After a search for an outside funding source turned up empty, NASA plans to end observations with the Spitzer Space Telescope in January to conclude a 16-year mission that discovered exoplanets, studied galaxies in the ancient Universe, and peered at planets and asteroids in our own Solar System.

NASA quietly announced the plan to end Spitzer’s observations in a blog post earlier this month. Astronomers hoped to keep Spitzer going until after the launch of the long-delayed James Webb Space Telescope, but the new observatory is now scheduled for launch in early 2021, and continues to dominate the budget for NASA’s astrophysics division.

“On January 30, 2020, NASA’s Spitzer Space Telescope will transmit the final science and engineering data to mission control and then be commanded off, ending its amazing and surprising mission,” wrote Lisa Storrie-Lombardi, Spitzer’s project manager at NASA’s Jet Propulsion Laboratory in Pasadena, California.

Scientists will archive the final data from Spitzer for use by future scientists.

“But even after Spitzer ceases transmissions, scientists will continue making discoveries from its 16 years of data for decades to come,” Storrie-Lombardi wrote. “Spitzer enables groundbreaking advances in our understanding of planetary systems around other stars, the evolution of galaxies in the nearby and distant universe, the structure of our Milky Way galaxy, the infinite variety in the lives of stars, and the constituents of our Solar System.”

A review of NASA’s operating astrophysics missions by an independent panel of scientists in 2016 ranked Spitzer at the bottom of a list of six projects examined by the board. While the independent panel, called a senior review, did not recommend shutting down any of the operating missions, NASA uses the senior review reports to prioritize spending on extended missions, in balance with expenditures to design, develop and build new astrophysics probes and telescopes.

The 2016 senior review recommended NASA continue operating Spitzer until 2019, after the Webb telescope’s then-scheduled launch date. Spitzer escaped cancellation in 2014 after project managers found ways to reduce the mission’s operating costs.

Thomas Zurbuchen, head of NASA’s science division, said on 21 May that agency followed guidance from the senior review in deciding when to shut down Spitzer.

“Every once in a while, that means that turn off a mission because the science return is no longer warranting keeping it going in the context of the other missions,” Zurbuchen said during a meeting of the NASA Advisory Council’s science committee. “It’s not that there’s no science return, but there’s less.”

Spitzer cost $11 million to operate in fiscal year 2018.

In 2017, NASA sought information from private entities, such as academic institutions, to take over Spitzer operations after NASA’s funding for the mission ran out. Two organizations submitted proposals to assume responsibility for Spitzer, but they were unable to secure the required funding, according to Felicia Chou, a NASA spokesperson.

Chou said Spitzer, which is in an Earth-trailing orbit around the Sun, can remain in its current orbit through the Solar System after NASA turns off the mission. While the spacecraft and its instruments remain functional, the distance between Earth and Spitzer is increasing, which reduces the data flowing from the telescope.

Built by Lockheed Martin, Spitzer was the last of NASA’s four original Great Observatories to launch, joining Hubble, the Compton Gamma-Ray Observatory, and the Chandra X-ray Observatory.

Designed for a five-year mission, Spitzer launched on 25 August 2003, aboard a Delta 2 rocket from Cape Canaveral.

Spitzer launched with a supply of super-cold liquid helium to cool its most sensitive infrared detectors, which were designed to image some of the coldest reaches of the universe. Since 2009, Spitzer has only been able to use two of its shorter wavelength imaging bands after running out of cryogenic helium. Detectors in the near-infrared bands do not need to be chilled to do their work.

Zurbuchen said NASA is ending the Spitzer mission with a “sense of celebration for a mission that’s exceeding any and all expectations.”

“Spitzer’s prime mission lasted more than twice the requirement, and I can assert with confidence that no one expected that the observatory would still be operating and doing exciting science in 2019, the tenth year of the extended mission,” Storrie-Lombardi wrote.

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