The NASA programme to conduct frequent, low-cost missions to explore the Solar System. Each Discovery mission must be developed, built and launched in less than three years for a total cost of under $299 million. One of the programme's aims is to encourage the use of new technology. The first Discovery mission was the NEAR Shoemaker asteroid rendezvous in February 1996, and launches have averaged one a year since then. In January 2017, NASA announced that the 13th and 14th missions will be to visit several asteroids and Trojans, including the metal-rich asteroid Psyche.