Moons of Mars attention when Houston's claim was repeated in earnest by a Soviet scientist, Iosif Shklovsky, who, based on a later-disproven density estimate, suggested Phobos was a hollow metal shell. Searches have been conducted for additional satellites. In 2003, Scott S. Sheppard and David C. Jewitt surveyed nearly the entire Hill sphere of Mars for irregular satellites. However scattered light from Mars prevented them from searching the inner few arcminutes where the satellites Phobos and Deimos reside. No new satellites were found to an apparent limiting red magnitude of 23.5, which corresponds to radii of about 0.09 km using an albedo of
Mars One before arrival at Mars) and a lander (see "Human Lander" below). In 2012, Mars One speculated that the Transit Living Module could potentially be designed and built by Thales Alenia Space. A concept study was produced by Lockheed Martin for a demonstration lander based on the 2008 "Phoenix" lander. In December 2013 Mars One awarded a contract to Surrey Satellite Technology for a study of the satellite technology required to provide 24/7 communication between Earth and the Mars base. Mars One proposed at least two satellites, one in areostationary orbit above Mars and a second at the Earth – Sun