The 18th and final major U.S. and Boeing-built element, the Starboard 6 Truss Segment, was delivered to the ISS in February 2009. With this, the full set of solar arrays could be activated, increasing the power available for science projects to 30 kW. That marked the completion of the United States Orbital Segment (USOS) of the station. On 5 March 2010, Boeing officially turned over the USOS to NASA. In 1962, the first Orbiting Solar Observatory was launched, followed by the Orbiting Astronomical Observatory (OAO) that carried out ultraviolet observations of stars between 1968 and 1972. These showed the value of space-based astronomy, and led to the planning of the Large Space Telescope (LST) that would be launched and maintained from the forthcoming space shuttle. Budget limitations almost killed the LST, but the astronomy community – especially Lyman Spitzer – and the National Science Foundation pressed for a major program in this area. Congress finally funded LST in 1978, with an intended launch date of 1983. MSFC was given responsibility for the design, development, and construction of the telescope, while Goddard Space Flight Center (GFC) was to develop the scientific instruments and ground-control center. The project scientist was C. Robert O’Dell, then chairman of the Astronomy Department at the University of Chicago. The telescope assembly was designed as a Cassegrain reflector with hyperbolic mirror polished to be diffraction limited; the primary mirror had a diameter of . The mirrors were developed by the optics firm Perkin-Elmer. MSFC could not test the performance of the mirror assembly until the telescope was launched and placed in service. The LST was named the Hubble Space Telescope in 1983, the original launch date. There were many problems, delays, and cost increases in the program, and the "Challenger" disaster delayed the availability of the launch vehicle. The Hubble Space Telescope was launched in April 1990, but gave flawed images due to a flawed primary mirror that had spherical aberration. The defect was found when the telescope was in orbit. Fortunately, the Hubble telescope had been designed to allow in-space maintenance, and in December 1993, mission STS-61 carried astronauts to the Hubble to make corrections and change some components. A second repair mission, STS-82, was made in February 1997, and a third, STS-103, in December 1999. Another servicing mission (STS-109) was flown on 1 March 2002.