Abstract
The Nuclear Compton Telescope (NCT) is a wide-field gamma-ray imager utilizing state of the art, cross-strip germanium detectors for Compton imaging of astrophysical sources. NCT underwent a prototype flight in 2005 to verify the instrumental background, and a first-light ConUS flight in 2009 which resulted in a detection of the Crab nebula as a verification of the instrument sensitivity. Unfortunately, a launch mishap during NCT's first science campaign in 2010 left the instrument largely destroyed. A rebuild of the NCT instrument is currently underway with an expected return to flight readiness in late 2013. The rebuilt NCT detector system is comprised of twelve high-purity germanium detectors and an active CsI scintillator shield. The cryogenics system has been redesigned and now employs a cryocooler, which, along with an all-new, low-mass gondola, qualifies NCT to fly on the Ultra Long Duration balloon (ULDB) platform. ULDB flights may last up to 100 days, effectively improving NCT's sensitivity over the course of a flight and opening up new science opportunities. The NCT collaboration is currently proposing to NASA for the science flight program, which will include an LDB flight from Kiruna, Sweden in 2014 and a ULDB flight from Wanaka, New Zealand in 2016. MEGAlib/GEANT4 simulations of the instrument were performed for the two launch scenarios and the instrument performance was determined. Primary science goals for the NCT balloon flights include mapping of the galactic bulge/disk positron annihilation line at 511 keV in order to shed light on the positron source(s), mapping of 26Al (1.809 MeV) and 60Fe (1.173 MeV and 1.333 MeV) emission to uncover the galactic history of core-collapse supernovae, and detection and measurement of polarization from gamma-ray bursts.