Discovery will air Sunday at 9 p.m., Eastern and Pacific times, the first episode in a series of 6 about the 50 years of space exploration since the National Aeronautics and Space Administration was created.

The six episodes will guide you through the most important events in these 50 years, presenting both the astronauts that took part in the missions as well as the people behind the events, the guys at the mission control.

The documentary, which is called ‘When we left Earth,’ will present some of the footage that NASA has not made public yet. This behind the scenes footage has been specially restored for this documentary, which will be aired in high definition format.

Besides archive footage, some of the legendary figures at NASA, like Buzz Aldrin, Neil Armstrong or Gene Kranz, the mission control chief for Apollo 11, which landed the first man on the moon, will tell the stories that have kept millions all over the world tuned to their TV sets as they saw them back then.

‘When we left Earth’ will present events that are more recent too. The effort that was made to build the International Space Station and to launch the Hubble telescope will be mentioned, and there will be shown just how important astronauts are for space explorations even now, when robots seem to provide both a safer and a cheaper way of doing the same things.

It seems that now is a good time for the young generation to find out about the sacrifices behind the space exploration. With the space shuttle fleet retiring in 2010 and without any NASA flight scheduled until at least 2015, such documentaries are necessary in order to make people understand just how important space exploration actually is.