Tag Archives: NEOWISE

Questions raised about NEOWISE asteroid data analysis

A computer entrepreneur has raised questions about the data analysis used by the scientists in charge of NASA’s NEOWISE space telescope (formerly called the Wide-field Infrared Space Telescope, or WISE).

Myhrvold, a former chief technologist for Microsoft, founded the patent-buying firm Intellectual Ventures in Bellevue, Washington, in 2000; on the side, he pursues interests ranging from modernist cuisine to palaeontology. A few years ago, he began exploring ways to detect dangerous space rocks. He soon argued3 that the Large Synoptic Survey Telescope, a ground-based telescope being built in Chile, would have the capacity to find nearly all the same asteroids as NASA’s proposed successor to NEOWISE, called NEOCam.

That turned his attention to how asteroids could be studied in space, and to the NEOWISE data. “I thought, this will be great, maybe we’ll be able to find some new and interesting things in here,” he says. But Myhrvold soon became frustrated with the quality and analysis of the data. He posted a critical preprint on arXiv in May 2016, and the peer-review game was on.

His first peer-reviewed critique was published in Icarus in March4. In it, he explored the mathematics of how asteroids radiate heat, and said that the NEOWISE team should have accounted for such effects more thoroughly in its work.

The latest paper1 holds the bulk of the NEOWISE critique. Among other things, Myhrvold argues that the NEOWISE team applied many different modelling techniques to many different combinations of data to achieve its final results. He also criticizes the choice to include previously published data on the diameter of certain asteroids in the data set, rather than using NEOWISE measurements — which, though less precise, are at least consistent with the rest of the database. Such choices undermine the statistical rigour of the database, he says.

Alan Harris, a planetary scientist with the consulting firm MoreData! in La Cañada Flintridge, California, was one of the paper’s reviewers. “In my opinion, it has important things to say,” he says. “It is my hope that the scientific community will read the paper and pay attention to the analysis Myhrvold has presented, as he has raised a number of significant issues.”

The disagreement involves the NEOWISE team’s estimate of asteroid sizes, based on the infrared data. Myhrvoid questions their estimates.

More details about the clashes between Myhrvoid and the NEOWISE science team over the past two years can be found here. The NASA scientists do not come off well. They appear to be very defensive, acting to stonewall any review of their work. Repeatedly they attempted to defy Myhrvoid’s FOIA requests (only made when they refused to release their raw data), including redacting significant information for no justifiable reason.

I have really only one question: Does the behavior of these NASA planetary scientists sound familiar? To me it does, and what it reminds me of speaks very badly for the science being done in the NEOWISE mission at NASA.

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The surface properties of 122 asteroids revealed

Using archive data produced by the Wide-field Infrared Explorer telescope (WISE, renamed NEOWISE) astronomers have been able to estimate the surface properties of 122 small asteroids located in the asteroid belt.

“Using archived data from the NEOWISE mission and our previously derived shape models, we were able to create highly detailed thermophysical models of 122 main belt asteroids,” said Hanuš, lead author of the paper. “We now have a better idea of the properties of the surface regolith and show that small asteroids, as well as fast rotating asteroids, have little, if any, dust covering their surfaces.” (Regolith is the term for the broken rocks and dust on the surface.)

It could be difficult for fast-rotating asteroids to retain very fine regolith grains because their low gravity and high spin rates tend to fling small particles off their surfaces and into space. Also, it could be that fast-rotating asteroids do not experience large temperature changes because the sun’s rays are more rapidly distributed across their surfaces. That would reduce or prevent the thermal cracking of an asteroid’s surface material that could cause the generation of fine grains of regolith. [emphasis mine]

If this conclusion holds, it means that mining these asteroids might be much easier. Dust can be a big problem, as it can clog up equipment and interfere with operations. It also acts to hide the underlying material, making it harder to find the good stuff.

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WISE completes another year of asteroid hunting

After being mothballed in space and then reactivated, NASA’s WISE infrared telescope (renamed NEOWISE for no good reason) has now completed its second year of observations, looking for near-Earth objects (NEOs).

NASA’s Near-Earth Object Wide-field Survey Explorer (NEOWISE) mission has released its second year of survey data. The spacecraft has now characterized a total of 439 NEOs since the mission was re-started in December 2013. Of these, 72 were new discoveries. Near-Earth Objects (NEOs) are comets and asteroids that have been nudged by the gravitational attraction of the giant planets in our solar system into orbits that allow them to enter Earth’s neighborhood. Eight of the objects discovered in the past year have been classified as potentially hazardous asteroids (PHAs), based on their size and how closely their orbits approach Earth. [emphasis mine]

Unfortunately, the press release does not provide any details about those eight potentially hazardous asteroids.

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The recently reactivated WISE space telescope has discovered its first new asteroid.

The recently reactivated WISE space telescope has discovered its first new asteroid.

2013 YP139 is about 27 million miles (43 million kilometers) from Earth. Based on its infrared brightness, scientists estimate it to be roughly 0.4 miles (650 meters) in diameter and extremely dark, like a piece of coal. The asteroid circles the sun in an elliptical orbit tilted to the plane of our solar system and is classified as potentially hazardous. It is possible for its orbit to bring it as close as 300,000 miles from Earth, a little more than the distance to the moon. However, it will not come that close within the next century.

WISE, renamed NEOWISE by NASA, is expected to come up with a lot more of these in the coming years.

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WISE, the Wide Field Infrared Survey Explorer, sent back its first images in almost three years this week.

Back from the dead: WISE sent back its first images in almost three years this week.

The Near-Earth Object Wide-field Infrared Survey Explorer spacecraft, or NEOWISE, has taken its first set of test images since being reactivated in September after a 31-month-long hibernation, NASA officials announced today (Dec. 19). The space agency wants NEOWISE to resume its hunt for potentially dangerous asteroids, some of which could be promising targets for future human exploration.

We should note that NASA had shut down this functional space telescope even though the cost to use it to hunt asteroids would be relatively little. Cost was cited as the reason, but I suspect it was a combination of the vast overruns for the James Webb Space Telescope and the Obama administration’s puzzling hostility to science at NASA.

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