Jan. 30, 2020

— NASA has ended the mission of one of its Great Observatories, 16 years after the space telescope began studying the universe in the infrared.

The Spitzer Space Telescope was decommissioned on Thursday (Jan. 30) by the Jet Propulsion Laboratory (JPL) in Pasadena, California, which sent the signals to shut it down. The telescope returned its last science data on Tuesday.

"We leave behind a powerful scientific and technological legacy," said Spitzer project manager Joseph Hunt, who declared the telescope's end at 5:34 p.m. EST (2234 GMT) after engineers confirmed that the spacecraft was placed in safe mode, ceasing all science operations. "Everyone who has worked on this mission should be extremely proud today. There are literally hundreds of people who contributed directly to Spitzer's success, and thousands who used its scientific capabilities to explore the universe."

NASA made the decision to retire the Spitzer four years ago based on a review of the agency's then-current and future missions. The infrared observations made by the Spitzer are planned to continue using the James Webb Space Telescope (JWST), which is targeted for launch in March 2021. Spitzer was originally slated to be shut off in 2018, but received a two-year extension after JWST faced delays.

Launched on Aug. 25, 2003, atop a Delta II rocket from Cape Canaveral, Florida, the Space Infrared Telescope Facility (SIRTIF) was renamed the Spitzer Space Telescope for the late astronomer Lyman Spitzer, whose idea it was to operate telescopes above Earth's atmosphere. Over the course of its decade and a half in service, the Spitzer was used to make discoveries that spanned from inside the solar system to nearly the edge of the universe.

"Spitzer taught us how important infrared light is to understanding our universe, both in our own cosmic neighborhood and as far away as the most distant galaxies. The advances we make across many areas in astrophysics in the future will be because of Spitzer's extraordinary legacy," Paul Hertz, NASA's director of astrophysics, said in a statement.

Spitzer Space Telescope mission overview. Click to enlarge in a new pop-up window. (NASA)

Designed to study "the cold, the old and the dusty," which resolves particularly well in infrared light, Spitzer, together with the Hubble Space Telescope was used to study distant galaxies, including the farthest galaxy observed to date. Light seen from that galaxy originated 13.4 billion years ago, when the universe was less than five percent its current age.

Spitzer also collected data about interstellar dust, including the material kicked up by NASA's Deep Impact 2005 collision with Comet Tempel 1 and the particles that comprised a previously unknown of ring around Saturn, the latter invisible to other observatories.

Some of Spitzer's discoveries, such as the detection of exoplanets, were not part of the telescope's original science goals. Using Spitzer's instruments to look for the dip in brightness that results from a planet passing in front of star, scientists were able to confirm the presence of two Earth-size worlds in the TRAPPIST-1 system. Spitzer then discovered another five Earth-size exoplanets in the same system, amounting to the largest batch of terrestrial-like bodies found around a single star.

Spitzer was also first in detecting molecules in the atmosphere of an exoplanet and it provided the first measurements of temperature variations and wind in an exoplanet atmosphere, as well.

"When Spitzer was being designed, scientists had not yet found a single transiting exoplanet, and by the time Spitzer launched, we still knew about only a handful," said Sean Carey, manager of the Spitzer Science Center at IPAC at the California Institute of Technology (Caltech) in Pasadena. "The fact that Spitzer became such a powerful exoplanet tool, when that wasn't something the original planners could have possibly prepared for, is really profound."

"And we generated some results that absolutely knocked our socks off," he said.

The Spitzer Space Telescope was one of NASA's four Great Observatories. It was the second to reach its mission's end after the Compton Gamma Ray Observatory, which was deorbited in 2000. The Hubble Space Telescope and Chandra X-Ray Observatory remain in use.

Now dormant, the 13-foot-long (4-meter) Spitzer will continue in its Earth-trailing orbit, growing more distant with each revolution around the Sun. Spitzer was originally planned to operate for only five years. In the decade that followed, the telescope's increasing separation — out to 160 million miles (260 million kilometers) — became a challenge. If it was not decommissioned, the spacecraft would have eventually moved out beyond where it could be used.

"It wasn't in the plan to have Spitzer operating so far away from Earth, so the team has had to adapt year after year to keep the spacecraft operating," said Hunt. "But I think overcoming that challenge has given people a great sense of pride in the mission. This mission stays with you."