Pale Blue Dot

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Pale Blue Dot is a photo of the planet Earth taken on February 14, 1990, by the Voyager 1 space probe from a record distance of about <6 billion kilometers ( 3.7 billion miles, 40.5 AU), as part of a series of pictures of the Solar System Family Series today.

In the photo, the real size of the Earth is less than a pixel; the planet appears as a small spot against the vastness of space, between the sunlight bands reflected by the camera.

Voyager 1 , who has completed his main mission and abandoned the Solar System, was ordered by NASA to rotate the camera around and take one last photo of Earth across a vast space, at the request of astronomer and writer Carl Sagan.

Video Pale Blue Dot

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In September 1977, NASA launched Voyager 1, a 722 kilogram (1,592 lb) robotic spacecraft on a mission to study the outer Solar System and finally the interstellar space. After meeting with the Jovian system in 1979 and the Saturn system in 1980, the primary mission was declared completed in November of the same year. Voyager 1 is the first spacecraft to provide detailed images of the two largest planets and their major moons.

The spacecraft, still traveling 64,000 km/h (40,000 mph), is the farthest man-made object from Earth and the first to leave the Solar System. Its mission has been extended and continues to this day, with the aim of investigating the boundaries of the solar system, including Kuiper belt, heliosphere and interstellar space. Operating for 40 years, 8 months and 23 days to today (May 30, 2018), he receives regular orders and sends data back to the Deep Space Network.

Voyager 1 is expected to work only through Saturn meetings. When the spacecraft passed through the planet in 1980, Sagan proposed the idea of ​​a space investigation that took one last picture of Earth. He acknowledges that such an image will not have much scientific value, because Earth will seem too small for the Voyager camera to create detail, but it will become meaningful as a perspective on where we are in the universe.

Although many in the NASA Voyager program support the idea, there is concern that taking a picture of Earth so close to the Sun risks damaging the spacecraft's imaging system irreversible. It was not until 1989 that the idea of ​​Sagan was practiced, but then the instrument calibration delayed further operations, and the personnel designing and sending radio commands to Voyager 1 were also dismissed or transferred to other projects. Finally, NASA administrator Richard Truly intervened to ensure that the photo was taken.

Maps Pale Blue Dot

Camera

Voyager 1 ' The Imaging Science Subsystem (ISS) consists of two cameras: 200 mm focal length, low resolution wide angle camera (WA), used for spatially expanded imagery, and 1500 mm height-camera settings narrow angle (NA) - one that takes Pale Blue Dot - is intended for detailed imaging of a specific target. Both cameras are a slow-scan vidicon tube type and are equipped with eight colored filters, mounted on a filter wheel placed in front of the tube.

The challenge is that, when the mission runs, the object to be photographed will be farther and will appear dimmer, requiring longer exposure and slewing (panning) from the camera to achieve acceptable quality. Telecommunications capability also decreases with distance, limiting the number of data modes that the imaging system can use. A series of commands are compiled and sent to Voyager, with images executed on February 14, 1990.

After taking the series Family Portrait , including Pale Blue Dot , the NASA mission manager ordered Voyager 1 to turn off the camera, as the spacecraft will not fly in near anything else that matters for the rest of its mission, while other instruments that still collect data require power for long journeys to interstellar space.

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Photos

The draft sequence order to be forwarded to the spacecraft and calculations for each photo exposure time was developed by space scientist Candy Hansen of NASA's Jet Propulsion Laboratory (JPL) and Carolyn Porco of the University of Arizona. After a planned imaging sequence was taken on February 14, 1990, the data from the camera was initially stored on an on-board tape recorder. Transmissions to Earth were also delayed by the Magellan and Galileo missions given priority over the use of the Deep Space Network. Then, between March and May 1990, Voyager 1 returns 60 frames back to Earth, with radio signals running at the speed of light for nearly five and a half hours to cover the distance.

Three of the received frames show the Earth as a small dot of light in an empty space. Each frame has been taken using different color filters: blue, green and purple, with exposure time of 0.72, 0.48 and 0.72 seconds respectively. The three frames were then combined to produce the image that became Pale Blue Dot .

