A spacecraft that helped bolster planetary defense is now at the end of its operational mission. On Thursday, engineers at NASA's Jet Propulsion Laboratory in California sent the Near-Earth Object Wide-field Infrared Survey Explorer (WISE) spacecraft into its final hibernation mode by shutting off its transmitter.
The order, issued from JPL's Earth Orbit Mission Operations Center, capped more than a decade of observations of comets and asteroids that helped improve understanding of celestial bodies that could pose a potential threat to Earth.
NEOWISE The spacecraft reached its swansong because it has no propulsion system and therefore could not stay in orbit. That, coupled with increased solar activity this year, meant the spacecraft will naturally drift down into orbit until it burns up in the atmosphere in late 2024.
Dozens of people who participated in the spacecraft's mission over the years gathered at JPL to witness the moment and celebrate years of scientific observations.
Today we bid farewell to NEOWISE and celebrate its fabulous team. The mission mapped the skies and advanced our nation's planetary defense strategy, and its legacy will live on in NEO Surveyor (being built in @NASAJPL now!) Thanks for all the science! https://t.co/yRhqvLJ5sj image.twitter.com/i3J5SCEtgv
-Laurie Leshin (@LaurieofMars) August 8, 2024
In the hours leading up to the spacecraft's final communications, Spaceflight Now spoke with Amy Mainzer, NEOWISE's principal investigator at the University of California, Los Angeles. She joined the original WISE mission in 2003, but said the end of NEOWISE was not a sad moment for her.
“I feel great, I have no regrets. This telescope was supposed to last seven months and it was launched in 2009. Now we’re in 2024, so who could ask for more?” Mainzer said. “My goodness, we’ve had a great run and we still have a lot of work to do. We’re going to be using this data for decades to come.”
“Right now, I have a couple of articles that we are trying to publish. We are very busy. There are many reasons to be happy and grateful.”
That primary seven-month mission ended in 2010 after the spacecraft not only completed its original infrared survey around Earth, but also because it ran out of its onboard coolant, which was needed to enable infrared observations.
That same year, NASA decided to rename the telescope “NEOWISE” and completed its study of main belt asteroids. After that, it went into hibernation in early 2011.
“(Cryogenics) lasted a little bit longer than anticipated, which was great, but it was over pretty quickly and we knew we could do more when it came to asteroids in particular and comets,” Mainzer said. “So it was very painful to have to watch it stop the first time because we thought, ‘Ah, this is a missed opportunity. We could do more. ’ But we got a second chance and that was really cool.”
That comeback moment came in 2013, when NEOWISE emerged from hibernation under a program called the Near-Earth Object Observations Program. That overall mission is now under the oversight of NASA's Planetary Defense Coordination Office.
Over the next decade, NEOWISE detected more than 3,000 near-Earth objects, including 215 that were first recorded by the spacecraft. On the day the final transmission was sent to NEOWISE, NASA shared its final exposure taken on August 1, 2024, showing part of the constellation Fornax.
The Dawn of the NEO Surveyor
With the conclusion of the NEOWISE program, NASA moves into its next phase of planetary defense with the upcoming NEO Surveyor While speaking to Spaceflight Now on Aug. 8, Mainzer looked around the clean room containing some of the telescope's parts.
In the room below the viewing gallery, a protective panel for the telescope was being unveiled as engineers elsewhere at JPL were working on mirrors for the 50-centimeter (nearly 20-inch) diameter telescope.
Looking ahead to developing NEO Surveyor, Congress has mandated NASA to make “significant progress” toward finding “more than 90 percent of all NEOs larger than 140 meters (460 feet) in diameter.” Mainzer said that will take time.
“We expect that after the first five years, we will probably have found more than two-thirds of them. It will take us a little bit longer than that to get to 90 percent. We think in about 10 years we will get there,” he said. “It takes a while because these objects are inherently faint. They are small. They are seen at a great distance. We want to see them when they are far away. We don’t want to wait until they are right on top of us.”
“But it still takes a long time. It is a difficult problem. And after about 10 years, we believe we will reach 90 percent.”
Mainzer says that during the interval between the end of NEOWISE and the launch of NEO Surveyor, which will not be before September 2027, NASA will rely on its ground assets in places like Hawaii and Arizona, as well as other global partners. Mainzer said she and her team will also be busy with NEOWISE data provided until its final downlink.
“We will analyze the NEOWISE data and see if we have incidental detections of some of the objects that were discovered or will be discovered in the next few years,” he said.
With NEO Surveyor launching in about three years at the earliest, Mainzer said she and her team will be incredibly busy transitioning from one spacecraft to the next.
“We have a lot of work to do, but when we’re done and this telescope is launched, we hope to have a great new capability to see what’s in the vicinity of Earth,” Mainzer said. “It won’t be perfect — nothing ever is — but it will really expand what we know about objects in our neighborhood. It will be part of a larger network of ground-based telescopes that will also help us fill in the gaps and really tell us what’s actually out there.”
