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Mercury
Country of origin	United States
Operator	National Reconnaissance Office; United States Air Force
Applications	Espionage
Specifications
Launch mass	4,000–5,000 kilograms (8,800–11,000 lb)
Regime	Geostationary
Production
Built	3
Launched	3
Failed	1
Maiden launch	27 August 1994, 8:56:58 UTC
Last launch	12 August 1998, 11:30:01 UTC
← Vortex

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. Two of the three launches from Cape Canaveral were successful, with the third failing to achieve orbit. The satellites collect SIGINT from near-geosynchronous orbits. Their precise mission and capabilities are highly classified, but they are widely believed to be successors to the Vortex/Chalet satellites.

The last launch attempt, on 12 August 1998 failed, with the US$700–800 million satellite and the $344 million Titan IV(401)A launch vehicle exploding over the Atlantic Ocean. The failure was caused by a short circuit in the guidance system, which lost power and reset, causing the vehicle to pitch over. This in turn led to premature separation of one of the SRBs, which automatically self-destructed. 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.^[2] Observers estimate each spacecraft has a mass of 4,000–5,000 kg.^[3]

Launches

Name	COSPAR ID SATCAT No.	Launch date (UTC)	Launch vehicle	Launch site	Launch designation	Longitude	Remarks
USA-105	1994-054A 23223	27 August 1994 08:56:58	Titan IV(401)A	CCAFS LC-41	N/A
USA-118	1996-026A 23855	24 April 1996 23:37:01	Titan IV(401)A	CCAFS LC-41	N/A
Unnamed	N/A	12 August 1998 11:30:01	Titan IV(401)A	CCAFS LC-41	NROL-7	N/A	Failed to orbit

References

^ "Titan IVA-20 Accident Investigation Board Summary".
^ "Archived copy". Archived from the original on 2009-05-04. Retrieved 2009-05-04.{{cite web}}: CS1 maint: archived copy as title (link)
^ Craig Covault and Joseph C. Anselmo (1998-08-17). "Titan explosion destroys secret 'Mercury' sigint". Aviation Week and Space Technology. 149.