Of the 640,000 individual pixels that make up each frame, Earth requires less than one (0.12 pixels, according to NASA). The light ribbon in the photograph is an artifact, the result of the rays reflecting off the camera and blinds, because of the relative distance between the Sun and the Earth. Voyager point of view is about 32 Â ° above the ecliptic. Detailed analysis shows that the camera also detects the Moon, although it is too pale to look without special processing.

The pale blue color of the dots is the result of the polarization and spreading of reflected light from Earth. Polarization in turn depends on various factors such as cloud cover, exposed areas of the oceans, forests, deserts, snow fields etc.

Pale Blue Dot , taken with a narrow angle camera, was also published as part of a composite image made from a wide-angle camera photograph showing the Sun and the spaces containing Earth and Venus. Wide angle images inserted with two narrow angle images: Pale Blue Dot and similar Venus photos. The wide-angle photo is taken with a dark filter (methane absorption band) and the shortest possible exposure (5 milliseconds), to avoid saturating the camera vidikon tube with scattered sunlight. Even so, the result is a burned-out image with some reflection from the optics in the camera and the Sun that looks much larger than the actual dimensions of the solar disk. The rays around the Sun represent a diffraction pattern of calibration lamps mounted in front of a wide-angle lens.

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Distance

According to the HORIZONS tool from NASA's Jet Propulsion, the distance between Voyager 1 and Earth on February 14 and May 15, 1990, is as follows:

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Reflection

During a public lecture at Cornell University in 1994, Carl Sagan presented pictures to the audience and shared reflections on the deeper meaning behind the Pale Blue Dot idea:

We managed to take that picture [from outer space], and, if you see it, you see a dot. It's home. That's us. On it, everyone you've ever heard, every human who ever lived, lived their life. Aggregate all our joys and sufferings, thousands of religious believers, economic ideologies and doctrines, every hunter and explorer, every hero and coward, every creator and destroyer of civilization, every king and farmer, every young couple in love, every expectant child, every mother and father, every inventor and explorer, every moral teacher, every corrupt politician, every superstar, every supreme leader, every saint and sinner in the history of our species, dwells there with more than dust, hanging in the sun.

Earth is a very small stage in the vast cosmic arena. Think of the rivers of blood shed by all generals and emperors so that in their glory and triumph they can become the momentary rulers of a split point. Think of the endless cruelty visited by the inhabitants from a point of point to the inhabitants who are barely distinguishable from some other angle from that point. How often is their misunderstanding, how eager they are to kill each other, how strong their hatred is. Our embodiment, our imagined self-interest, the delusion that we have a privileged position in the universe, is challenged by this pale point of light. Our planet is a quiet spot in the cosmic dark that envelops. In our obscurity - in all this vastness - there is no indication that help will come from elsewhere to save us from ourselves. It's up to us. It is said that astronomy is degrading, and I might add, the experience of character building. In my mind, there may not be a better demonstration of the stupidity of human pride than the distant imagery of our small world. To me, this underscores our responsibility to deal better and more lovingly with each other and to preserve and appreciate the pale blue dot, the only house we have ever known.

Sagan also titled his 1994 book Pale Blue Dot: The Vision of the Future of Humans in Space after the photo.

By 2015, NASA recognizes the 25th anniversary of Pale Blue Dot .

Twenty-five years ago, Voyager 1 looked toward the Earth and saw a 'pale blue dot', "an image that continues to inspire wonders about the place we call home,

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See also

• Earthrise
• Family Portrait (MESSENGER)
• Marble Blue
• Earth Day Smile

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References

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Further reading

• Sagan, Carl; Head, Tom (2006). Conversation with Carl Sagan (1st ed.). United States: The University Press of Mississippi. ISBNÃ, 1-57806-736-7
• Sagan, Carl; Freeman J., Dyson; Jerome, Agel (2000). Cosmic Connection Carl Sagan: An Ecstratrical Perspective . Cambridge University Press. pp.Ã, XV, 302. ISBNÃ, 0-521-78303-8

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External links

• Audio recording from Carl Sagan's Reading of Pale Blue Dot , from the US Congress Library, Seth MacFarlane Collection of the Carl Sagan and Ann Druyan Archive
• Video produced for Pangea Day with Sagan reading from Pale Blue Dot
• Sagan reason for human space - Articles on Space Reviews

Source of the article : Wikipedia