GRAINE (Gamma-Ray Astro-Imager with Nuclear Emulsion)

Developed by Kobe University / Nagoya University / Okayama University of science / Aichi University of Education / Gifu University / Japan Aerospace Exploration Agency (JAXA)

Balloon launched on 4/29/2023, from Australian Balloon Launching Station, Alice Springs, Australia

Purpose of the flight and payload description

GRAINE is the acronym for Gamma-Ray Astro-Imager with Nuclear Emulsion, is a high-resolution gamma-ray telescope for the observation of cosmic gamma-rays onboard long duration balloon missions. The instruments observes particles in the energy range between 10 MeV and 100 GeV, with emulsion plates that combines high precision, sensibility to the polarization and large-aperture-area. It was developed by an extensive collaboration that includes Kobe University, Nagoya University, Okayama University of science, Aichi University of Education and Gifu University and counts with the fundamental support of the balloon program of the Japan Aerospace Exploration Agency (JAXA).

Basically, the instrument is composed by a converter, a timestamper, a calorimeter and an attitude monitor. The converter consists of an stack of emulsion films (with metal foils) where the beginning of electron pairs are detected. The timestamper is composed by a multi-stage shifter which gives a time resolution below a second to events at the converter. The calorimeter consists of a stack of emulsion films with metal plates that measures high energy particles either by measuring the energy of the electro-magnetic shower or the momentum of electron pair with multiple coulomb scattering. Particles of low energies are measured at the converter by measuring the momentum of electron pair with multiple coulomb scattering.

The attitude monitor consists of a star camera located outside the gondola. By combining the attitude monitor information and the event timing, the gamma-ray direction relative to the celestial sphere could be determined.

At left we can see a basic scheme of the instrument in the version flown in 2023.

Details of the balloon flight

Balloon launched on: 4/29/2023 at 21:02 utc
Launch site: Australian Balloon Launching Station, Alice Springs, Australia  
Balloon launched by: Japan Aerospace Exploration Agency (JAXA)
Balloon manufacturer/size/composition: Zero Pressure Balloon model B300 300.000 m3
Flight identification number: B23-01
End of flight (L for landing time, W for last contact, otherwise termination time): 4/30/2023 at 23:17 utc
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): 26 h 45 m
Landing site: 220 km S of Longreach, Queensland, Australia

External references

Images of the mission

Assembling the nuclear emulsion film in the gondola Lowering the top half of the container, note it is deflated. Later will be presurized and would acquire its final cylindrical shape. The finaly assembled instrument and the team a few days before the flight The launch vehicle hoisting the GRAINE instrument. Inthe background, the balloon still being inflated. The balloon ascending with the payload.

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