The standard and XL variants of Pegasus can leave one or two stages in Earth orbit. On some Pegasus missions a fourth stage, HAPS, is carried. That stage was redesigned after its first two missions to improve the vehicle and to permit more complete passivation. Residual hydrazine is burned and residual nitrogen used for attitude control is vented. The helium pressurant is not vented, but its pressure is reduced well below maximum operating pressures.
Batteries are limited to lifetimes of four hours and no range safety systems are carried.
One piece of mission-related debris may be produced. The final stage of Taurus is the Orion 38 and it is passivated as on Minotaur and Pegasus missions. One piece of mission-related debris may be generated. Titan Like Atlas and Delta, the Titan space launch vehicle has been in service for the United States since the 1960s. Since most Titan II payloads perform their own orbital insertion manoeuvres, to date only two recent-era missions have left a second stage in Earth orbit.