The Large Observatory for X-ray Timing (LOFT), a mission devoted to investigating the behaviour of matter under extreme conditions by means of X-ray timing, was proposed as a candidate M-class mission in response to the 2010 Call for Medium-size Missions for ESA's Cosmic Vision plan. In February 2011, LOFT was one of four missions selected by ESA for a study and assessment phase.

A Science Study Team has been appointed by the Director of Science and Robotic Exploration to support ESA with evaluation and advice during this study phase, with particular emphasis on issues of scientific performance.

A study at the ESA Concurrent Design Facility (CDF) will be conducted in September 2011 to investigate a technical approach that is feasible within the cost and technical constraints of Cosmic Vision M-class missions. The results of the CDF study will be used to prepare an open Invitation to Tender to be issued to Industry in Autumn 2011. Industrial activities will have a typical duration of about 1 year.

In parallel, a consortium of institutes selected by ESA through an open call will carry out the nationally-funded assessment studies for the instruments and the development of critical technologies for the payload, including detectors, electronics, and collimator elements.