A former Microsoft executive is pulling no punches in taking on NASA, ripping the space agency for papers he says are riddled with errors.

Nathan Myhrvold, the former chief technologist for Microsoft, wrote a paper in 2013 that pointed out statistic errors in a Florida State University paper on the growth rate of dinosaurs that ultimately resulted in corrections, and now he is coming after NASA over how the agency identifies and describes asteroids, according to a New York Times report.

Lindley Johnson, head of NASA’s planetary defense program, struck back at Myhrvold, saying that while he was a “smart man,” it doesn’t mean he is an “expert in everything,” according to the Times report.

Myhrvold is basically arguing that research conducted by NASA spacecraft charged with gathering data on celestial objects since 2009 is fundamentally flawed. Specifically, Myhrvold is targeting NASA’s Wide-field Infrared Survey Explorer (WISE) spacecraft, as well as NEOWISE, an offshoot of the WISE mission. They calculate the size and reflectivity of asteroids in space, determining their diameter within 10 percent of their actual size. However, Myhrvold argues that the estimates could be more than 100 percent off.

NASA officials slammed Myhrvold’s observations, in one case arguing that he mixed up diameter and radius in one of his formulas, an embarrassing fundamental error, the Times reported.

“The new analysis finds asteroid diameter and other physical properties that have large differences from published NEOWISE results, with greatly increased error estimates,” Myhrvold wrote in his abstract. “NEOWISE results have a claimed ±10% accuracy for diameter estimates, but this is unsupported by any calculations and undermined because NEOWISE results for 102 asteroids appear to have had the diameter from prior radar and occultation studies simply copied rather than being due to NEOWISE thermal modeling. Diameter estimates from bootstrap calculations appears to be no better than ±29.5% accurate when compared to diameters from radar, stellar occultations and spacecraft.”