There have been a few missions that have flown by or orbited Mercury:

* Mariner 10 (1974-1975): This was the first spacecraft to fly by Mercury, providing the first close-up images.

* MESSENGER (2011-2015): This was the first spacecraft to orbit Mercury. It collected a vast amount of data about the planet's surface, composition, and magnetic field.

However, there are no active satellites currently orbiting Mercury.