NASA astronaut and University of Tennessee Space Institute graduate Scott Kelly is officially retiring from the space program on Friday.
Kelly joined NASA in 1996 and currently holds the American record for most time spent in space.
He holds the NASA record for 340 consecutive days in space. Counting his last three trips to space, Kelly has spent a total of 520 days in orbit.
Upon retirement, Kelly will continue to participate in the ongoing research related to his nearly one year long mission in space.
Kelly flew in space four times beginning with a mission to the Hubble Space Telescope aboard the shuttle Discovery in 1999.
On his second mission, he crossed the threshold of the International Space Station as commander of the space shuttle Endeavour.
He then returned to space in 2010 for a six-month stay aboard the International Space Station.
