Can a weather satellite read your license plate?

A question that I am often asked is: what are the finest details observable from weather satellites?

Let me show you some examples. Most of the weather satellite imagery you see on TV and the web is from the geostationary weather satellites, located over the equator at an altitude of 36,000 km. In that orbit they remain over the same portion of the earth as the earth rotates during the day. There are five of these satellites, two owned by the U.S.

The highest resolution imagery from those satellites are in the visible part of the spectrum (roughly .4 to .7 microns...millions of a meter), the wavelength your eyes are most sensitive. The pixel size over the equator is roughly 1 km and that resolution degrades a bit as the satellite observes to the north and south. Here is an example of a high-resolution visible image from one of these satellites (GOES-W, position at 135W) on March 23rd at 1 PM PDT.

And to illustrate what it can see better, let me show you a blow up over Puget Sound.

If you look carefully, Lake Washington and Lake Samamish are visible, as are the major river valleys in the Cascades. No worries about license-plate reading!

But there is another class of satellite, called polar orbiters, that is positioned much closer to the surface (only about 800 km above) in orbits that allow them to see constantly changing swaths (often about 1000-2000 km wide) of the earth below. I often show imagery from the MODIS polar orbiting satellites on this blog and they have pixel size of 250 meters. Let me show you a sample of this for nearly the same time as the geostationary satellite image shown above, again for visible wavelengths.

You see the difference? Much sharper. And you can see the individual puffy cumulus clouds that were forming over land that day (as the land heated up the atmosphere destabilized, producing convection). Look how well defined Seattle's harbor....Elliot Bay.. is! You can even see the sand spit at Sequim. One can learn a lot from such images.

Now there are other, non-meteorological, satellites that have much finer resolution. For example, LANDSAT imagery has resolution of 15-30 meters. Here is a sample:

And I assume that the CIA has satellite imagery capable of doing much better....

Want to look at the weather satellite imagery yourself? A few good websites:

National Weather Service Western U.S. Products: http://www.wrh.noaa.gov/satellite/?wfo=sew

NWS Aviation Weather Center Server: http://aviationweather.gov/adds/satellite/

NCAR RAP Satellite Server: http://weather.rap.ucar.edu/satellite/