The US has placed a big reconnaissance satellite into orbit. Reputed to be the largest satellite sent into space and shrouded in secrecy the satellite was put into orbit by a heavy lift Delta-4 rocket from Cape Canaveral on Sunday evening.

Launched on behalf of the National Reconnaissance Office (NRO) who have not disclosed the purpose of the satellite, but it is thought to be for eavesdropping on enemy communications.

At the Air Force Association’s Air and Space Conference in September, NRO director, retired Air Force Gen. Bruce Carlson told the audience that the Delta-4 rocket “would launch with the largest satellite in the world on it”.

At present the largest commercial satellite so far launched was the Terrestar-1 telecommunications satellite that weighed in at 15,233 pounds (7000kg). It has an 18m wide antenna-reflector for relaying data and phone traffic and was placed in orbit by an Arianne 5 ECA rocket. The Skyterra-1 satellite launched earlier this month has deployed a 22m wide antenna-reflector and weighs 11900 pounds (5400 kg).

The new secret satellite, known as the NROL-32, is rumored on internet websites to have a larger mesh antenna than the other spacecraft.

The Delta-4 heavy lift rocket, there are for other versions, was designed to meet the needs of the US military. It features three core boosters strapped together and each having a Rocketdyne RS-68 engine burning liquid hydrogen and liquid oxygen. Sunday’s launch was only the fourth time that the heavy rocket has been deployed.

The National Reconnaissance Office is one of the 16 US intelligence services and designs, builds and operates spy satellites. It also coordinates collecting and analyzing information from aircraft and satellite reconnaissance by the US military and the CIA. The agency is part of the US Defense Department and was established in August 1960.