Some spacecraft are built to arrive and stay. An orbiter enters orbit around a target body and studies it over months or years, collecting data across many passes rather than during a brief flyby.

The trade-off is fuel. Entering orbit around a distant planet requires a large velocity change, which means either a heavy propulsion system or a slow, fuel-efficient approach using gravity assists and aerobraking.

Notable orbiters

• Mars Reconnaissance Orbiter
• Cassini at Saturn
• Lunar Reconnaissance Orbiter
• Juno at Jupiter

Orbiters often carry multiple instruments: cameras, spectrometers, radar, and magnetometers. Data returns slowly over a small radio link, so onboard storage and compression matter as much as the instruments themselves.