The Perseid meteor shower, which peaks in August of each year, was twice as active in 2016 compared to other years. The Perseids are always a major shower and move at very high speeds, so monitoring is essential for the safety of NASA’s spacecraft as there is great potential for high-energy impacts. Increases in activity, like that seen this year, add additional mission risks.

“We do annual shower forecasting, and the reason is that if there is a short-term increase in the hazards posed by meteoroids, we want to let programs know so they can assess if that’s a concern for them or not,” explained Althea Moorhead, aerospace technologist for planetary studies, part of NASA’s Meteoroid Environments Office (MEO).

The increase in activity was due to Jupiter moving several streams of the meteor shower closer to Earth. The short-duration sharp peak of the shower exhibits the most influence from the additional stream particles, but the shower lasts weeks — middle of July well into August — with much lower activity levels.

According to MEO lead Bill Cooke, the office used a series of cameras to observe this year’s shower. As always, MEO used NASA’s All Sky Fireball Network, but because the network only captures images on a nightly basis, this year scientists wanted additional means to attain high-time resolution data to monitor the increase in activity. As a result, members of MEO reached out to the International Meteor Organization for data and video footage and worked with the Canadian Meteor Orbit Radar in Ontario and the Middle Atmosphere Alomar Radar System (MAARSY) in Norway. Cooke explained this shower was the first time NASA used MAARSY, a high-power, large-aperture radar recently equipped with sensitive optical cameras by MEO and its colleagues at the University of Western Ontario.

Using the combined observations, MEO was able to confirm its prediction of heightened activity this year, as well as its suspicions that the shower profile would be slightly different.

“Normally we model the Perseids as having one sharp peak, one point in time where the activity picks up, but this year, in addition to what we call the traditional peak, 12-15 hours earlier we had an additional peak,” said Moorhead of the unusual pattern. “It gives us confidence in our models. [When] we can model a stream, like the way we did the Perseids, and see agreement between our models and reality, it indicates we can continue to use that model in the future.”

These models are used to predict the time that meteors pass close to near-Earth space, which informs programs when their spacecraft might be at risk. Although MEO’s predictions were largely on point, the office noted that the forecast activity was broader than what was actually observed. As a result, MEO plans to adjust future forecasts, permitting better Perseid risk estimates for future outbursts.