Mercury, also known as Advanced Vortex, was a series of three United States spy satellites launched in the 1990s.

These satellites were launched and operated by the National Reconnaissance Office with the participation of the United States Air Force.

Their precise mission and capabilities are highly classified, but they are widely believed to be successors to the Vortex/Chalet satellites.

The resulting explosion also destroyed the core vehicle, and the second SRB then initiated its own self-destruction.

[1] Roughly 4 seconds later the Range Safety Officer also issued a self-destruct signal to the rocket.