Landsat 8 and Landsat 9 work as a satellite constellation. This means that these two nearly identical satellites work in tandem as a system. Each satellite circles the Earth every 16 days, with their two orbits offset by time so that every location on the planet is imaged every eight days. The satellite constellation of Landsat 8 and Landsat 9 is in a near-polar orbit on the Worldwide Reference System-2.
Landsat Next, planned for a 2030 launch, will include three observatories (three separate satellites) and a new Worldwide Reference System.