onorbit

Onorbit is a term used in aerospace to describe an object or operation that is in orbit around a celestial body. The standard term is on-orbit; onorbit or OnOrbit appears in branding, software, or as a proper name. In general usage, on-orbit denotes the phase during which a spacecraft has completed launch and insertion and executes its mission from an orbital platform.

Objects designated as on-orbit include satellites, space stations, servicing vehicles, and probes that have achieved stable orbit. On-orbit operations cover attitude control, communications, power and thermal management, science payload operations, and occasional orbital maintenance such as burns to adjust altitude or inclination. Some missions include on-orbit servicing, refueling, or debris removal, though these activities require specialized propulsion and coordination with ground control and other operators.

Orbital regimes are defined by altitude and dynamics: LEO, MEO, GEO, and HEO, among others. The duration of the on-orbit phase varies by mission life, docking schedule, or decommissioning plan, which may culminate in relocation, deorbit, or passive disposal. Safety and sustainability concerns include space debris, conjunction assessment, shielding from radiation, and end-of-life deorbiting to minimize long-term risk.

The concept is central to space policy and mission design. See also on-orbit servicing, satellite, orbital mechanics, and space debris.