During the past 10 years NASA's Hubble Space Telescope has pushed back the frontier of virtually every area of astronomy. Hubble has made dramatic contributions in understanding:

• the atmospheres of planets
• the birth, life, and death of stars
• the properties of galaxies out to the farthest reaches of the universe
• supermassive black holes and their galactic hosts
• the abundance of light and heavy elements in the universe
• the age of the universe
• the fate of the cosmic expansion

Some Hubble "firsts" include:

• discovering that the sizes of galaxies are smaller in the distant universe
• sketching the cosmic star formation rate into the early history of the universe
• discovering young, massive star clusters formed in the collisions of galaxies
• identifying absorbers of quasar light as galaxies
• determining accurate distances to variable stars in the Virgo cluster of galaxies
• imaging the plume resulting from the impact of comet fragments on Jupiter and of the "scars" at the impact sites
• imaging jets emanating from the center of an accretion disk around a young star

At the conclusion of Servicing Mission 4, scheduled for 2003, astronomers will leave Hubble with the most powerful suite of scientific instruments ever flown on the observatory.

During Hubble's second decade, the science program will differ from the present one in two important respects. In the second decade the remaining two Great Observatories - the Chandra X-ray Observatory and the Space Infrared Telescope Facility - will be in full operation. The Next Generation Space Telescope will be launced two years before Hubble's retirement. Coordinated research campaigns involving all four of these extremely powerful telescopes will be common.

It is difficult to imagine a larger "quantum leap" in astronomy than that provided by a view of the universe in which astronomers will have simultaneous coverage from X-rays through optical and near-infrared wavelengths to the deep infrared using this fleet of major space telescopes.

Secondly, special emphasis will be placed on large programs intended to push Hubble to its limits and to address the most important scientific questions that can be answered by the telescope before its mission comes to an end. These are called "Treasury Programs." Past examples of this approach include the Hubble Deep Field, the Hubble Constant Key Project, and the comet Shoemaker-Levy 9 impact on Jupiter. All of these programs had a huge impact on science.