Jan. 23, marks a day of remembrance for NASA and the Astronauts Memorial Foundation. The solemn ceremony pays tribute to the lives lost in three of the most tragic moments in NASA's history.

We've come years in our journey to explore the unknown, but none of that would be possible without those who made the ultimate sacrifice towards the exploration.

NASA's Day of Remembrance honored the brave astronauts, test pilots, and crew members of Apollo 1, Challenger, and Columbia who gave their lives exploring the unknown. This tribute serves as a heartfelt reminder of their sacrifice and the critical need for safety in space exploration.

NASA’s Day of Remembrance remembers all fallen space heroes but specifically the crews of Apollo 1 and the space shuttles Challenger and Columbia. After each fatality, NASA said it has made spacecrafts safer with design and engineering changes. The Marshall Space Flight Center in Huntsville held a special candle-lighting ceremony earlier Thursday.

An annual memorial was held at the Kennedy Space Center Visitor Complex. Every fourth Thursday in January, NASA remembers fallen astronauts.

It was a cloudy Saturday morning on the Space Coast when 12-year-old Tal Ramon anxiously waited with his family for the return of his father Ilan on Space Shuttle Columbia in 2003. Ilan and his six crewmates flying on STS-107 never made it home.

The space agency will honor all its fallen members from the crews of Apollo 1 and space shuttles Challenger and Columbia.

It honors astronauts who died pursuing space exploration and discovery – specifically the crews of Apollo One and the space shuttles Challenger and Columbia.

NASA observed its annual Day of Rembrance today honoring those who lost their lives in the pursuit of space exploration.