SOFIA flying observatory takes final flight

Grounded for good

But despite its accomplishments, the recently published decadal survey, also called Astro2020, stated that SOFIA’s yearly operating price tag of $86 million USD — on par with the Hubble Space Telescope and Chandra X-ray Observatory — could not be justified by its “modest” scientific output as measured by the number of published papers based on data taken from the telescope. 

From 2014 to 2020, the survey said, SOFIA flights resulted in 178 scientific papers. Hubble and Chandra data combined were used in more than 2,700 papers over that same period. “The committee found no path by which SOFIA can significantly increase its scientific output to a degree that is commensurate with its cost,” the survey said. Ultimately, the committee endorsed NASA’s existing plan to end SOFIA’s operations.

But SOFIA’s six instruments covered a wavelength range of 0.3 to 1,600 µm — essentially the entire infrared spectrum. This is a range JWST cannot replicate. Although its 6.5-meter mirror is larger, JWST only observes from 0.6 to 28.3 μm. So, SOFIA could see into the far infrared, revealing portions of the universe permanently inaccessible to JWST.

“The loss of SOFIA simply means loss of access to the far-infrared window for at least the next 10 years,” says Dario Fadda, a senior scientist in astronomy at the SOFIA Science Center.

Fadda and Ashton both worry shutting down SOFIA will push students and early-career researchers away from far-infrared research and into other wavelength regimes. Both are also concerned that as older scientists experienced with the kind of data SOFIA churned out retire, that institutional knowledge will be lost and will need to be rebuilt. 

“SOFIA was not only important for the science which was done, but also to preserve a nucleus of people with knowledge of infrared astronomy. As with any human achievement, science needs continuity,” Fadda says.

But there are still valuable takeaways from SOFIA’s success. “I think the lesson of SOFIA is that there is some science that you just can’t get by building a scaled-up version of something else, with bigger mirrors, more detectors, etc.,” says Ashton. “I hope it serves as a reminder that sometimes the best tool for the job might look wildly different than anything you’ve ever seen before.”

SOFIA principal systems engineer Nancy McKown, who previously served as the observatory’s Mission Operations Manager and Mission Director, flew more than 100 times on the aircraft, including its first light flight in 2010. “I cherish the memories of the scientists’ smiles and shouts of joy when a difficult observation was executed flawlessly,” she says, admitting her last flights on SOFIA were bittersweet.

There are no current plans for a future flying observatory, but the proposed Origins Space Telescope, which could potentially launch in 2035, would reopen the far infrared to astronomers. Alternatively, the Astro2020 committee suggested development of a combination X-ray and infrared space telescope. But even if proposed and picked up by funding agencies, its launch would be just as far off.

Nevertheless, McKown remains hopeful. “There may be some gaps now, but I’m confident that the thirst for knowledge will keep it in the long view of the big picture,” she says. “After all, the data will still be there for us to capture in the future.”