ISS orbit, with inclination ~52°, which smoothes out much of the nonuniformity.