Flightradar24.com has two civilian Gulfstream jets registered to the US Missile Defense Agency (HALO 02 and HALO 052), plus a third civilian Gulfstream (GLF 02) registered to L3 Harris (a high-tech defense contractor) over the Pacific off VSFB.
Looks to me like they are preparing to conduct an Anti-Ballistic-Missile (ABM) test.