which reached an apogee of before parachuting into the Atlantic Ocean. The Space Shuttle continued its ascent using only the RS-25 engines. On earlier missions, the Space Shuttle remained in the heads-down orientation to maintain communications with the tracking station in Bermuda, but later missions, beginning with STS-87, rolled to a heads-up orientation at T+6 minutes for communication with the tracking and data relay satellite constellation. The RS-25 engines were throttled at T+7 minutes 30 seconds to limit vehicle acceleration to 3 g. At 6 seconds prior to main engine cutoff (MECO), which occurred at T+8 minutes 30 seconds, the RS-25 engines were throttled down to 67%. The GPCs controlled ET separation and dumped the remaining liquid oxygen and hydrogen to prevent outgassing while in orbit. The ET continued on a ballistic trajectory and broke up during reentry, with some small pieces landing in the Indian or Pacific Ocean. Early missions used two firings of the OMS to achieve orbit; the first firing raised the apogee while the second circularized the orbit. Missions after STS-38 used the RS-25 engines to achieve the optimal apogee, and used the OMS engines to circularize the orbit. The orbital altitude and inclination were mission-dependent, and the Space Shuttle's orbits varied from to . In orbit The type of mission the Space Shuttle was assigned to dictate the type of orbit that it entered. The initial design of the reusable Space Shuttle envisioned an increasingly cheap launch platform to deploy commercial and government satellites. Early missions routinely ferried satellites, which determined the type of orbit that the orbiter vehicle would enter. Following the Challenger disaster, many commercial payloads were moved to expendable commercial rockets, such as the Delta II. While later missions still launched commercial payloads, Space Shuttle assignments were routinely directed towards scientific payloads, such as the Hubble Space Telescope, Spacelab, and the Galileo spacecraft. Beginning with STS-74, the orbiter vehicle conducted dockings with the Mir space station. In its final decade of operation, the Space Shuttle was used for the construction of the International Space Station. Most missions involved staying in orbit several days to two weeks, although longer missions were possible with the Extended Duration Orbiter pallet. The 17 day 15 hour STS-80 mission was the longest Space Shuttle mission duration. Re-entry and landing Approximately four hours prior to deorbit, the crew began preparing the orbiter vehicle for reentry by closing the