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Saturn Disappears Behind the Sun.
Saturn is about to go behind the Sun. For a few days, NASA won't be able to communicate with Cassini since it's currently in orbit the planet. As Saturn neared the edge on July 24, radio distortion from the Sun made communications with Cassini impossible. NASA expects to reacquire a signal from Cassini on July 27. This situation gives scientists an opportunity to probe the Sun's corona, since communications will have to pass through it. This photograph was taken by SOHO, which is parked in a gravitationally stable spot between the Earth and Sun.
In this SOHO image taken July 21, 2005, the Sun is represented by the white circle in the center. Saturn is the bright object to the left of the Sun. Interestingly, the streak accompanying Saturn is not the rings but a distortion caused by Saturn's brightness.
Saturn is approaching "superior conjunction," that is, it will be almost directly behind the Sun from Earth - thus the Cassini spacecraft, in orbit around Saturn, will not be able to send or receive transmissions normally. Regular science data collection has been temporarily suspended.
As Cassini passes closest by the limb (edge) of the Sun on July 24 PDT, communications will be impossible because of the Sun's radio noise. The spacecraft will regain full communication with Earth on July 27, once again returning Saturn science data. In the meantime, controllers are sending approximately 100 commands per day to test communication status. Cassini radio scientists are taking advantage of this opportunity to study the Sun's corona from its effects on the radio signals that reach Earth.
SOHO (Solar and Heliospheric Observatory Satellite) orbits the Sun parked in one of the five gravitational-neutral spots, called Lagrange Points. This specific spot, called L1, stays in the same place relative to the Sun and the Earth, offering a continuously uninterrupted view of the Sun.
Saturn is not in sight again until the evening of July 24. After that date, it will be to the RIGHT of the sun.
For more information on "superior conjunction," visit: http://www.jpl.nasa.gov/basics/bsf1-2.html#conj.
For more information on the Lagrange Points, visit: http://map.gsfc.nasa.gov/m_mm/ob_techorbit1.html
For more information on SOHO, visit: http://sohowww.nascom.nasa.gov/.
Finally, the latest SOHO images are available at: http://sohowww.nascom.nasa.gov/data/realtime/c3/1024/latest.gif.
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