NASA has launched a concept study to evaluate options for acquiring a new fleet of large payload, long endurance unmanned aircraft systems (UAS) within five to 10 years, the agency says.

The study was revealed shortly after NASA briefly posted an online request for information to industry, seeking options that meet the agency’s requirements for the Earth observation mission.

The request was quickly removed to be reworded to emphasise the information would inform a concept study, rather than serve as a prelude to an imminent acquisition, the agency says.

The reworded request for information is expected to be reposted to, a web site listing all business opportunities with the US federal government.

NASA currently operates one of the first Northrop Grumman RQ-4 Global Hawks developed under an advanced concept technology demonstration programme sponsored in the late-1990s by the Defense Advanced Research Projects Agency.

A version of the General Atomics Aeronautical Systems Predator, the Ikhana, also belongs to NASA, and is co-located with the Global Hawk at the NASA Armstrong research centre at Edwards AFB, California.

NASA has used the aircraft in Earth science missions, including the airborne tropical tropopause experiment and the hurricane and severe storm sentinel mission.

The original request for information, posted on 7 July, said NASA wants future UAS with a minimum ability of carrying 300kg (661lb) as payload, with a 3kW power supply. The agency also wants aircraft that can fly for more than 24h.