FIGSAG: An Overview of Future Innovations in Gamma-ray Science

We present an overview of the FIGSAG Report. There are some science questions that can only be answered by observing gamma rays from space. Neither MeV nor GeV gamma rays can be observed from the ground due to atmospheric absorption. The MeV band has historically been underexplored, but new developments in Compton event reconstruction now make it technologically feasible to dramatically increase observational sensitivity. This new window into the extragalactic universe of blazars and GRBs brings the opportunity to change the paradigm on questions of jet launching, black hole dynamics, and particle acceleration that have pervaded our field for over 50 years. In the GeV range, where Fermi-LAT revolutionized so many fields, but has also highlighted new populations. The number of pulsars known in the gamma rays has grown by orders of magnitude since Fermi launched, and we cannot see to even the center of the galaxy. Pulsars are now used in a timing array to detect gravitational waves from supermassive black hole mergers - PTAs are the only way to detect the largest black hole mergers. GeV PTAs are more scalable than radio and could, with sufficient sensitivity include pulsar baselines throughout the whole galaxy. How black holes form, merge and influence their environments is fundamentally gamma-ray science and requires targeted investment from NASA Astrophysics.