Space Shuttle Discovery is launched on STS-103, the third Hubble Space Telescope servicing mission.

Space Shuttle Discovery is a retired American Space Shuttle orbiter. The spaceplane was one of the orbiters from NASA's Space Shuttle program and the third of five fully operational orbiters to be built. Its first mission, STS-41-D, flew from August 30 to September 5, 1984. Over 27 years of service it launched and landed 39 times, aggregating more spaceflights than any other spacecraft as of December 2024. The Space Shuttle launch vehicle had three main components: the Space Shuttle orbiter, a single-use central fuel tank, and two reusable solid rocket boosters. Nearly 25,000 heat-resistant tiles cover the orbiter to protect it from high temperatures on re-entry.

STS-103, the 96th launch of the Space Shuttle and the 27th launch of Space Shuttle Discovery, was a Hubble Space Telescope servicing mission. It launched from Kennedy Space Center, Florida, on 19 December 1999 and returned on 27 December 1999 and was the last Shuttle mission of the 1990s. It was the only mission to span through Christmas after being delayed by 13 days for technical and weather reasons.

The Hubble Space Telescope is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versatile, renowned as a vital research tool and as a public relations boon for astronomy. The Hubble Space Telescope is named after astronomer Edwin Hubble and is one of NASA's Great Observatories. The Space Telescope Science Institute (STScI) selects Hubble's targets and processes the resulting data, while the Goddard Space Flight Center (GSFC) controls the spacecraft.

December 19 is the 353rd day of the year in the Gregorian calendar; 12 days remain until the end of the year.