Explore Worlds
Find Life
Defend Earth
Greg Holt
Orion Multi-Purpose Crew Vehicle Navigation Lead, NASA Johnson Space Center
Latest Planetary Radio Appearances
Something Old and Something New: Exciting Research on the International Space Station
Sextants have helped sailors find their way across oceans for centuries. Now one is onboard the International Space Station so that astronauts can learn to find their way across the solar system even if other technologies fail.