NASA Launches the Hubble Space Telescope

Date April 24, 1990

After twenty years of delays, the Hubble Space Telescope was placed in orbit around Earth by the space shuttle Discovery.

Locale Cape Canaveral, Florida

Key Figures

• Charles Robert Odell (b. 1937), professor of physics and astronomy at Rice University and project scientist for the Hubble Space Telescope, 1972-1974
• Hermann Oberth (1894-1989), German rocket pioneer

Summary of Event

When the Hubble Space Telescope (HST) was successsfully placed in orbit 612 kilometers above the earth by astronauts aboard the space shuttleDiscovery, one excited astronomer remarked, “At last we are out of the ocean!” His statement summarized the feelings of astronomers who have had to deal with the frustration of viewing the universe through Earth’s atmosphere. No telescope can realize its full potential under 100 kilometers of atmosphere that absorbs much of the visible starlight and particularly the astrophysically important ultraviolet and infrared wavelengths. In 1923, Hermann Oberth, a German rocket pioneer, published Die Rakete zu den Planetenräumen (the rocket into interplanetary space), in which he proposed orbiting a telescope as a unique solution to the problem of peering through the distortion and absorption of light by Earth’s atmosphere.

In 1962, a Large Space Telescope (LST), 305 centimeters in diameter, was proposed in a report of the National Academy of Sciences titled “The Future of Space Science.” Ten years later, the National Aeronautics and Space Administration (NASA) established the LST headquarters at the Marshall Space Flight Center in Huntsville, Alabama, and appointed Charles Robert Odell as lead scientist for the LST project. In 1978, Congress approved the LST project; it later changed the name to the Edwin Powell Hubble Space Telescope (HST) and reduced the mirror diameter to 240 centimeters.

The HST was originally scheduled for launch on December 15, 1983, but political and technical issues resulted in delays, and the launch was rescheduled for August, 1986. Unfortunately, the space shuttle Challenger disaster in January, 1986, further delayed the HST’s launch while technical problems of the launch vehicle were solved. The HST got as close as the launch pad on March 25, 1990, but again problems prevented a launch. Finally, on April 24, 1990, the hundreds of scientists and engineers associated with the project witnessed the culmination of twenty years of their work as the HST was launched into space.

The Hubble Space Telescope was by far the most ambitious and expensive scientific tool constructed up to that time. Approximately $1.6 billion had been spent on the creation of an instrument whose output was expected to alter the way humankind thinks about the universe. The technical specifications for the optics and supporting hardware pushed industrial standards of precision, innovation, and design beyond previous benchmarks of excellence. Both the technical and the organizational problems posed by building the telescope were complex. For example, scientists and engineers needed to devise a way to keep the telescope (measuring 13.1 meters long and 4.3 meters wide, and weighing approximately 11,600 kilograms, or more than 25,000 pounds) pointing toward one tiny spot in space while orbiting 611 kilometers above the earth at a speed of 27,359 kilometers per hour. Different kinds of problems were how to enlist the support of astronomers and engineers for an untried and unproved long-term project and how to organize them into a coherent team.

The HST was designed to function somewhat like an Earth-based telescope. As the HST orbits Earth, two solar panels point toward the Sun to generate energy for the telescope’s scientific instruments. A door at one end of the telescope opens, and light strikes the larger (primary) mirror, which is 94.5 inches in diameter. This mirror reflects light toward the smaller (secondary) mirror, which is 12.2 inches in diameter. From there, the light is again reflected and passes through a hole in the primary mirror. The focused light is converted to an electrical signal, which is transmitted by satellite to White Sands, New Mexico, and then on to the Goddard Space Flight Center and the Space Telescope Science Institute, both of which are in Maryland.

The scientific instruments on the HST help scientists analyze the light that the telescope gathers. The instruments include a wide-field/planetary camera, a faint-object spectrograph, a high-resolution spectrograph, a high-speed photometer, a faint-object camera, and fine-guidance sensors. All these instruments are modular in design so that they can be replaced in case of a system failure.

The HST was designed as part of a series of orbiting observatories dedicated to measuring many parts of the electromagnetic spectrum. The instruments on the HST make possible measurements of infrared and ultraviolet radiation as well as visible light. Other orbiting observatories in the series are the Gamma Ray Observatory, the Advanced X-Ray Astrophysics Facility, and the Space Infrared Telescope Facility.

The HST was loaded into the cargo bay of the space shuttle Discovery and launched into orbit from Cape Canaveral, Florida, on April 24, 1990. On the following day, astronaut Steven A. Hawley deployed the telescope by using a 50-foot mechanical arm.

Two months after the HST was deployed, astronomers discovered that the telescope’s primary mirror—which had been designed at the Perkin-Elmer Corporation in Danbury, Connecticut—had been made slightly too flat, causing starlight to be out of focus; the telescope was producing fuzzy images. Once the defect was identified, scientists began planning a mission in which astronauts would repair the HST so that it would focus light as originally planned.

On December 2, 1993, seven astronauts aboard the space shuttle Endeavour were launched into a 575-kilometer-high Earth orbit with the mission of repairing the HST. Aboard the shuttle they carried a number of instrument packages to repair and improve the telescope, including new gyroscopes, solar panels for power generation, and two packages containing the corrective mirrors that they would add to the faulty primary mirror to bring the starlight into focus. The astronauts planned to make at least five space walks during the eleven-day mission in order to install the new and corrective devices.

