NASA's hardy Voyager 1 probe, 3.7 billion miles from Earth, aimed its aging cameras back toward home Tuesday for a historic, once-in-a-lifetime family portrait showing seven of the solar system's nine planets in an unprecedented mosaic.
'This is not just the first time, but perhaps the only time for decades that we'll be able to take a picture of the planets from outside the solar system,' said Voyager project scientist Edward Stone of the California Institute of Technology.
With Earth showing up as little more than a bright speck against the star-dusted backdrop of an unimaginably vast cosmos, the 'picture of the century' will be more important symbolically than scientifically.
'It's almost gotten to be trite, the old stuff about 'planet Earth,' and 'spaceship Earth,'' said imaging scientist Candy Hansen at the Jet Propulsion Laboratory in Pasadena, Calif.
'But to have something that graphically demonstrates this little teeny, tiny, fragile body out there amongst its neighbors, I think is going to be a powerful statement.'
Twelve years outbound from Earth, Voyager 1's two 1970s-era television cameras were scheduled to take a series of 64 photographs of the home solar system over a four-hour period beginning at 8:12 p.m. EST.
The images, recorded on magnetic tape aboard the spacecraft, will be radioed back to Earth in late March when scientists at JPL will begin assembling the unprecedented mosaic. At Voyager 1's vast distance, it will take the radio signals, traveling at 186,000 miles per second, 5 hours to reach Earth.
The first pictures will be released to the public in late April. Only mighty Jupiter will show a clearly discernible disk, with Earth showing up only as a brilliant star-like point of light.
'It was a little hard to formulate what we wanted to do,' Hansen said. 'People had different ideas of what they wanted this observation to be. Some wanted to show where has Voyager has been. The portrait of the solar system said get everything. We went for the get everything.'
Launched at 8:46 a.m. EDT on Sept. 5, 1977, the nuclear-powered Voyager 1 sailed past Jupiter in March 1979, using the giant planet's gravity for a slingshot-like boost on to ringed Saturn in November 1980.
Unlike Voyager 2, which utilized repeated 'gravity assist' flybys to visit Jupiter, Saturn, Uranus and Neptune, Voyager 1 used Saturn's gravity to fling it up out of the plane of the solar system for an encounter with the moon Titan.
Since then, Voyager 1 has been cruising toward the edge of the solar system on an endless space odyssey. It currently is some 3.7 billion miles from Earth and 2 billion miles above the plane of the solar system.
The family portrait was designed to begin with three narrow-angle shots of Neptune, the giant blue planet visited by Voyager 2 last August. Then its wide-angle camera was to take a series of overlapping pictures covering the space between Neptune and Uranus.
Three narrow-angle views of Uranus then were planned before the cameras tracked inward to Saturn for more narrow angle views.
After that, the cameras were to take a series of shots toward the inner solar system, ultimately photographing the sun, Venus, Earth and, it is hoped, Mars -- a difficult shot from Voyager 1's position -- before closing out with Jupiter.
'First of all, you have to imagine that this thing is enormous in scale,' Hansen said, adding that a mosaic of the wide-angle shots alone would spread over three large tables.
'If you made the narrow angles that size, you have to expand that by a factor of seven,' she said. 'So we're talking about a wall mural!'
To produce a more reasonably-sized picture, JPL engineers will combine narrow-angle views of the inner planets with wide-angle shots to produce a mosaic of the inner solar system.
'We thought what we'd try ... is to take the wide-angle (shots) that will have the sun and enlarge that and embed the two narrow angles that have the Earth and Venus,' Hansen said. 'So now you're talking about an 11-by-14 or something like that that has the sun, the Earth and Venus.'
'That gives you your context, it gives you a feeling of scale. Earth and Venus will still be just two little dots, but the sun will be fairly substantial in size by the time we scale everything. If the Mars picture works, we'll mosaic Mars in as well.'
Hansen said the imaging team also is considering a poster-sized shot that would include Jupiter and Saturn and ultimately, the entire solar system mosaic may be released on slides for use by planetariums.
