A next generation Ultra-Fast Flash Observatory (UFFO-100) for IR/optical observations of the rise phase of gamma-ray bursts

Abstract

The Swift Gamma-ray Burst (GRB) observatory responds to GRB triggers with optical observations in ̃ 100 s, but cannot respond faster than ̃ 60 s. While some rapid-response ground-based telescopes have responded quickly, the number of sub-60 s detections remains small. In 2013, the Ultra-Fast Flash Observatory-Pathfinder is expected to be launched on the Lomonosov spacecraft to investigate early optical GRB emission. Though possessing unique capability for optical rapid-response, this pathfinder mission is necessarily limited in sensitivity and event rate; here we discuss the next generation of rapid-response space observatory instruments. We list science topics motivating our instruments, those that require rapid optical-IR GRB response, including: A survey of GRB rise shapes/times, measurements of optical bulk Lorentz factors, investigation of magnetic dominated (vs. non-magnetic) jet models, internal vs. external shock origin of prompt optical emission, the use of GRBs for cosmology, and dust evaporation in the GRB environment. We also address the impacts of the characteristics of GRB observing on our instrument and observatory design. We describe our instrument designs and choices for a next generation space observatory as a second instrument on a lowearth orbit spacecraft, with a 120 kg instrument mass budget. Restricted to relatively modest mass, power, and launch resources, we find that a coded mask X-ray camera with 1024 cm2 of detector area could rapidly locate about 64 GRB triggers/year. Responding to the locations from the X-ray camera, a 30 cm aperture telescope with a beam-steering system for rapid (̃ 1 s) response and a near-IR camera should detect ̃ 29 GRB, given Swift GRB properties. The additional optical camera would permit the measurement of a broadband optical-IR slope, allowing better characterization of the emission, and dynamic measurement of dust extinction at the source, for the first time. © 2012 SPIE.