On Tuesday, July 21st, astronauts Chris Cassidy and Bob Behnken will finish a 3.5-year-long effort to upgrade to the International Space Station's power system, marking the 300th spacewalk completed by U.S. astronauts.
On Tuesday, July 21st, astronauts Chris Cassidy and Bob Behnken will finish a 3.5-year-long effort to upgrade to the International Space Station's power system, marking the 300th spacewalk completed by U.S. astronauts.
Fifteen years ago, human hands touched NASA's Hubble Space Telescope for the last time.
As astronauts performed..