The VERITAS reflector design is similar to the earlier Whipple 10-meter gamma-ray telescope, located at the same site, but is larger in size and has a longer focal length for better control of optical aberrations.

Multiple telescopes in an array are needed for stereoscopic observations of the Cherenkov light produced in extensive air showers.

These stereoscopic observations allow precise reconstruction of the particle shower geometry, thus giving greatly improved angular and energy resolution compared to a single telescope.

[2] The reflector consists of 350 individual mirror facets, hexagonal in shape, mounted on a rigid optical support structure.

VERITAS, like other IACTs, is sensitive to primary particles that produce sufficient atmospheric Cherenkov light to be detectable at the ground.

A very weak astrophysical source with a gamma-ray flux only 1% of the Crab Nebula can be detected by VERITAS in under 25 hours of observation.

[3] The Cherenkov light that is produced by gamma rays in the upper atmosphere is very dim, so VERITAS observes best under clear, dark skies.

The Whipple telescope pioneered the use of an imaging Cherenkov camera, coupled with a large 10 m diameter reflector, to make the first definitive detection of a VHE gamma-ray source, the Crab Nebula in 1989.

VERITAS combines the benefits of stereoscopic observations in an array with large reflectors for a low energy threshold.

Compared to the Whipple telescope, VERITAS employs larger 12 m diameter reflectors, improved optics and light collection efficiency, and a finer pixelated camera.

Both the recording (using 500 MS/s custom-made Flash-ADCs) and trigger electronics (using a sophisticated three-level system) were significantly improved compared to earlier instruments.

In 2000, the concept of VERITAS as a seven telescope array was recommended by the 2000 Decadal Survey in Astronomy and Astrophysics as a moderate-sized project.

The proposal for a four telescope array (now with 12 m diameter reflectors) was favorably reviewed in 2002 and construction of VERITAS started in 2003 at the Fred Lawrence Whipple Observatory.

[1] Between 2009 and 2011 an upgrade program was carried out that improved the alignment of the VERITAS mirror facets and replaced the level 2 trigger system.

The basic questions pursued include: understanding cosmic particle acceleration in our Galaxy (with special emphasis on understanding the origin of cosmic rays) and beyond our Galaxy, probing extreme environments near compact objects such as neutron stars and black holes, the nature of dark matter and the intergalactic magnetic field, and whether the speed of light is constant at these extreme gamma-ray energies.

An important component of VERITAS observations is that associated with multi-wavelength and multi-messenger follow up, including fast radio burst (FRB), high energy neutrino, and gravitational wave events.

Starting in 2017, the VERITAS science program was expanded to include observations in the optical waveband through high-time-resolution measurements of asteroid occultations and stellar intensity interferometry.

Representatives from the member institutions form the VERITAS Executive Council (VEC), that serves as the ultimate decision-making authority within the collaboration.