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Atlas launches Superbird
The Lockheed Martin Atlas 2AS rocket launches the Japanese Superbird 6 communications spacecraft from Cape Canaveral, Florida. (3min 09sec file)
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Lion King panorama
The stunning "Lion King" high-resolution color panorama from the Opportunity rover shows the vast landing site. Expert narration by Jason Soderblom, science team collaborator. (2min 12sec file)
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Changing NASA's culture
Administrator Sean O'Keefe holds a discussion with agency workers around the country about organizational culture change at NASA. (56min 12sec file)
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Yuri Gagarin
Historical footage documents the flight of cosmonaut Yuri Gagarin, the first human in space. (2min 25sec file)
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Cosmonautics Day
Expedition 8 crewmembers Michael Foale and Alexander Kaleri celebrate Cosmonautics Day aboard the International Space Station. (3min 07sec file)
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Mars rover briefing
Officials discuss the extended missions for the Mars rovers and present the latest pictures at this briefing from Thursday, April 8. (34min 10sec file)
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Gravity Probe-B preview
Scientists and mission officials preview the Gravity Probe-B project in this pre-flight news briefing from Friday, April 2. (62min 25sec file)
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NEW! X-43A in infrared
This newly-released infrared video, captured by a U.S. Army aircraft tracking the launch, shows the X-43A research vehicle flying away from its Pegasus rocket booster.
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NEW! Aboard Pegasus
A camera mounted on the Pegasus rocket booster shows the X-43A research vehicle separating to perform its scramjet experiment over the Pacific Ocean.
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This date in history
On April 5, 1991, space shuttle Atlantis lifted off from Kennedy Space Center carrying the Compton Gamma Ray Observatory -- NASA's second Great Observatory. (3min 15sec file)
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Cassini spots Saturn moons
NASA/JPL NEWS RELEASE
Posted: April 17, 2004


Photo: NASA/JPL/Space Science Institute
 
Cassini has sighted Prometheus and Pandora, the two F-ring-shepherding moons whose unpredictable orbits both fascinate scientists and wreak havoc on the F ring.

Prometheus (102 kilometers, or 63 miles across) is visible left of center in the image, inside the F ring. Pandora (84 kilometers, or 52 miles across) appears above center, outside the ring. The dark shadow cast by the planet stretches more than halfway across the A ring, the outermost main ring. The mottled pattern appearing in the dark regions of the image is 'noise' in the signal recorded by the camera system, which has subsequently been magnified by the image processing.

The F ring is a narrow, ribbon-like structure, with a width seen in this geometry equivalent to a few kilometers. The two small, irregularly shaped moons exert a gravitational influence on particles that make up the F ring, confining it and possibly leading to the formation of clumps, strands and other structures observed there. Pandora prevents the F ring from spreading outward and Prometheus prevents it from spreading inward. However, their interaction with the ring is complex and not fully understood. The shepherds are also known to be responsible for many of the observed structures in Saturn's A ring.

The moons, which were discovered in images returned by the Voyager 1 spacecraft in 1980, are in chaotic orbits--their orbits can change unpredictably when the moons get very close to each other. This strange behavior was first noticed in ground-based and Hubble Space Telescope observations in 1995, when the rings were seen nearly edge-on from Earth and the usual glare of the rings was reduced, making the satellites more readily visible than usual. The positions of both satellites at that time were different than expected based on Voyager data.

One of the goals for the Cassini-Huygens mission is to derive more precise orbits for Prometheus and Pandora. Seeing how their orbits change over the duration of the mission will help to determine their masses, which in turn will help constrain models of their interiors and provide a more complete understanding of their effect on the rings.

This narrow angle camera image was snapped through the broadband green spectral filter, centered at 568 nanometers, on March 10, 2004, when the spacecraft was 55.5 million kilometers (34.5 million miles) from the planet. Image scale is approximately 333 kilometers (207 miles) per pixel. Contrast has been greatly enhanced, and the image has been magnified to aid visibility of the moons as well as structure in the rings.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Office of Space Science, Washington, D.C. The imaging team is based at the Space Science Institute, Boulder, Colo.

Ares 1-X Patch
The official embroidered patch for the Ares 1-X rocket test flight, is available for purchase.
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Apollo Collage
This beautiful one piece set features the Apollo program emblem surrounded by the individual mission logos.
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Expedition 21
The official embroidered patch for the International Space Station Expedition 21 crew is now available from our stores.
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Hubble Patch
The official embroidered patch for mission STS-125, the space shuttle's last planned service call to the Hubble Space Telescope, is available for purchase.
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