Honey, I shrunk the data!
Spacecraft that study Earth collect HUGE amounts of data every second!
Sending all the data down to Earth would take a lot longer than the time it takes to collect it. The spacecraft computer would quickly overflow with un-sent data. And what if the spacecraft is watching a fast-moving hurricane in the Atlantic Ocean? It's important to rush the images down to the weather forecasters on Earth so they can warn ships in the area and people who live where the hurricane might hit land.
The Earth Observing 3 mission studies Earth's atmosphere to help scientists better understand weather. It also tested and now uses some new and better ways to compress—or shrink—the data before sending it down to Earth. Some ways to shrink data are . . .
Keep them all and make them small:
Just re-package the data. For example, 100 pennies weighs a lot more than a 1-dollar bill. But they are worth the same! Space engineers call this method "lossless compression," meaning no data get lost.
Squeeze them more and open the door:
Some data that are not very important or useful may escape. But the important data can then be squeezed into an even smaller package. Space engineers call this method "lossy compression," meaning some data get lost.
Save the best and scrap the rest:
Special data are selected for a special reason. For example, scientists might want to know how fast the clouds are moving at 5 miles above Earth's surface. These data are separated from the rest, and the rest are thrown out. Space engineers call this method "superchannel data compression," since only one kind (channel) of data are saved.
All this data shrinking is done with computer software and math.
Earth Observing 3 is one of the missions of NASA's New Millennium Program. The main job of these new technology missions is to make sure they work in space. This way, future science missions can make good use of them knowing they will work just fine.