1990

Hubble Space Telescope

Lyman Spitzer (1914–1997)

The first astronomical telescopes, developed in the early seventeenth century, opened the skies to astronomers; they and subsequent larger and more advanced instruments enabled amazing discoveries about the solar system, galaxy, and universe. But astronomers have always known that even the largest telescopes on Earth are fundamentally limited in two important ways: first, the unavoidable shimmering and twinkling of our atmosphere limit the resolution to much less than a large telescope’s theoretical limit; and second, our atmosphere blocks many parts of the spectrum—especially in the ultraviolet and infrared ranges—making ground-based observations difficult or impossible at key wavelengths.

With the advent of space satellites in the 1960s, astronomers began advocating within NASA for a dedicated, space-based telescope to overcome those limitations. A chief champion of an orbiting space telescope was the American astronomer Lyman Spitzer, who led a critical grassroots lobbying campaign for the necessary support and funding of the project. After many bureaucratic hurdles and a forged partnership with the European Space Agency, the Large Space Telescope, later named the Hubble Space Telescope (HST) after astronomer Edwin Hubble, was approved in 1978. HST was eventually launched into low Earth orbit—about 350 miles (570 kilometers) above the surface—by the Space Shuttle Discovery in April 1990.

Shortly after launch, HST was discovered to have a major flaw in its primary mirror design. Fortunately, the telescope could be serviced by space shuttle astronauts, and five shuttle missions between 1993 and 2009 fixed the telescope and upgraded key instruments and components. As a result, HST serves as a cosmic time machine that uses CCD imaging and spectroscopy to determine the nature and even the age of our universe. By today’s giant telescope standards, HST is only a medium-size telescope, but its constant clear-sky and full-spectrum view of the cosmos have enabled it to realize the dreams of Spitzer and other early supporters, and fundamentally revolutionize modern astronomy and astrophysics.

The Hubble Space Telescope floats freely about 350 miles (560 kilometers) above Earth’s surface after being released by the space shuttle Discovery during a servicing mission in February 1997. The telescope is about 8.2 feet (2.5 meters) in diameter and about 43 feet (13.1 meters) long, or slightly longer than an average school bus.