NASA Space Shuttle ''Explorer'', commanded by veteran astronaut Matt Kowalski, is in Earth's orbit on Mission STS-157 to service the Hubble Space Telescope. Dr. Ryan Stone is aboard on her first space mission as a mission specialist, to perform a set of hardware upgrades on the Hubble. During a Extra-vehicular activity, Christopher C. Kraft Jr. Mission Control Center in Houston warns ''Explorer''s crew about a Russian Anti-satellite weapon, which has inadvertently caused a Kessler syndrome forming a rapidly-expanding cloud of space debris, and orders the crew to return to Earth immediately. Communication with Mission Control is lost shortly thereafter as more and more communication satellites are knocked out by the debris.