Atransatmospheric orbit (TAO) is an orbit around a celestial body in which a portion of the orbit intersects with thedefined atmosphere.[1][2][3] Transatmospheric Earth orbits generally use theFAI definedKármán line of 100 km (62 mi) altitude to differentiate between transatmospheric Earth orbits orlow Earth orbits but altitudes such as the U.S. defined 50 mi (80 km) line may be used. Such orbits are subject to significantatmospheric drag, causing rapidorbital decay if left unchecked.
A number ofartificial satellites have been placed into transatmospheric Earth orbits,[4] usually due to alaunch vehicle malfunction. Such satellites includeEOS 02 andAzaadiSAT, which were deployed into a 76 km × 356 km (47 mi × 221 mi) transatmospheric orbit due to an upper-stage malfunction on theSSLV rocket. Transatmospheric orbits have limited practical applications because objects placed into such orbits are subject to rapidorbital decay. One such application was used to test the reentry of theIXV spaceplane. It was launched into a 76 km × 416 km (47 mi × 258 mi) transatmospheric orbit.[5]
TheBoeing Starliner spacecraft was placed in a transatmospheric orbit by theAtlas V launcher. It used its onboard propulsion to reach theInternational Space Station in LEO.
Astrobotic Technology'sPeregrine lunar lander was moved to a transatmospheric orbit following a fuel leak to avoid becoming hazardousspace debris.[6]
Transatmospheric orbit (TAO): orbital flight with perigee less than 80 km but more than zero. Potentially used by aerobraking missions and transatmospheric vehicles, also in some temporary phases of orbital flight (e.g. STS pre OMS-2, some failures when no apogee restart)
