Instruments carried aloft by rockets, balloons, and satellites allow us to avoid atmospheric obscuration, and obtain valuable astrophysical knowledge that is unavailable by ground observations. Our project consists of the following two topics.

(Sub-project 1) Cosmic X-ray and gamma-ray studies with scientific satellites

Scientific satellites allow us to detect cosmic X-ray and gamma-ray photons, which carry valuable information from mass-accreting black holes, fast-rotating pulsars, expanding supernova remnants, active galactic nuclei, hot gases in clusters of galaxies, and gamma-ray bursts. We have developed the Hard X-ray Detector, and put it onboard the Suzaku satellite (Figure 1) launched in 2005. Our Suzaku studies clarified the physical condition of mass streams onto black holes, yielded some hints on general relativistic effects therein, and detected enigmatic hard X-rays form so-called $B!H(Bmagnetars$B!I(B. Our results also include accurate deerminations of the masses of white dwarfs, and a discovery of extremely hot gas in a cluster of galaxies. In gamma-ray energies, the data from the Fermi gamma-ray space telescope, launched in 2008 June, are utilized, to measure cosmic-ray fluxes outside the Solar system. We also develop new instruments to be onboard ASTRO-H, scheduled for launch in 2013 as a successor to Suzaku.

Figure 1 : The launch of the Suzaku X-ray observatory, by an M5 rocket from the Uchinoura Space Center at Kagoshima. It took place on 2005 July 10.

(Sub-project 2) Balloon observations of cosmic anti-protons

Cosmic rays reaching the Earth contain a trace amount of anti-protons, which are produced in the interstellar space via cosmic ray collisions with interstellar medium. However, lower-energy anti-protons may be produced via more exotic processes, including annihilation of heavy relic particles, or evaporation of primordial black holes. In search for such anti-proton components, we have been conducting a balloon experiment called BESS (Balloon Experiment with Superconducting Spectrometer) since 1993, in Canada and other places where the geomagnetic barrier for cosmic rays is rather low. The experiment utilizes a specially developed superconducting solenoid for particle identification. The most recent two balloon flights were conducted in Antarctica, to realize long-duration observations. We have already detected more than 3000 anti-protons, and keep examining the data for any hint of excess anti-proton flux indicative of the exotic processes. In addition, we have derived stringent upper limits on the flux of cosmic anti-helium nuclei, which cannot be produced by cosmic ray collisions.

Figure 2 : The launch of a balloon carrying the BESS Polar-II experiment, from Williams Field, near the McMurdo Station, in Antarctica (2007 December 23).