Ready to fly through the ionosphere? W. Kent Tobiska, president of Space Environment Technologies, offers these simple instructions:

"One, download and install Google Earth."

"Two, visit our web site and click on the link 'Total Electron Content.'"

Wait for the file to load and presto—you're flying through the ionosphere. A typical screenshot looks like this:

In addition to total electron content, the 4D model also can be configured to display available radio frequencies, maximum usable frequencies, and the critical "bounce frequency" of the ionosphere's f2-layer—terms well known to hams and other experts. The corresponding files are all available at the CAPS web site.