NASA's comeback kid, the NEOWISE spacecraft, was this week shut down for the final time as its transmitter was turned off ahead of a reentry into the Earth's atmosphere later this year.

The Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) is at the end of its second mission, after completing its first mission as the WISE (Wide-field Infrared Survey Explorer) telescope in February 2011.

The spacecraft was launched in December 2009 with a six-month assignment to scan the entire infrared sky. It completed this in July 2010, and NASA extended the program until 2011.

However, all good things must come to an end, and with the depletion of the cryogenic coolant required to offset the heat generated by the spacecraft, WISE was put into hibernation. During its first mission, the telescope had mapped the night sky twice and demonstrated its prowess at spotting near-Earth objects.

Engineers and scientists were not done with WISE, though. In 2013, the telescope was brought out of hibernation under the Near-Earth Object Observations Program, which preceded NASA's Planetary Defense Coordination Office. The project was then called NEOWISE.

While the depletion of coolant meant that NEOWISE could no longer observe the faintest infrared objects in the universe, it could still be used to hunt for asteroids and other near-Earth objects.

Joseph Masiero, NEOWISE deputy principal investigator, said, "Without coolant, we had to find a way to cool the spacecraft down enough to measure infrared signals from asteroids.

"By commanding the telescope to stare into deep space for several months, we determined it would radiate only enough heat to reach lower temperatures that would still allow us to acquire high-quality data."

Scientists have known for a while that the end was coming and planned accordingly.

At the end of 2023, Masiero said, "The mission has planned for this day a long time. After several years of calm, the Sun is waking back up.

"We are at the mercy of solar activity, and with no means to keep us in orbit, NEOWISE is now slowly spiraling back to Earth."

NEOWISE's survey concluded on July 31, and on August 8, mission controllers at NASA's Jet Propulsion Laboratory sent the command to turn off the spacecraft's transmitters, effectively ending that portion of the operation.

Masiero said, "This is a bittersweet moment. It's sad to see this trailblazing mission come to an end, but we know there's more treasure hiding in the survey data.

"NEOWISE has a vast archive, covering a very long period of time, that will inevitably advance the science of the infrared universe long after the spacecraft is gone."

A follow-up to NEOWISE is planned: NEO Surveyor. NEO Surveyor is currently due for launch in September 2027 and will consist of a 50-centimeter-diameter telescope capable of detecting both light and tricky-to-spot dark asteroids. According to NASA, "NEO Surveyor will conduct a five-year baseline survey to find at least two-thirds of the near-Earth objects larger than 140 meters (460 feet).

"These are the objects large enough to cause major regional damage in the event of an Earth impact." ®

https://www.theregister.com//2024/08/09/nasas_asteroid_spotter_turned_off/