Friday, September 14, 2012

Voyager - The Last Photo

Most people like family photos, and the more participants the merrier. But there is one family that it is particularly hard to photograph together, mainly because the distances between the brothers and sisters of this family can be above 5 billion KM and they will never get any closer. An experienced photographer will distance himself as far as possible and try to get just the right angle to include as many members of the family as possible. The family we are discussing is the solar system with the Sun and the planets. When Voyager finished the grand tour, it was in a great position to catch most of the family members in one photo. The spaceships' cameras were not needed anymore, both spaceships were not expected to observe additional celestial objects, and the decision was to take one last photo before shutting the cameras down forever. You remember that there were two Voyager spaceships, and to take that special photo, Voyager 1 was chosen, simply because it had a better viewing point. Voyager 1 left the ecliptic plane and was high above it, providing a better photography angle than Voyager 2 who was still near the ecliptic.
There were some other obstacles. The sun (the old grandmother of the family) is extremely bright. The planets (brothers and sisters) are dim and far apart from each other, and the moons (grandchildren) are just too small and dim, so the family portrait  is not really a single picture but a mosaic of about 60 photos combined together, taken with different exposure times and filter. The last of the Voyager mosaic is shown below, taken on February 14th 1990.
Voyager I portrait of the solar system.
Voyager I portrait of the solar system. Credit: NASA
OK, I am sure you did not exactly expect this as a family portrait but it is the best possible composition. The grey squares are the individual pictures, as mentioned, more than 60 frames were needed to get all members of the family, but as often happens, someone is still missing. The letters designate the planets (J - Jupiter , E - Earth, V - Venus , S - Saturn, U - Uranus, N - Neptune) and the bright dot is the sun.  Mercury and Mars are missing from the portrait. Mercury was too close to the sun, and Mars could not be found. Pluto which in 1990 was closer to the sun than Neptune and still a distinguished member of the solar system (until it was kicked out to be a dwarf planet) was too dim and was not included in this picture, maybe as a prophecy to its destiny 15 years later.
The picture is in a very high resolution so please click on it to enlarge it. You will see excerpts presenting the planets themselves. It is possible to see some details on Jupiter and a hint of Saturn's rings. Uranus and Neptune seem larger but this is because the long exposure time of 15 seconds which gave them a little smudge. The sunlight is visible in many pictures, and the camera hardly managed to capture planet Earth. The size of our little planet is less than one pixel and the photograph that shows it got its iconic name by no other than Carl Sagan: "The pale blue dot"

Pale Blue Dot
The pale blue dot. Credit: NASA

After these photos, the Voyagers' cameras were shut down forever. Cameras need power, and power is a rare resource in a little spaceship, but these photos are part of the heritage that Voyager left us.

Previous Articles in the Voyager's series:
Voyager - The Grand Tour

2 comments:

  1. It's too bad the Voyager's cameras were shut down. For years, it has been the source of photos of the universe and it has produced a lot of stunning and interesting pictures.

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  2. There is no need for cameras anymore. Where Voyager are, there is nothing to photograph. The energy is needed for more important things, and to keep these spaceship alive as long as possible.

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