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STS-51B: Monkeys, bubbles and auroras
The flight of Spacelab 3 aboard Challenger in April/May 1985 was a week-long scientific research mission using a laboratory tucked in the shuttle's payload bay. Experiments focused on material and fluid behaviors in weightlessness, plus observations of monkeys in the lab. The crew also watched amazing auroral displays over Earth. This post-flight crew film shows the highlights of STS-51B and includes remarkable views out the shuttle cockpit window during launch showing the Chesapeake Bay, New York City and Cape Cod as Challenger soared up the eastern seaboard.

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STS-51D: Flyswatter spacewalk
Discovery launched April 12, 1985 on the STS-51D mission. A U.S. military communications satellite, known as Leasat 3, failed to activate after its deployment from the payload bay. That set the stage for a spacewalk -- the shuttle program's first unplanned EVA -- to attach handcrafted "Flyswatter" objects on the shuttle robotic arm to hit a timing switch on the satellite. The rescue attempt did not succeed. Upon landing at Kennedy Space Center, Discovery blew a tire. The crew, including Senator Jake Garn of Utah, narrate this post-flight film of highlights from the week-long mission.

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Fuel tank update
NASA managers hold this news conference April 28 to give an update on plans for the next space shuttle mission, the ongoing external fuel tank testing and debates over further modifications.

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CALIPSO and CloudSat
The Boeing Delta 2 rocket carrying the CALIPSO and CloudSat atmospheric research spacecraft lifts off at 3:02 a.m. local time April 28 from Vandenberg Air Force Base, California.

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Tank meets SRBs
Inside the Vehicle Assembly Building, the external fuel tank for the STS-121 space shuttle mission is hoisted into position for attachment with the twin solid rocket boosters atop a mobile launch platform. The tank, ET-119, will carry the liquid oxygen and liquid hydrogen to feed Discovery's three main engines during launch.

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Discovery payload bay
In preparation for space shuttle Discovery's departure from its Orbiter Processing Facility hangar for rollover to the Vehicle Assembly Building and mating with the tank and boosters, the ship's 60-foot long payload bay doors are swung shut.

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Progress docking
Take a virtual ride aboard the Russian Progress 21P cargo freighter as it docks with the International Space Station. This movie captures the final approach and successful linkup from a camera on the Progress craft's nose.

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"Seas" of Titan are sand
UNIVERSITY OF ARIZONA NEWS RELEASE
Posted: May 5, 2006

Until a couple of years ago, scientists thought the dark equatorial regions of Titan might be liquid oceans.

New radar evidence shows they are seas -- but seas of sand dunes like those in the Arabian or Namibian Deserts, a University of Arizona member of the Cassini radar team and colleagues report in Science (May 5).

Radar images taken when the Cassini spacecraft flew by Titan last October show dunes 330 feet (100 meters) high that run parallel to each other for hundreds of miles at Titan's equator. One dune field runs more than 930 miles (1500 km) long, said Ralph Lorenz of UA's Lunar and Planetary Laboratory.

"It's bizarre," Lorenz said. "These images from a moon of Saturn look just like radar images of Namibia or Arabia. Titan's atmosphere is thicker than Earth's, its gravity is lower, its sand is certainly different -- everything is different except for the physical process that forms the dunes and resulting landscape."

Ten years ago, scientists believed that Saturn's moon Titan is too far from the sun to have solar-driven surface winds powerful enough to sculpt sand dunes. They also theorized that the dark regions at Titan's equator might be liquid ethane oceans that would trap sand.

But researchers have since learned that Saturn's powerful gravity creates significant tides in Titan's atmosphere. Saturn's tidal effect on Titan is roughly 400 times greater than our moon's tidal pull on Earth.

As first seen in circulation models a couple of years ago, Lorenz said, "Tides apparently dominate the near-surface winds because they're so strong throughout the atmosphere, top to bottom. Solar-driven winds are strong only high up."

The dunes seen by Cassini radar are a particular linear or longitudinal type that is characteristic of dunes formed by winds blowing from different directions. The tides cause wind to change direction as they drive winds toward the equator, Lorenz said.

And when the tidal wind combines with Titan's west-to-east zonal wind, as the radar images show, it creates dunes aligned nearly west-east except near mountains that influence local wind direction.

"When we saw these dunes in radar it started to make sense," he said. "If you look at the dunes, you see tidal winds might be blowing sand around the moon several times and working it into dunes at the equator. It's possible that tidal winds are carrying dark sediments from higher latitudes to the equator, forming Titan's dark belt."

The researchers' model of Titan suggests tides can create surface winds that reach about one mile per hour (a half-meter per second). "Even though this is a very gentle wind, this is enough to blow grains along the ground in Titan's thick atmosphere and low gravity," Lorenz said. Titan's sand is a little coarser but less dense than typical sand on Earth or Mars. "These grains might resemble coffee grounds."

The variable tidal wind combines with Titan's west-to-east zonal wind to create surface winds that average about one mile per hour (a half meter per second). Average wind speed is a bit deceptive, because sand dunes wouldn't form on Earth or Mars at their average wind speeds.

Whether the grains are made of organic solids, water ice, or a mixture of both is a mystery. Cassini's Visual and Infrared Mapping Spectrometer, led by UA's Robert Brown, may get results on sand dune composition.

How the sand formed is another peculiar story.

Sand may have formed when liquid methane rain eroded particles from ice bedrock. Researchers previously thought that it doesn't rain enough on Titan to erode much bedrock, but they thought in terms of average rainfall.

Observations and models of Titan show that clouds and rain are rare. That means that individual storms could be large and still yield a low average rainfall, Lorenz explained.

When the UA-led Descent Imager/Spectral Radiometer (DISR) team produced images taken during the Huygens probe landing on Titan in January 2005, the world saw gullies, streambeds and canyons in the landscape. These same features on Titan have been seen with radar.

These features show that when it does rain on Titan, it rains in very energetic events, just as it does in the Arizona desert, Lorenz said.

Energetic rain that triggers flash floods may be a mechanism for making sand, he added.

Alternatively, the sand may come from organic solids produced by photochemical reactions in Titan's atmosphere.

"It's exciting that the radar, which is mainly to study the surface of Titan, is telling us so much about how winds on Titan work," Lorenz said. "This will be important information for when we return to Titan in the future, perhaps with a balloon."

An international group of scientists are co-authors on the Science article, "The Sand Seas of Titan: Cassini Observations of Longitudinal Dunes." They are from the Jet Propulsion Laboratory, California Institute of Technology, U.S. Geological Survey - Flagstaff, Planetary Science Institute, Wheeling Jesuit College, Proxemy Research of Bowie, Md., Stanford University, Goddard Institute for Space Studies, Observatoire de Paris, International Research School of Planetary Sciences, Universita' d'Annunzio, Facolt di Ingegneria, Universit La Sapienza, Politecnico di Bari and Agenzia Spaziale Italiana. Jani Radebaugh and Jonathan Lunine of UA's Lunar and Planetary Laboratory are among the co-authors.

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 mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter was designed, developed and assembled at JPL.

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Final Shuttle Mission Patch

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STS-134 Patch

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The final planned flight of space shuttle Endeavour is symbolized in the official embroidered crew patch for STS-134. Available in our store!
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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
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Project Orion
The Orion crew exploration vehicle is NASA's first new human spacecraft developed since the space shuttle a quarter-century earlier. The capsule is one of the key elements of returning astronauts to the Moon.
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Fallen Heroes Patch Collection
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Columbia Report
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