Designed by the crewmembers, the STS-103 emblem depicts the Space Shuttle Discovery approaching the Hubble Space Telescope (HST) prior to its capture and berthing. The purpose of the mission is to remove and replace some of the Telescope's older and out-of-date systems with newer, more reliable and more capable ones, and to make repairs to HST's exterior thermal insulation that has been damaged by more than nine years of exposure to the space environment. The horizontal and vertical lines centered on the Telescope symbolize the ability to reach and maintain a desired attitude in space, essential to the instrument's scientific operation. The preservation of this ability is one of the primary objectives of the mission. After the flight, the Telescope will resume its successful exploration of deep space and will continue to be used to study solar system objects, stars in the making, late phases of stellar evolution, galaxies and the early history of the universe. HST, as represented on this emblem was inspired by views from previous servicing missions, with its solar arrays illuminated by the Sun, providing a striking contrast with the blackness of space and the night side of Earth.
The NASA insignia design for Shuttle flights is reserved for use by the astronauts and for other official use as the NASA Administrator may authorize. Public availability has been approved only in the form of illustrations by the various news media. When and if there is any change in this policy, which is not anticipated, it will be publicly announced.
http://spaceflight.nasa.gov/gallery/images/shuttle/sts-103/html/sts103s001.html
NASA