NASA needs a camera to spot killer asteroids – Quartz


Astronomers tend to be patients. As far as the stars are concerned, much of what they look at happened millions of years ago. For space probes, even pre-launch preparation can take a decade or more.

But they are starting to look forward to launching an infrared space telescope called NEOCam. Its mission is very specific: to locate objects close to the Earth – astronomical bodies, mostly asteroids, whose orbits around the sun could pass close to the Earth and potentially hit our planet, some of which could damage or destroy the planet. civilization itself.

This is not speculative; a major meteorological impact is inevitable and we need to better monitor the solar system.

"The question is when will the next event occur humanly and geologically," says Amy Mainzer, a scientist at CalTech's Jet Propulsion Laboratory and a senior researcher on the NEOCam project.

It's not that the US government is not interested. NASA has already cataloged all the asteroids close to the Earth whose diameter is greater than 1 km. Congress passed a law in 2005 requiring NASA to find 90% of objects near the Earth whose diameter is greater than 140 meters (460 feet). .

In 1908, one of the largest well documented aerial asteroid radars over Tunguska (Russia) razed 2,000 km 2 of forest. Scientists think it was between 40 and 60 meters in diameter.

The space agency received a deadline of 2020 to find these objects close to the Earth. It will not do it. In June 2018, NASA's global defense officer, Lindley Smith, said that about 8,000 objects of this type have been detected, but scientists expect that twice as much objects are discovered. To illustrate the urgency, Smith then stated that if any of these unknown objects posed a danger to the Earth, sending a spacecraft to intercept it would require a warning 10 years old.

There is still no plan to fulfill the mandate of the Congress. NASA said it was waiting for a panel of the National Science Foundation (NSF) to complete a study of the best methods for finding near-Earth objects, expected this spring, before making its decision on NEOCam.

"I do not lose my sleep because of the risk that an undiscovered asteroid will impact Earth, because the chances are minimal, but they are not zero," says Richard Binzel, MIT planetary scientist, who does not is not part of the NEOCam team but has pleaded for its need for the NSF panel. "We have the ability, the responsibility of adults, to just know what's going on. And NEOCam is basically ready to go. "

Another space probe, called IMAP, will be launched in 2024 to study the solar wind and move to an ideal orbit also for NEOCam. There is room on its rocket for an extra payload, and asteroid researchers say it's the best opportunity to launch NEOCam, which Maizer had proposed for the first time in 2005 and which has spent 14 years at the refining. But they will soon need approval and funding to build the telescope on time.

The Large Synoptic Survey Telescope, or LSST, is another important source of data on near-Earth objects. Funded by the NSF, he will install a mirror the size of a tennis court on a mountain in Chile. By 2023, the telescope will begin a ten-year study to repeatedly capture large-scale images of the night sky. Asteroid researchers expect to collect enough data to find about 75% of NEO objects 140 meters or more.

However, achieving the 90% mandate will require infrared space observations, such as those NEOCam is designed to collect. Infrared observations can do something that ground-based telescopes can not: estimate the size of an asteroid. At visual wavelengths, astronomers have trouble distinguishing between large dark objects and small bright objects, but infrared data can be used to solve this problem. This will be particularly important once the LSST has started its work.

"I do not think anyone appreciates how much the beginning of the [LSST Survey] will be, when we start seeing everything there, "says Binzel. "A 10-meter object goes inside the moon's orbit every week – and we'll start seeing objects worth several years long before they approach them." first orbit solutions will not be able to distinguish between "shots or blows." We need to focus our attention on the larger objects of this incoming stream – and we need the [infrared] characterization to solve this problem. "

NEOCam's plan is a bit complicated by the work of Nathan Myhrvold, a physicist and former Microsoft executive. He published research indicating that NASA's near-Earth data was more uncertain than its collectors believe, in part because the source of this data, a space telescope called NEOWISE, was not designed originally to locate objects as close to our planet.

Mainzer, who is also the principal investigator of NEOWISE, claims that Myhrvold's analysis is flawed and that asteroid data has been confirmed by independent data and models by other independent researchers. And NEOCam is optimized for observing near-Earth objects, with specialized imaging chips that have been refined to capture high-resolution infrared images at a temperature of 40 ° K, about -387 ° F, which is much hotter than the WISE chips, which run at 8 ° K. This will allow NEOCam to collect data for a much longer time.

Beyond the import into civilization, collecting data on asteroids could have other goals for NASA. The cataloging of asteroids could give the agency – and its many trading partners – targets for future space missions, and opinion polls suggest that Americans would prefer NASA to spend more time in the future. Worry about asteroidal impacts that, for example, send people on Mars.

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