21st Space Operations Squadron (21st SOPS) is a unit tasked with satellite monitoring. Here's more according to the commander:
21 SOPS is a squadron in the 50th Network Operations Group, physically located at Vandenberg Air Force Base, California. If you have heard of 21 SOPS; you probably know it to be the location for the continuity of operations it provides to many 50th Space Wing space operations squadrons. The squadron oversees Air Force Satellite Control Network sites at Diego Garcia (REEF), Guam (GUAM), Hawaii (HULA), and Vandenberg (COOK). The squadron operates one of the two operational control nodes (DICE) that enable AFSCN traffic between various satellite operations centers and the worldwide network of remote sites used to communicate with more than 175 satellites. The squadron also oversees GPS facilities at Diego Garcia and Kwajalein Atoll, as well as a monitoring station in Hawaii. In addition, 21 SOPS operates two wideband earth terminals used to support various users of the Wideband Global SATCOM constellation in the Pacific. Finally, the squadron is a key element of AFSCN defensive cyber operations.
https://schriever.af.mil/News/Commentaries/Display/Article/1061861/21-sops-mission-heritage-impact/