VERITAS (Very Energetic Radiation Imaging Telescope Array System) is a ground-based gamma-ray instrument operating at the Fred Lawrence Whipple Observatory (FLWO) in southern Arizona, USA. It is an array of four 12m optical reflectors for gamma-ray astronomy in the GeV - TeV energy range. These imaging Cherenkov telescopes are deployed such that they have the highest sensitivity in the VHE energy band (50 GeV - 50 TeV), with maximum sensitivity from 100 GeV to 10 TeV. This VHE observatory effectively complements the NASA Fermi mission.
We use ROOT for some of our analysis code but the data are stored in files that are in a VERITAS-specific format.
In the VERITAS collaboration we give this topic some thought from time to time but it suffers from a lack of manpower.
Also the problem is not a big one since we an2cipate the data set to be 500 TB at the end of data-taking and we'll reduce that to 50 TB with mild cuts for long-term storage.