Pioneer rocket scientist Robert H. Goddard once said, 'It is difficult to say what is impossible, for the dream of yesterday is the hope of today and the reality of tomorrow.' Fifty years after its inception, NASA's Goddard Space Flight Center continues to live by these words, advancing science and engineering to new limits once thought impossible as it explores of the Earth, the sun, the solar system, and the universe.
GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 188.8.131.52.0