Discoverer 18, also known as Corona 9013, was an American optical reconnaissance satellite which was launched in 1960. It was a KH-2 Corona satellite, based on an Agena-B.
The launch of Discoverer 18 occurred at 20:20:58 UTC on 7 December 1960. A Thor DM-21 Agena-B rocket was used, flying from Launch Complex 75-3-4 at the Vandenberg Air Force Base. Upon successfully reaching orbit, it was assigned the Harvard designation 1960 Sigma 1.
Discoverer 18 was operated in a low Earth orbit, with a perigee of 272 kilometres (Template:Convert/round mi), an apogee of 535 kilometres (Template:Convert/round mi), 81.4 degrees of inclination, and a period of 92.6 minutes. The satellite had a mass of 1,240 kilograms (Template:Convert/round lb), and was equipped with a panoramic camera with a focal length of 61 centimetres (Template:Convert/round in), which had a maximum resolution of 7.6 metres (Template:Convert/round ft). Images were recorded onto 70-millimeter (Template:Convert/LoffAonSon) film, and returned in a Satellite Recovery Vehicle, which was recovered three days after the launch. The Satellite Recovery Vehicle used by Discoverer 18 was SRV-508. Following the return of its images, Discoverer 18 remained in orbit until it decayed on 2 April 1961. It was the first KH-2 satellite to complete its mission successfully.