GRBAlpha: The smallest astrophysical space observatory

I. Detector design, system description, and satellite operations

¹ Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Konkoly-Thege M. út 15-17, 1121 Budapest, Hungary
e-mail: apal@szofi.net
² Hiroshima University, School of Science, 1-3-1 Kagamiyama, Higashi-Hiroshima, Japan
³ Department of Theoretical Physics and Astrophysics, Faculty of Science, Masaryk University, Kotlárská 267/2, Brno 611 37, Czech Republic
⁴ Spacemanic Ltd, Jablonec 110, 900 86 Jablonec, Slovakia
⁵ Faculty of Aeronautics, Technical University of Košice, Rampová 1731/7, 040 01 Košice, Slovakia
⁶ Department of Radio Electronics, Faculty of Electrical Engineering and Communication, Brno University of Technology, Technická 3058/10, 616 00 Brno-Královo Pole, Czech Republic
⁷ Needronix Ltd, Geologická 1, 821 06 Bratislava, Slovakia
⁸ Department of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
⁹ EDIS vvd., Rampová 7, 041 21 Košice, Slovakia
¹⁰ INAF Istituto di Astrofisica Spaziale e Fisica Cosmica, via Bassini 15, 20133 Milano, Italy
¹¹ Institute of Earth Physics and Space Science (EPSS), Csatkai E. u. 6-8, 9400 Sopron, Hungary
¹² Department of Physics and Astronomy, Universiteit Gent, Proeftuinstraat 86, 9000 Gent, Belgium
¹³ School of Science, Kyoto University, 1 Matsugasakihashigami-cho, Sakyo-ku, Kyoto, Japan
¹⁴ Eötvös Loránd University, Institute for Physics, Pázmány Péter stny. 1/A, Budapest, Hungary
¹⁵ Wigner Research Centre for Physics, Konkoly-Thege Miklós út 29-33, 1121 Budapest, Hungary
¹⁶ Department of Physics, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima-ku, Tokyo, Japan
¹⁷ Department of Theoretical Physics, Institute of Physics, Budapest University of Technology and Economic, M˝uegyetem rkp. 3, 1111 Budapest, Hungary
¹⁸ MTA-BME Quantum Dynamics and Correlations Research Group, Budapest University of Technology and Economics, M˝uegyetem rkp. 3, 1111 Budapest, Hungary
¹⁹ Department of Earth and Space Science, Osaka University, 1-1 Machikaneyamacho, Toyonaka, Osaka, Japan
²⁰ Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Japan
²¹ Tokyo University of Science, 2641 Yamazaki, Noda, Chiba, Japan

Received: 18 February 2023
Accepted: 27 March 2023

Abstract

Aims. Since it launched on 22 March 2021, the 1U-sized CubeSat GRBAlpha operates and collects scientific data on high-energy transients, making it the smallest astrophysical space observatory to date. GRBAlpha is an in-orbit demonstration of a gamma-ray burst (GRB) detector concept suitably small to fit into a standard 1U volume. As was demonstrated in a companion paper, GRBAlpha adds significant value to the scientific community with accurate characterization of bright GRBs, including the recent outstanding event of GRB 221009A.

Methods. The GRB detector is a 75 × 75 × 5 mm CsI(Tl) scintillator wrapped in a reflective foil (ESR) read out by an array of SiPM detectors, multi-pixel photon counters by Hamamatsu, driven by two separate redundant units. To further protect the scintillator block from sunlight and protect the SiPM detectors from particle radiation, we applied a multi-layer structure of Tedlar wrapping, anodized aluminium casing, and a lead-alloy shielding on one edge of the assembly. The setup allows observations of gamma radiation within the energy range of 70–890 keV with an energy resolution of ~30%.

Results. Here, we summarize the system design of the GRBAlpha mission, including the electronics and software components of the detector, some aspects of the platform, and the current semi-autonomous operations. In addition, details are given about the raw data products and telemetry in order to encourage the community to expand the receiver network for our initiatives with GRBAlpha and related experiments.