Tuesday, October 25, 2011

Orion's Belt Lights Up Cassini's View Of Enceladus


NASA's Cassini mission will take advantage of the position of two of the three stars in Orion's belt when the spacecraft flies by Saturn's moon Enceladus on Wed., Oct. 19. As the hot, bright stars pass behind the moon's icy jets, Cassini's ultraviolet imaging spectrograph will acquire a two-dimensional view of these dramatic plumes of water vapor and icy material erupting from the moon's southern polar region. This flyby is the mission's first-ever opportunity to probe the jets with two stars simultaneously, a dual stellar occultation.

From Cassini's viewpoint, the closest of Orion's stars will appear about 9 miles (15 kilometers) above the moon's limb, or outer edge. The second star will appear higher, about 19 miles (30 kilometers) from the limb. In the foreground will be Enceladus' icy plumes, which extend hundreds of miles into space.

As the spacecraft passes Enceladus, its infrared instruments, cameras and other instruments will also be monitoring activity on the moon. The orbiter will fly within about 765 miles (1,230 kilometers) of Enceladus' surface.

This flyby will provide researchers with new insight into the jets--their content, the speed at which they are travelling and how they vary. It will also provide new information on the famed "tiger stripes" from which the jets erupt. These fissures in Enceladus' surface are the "nozzles" from which the plumes are propelled at supersonic speeds. Knowing more about their structure may help unlock some of the secrets within Enceladus' interior, including the source of the water-rich plumes.

The Cassini mission celebrated the 14th anniversary of the spacecraft's launch last week. Having completed its four-year prime mission in 2008, the mission is now on its second extension, the Cassini Solstice Mission. One of the mission's goals is to provide further information on previous Cassini discoveries, such as lakes on Titan and plumes on Enceladus, first detected by Cassini in 2005.

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 in Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL.

Wednesday, October 12, 2011

ESA To Collaborate with NASA on Solar Science Mission

Solar Orbiter viewing the sun
On October 4, 2011, the European Space Agency announced it's two next science missions, including Solar Orbiter, a spacecraft geared to study the powerful influence of the sun. Solar Orbiter will be an ESA-led mission, with strong NASA contributions managed from Goddard Space Flight Center in Greenbelt, Md.

Solar Orbiter will venture closer to the Sun than any previous mission. The spacecraft will also carry advanced instrumentation that will help untangle how activity on the sun sends out radiation, particles and magnetic fields that can affect Earth's magnetic environment, causing aurora, or potentially damaging satellites, interfering with GPS communications or even Earth's electrical power grids.

"Solar Orbiter will use multiple gravity assists from Venus to tilt its orbit until it can see the poles of the Sun, and that's never been done before," said Chris St. Cyr, NASA's project scientist for Solar Orbiter at Goddard. "A full view of the solar poles will help us understand how the sun's magnetic poles reverse direction every 11 years, causing giant eruptions and flares, called space weather, that can affect the rest of the solar system."

Being so close to the sun also means that the Solar Orbiter will stay over a given area of the solar surface for a longer time, allowing the instruments to track the evolution of sunspots, active regions, coronal holes and other solar activity far longer than has been done before.

Solar Orbiter is also designed to make major breakthroughs in our understanding of how the sun generates and propels the flow of particles in which the planets are bathed, known as the solar wind. Solar activity and solar eruptions create strong perturbations in this wind, triggering spectacular auroral displays on Earth and other planets. Solar Orbiter will be close enough to the sun to both observe the details of how the solar wind is accelerated off the sun and to sample the wind shortly after it leaves the surface

The mission's launch is planned for 2017 from Cape Canaveral, Florida aboard a NASA-provided launch vehicle. Solar Orbiter will be placed into an elliptical orbit around the sun. Its closest approach will be near the orbit of Mercury, 75% of the distance between Earth and the sun – some 21,000,000 miles away from the sun's surface.

Tuesday, October 4, 2011

NASA's Dawn Spacecraft Begins New Vesta Mapping Orbit

NASA's Dawn Spacecraft Begins New Vesta Mapping Orbit
NASA's Dawn spacecraft has completed a gentle spiral into its new science orbit for an even closer view of the giant asteroid Vesta. Dawn began sending science data on Sept. 29 from this new orbit, known as the high altitude mapping orbit (HAMO).

In this orbit, the average distance from the spacecraft to the Vesta surface is 420 miles (680 kilometers), which is four times closer than the previous survey orbit. The spacecraft will operate in the same basic manner as it did in the survey orbit. When Dawn is over Vesta's dayside, it will point its science instruments to the giant asteroid and acquire data, and when the spacecraft flies over the nightside, it will beam that data back to Earth.

Perhaps the most notable difference in the new orbit is the frequency with which Dawn circles Vesta. In survey orbit, it took Dawn three days to make its way around the asteroid. Now in HAMO, the spacecraft completes the same task in a little over 12 hours. HAMO is scheduled to last about 30 Earth days, during which Dawn will circle Vesta more than 60 times. For about 10 of those 30 days, Dawn will peer straight down at the exotic landscape below it during the dayside passages. For about 20 days, the spacecraft will view the surface at multiple angles.

Scientists will combine the pictures to create topographic maps, revealing the heights of mountains, the depths of craters and the slopes of plains. This will help scientists understand the geological processes that shaped Vesta.

HAMO, the most complex and intensive science campaign at Vesta, has three primary goals: to map Vesta's illuminated surface in color, provide stereo data, and acquire visible and infrared mapping spectrometer data. In addition, it will allow improved measurements of Vesta's gravity.

Dawn launched in September 2007 and arrived at Vesta in July 2011. Since beginning its first survey orbit in August, Dawn has been extensively imaging this intriguing world, sending back a bounty of images and other data. NASA-funded scientists and European scientists on the Dawn mission team will present a wealth of new findings at the joint meeting of the American Astronomical Society's Division for Planetary Sciences and the European Planetary Science Congress next week at La Cite Internationale des Congres Nantes Metropole, Nantes, France.

These findings about the giant asteroid Vesta will include information about the new coordinate system and official names of Vesta's prominent features.