Complex sentence: The primary instrument is the Large Area Telescope (LAT), that is sensitive in the photon energy range of 8 keV to greater than 300 GeV, and can view about 20% of the sky at any given moment.
Split into simpler sentences: The primary instrument is the Large Area Telescope (LAT) that is sensitive in the photon energy range of 8 to greater than 300 GeV. It can view about 20% of the sky at any given moment.