The Discovery Channel and NASA have restored 50 years of history for the U.S. space agency's archives.  Discovery has used the material to produce a documentary series called, When We Left Earth: The NASA Missions.  It will be broadcast internationally next month. This week in Washington, former senator and astronaut John Glenn joined members of the U.S. Congress, officials from NASA and others for a sneak preview.  VOA's  Paul Sisco reports.