Recent results from observations with ground-based instruments H.E.S.S., MAGIC and VERITAS have shown that very-high-energy (VHE; E > 100 GeV) gamma-ray astronomy is a powerful tool for the exploration of the non-thermal universe. These instruments have reached a level of sensitivity that allows them to detect gamma rays from a large number of new sources, both inside and outside of the Galaxy. Some of these new sources are further examples of classes of astronomical objects previously known to emit VHE gamma rays, such as Blazars (a type of galaxy with an active nucleus) and supernova remnants. Other new sources represent classes of objects which are new to gamma-ray astronomy, such as binary stars, flat spectrum radio quasars (FSRQs), cosmic ray interactions with gas in the Galaxy and Dark Accelerators, mysterious sources which do not seem to have any known counterparts at other energies. These instruments will likely operate for the next ten years, during which time they will continue to detect new sources and increase our understanding of the highest energy processes in the universe. However, despite their successes, the current generation ground-based instruments are ultimately limited by their angular resolution, collecting area and sensitivity to weak sources.

The Advanced Gamma-ray Imaging System (AGIS) is a next-generation ground-based gamma-ray observatory being planned in the U.S. The AGIS project mirrors the Cherenkov Telescope Array project being discussed in Europe. It is possible that the efforts currently ongoing in the U.S., Europe, and Japan may unify into a world-wide collaboration to construct a gamma-ray observatory capable of addressing the needs of the astronomical community for the next several decades.

AGIS will improve on the sensitivity of the current experiments by one order of magnitude, allowing it to detect gamma-ray emission from a large number of galactic and extra-galactic sources which are too weak for H.E.S.S. and VERITAS to detect, and perhaps to discover evidence of dark matter self-annihilation in the dwarf satellite galaxies of the Milky Way. AGIS will also have substantially improved angular resolution, which will constrain the origin of detected gamma-rays more tightly, enabling astronomers to better model the mechanisms responsible for emission. The energy range over which AGIS is sensitive will also be larger than available in the present day. This will allow detection of more distant sources, from which higher energy gamma-rays are absorbed. Although the exact configuration of the AGIS observatory has not been specified, it will likely consist of a large array of moderate sized Atmospheric Cherenkov Telescopes covering an area of 1 km² on the ground. The science for which this instrument is designed to address is discussed in detail in the upcoming white paper on the status and future of ground-based gamma-ray astronomy and outlined in the science section of this website.

AGIS will require substantial investments for research and development (R&D) of critical technology and for the actual design, construction, and operation. It is clear that national and international collaboration will be instrumental. In the U.S. and abroad, the next step will be an R&D phase, lasting three to five years. Construction of the experiments could start between 2011-2013.