National Geophysical Data Center
http://www.ngdc.noaa.gov/mgg/mggd.html
THE LINKS AND PAGES HAVE CHANGED. IT IS NO LONGER EASILY POSSIBLE TO ANSWER QUESTIONS OF PART 1.
GO DIRECTLY TO PART 2 AND CONTINUE.
NASA's Laboratory For Terrestrial Physics
http://ltpwww.gsfc.nasa.gov/
No Change