The gamma-ray lens technology reference study

Abstract The Science Payload and Advanced Concepts Office (SCI-A) at the European Space Agency (ESA) conducts technology reference studies (TRSs), hypothetical science driven missions that are not currently part of the ESA science programme. The purpose of the TRS programme is to establish a series of preliminary scientific requirements and, from these, define technology development activities required in order to realise similar potential future missions. One such TRS has been conducted on a gamma-ray lens (GRL) mission. In response to the realisation that greatly increased sensitivity in gamma-ray astronomy requires a focusing optic, the GRL TRS investigates the application of a broad bandpass Laue crystal lens, a novel high-energy focusing optic, to a gamma-ray observatory. Two mission concepts are considered: a Soyuz Fregat, dual-launch mission and a larger Ariane 5 mission. Due to the long focal length of the optics, both mission scenarios require formation flying between two spacecraft. This paper focuses on the establishment of a baseline mission design capable of meeting a set of reference science objectives. The key mission and spacecraft design drivers are introduced and preliminary mass budgets are established. Finally, necessary areas for future study and technology development, key to the realisation of a gamma-ray focusing mission using Laue crystals, are presented, in line with the main objective of TRSs.