GPS (Global Positioning System) navigational devices are as ubiquitous as cell phones, freely used by commercial and government users to determine location, time, and velocity. These tools, however, are only as good as the signals they receive. NASA engineers from Goddard Space Flight Center in Greenbelt, MD, have found a way to improve the reception of those signals.
Spacecraft operating in weak-signal areas — such as geosynchronous orbits where communications and weather satellites typically operate — will be able to acquire and track the weak GPS signals to determine their locations, much like motorists who use GPS to determine where they are. Onboard GPS navigation for spaceflight operations has been challenging, particularly for spacecraft operating above the GPS constellation, which is about 12,727 miles above Earth in an area normally referred to as high-Earth orbit. That is because existing GPS receivers could not adequately pick up the GPS signal, which is transmitted toward Earth, not away from it.
The Navigator team developed algorithms and hardware for a prototype spacecraft GPS receiver that would allow spacecraft to acquire and track weak GPS signals at an altitude of 62,137 miles, well above the GPS constellation and roughly one-quarter of the distance to the Moon.
For more information, visit www.nasa.gov/topics/technology/features/navigator-gps.html.