Apolar orbit is one in which asatellitepasses above or nearly above bothpoles of the body beingorbited (usually a planet such as theEarth, but possibly another body such as theMoon orSun) on each revolution. It has aninclination of about 60–90degrees to the body'sequator.^[1]

Launchingsatellites into polar orbit requires a largerlaunch vehicle to launch a given payload to a given altitude than for anear-equatorial orbit at the same altitude, because it cannot take advantage of theEarth's rotationalvelocity. Depending on the location of thelaunch site and theinclination of the polar orbit, the launch vehicle may lose up to 460 m/s ofDelta-v, approximately 5% of the Delta-v required to attainLow Earth orbit.

Polar orbits are used forEarth-mapping,reconnaissance satellites, as well as for someweather satellites.^[2]TheIridium satellite constellation uses a polar orbit to provide telecommunications services.

Near-polar orbiting satellites commonly choose asun-synchronous orbit, where each successive orbitalpass occurs at the same local time of day. For some applications, such asremote sensing, it is important thatchanges over time are not aliased by changes in local time. Keeping the same local time on a given pass requires that thetime period of the orbit be kept as short, which requires a low orbit. However, very low orbits rapidlydecay due todrag from the atmosphere. Commonly usedaltitudes are between 700 and 800 km, producing anorbital period of about 100 minutes.^[3] The half-orbit on the Sun side then takes only 50 minutes, during which local time of day does not vary greatly.

To retain a Sun-synchronous orbit as theEarth revolves around the Sun during the year, the orbit mustprecess about the Earth at the same rate (which is not possible if the satellite passes directly over the pole).Because of Earth'sequatorial bulge, an orbitinclined at a slight angle is subject to atorque, which causesprecession. An angle of about 8° from the pole produces the desired precession in a 100-minute orbit.^[3]

• List of orbits
• Molniya orbit
• Tundra orbit
• Vandenberg Air Force Base, a major United States launch location for polar orbits

• Orbital Mechanics (Rocket and Space Technology)