5@5 - a 5 GeV energy threshold array of imaging atmospheric Cherenkov   telescopes at 5 km altitude
  We discuss the concept and the performance of a powerful future ground-based astronomical instrument - a stereoscopic array of several large imaging atmospheric Cherenkov telescopes installed at a very high mountain elevation of about 5 km a.s.l. or more - for the study of the gamma-ray sky at energies from several GeV to 100 GeV. 
F.A. Aharonian, A.K. Konopelko, H.J. Voelk, and H. Quintana