An expensive telescope on an airplane is finally in danger of being terminated after years of problems

The onboard SOFIA telescope will make its final observations by September 30.Credit: Joshua Fisher/NASA

NASA and the German space agency are permanently closing the Stratospheric Observatory for Infrared Astronomy (SOFIA), an in-plane telescope that has been scrutinized for years for its high cost and low scientific output. Since 2014, the observatory has been hovering over water vapor in Earth’s atmosphere to get a clear view of celestial objects and collect data at infrared wavelengths.

Over the past few years, SOFIA has measured magnetic fields in galaxies1dappled water on the sunlit parts of the Moon2 and detected the first type of ion to form in the Universe, helium hydride3. But running it costs NASA about $85 million a year, almost as much as the expenses of running the Hubble Space Telescope. On April 28, NASA and the German Space Agency, the two SOFIA partners, announced the closure of the observatory by September 30.

The observatory’s high price tag, combined with its relatively low scientific output, earned it a low ranking in the last ten-year survey of the future of American astronomy and astrophysics. NASA cited the survey’s recommendation to shut down SOFIA — put forward by the astronomical community — in its decision. The observatory was originally intended to have a 20-year lifespan, but will now be decommissioned after just eight years.

“It’s a very difficult decision, and certainly a very painful one for everyone who worked on the mission,” says John O’Meara, chief scientist at the WM Keck Observatory in Kamuela, Hawaii, who worked on the planning. term of American astronomy. and astrophysics. But “it’s the right choice”.

SOFIA costs more to run each year than most other NASA astrophysics missions combined. The German Space Agency contributes 20% of the operating costs on top of NASA’s share. The observatory is expensive as it requires pilots and personnel to fly and refuel it.

” Unique in the world “

SOFIA is a Boeing 747 with a hole drilled in the side to accommodate a 2.5-meter-wide, 17-tonne telescope, which peers into the Universe as the plane flies at altitudes between about 11 and 14 kilometers. It has performed approximately 800 science flights since becoming operational in 2014. And it flies primarily from its home base in Palmdale, California, although it has also deployed to places such as Germany, Chile and New Zealand – the latter for observing celestial objects that are only visible from the southern hemisphere.

Technicians introduce liquid nitrogen into an instrument connected to the SOFIA telescope to remove as much heat as possible.

Technicians cool one of SOFIA’s instruments with liquid nitrogen in 2013.Credit: Carla Thomas/NASA

SOFIA collects data that bridges a gap between what is collected by ground-based observatories and space-based infrared telescopes, such as the recently launched James Webb Space Telescope. It is the only observatory that can currently make observations at certain far infrared wavelengths. “SOFIA is unique in the world,” said Walther Pelzer, head of the German Space Agency, in a statement announcing its closure.

Infrared observations allow SOFIA to make other unique observations, such as detecting water on the Sunlit Moon. “The shutdown is unfortunate for lunar science and exploration, as we have just begun mapping water on the Moon with SOFIA,” says Paul Lucey, a planetary scientist at the University of Hawaii at Manoa in Honolulu. “SOFIA’s capability is unique – there are no other observatories or spacecraft capable of mapping the water molecule on the illuminated Moon.”

Under surveillance

SOFIA’s scientific output has long been questioned. In 2019, five years after it began flying, a pair of reviews commissioned by NASA pointed out that the observatory had not resulted in a large number of highly cited publications. In the first six years after beginning operations, it produced 178 scientific papers, compared to more than 900 for Hubble in its first six years.

In response, SOFIA hired a new director and intensified its focus on scientific productivity. A December 2021 update on the SOFIA website states that the observatory has doubled its publications over the past three years and that the ten-year survey “has placed SOFIA in a static box that misses the tremendous scientific growth that SOFIA has known”.

When asked if NASA took recent developments into account when making its decision, agency spokeswoman Alise Fisher pointed to the 10-year survey, which says it “don’t found no evidence that SOFIA could, in fact, transition to a significantly more productive future.”

Charles Woodward, an astronomer at the University of Minnesota in Minneapolis, says SOFIA’s closure has led to a feeling of “melancholy” among infrared astronomers, given that its productivity had recently increased. “A significant portion of the community will think SOFIA has had the short end of the stick,” he says.

In recent years, several budget requests from US presidents have recommended ending SOFIA. In any case, Congress — usually led by House Minority Leader Kevin McCarthy, who represents a district near Palmdale — provided funds to keep it going. The new decision could render Congress’s wishes moot.

By September 30, SOFIA is expected to make its final observations, possibly including a deployment to New Zealand. NASA and the German Space Agency will then decommission the aircraft.

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