text: four 12-m 
  atmospheric-Cherenkov telescopes located in Arizona, 
  is used to study VHE γ-rays from a variety of astro- 
  physical sources [4]. VERITAS began scientiﬁc obser- 
  vations with a partial array in September 2006 and has 
  routinely observed with the full array since Septem- 
  ber 2007. The performance metrics of VERITAS in- 
  clude an energy threshold of ∼100 GeV, an energy 
  resolution of ∼15%, an angular resolution of ∼0.1◦, 
  and a sensitivity yielding a 5σ detection of a 1% Crab 
  Nebula ﬂux object in <30 hours1. VERITAS has an 
  active maintenance program (e.g. frequent mirror re- 
  coating and alignment) to ensure its continued high 
  performance over time, and an upgrade improving 
  both the camera (higher quantum-eﬃciency PMTs) 
  and the trigger system has been proposed to the fund- 
  ing agencies. 
  
  VERITAS, a stereoscopic array of 
  
  VHE blazars have double-humped spectral energy 
  distributions (SEDs), with one peak at UV/X-ray en- 
  ergies and another at GeV/TeV energies. The ori- 
  gin of the lower-energy peak is commonly explained 
  as synchrotron emission from the relativistic electrons 
  in the blazar jets. The origin of the higher-energy 
  peak is controversial, but is widely believed to be the 
  result of inverse-Compton scattering of seed photons 
  oﬀ the same relativistic electrons. The origin of the 
  seed photons in these leptonic scenarios could be the 
  synchrotron photons themselves, or photons from an 
  external source. Hadronic scenarios are also plausible 
  explanations for the VHE emission, but generally are 
  not favored. 