NASA will pause today (Jan. 30) to reflect on the lives lost in the pursuit of space exploration during the agency's annual "Day of Remembrance," a time when the agency recalls three of its darkest moments.

The last week of January is always a somber time for NASA. In the space of six days, the agency recalls three fatal space tragedies: the Apollo 1 fire of Jan. 27, 1967, the Challenger shuttle disaster of Jan. 28, 1986 and the Columbia shuttle accident of Feb. 1, 2003.

"NASA Administrator Jim Bridenstine, along with other senior agency officials, will lead an observance at Arlington National Cemetery in Virginia beginning at 1 p.m. EST," NASA officials said in a statement. "A wreath-laying ceremony will take place at the Tomb of the Unknown Soldier, followed by observances for the Apollo 1, Challenger and Columbia crews."

Related: NASA's fallen astronauts: A photo memorial

The Apollo 1 fire killed astronauts Gus Grissom, Roger Chaffee and Ed White II during a test on the launchpad.The astronauts were performing a dress rehearsal for the first launch of the Apollo program aimed at sending astronauts to the moon.

Seven astronauts died in the Challenger shuttle disaster when the orbiter broke apart after an explosion. The crew included commander Francis "Dick" Scobee, pilot Mike Smith, mission specialists Judy Resnik, Ellison Onizuka and Ron McNair, and payload specialists Greg Jarvis and Christa McAuliffe, who was set to be the first teacher in space.

The Columbia orbiter broke apart during reentry due to wing damage sustained two weeks earlier during launch. Killed in that tragedy were commander Rick Husband, commander, pilot William McCool, payload commander Michael Anderson, mission specialists David Brown, Kalpana Chawla and Laurel Clark, and Ilan Ramon, a payload specialist from the Israeli Space Agency.

Today, NASA will honor the sacrifice of those astronauts and pay tribute to all NASA astronauts and employees who lost their lives in the line of duty.

Here is a list of Day of Remembrance ceremonies across the country from NASA's official announcement.

"NASA's Kennedy Space Center, in partnership with The Astronauts Memorial Foundation and Kennedy Space Center Visitor Complex, will host Day of Remembrance observance activities, including a wreath-laying ceremony at 10 a.m. at the Astronauts Memorial Foundation Space Mirror Memorial in the Kennedy Space Center Visitor Complex. Thad Altman, president and chief executive officer of the Astronauts Memorial Foundation, and Kelvin Manning, Kennedy associate director, technical, will speak at the ceremony. This ceremony is open to the public."

"NASA's Johnson Space Center will hold a commemoration for employees at the Astronaut Memorial Grove to honor Apollo 1, Challenger and Columbia crews."

"NASA's Stennis Space Center will host a Day of Remembrance ceremony memorializing crew members of the Apollo 1, Challenger and Columbia missions, as well as members of the Stennis Space Center family lost in the past year. It will feature the laying of a ceremonial wreath in memory of those who have sacrificed in support of the nations space program.

"NASA's Marshall Space Flight Center will observe Day of Remembrance with a candle-lighting ceremony for employees at 9 a.m. CST. Marshall Associate Director Steve Miley and former astronaut Jan Davis will offer remarks."

Email Tariq Malik attmalik@space.comor follow him@tariqjmalik. Follow us@Spacedotcom, Facebook and Instagram.

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NASA honors astronauts lost in 3 space tragedies with Day of Remembrance - Space.com