The Mercury Planetary Orbiter (inner orbit) and the Mercury Magnetospheric Orbiter (outer orbit), in their elliptical polar orbits around Mercury.
The Mercury Planetary Orbiter will operate in a 2.3 hour orbit from an altitude of 480 x 1500 km above the planet’s surface; the Mercury Magnetospheric Orbiter will take 9.3 hours to orbit the planet in its 590 x 11640 km orbit.