(CNN) - NASA will pay tribute to those who lost their lives in the pursuit of space exploration.
January 28th is NASA's Day of Remembrance.
The entire agency is set to commemorate space missions that ended in tragedy.
They will honor the crews of Apollo One, Space Shuttle Columbia and the Space Shuttle Challenger.
Thursday also marks 35 years since the Challenger Explosion.
In 1986, the Space Shuttle broke apart, 73 seconds into flight. Seven crew members were killed, including Christa McAuliffe, who wold have been the first teacher in space.