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A prominent technologist is calling into question estimates of asteroid sizes made by a NASA space telescope.

A prominent technologist is calling into question estimates of asteroid sizes made by a NASA space telescope.


Billionaire technologist accuses NASA asteroid mission of bad statistics

Nathan Myhrvold—ex–Microsoft billionaire, patent accumulator, dinosaur geek, and noted molecular gastronomist—has a new obsession: asteroids. The CEO of Bellevue, Washington–based Intellectual Ventures says that scientists using a prominent NASA space telescope have made fundamental mistakes in their assessment of the size of more than 157,000 asteroids they have observed.

In a paper posted to the e-print repository on 22 May, Myhrvold takes aim at the Wide-field Infrared Survey Explorer (WISE), a space telescope launched in 2009, and a follow-on mission, NEOWISE, which together are responsible for the discovery of more asteroids than any other observatory. Yet Myhrvold says that the WISE and NEOWISE teams’ papers are riddled with statistical missteps. “None of their results can be replicated,” he tells ScienceInsider. “I found one irregularity after another.”

In a 2011 paper, the WISE and NEOWISE teams claim to determine the diameter of asteroids with an accuracy of better than 10%. But Myhrvold says they made mistakes, such as ignoring the margin of error introduced when extrapolating from a small sample size to an entire population. They also neglected to include Kirchhoff’s law of thermal radiation in their thermal models of the asteroids. Based on his own models, Myhrvold says that errors in the asteroid diameters based on WISE data should be 30%. In some cases, the size errors rise to as large as 300%. “Asteroids are more variable than we thought they were,” he says. He has submitted the paper to the journal Icarus for review.

The WISE and NEOWISE teams are standing by their results, and say that Myhrvold’s criticism should be dismissed. “For every mistake I found in his paper, if I got a bounty, I would be rich,” says Ned Wright, the principal investigator for WISE at the University of California, Los Angeles. Wright says that WISE’s data match very well with two other infrared telescopes, AKARI and IRAS. To find out how accurately those infrared data determine the size of an asteroid, scientists have to calibrate them with radar observations, other observations made when asteroids pass in front of distant stars, and observations made by spacecraft up close. When they do that, Wright says, WISE’s size errors end up at roughly 15%.

Amy Mainzer, the principal investigator for NEOWISE at the Jet Propulsion Laboratory in Pasadena, California, points out some of the specific goofs in Myhrvold’s study. In one formula, he confuses diameter for radius, she said in a statement. “Our team has seen the paper in various versions for many months now, and we have tried to point out problems to the author,” she states. “We have strongly encouraged that the paper be submitted to a journal and peer reviewed. Instead, he released it without peer review.”

Myhrvold retorts that he is fixing the errors, which he says are cosmetic and do not alter the thrust of his criticism. He says the NEOWISE scientists are defensive because many are involved in a proposal for a future asteroid-hunting telescope called NEOCam, one of five finalists in NASA’s Discovery program. “They’re up for this NEOCam thing and they’re afraid it looks bad. And it does look bad,” he says.

This is not the first time that Myhrvold has been a thorn in scientists’ sides. In 2013, he found flaws in studies of dinosaur growth rates. He says his outsider, amateur status allows him to stir the pot in ways that insiders are unable to.

Myhrvold has been interested in dinosaurs and asteroids ever since 1980, when he was a physics graduate student at Princeton University and heard a talk about the Alvarez asteroid impact theory. Last year, he says he was approached by the B612 foundation—which has been pushing for a privately funded asteroid-hunting space telescope of its own. “They came to see me hoping I would give them money or introduce them to my rich friends,” he says. He didn’t give B612 money, but he did begin to assess the relative merits of the different projects: B612’s proposed Sentinel telescope; NEOCam; and the Large Synoptic Survey Telescope, a ground-based telescope under construction in Chile. “Each of the projects had different assumptions, which is why each project has simulations which claim theirs is the best.”

In the wake of that assessment, which was published last year, Myhrvold got interested in the WISE and NEOWISE data, and kept finding things to investigate. “I just got really stubborn,”  he says.

Wright says his team doesn’t have Myhrvold’s computer codes, “so we don’t know why he’s screwing up.” But Wright archly noted that Myhrvold once worked at Microsoft, so “is responsible in part for a lot of bad software.”