The Gamma RAy Polarimeter Experiment (GRAPE) was first own on a 26-hour balloon flight in the fall of 2011. GRAPE consists of an array of Compton polarimeter modules (based on traditional scintillation technologies) designed to operate in the energy range from 50 keV up to 500 keV. The ultimate goal of our program is to operate GRAPE in a wide FoV configuration for the study of gamma-ray bursts. For the first balloon flight, GRAPE was configured in a collimated mode to facilitate observations of known point sources. The Crab nebula/pulsar, the active Sun, and Cygnus X{1 were the primary targets for the first flight. Polarization results from this flight are summarized. Plans for the next GRAPE balloon flight, which is scheduled to take place in the fall of 2014 from Ft. Sumner, NM, will also be presented. These plans involve modifications designed to improve the polarization sensitivity, including an expansion of the array of polarimeter modules from 16 to 24 and improvements to the instrument shielding. These improvements to the instrument will significantly improve the polarization sensitivity, enabling a measurement of the Crab Nebula polarization to be made during the 2014 balloon flight.

Date Published: 25 July 2014
PDF: 10 pages
Proc. SPIE 9144, Space Telescopes and Instrumentation 2014: Ultraviolet to Gamma Ray, 91443P (25 July 2014); doi: 10.1117/12.2056886

Published in SPIE Proceedings Vol. 9144:
Space Telescopes and Instrumentation 2014: Ultraviolet to Gamma Ray
Tadayuki Takahashi; Jan-Willem A. den Herder; Mark Bautz, Editor(s)