A polar orbit is a low-Earth orbit in which the satellite crosses over both poles on each revolution.
Advantages: high-resolution images, able to map the entire Earth with time
Altitude: most common is 1000 km
Satellite period: 100 minutes
Satellite examples: CryoSat-2, Landsat 7
Dr Wolfgang Rack
On this pathway, the satellites cross over the poles and in a north-south direction on the equators, and this has certain advantages especially for Earth observation. So for Earth observation satellites, mostly polar orbits are chosen because they can fly relatively low and can map the Earth’s surface in a high resolution.
Primarily it’s a matter of the pixel resolution of the imagery which we would like to get. So this is not possible from a geostationary orbit where the satellites are more than 35 000 kilometres above the Earth’s surface. But for polar orbits, satellites fly very low. And another advantage why it is frequently chosen for Earth’s satellites, it is possible that the orbits are Sun-synchronous. Which means that satellites are able to map the Earth’s surface every day at the same local time.
The satellites fly very fast, but because the Earth rotates under the satellite orbit, it is possible that satellites in a polar orbit map actually the whole Earth’s surface with time.
Dr Allan McInnes
What application do polar orbits have? Well, basically anything where you want to be able to see the whole Earth, so scientific satellites use them quite a lot because they can see all of the ocean or all the continents and take measurements of them. Some weather satellites and some disaster monitoring satellites, things like that.