Super-TIGER launched Dec. 8, 2012, from the long duration balloon site near McMurdo Station, Antarctica. The massive 39-million cubic foot scientific balloon carries the 6,000 pound Super-TIGER payload -- equivalent to a large sports utility vehicle -- at a float altitude of 127,000 feet, more than four times the altitude of most commercial airliners. Size-wise, more than 200 blimps could fit inside the balloon. The Super-TIGER collaboration includes Washington University in St. Louis, GSFC, Caltech, and JPL.
Super-TIGER will measure the individual abundances of elements over the range 30 ≤ Z ≤ 42 with high statistical accuracy to test and clarify the emerging model of cosmic-ray origin in OB associations and models for atomic processes by which nuclei are selected for acceleration. Exploratory measurements with lower statistics will extend to Z = 60. Super-TIGER will also measure, with excellent statistical precision, the energy spectra of the more abundant elements 14 ≤ Z ≤ 28 at energies 0.8 ≤ E ≤ 10 GeV/nucleon. These measurements will provide a sensitive test of the hypothesis that microquasars or other phenomena could superpose features on the otherwise smooth energy spectra.
Super-TIGER is based on experience with the smaller TIGER instrument that was flown from Antarctica in 2001 and 2003 for a total of 50 days and produced the first measurements of individual element abundances for 31Ga, 32Ge, and 34Se. Three layers of plastic scintillator and two Cherenkov detectors, one with an acrylic radiator and one with a silica aerogel radiator determine the charge and energy of incident nuclei. A scintillating optical fiber hodoscope gives particle trajectories to enable corrections for pathlength through the detectors, detector response maps, and interactions in the atmosphere and in the instrument.
Super-TIGER uses two independent detector modules, each with a 1.15 m × 2.3 m active area, giving a total detection area of 5.4 m2. Each module is only 60 cm thick to maximize its geometric acceptance. The detector layout and minimal column density give an effective geometry factor of 2.5 m2 sr at Z = 34, over 4 times larger than TIGER. In two flights, Super-TIGER will achieve nearly an order of magnitude improvement in statistics compared to TIGER.
GSFC is responsible for the acrylic and aerogel Cherenkov detectors, the scintillators, and the mechanical structure of the instrument and payload. In addition, instrument and payload integration will be carried out at GSFC. Detector and payload system designs were finalized this year and construction is underway. Instrument integration will begin in November 2011.
Super-TIGER is a forerunner of the ENTICE (Energetic Trans-Iron Composition Experiment) instrument proposed for the OASIS (Orbiting Astrophysical Spectrometer in Space) mission. In a three-year mission, ENTICE would provide the first statistically significant elemental-abundance measurements in the actinide range.