In 1998, the United States Naval Academy dropped celestial navigation from its curriculum. If a naval officer wished to know where he or she was, the officer simply had to read the display on a GPS (Global Positioning System) receiver.  Sextants, chronometers, and nautical almanacs became artifacts of another, less technological time.  Now, a decade and a  the Navy has had second thoughts. Recent concerns about potential cyber-attacks on global positioning satellite software and data, which could disable or spoof GPS navigation systems world-wide, has led the Navy to return to teaching  celestial navigation to midshipmen at the Naval Academy. Time to brush off the sextants.

Navigation with GPS can fix a position to within a few feet, (which of course, hasn’t stopped groundings.) The US established the space-based navigation system in 1973, which provides location and time information in all weather conditions, anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites.  There are now 31 GPS satellites in service.  There are now serious concerns that the GPS network might be an easy target for hackers. GPS signals have never been encrypted so they might be intercepted and spoofed. Likewise, a cyber-attack on GPS control stations might bring the entire down.

Celestial navigation, on the other hand, is accurate to only about a mile or two. Nevertheless, it is dependent only on a view of the sky, a chronometer, and a sextant to measure the angle between a celestial body and the horizon. No one has figured out how to hack the sun or the stars.