# How “big” objects can WISE and NEOWISE detect?

I mean WISE is monitoring near-Earth objects, but cannot see the latest Russian meteor and others. Why can it not detect small objects?

What is the limit of it's infrared detectors?

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1. They're tiny - All telescopes have a limited resolution, below which we cannot accurately tell what we're looking at. The resolution for optical telescopes are much larger than radio and microwave, but the Russian meteor was about $15$ $m$ in diameter, which would have only been detectable at $\sim 1000$ $km$ away from the Earth's surface.
2. They're fast - The detection and identification of objects in the sky requires us to resolve them (in both time and space) so that we can look at them and figure it out. But this asteroid was moving at about $60,000$ $km/hr$, which is really fast for an object that close to us. It's quite hard to resolve objects moving across the sky that quickly, since the telescopes can't track the object across the sky.