Navigation is key to all of NASA's missions. Without accurate location data, satellites would be lost in space. Near Earth, spacecraft can rely on signals from global navigation satellite systems (GNSS) that they receive. GNSS refers to the six constellations of navigation satellites (including GPS) operated by the US and other nations. Together, these constellations provide near-Earth satellites with all the timing information they need to navigate space, just as they do to navigate here on the ground.
The area of space that can use GNSS signals starts at the Earth’s surface and extends up through what is called the Space Service Volume. Geosynchronous orbit, some 22,000 miles from Earth, is considered the formal outer limit of this region – but that hasn’t stopped NASA engineers from reaching higher.
In fact, NASA simulations show GNSS signals could even be used for reliable navigation in lunar orbit, far outside the Space Service Volume, over 200,000 miles from Earth. Engineers are considering using GNSS signals in the navigation architecture for the Gateway, an outpost in orbit around the Moon that will enable sustained lunar surface exploration.
This geocache is hidden on the grounds of Goddard Space Flight Center's Visitor Center. To open the cache, answer the question on the outside and enter it into the lock. Inside, you'll find a cryptex and another riddle to be solved.
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**Please note that while this cache technically accessible 24/7, it is requested that geocachers search for this cache during regular operating hours of the Goddard Visitor Center so that they may take full advantage of the facility's offerings.
September through June
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Saturday, Sunday: noon - 4 p.m.
July through August
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