Jun Nishimura

γ-Ray burst observed at balloon altitude

SINCE the γ-ray burst was discovered in 1973, approximately 50 events have been observed using artificial satellites1,2. In addition, several bursts of smaller size have been found using balloon-borne detectors3–6 with large sensitive areas. No burst has yet been located on the celestial sphere, with an adequate precision to associate it with an astronomical object. To determine the precise position of a γ-ray burst which had not been predicted to occur, the detector must have a wide field of view and the capability of precise location of the source. A rotating cross-modulation-collimator (RCMC) proposed7 as a device to fulfill these apparently conflicting requirements was used in the series of balloon observations reported here. A small γ-ray burst was found during ∼ 150 h of observations and its celestial position was determined with a precision of ∼ 0.3°.

A development of a balloon made of fiber reinforced film

In present ballooning missions, as payloads increasingly become heavier and more sophisticated, much higher reliability is required in the balloon itself and in the launch operational technique. Hence, ISAS (the Institute of Space and Astronautical Science) has developed a balloon made of relatively thick films reinforced with high-strength fiber fabric (ref. 1 to 3). In order to verify structural properties and manufacturing quality, partial strength tests together with a trial production of small scale balloons have been car ied 5 . out. In 1990, a sub-scale B5 (5,000 m In volume) size balloon was produced, and a full inflation test on the ground prior to a flight experiment was implemented on account of demonstrating the basic capability of the fiber reinforced balloon. This paper describes research and development of the proposed balloon associated with selection and verification study of the high-strength fiber reinforced film.