Tributes to first moonwalker Neil Armstrong play out on air and at sea See images from the career of astronaut and American hero Neil Armstrong. While the world watches over the Internet, luminaries from the world of space exploration and politics will mix with ordinary people at 10 a.m. ET Thursday to pay tribute to first moonwalker Neil Armstrong at Washington National Cathedral in the nation's capital. But the final farewell to his mortal remains will take place out of the spotlight, during a burial at sea on Friday. U.S. flags will be flying at half-staff on that day, in accordance with the presidential proclamation issued after Armstrong's death. Many of those same flags were lowered in Armstrong's honor on Aug. 31, when the family conducted a private memorial ceremony in Cincinnati. President Barack Obama specified, however, that the "mark of respect" should be given on the day of the astronaut's interment - and Friday is that day. Armstrong is thus coming in for a double helping of half-staff honors, plus Thursday's national memorial service. Armstrong passed away on Aug. 25, less than three weeks after celebrating his 82nd birthday and undergoing quadruple-bypass heart surgery. If people told him while he was alive that he would be in for three widely publicized tributes to his life and legacy, he might have asked them to turn the dial down a notch. After all, the man who took "one giant step for a man ... one giant leap for mankind" in 1969 was famously wary of fame. Even the family's announcement of his death called him "a reluctant American hero who always believed he was just doing his job." Thursday's memorial ceremony isn't just about one man, however: It's also a memorial for an age when mankind made its first moves beyond its home planet. Eleven other NASA astronauts walked on the moon after Armstrong took his one small step as part of the Apollo 11 mission, but that age ended 40 years ago when Apollo 17's Gene Cernan climbed up the ladder to the Challenger lunar module. "We leave as we came and, God willing, as we shall return: with peace and hope for all mankind," Cernan, who is due to speak at Thursday's service, said in 1972. No one has returned to the moon since. The evocation of NASA's golden age is one of the reasons why the space agency is airing the service on television and streaming it on the Internet. (The cathedral will be streaming the service as well, along with various media outlets. You can watch NBC News' video stream here.) In fact, NASA is providing live coverage on three channels, starting at 9:45 a.m. NASA TV's Public Channel will carry the service in HD with on-screen identification of the participants. The Media Channel will broadcast a "clean feed" in HD without on-screen legends. The Education Channel will carry the complete service in standard definition. All three streams are available via the NASA TV website. NASA says the agency's chief historian, Bill Barry, will conduct an online chat on UStream, supplementing the video coverage with background information about the speakers and their connection to Armstrong and the space effort. On the NASA website, you can see the full program for the service (PDF file), including hymns and readings. One of Armstrong's Apollo 11 crewmates, Michael Collins, will lead prayers. In addition to Cernan, NASA Administrator Charles Bolden and former Treasury Secretary John Snow are due to deliver tributes. The Rt. Rev. Mariann Edgar Budde, bishop of the Episcopal diocese of Washington, will give the homily. Jazz singer-songwriter Diana Krall will sing Frank Sinatra's arrangement of "Fly Me to the Moon." Other musicians include the U.S. Navy Band "Sea Chanters," the Cathedral Choir and the Metropolitan Opera Brass. NASA said the guest list for the service includes Apollo 11's Buzz Aldrin, who joined Armstrong on that first moonwalk; Mercury astronauts John Glenn and Scott Carpenter; and Apollo 7's Walt Cunningham, along with other astronauts from the Apollo era and space shuttle era. NASA's deputy administrator, Lori Garver, and other agency officials will be there. Lawmakers on the list include U.S. Sens. Bill Nelson (D-Fla.) and Rob Portman (R-Ohio); House Speaker John Boehner and Minority Leader Nancy Pelosi; and U.S. Rep. Ralph Hall, chairman of the House Science, Space and Technology Committee. White House Chief of Staff Jack Lew and other Obama administration officials are due to attend, space agency representatives said. In addition to the tickets set aside for VIPs, family members, friends and journalists, NASA made tickets to the ceremony available to members of the general public. Those tickets were quickly swept up, and the cathedral says "all passes have now been allocated." Washington National Cathedral Washington National Cathedral's Space Window incorporates a moon rock from Apollo 11 at the center of the red circle in the stained glass. The cathedral was chosen for the public service because it's "a historic landmark symbolizing the role of faith in America, and its iconography tells the stories that have shaped the nation's identity," NASA said. Armstrong, Aldrin and Collins presented the cathedral with a moon rock from the Apollo 11 mission on July 21, 1974, during a service commemorating the fifth anniversary of the first moon landing. That rock was later incorporated into the cathedral's Space Window - which is in the spotlight due to Thursday's service. After the service, there's one more ceremony to perform: Armstrong's burial at sea, which was organized in accordance with his wishes. In addition to being the first man to walk on the moon, Armstrong was a U.S. Navy aviator who served with distinction during combat in the Korean War - and had the right to choose a sea burial over, say, a grave at Arlington National Cemetery. When Armstrong died, Navy Secretary Ray Mabus issued a statement noting that Armstrong "never wanted to be a living memorial, and yet to generations the world over his epic courage and quiet humility stands as the best of all examples." NASA spokesman Michael Cabbage confirmed that the at-sea ceremony would take place Friday, on the same day as the half-staff tribute. The arrangements mean that Armstrong's remains will never lie under an earthly shrine - which may be the most fitting end for a man whose voyages ranged from the sea, to the air, to "this new ocean" of outer space. More about Neil Armstrong: