In the late summer of 1977, NASA launched the twin Voyager spacecraft. These remote ambassadors still beam messages back to Earth 40 years later, with data from their deep space travels.

Transcript:

3, 2, 1. We have ignition, and we have lift off! We have lift off of the Titan Centaur carrying the first of two Voyager spacecraft to extend man's senses farther into the solar system than ever before.

The "dark room" is the "Center of the Universe." It's where we communicate with the deepest spacecraft we have out. We still communicate with the Voyagers, they send up signals every day. You can see Voyager Two is being tracked both by Antenna 35 and Antenna 36. Voyager has been a real mission of discovery. Every planet we flew by, we got more questions than answers.

I think none of us knew when we launched 40 years ago that anything would be working for such a wonderful long journey. We had hoped that we could reach interstellar space. We reached that with Voyager One, and we're about to reach it with Voyager Two.

Voyager One is the further of the two spacecraft, and it's currently at about 13 billion miles from us here on Earth. The transmitters on the Voyager spacecraft are slightly over 20 watts, about what your refrigerator light bulb would give off. So when the signal crosses that vast distance to us, the strength of the signal is one ten trillionth of a billionth of a watt, which is the equivalent of one divided by ten with 21 zeros after it.

A real opportunity on Voyager Two of course, is because we have a working solar wind instrument to measure the solar wind itself. It's currently measuring the solar wind inside the bubble. When it leaves the bubble, it will then enter interstellar space where there's an interstellar wind, which has come from other stars that blew up. And so we'll have a chance with that instrument to actually measure the wind for the first time directly. The wonderful thing about the journey is not just that it's 40 years long, but, in fact, it's still discovering new things because it's going where nothing has been before. They will continue until they finally run out of power, but they will orbit at the center of the Milky Way galaxy-- for billions of years, our silent ambassadors.

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