KENNEDY SPACE CENTER, FLA. -- Workers evaluate the placement of a transporter below a Pegasus XL Expendable Launch Vehicle before its detachment from the underside of an Orbital Sciences L-1011 aircraft. The aircraft, with the launch vehicle nestled beneath, arrived at the Cape Canaveral Air Force Station Skid Strip on Dec. 17. The Pegasus XL will undergo three flight simulations prior to its scheduled launch in late January 2003. It will carry NASA's Solar Radiation and Climate Experiment (SORCE) spacecraft into orbit. Built by Orbital Sciences Space Systems Group, SORCE will study and measure solar irradiance as a source of energy in the Earth's atmosphere with instruments built by the University of Colorado's Laboratory for Atmospheric and Space Physics (LASP).