In our American system, government agencies such as the National Institutes of Health (NIH), National Science Foundation (NSF), Department of Energy (DOE), and various Department of Defense (DoD)-related research offices [i.e., Army, Navy, Air Force, DARPA (Defense Advanced Research Project Agency)] are some of the major sources of support. These research agencies are basically independent of each other and are even in some friendly competition. In my view, this helps to keep American science vibrant, highly competitive, and active. In most other countries there is generally a single central research support agency.

George A. Olah, A Life of Magic Chemistry : Autobiographical Reflections of a Nobel Prize Winner, Wiley-Interscience, 2001, p.228.

DOD abbreviation
Department of Defense (the government department in the US that is responsible for defence) [OALD]

American scientists figured out that if they knew the satellite’s precise orbital position, they could accurately locate their exact position on Earth by listening to the pinging sounds and measuring the satellite’s radio signal Doppler shift. Satellites offered some possibilities for a navigation and positioning system, and the U.S. Department of Defense (DoD) explored the concept.

By the 1960s, several rudimentary satellite-positioning systems existed. The U.S. Army, Navy, and Air Force were all working on independent versions of radio navigation systems that could provide accurate positioning and all-weather, 24-hour coverage. In 1973, the Air Force was selected as the lead organization to consolidate all the military satellite navigation efforts into a single program. This evolved into the NAVSTAR (Navigation Satellite Timing and Ranging) Global Positioning System, which is the official name for the United States’ GPS program.

Joel McNamara, GPS For Dummies, Wiley, 2004, p.50.