Walking home from school, Alex is lost in thought. He suddenly hears a strange sound from above. A bird? A squirrel? ... A small, red monkey?

What!? What's a monkey doing here? he thinks.

He grabs his cellphone camera, snaps a picture, and sends it to three friends, texting them to come quickly. Alex and the monkey keep an eye on each other. Soon, two of the friends approach. One also has a cellphone camera. The other has a real camera that records videos with sound. Now, all three of them watch the monkey, recording photos, videos, and monkey chirps. A monkey loose anywhere in the city is exciting. But bigger events happen around our planet every day. A 'dead' volcano heats up. A wildfire threatens homes. A river overflows its banks. Often no one is around to see these events. Or they are stuck in the middle of it and can't see how big it is. Fortunately, many Earth-watching satellites do see such events. They also tell their satellite "friends" to come and help them observe. All with no help from us humans.

This system of satellite "friends" is called a Sensor Web. This useful technology started with some intelligent computer software that can figure out from a satellite picture whether something new and different is happening.

It can then tell other satellites, as well as monitoring stations on the ground, to pitch in and help study the new event.

So what's the point? The satellites get right to work without being told. An intelligent sensor web gathers more information faster than if human were in the loop. Also, future space missions will benefit. It will take an hour or more for signals to travel from Earth to, say, Jupiter's mysterious moon Europa. NASA's robotic space explorers will have to figure out for themselves what to observe and measure, rather than waiting for directions from Earth. Back on Earth, one spacecraft often called on to take a better look at new events is Earth Observing 1, because its imagers have super-duper vision. Check out its amazing eyesight at http://spaceplace.nasa.gov/en/kids/eo1_1.shtml.

After spending the rest of the afternoon observing the monkey, Alex and his friends send their photos, videos, and audio files to a primate scientist at the city zoo. Their observations make a valuable contribution to human understanding of these creatures.

This article was written by Diane K. Fisher and provided courtesy of the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA.