ASTROGAM is a space mission dedicated to the observation of the Universe with unprecedented sensitivity in the mostly unexplored energy range 0.3 MeV - 100 MeV (extending up to GeV energies). It has been proposed for the 2014 ESA M4 Call. ASTROGAM is designed to achieve:

  1. the best gamma-ray sensitivity (by a factor of 10-30) ever obtained in the range 0.3 MeV - 100 MeV;
  2. an exceptional angular resolution for gamma-rays in the range 50 MeV – 1 GeV (0.15 deg at 1 GeV);
  3. a very large field of view (2.5 sr);
  4. polarization capability for both steady and transient sources;
  5. sub-millisecond trigger, fast processing, and alert capability for cosmic and terrestrial transients.

This performance is to be obtained by Silicon detector technology with analog readout, a technique already successfully employed in space. ASTROGAM is based on the AGILE, Fermi, PAMELA and AMS heritage, and has mostly readiness > 6 for the space and ground segments.

ASTROGAM will focus on the 0.3-100 MeV energy range. This energy window is unique for studying matter evolution, antimatter generation and very energetic phenomena in compact objects and massive black holes. ASTROGAM’s wide field of view opens up the transient sky, rich with the prospect of unanticipated discoveries. Until now, instruments in this energy range lacked the sensitivity for a breakthrough. The ASTROGAM sensitivity will improve that of previous detectors by a factor of 10-30 in the 0.3-30 MeV range, it will explore for the first time the 30-100 MeV range, and will substantially improve the Fermi sensitivity in the 100 MeV – 1 GeV range by a combination of excellent angular resolution and optimized pointing strategy. Polarization can be very effectively measured in the MeV range and above.

Definite answers about fundamental questions regarding our Universe can be provided only by high-sensitivity observations in the 0.3-100 MeV range. ASTROGAM is ideally equipped to focus on three main themes:

  1. matter and antimatter in our Galaxy and beyond;
  2. accelerators in the close and far Universe;
  3. fundamental physics and new messengers.

A large number of fundamental issues are still unsolved from previous and current high-energy astrophysics missions (X-ray missions, CGRO, Integral, AGILE and Fermi) in the energy range from hard X-rays up to tens or hundreds of 100 GeV. Planned or to-be-developed detectors/telescopes in other wavelengths for the next decade (including SKA, advanced LIGO and VIRGO, CTA, Athena, possibly GAMMA-400) will not be able to significantly address the ASTROGAM science drivers. On the other hand, working in synergy with the aforementioned instruments, ASTROGAM will be absolutely crucial and unique in the next decade.

The 0.3-30 MeV energy range is notoriously difficult to study. It requires an efficient instrument working in the “Compton regime” with an excellent background subtraction: since COMPTEL, no space instrument obtained extra-solar gamma-ray data in the 2-30 MeV range. ASTROGAM resolves the technical issues regarding on-board Compton event detection and background subtraction by an optimal instrument configuration based on Silicon technology, state-of-the-art analog readout, and efficient data acquisition.

ASTROGAM will open a new window of opportunity for discovery in the high-energy Universe. It will work in full synergy with space and ground detectors including radio and optical telescopes, TeV instruments, gravitational wave detectors and neutrino experiments. ASTROGAM data, to be distributed to the community through a Guest Observer Programme, will have a huge impact on a broad variety of topics including baryogenesis and fundamental physics, nucleosynthesis and cosmic rays, compact objects, AGNs, GRBs.