# A Review of Requirements for Gamma Radiation Detection in Space Using CubeSats
## 1 Introduction  
The aim of this work is to provide an overview about gamma-ray detection in space by means of instruments on-board CubeSat spacecrafts. CubeSat missions represent a relatively new way of accessing space by typically investing a few hundred thousands USD, including the launch costs. CubeSats were originally proposed by Professor [PERSON] at California Polytechnic State University (Cal Poly) and Professor [PERSON] at Stanford University's Space Systems Development Laboratory (SSDL) to \"develop a pico-satellite standard that significantly reduces the cost and development time of student satellites\" [1]. Ever since, the concept gained significant attention and has led to several universities and \"new space\" companies around the world adopting the standard with over 1500 CubeSats already launched and several hundreds of them expected to be launched in next two years [2]. Although initially intended for education purposes, CubeSats nowadays are increasingly being developed by commercial and governmental entities [3]. The technological advances leading to miniaturization of components, development of lighter and stronger materials suitable for space environment, and increasing efficiency of power generation and power storage systems have led to the so-called \"new space\" paradigm and has ushered the new era of wider private sector engagement in space activities. The evolution of CubeSats played a crucial role in this paradigm shift as they provided cheaper and faster ways to demonstrate novel technologies for space applications [4]. The unprecedented selection of miniaturized electronic components offering high performance at low power budget, new cost-effective photosensing technologies that are largely accessible, along with the development of additive manufacturing techniques, made CubeSats the ideal tools for the investigation of astronomical and atmospheric events involving the emission of high energy photons. Detection of gamma-rays in space earned more and more relevance over the last sixty years [5]. This was initiated with the deployment of constellations of satellites for homeland security and nuclear proliferation monitoring, and it quickly opened a new era in science with the serendipitous detection of Gamma-Ray Bursts (GRB) [6; 7; 8; 9; 10; 11; 12], lately evolving into a diverse population of gamma-ray detectors already orbiting (or planned to orbit) around the Earth at various elevations to accommodate the science targets for various applications such as cosmology, general relativity, astroparticle physics, astrophysics, high energetic atmospheric physics, etc. However, most of these detectors are either bulky or require significant power making them not suitable for inclusion in small satellite missions. Modern instruments for gamma-ray detection are often required to provide timing and spectroscopic details of collected events. This is usually achieved by instrumenting the payload with multiple and optically independent scintillating crystals coupled to a photosensing technology, that is typically based on the use of Photomultiplier Tubes (PMT), Avalanche Photodiodes (APD) and, more recently, Silicon Photomultipliers (SiPM) and Multi-Pixel Photon Counters (MPPC) and with custom designed readout electronics. Using CubeSats as platform opens up new possibilities for sending compact gamma-ray detectors in space, possibly creating constellations with the capability of detecting GRBs or other transient gamma ray emissions such as Terrestrial Gamma Ray flashes (TGFs) [13], or as atmospheric radiation monitors [14; 15]. The paper outlines recommendations for a candidate detector as core instrument of (2U or larger) CubeSat missions targeting gamma-rays and orbiting in Low-Earth Orbit (LEO).