Inmarsat owns and operates 13 geostationary satellites. They continuously orbit over 22,000 miles above Earth staying in line with the equator. Each satellite fleet utilizes a mix of wide beams and narrow spot beams to ensure overlapping coverage around the globe. At this time (and you can see this on the coverage map visual), the polar regions cannot be reached by way of the current satellite setup. But Inmarsat’s fully funded technology roadmap includes reaching the polar regions within the next few years.
You can read here for an in-depth overview of Inmarsat’s entire network of satellites and how they operate to offer coverage.