[amelius]

Perhaps they went missing when it was cloudy?

[bumby]

From the article: "trained to locate the sources of electromagnetic emissions with wavelengths ranging from roughly 2 meters down to 2 centimeters"

These types of signals wouldn't be obscured by clouds, presumably.

[ehsankia]

wouldn't some IR go through clouds? I thought that was the point of using IR.

That being said, the more important question is, how's the temporal resolution.