Complex sentence: Servicing missions, launched every 5 to 7 years, would allow astronomers to upgrade the ATLAS Telescope with new instruments and technologies that will come online down the road, and like the HST, ATLAST should have a 20-year lifespan.
Split into simpler sentences: Servicing missions, launched every 5 to 7 years, would allow astronomers to upgrade the ATLAS Telescope with new instruments and technologies. Like the HST, ATLAST should have a 20-year lifespan.