The most important of these devices were the corrective mirrors, which NASA had commissioned to a small firm, Tinsley Laboratories, located behind a shopping mall in the San Francisco suburb of Richmond. Despite its low profile, Tinsley was the right choice: Larger corporations such as Kodak, Hughes, and United Technologies had been unable or unwilling to meet NASA’s exacting requirements for grinding the mirrors, whereas Tinsley not only ground the mirrors to within a few atoms’ length of their specified dimensions but also accomplished this amazing feat well within the twelve-month schedule and at half the cost that NASA had anticipated.

The shuttle was piloted by Colonel Richard O. Covey of the Air Force and Commander Kenneth D. Bowersox of the Navy. Claude Nicollier, a Swiss astrophysicist with the European Space Agency, would be the one to operate the shuttle’s mechanical arm, which would reach out to grab the telescope. The remaining four astronauts—F. Story Musgrave, a physician; Jeffrey A. Hoffman, an astrophysicist; Kathryn C. Thornton, a physicist; and Lieutenant Colonel Thomas D. Akers of the Air Force—would perform the space walks necessary to repair the telescope. They would install two new gyroscopes, replace the HST’s tracking system (to enable it to point at appropriate celestial objects), replace wobbly solar arrays, and, most important, install the wide-field planetary camera and a set of new instruments—a faint-object camera and two spectrographs.

As the world watched, the spacewalkers performed the intricate maneuvers to place the instruments and make the necessary repairs over the following days. The operations went smoothly, and when the shuttle returned safely to Earth, scientists and astronauts were ecstatic; the great scientific promise of the telescope, which had been delayed for nearly four years since the launching of the HST, now seemed on the verge of being fulfilled. When the telescope began to transmit its first images in January of 1994, the incredibly clear detail astonished astronomers as well as the general public. The HST, according to the mission’s chief scientist, Edward Weiler, had been “fixed beyond our wildest expectations,” and James Crocker, who had overseen part of the corrective mirror project, stated of the test pictures, “These images are as perfect as engineering can achieve and the laws of physics allow.”

Significance

The original HST had cost $1.6 billion; the repair mission cost $629 million. In comparison with the Superconducting Super Collider (SSC), another “basic science” project funded with taxpayers’ money, these costs were reasonable: The SSC cost $2 billion before its funding was canceled in October, 1993; the Hubble Space Telescope, for about the same cost complete, delivered answers to some of the most fundamental questions about the creation and workings of the universe into the early twenty-first century. Astronomers saw objects 10 to 12 billion light-years away—almost as old as the universe itself. (A light-year is the distance light travels in a vacuum in one year, approximately 5.88 trillion miles, or 9.46 trillion kilometers.) Such sharp “vision” is comparable to seeing a firefly eight thousand miles in the distance.

The HST took pictures of “benchmark” stars that will help scientists to calculate the universe’s size and shape. It provided valuable pictures of the globular cluster 47 at Tucanae, 16,000 light-years away, for example, that revealed some previously unknown white dwarf stars; another picture, of the remnants of Supernova 1987A, was extremely sharp and clear.

Some Americans have criticized the spending of federal funds on basic science in view of the nation’s overwhelming budget deficit and the need for reform of health care and other basic social systems. When compared with the projected costs of such programs, however, the funds directed to the HST were minimal and the promised returns unimaginable. The repair mission alone taught scientists and engineers much that was used on future missions that paved the way toward long-term inhabitation of space. Moreover, basic research, far from being useless, has resulted in countless useful technologies, from the lightbulb to computers.

Bibliography

Chien, Philip. “The Launch of HST.” Astronomy 18 (July, 1990): 30-37. Very readable article recounts the events that took place at the culmination of twenty years of waiting for the launch. Captures the excitement of the first tense moments and the beginning of the HST’s fifteen-year mission. Well illustrated with launch and orbit photographs.

Dunkle, Terry. “The Big Glass.” Discover 7 (July, 1989): 69-72. Presents an exciting, nontechnical account of the construction of the HST’s optics. Emphasizes the personalities, skills, and dedication of the people associated with the project.

Field, George, and Donald Goldsmith. The Space Telescope. Chicago: Contemporary Books, 1989. Very readable discussion of the HST provides an appropriate starting place for the general reader. Well supported with illustrations, glossary, and suggestions for additional reading.

Leverington, David. New Cosmic Horizons: Space Astronomy from the V2 to the Hubble Space Telescope. New York: Cambridge University Press, 2000. Presents the history of space-based astronomy since World War II, devoting the final chapter to discussion of the HST. Includes illustrations, glossary, bibliography, and indexes.

Maran, Stephen P. “The Promise of the Space Telescope.” Astronomy 18 (January, 1990): 38-43. Presents a well-written account of the main objectives and expected results of the HST.

Petersen, Carolyn Collins, and John C. Brandt. Hubble Vision: Further Adventures with the Hubble Space Telescope. 2d ed. New York: Cambridge University Press, 1998. Comprehensive discussion of the astronomical discoveries made possible by the HST. Includes many illustrations, glossary, bibliography, and index.

Smith, Robert W. The Space Telescope: A Study of NASA, Science, Technology, and Politics. New York: Cambridge University Press, 1993. Provides a detailed chronological account of the construction of the telescope from its inception to launch preparation. One of the most complete works available on the subject; includes historical background as well as discussion of the involvement of NASA, industry, and the scientific community.