NASA Saturn Cassini VIMS Instrument re-assigned to Venus watching

This image shows the visual and infrared mapping spectrometer instrument (VIMS) just before it was attached to NASA's Cassini spacecraft. 

Cassini launched in 1997 and has been exploring the Saturn system since 2004.

Credit: NASA/JPL-Caltech/University of Arizona.

For seven years, a mini-fridge-sized instrument aboard NASA's Cassini spacecraft reliably investigated;

• weather patterns swirling around Saturn; 
• the hydrocarbon composition of the surface of Saturn's moon Titan;
• the aerosol layers of Titan's haze; and 
• dirt mixing with ice in Saturn's rings. 

But this year the instrument - the visual and infrared mapping spectrometer - has been testing out some new telescopic muscles.

This Friday, Dec. 21, the spectrometer will be tracking the path of Venus across the face of the sun from its perch in the Saturn system.

Earthlings saw such a transit earlier this year, from June 5 to 6, but the observation in December will be the first time a spacecraft has tracked a transit of a planet in our solar system from beyond Earth orbit.

Cassini will collect data on the molecules in Venus's atmosphere as sunlight shines through it.

But learning about Venus actually isn't the point of the observation. Scientists actually want to use the occasion to test the VIMS instrument's capacity for observing planets outside our solar system.

"Interest in infrared investigations of extra-solar planets has exploded in the years since Cassini launched, so we had no idea at the time that we'd ask VIMS to learn this new kind of trick," said Phil Nicholson, the VIMS team member based at Cornell University, Ithaca, N.Y., who is overseeing the transit observations. "But VIMS has worked so well at Saturn so far that we can start thinking about other things it can do."

VIMS will be able to complement exoplanet studies by space telescopes such as NASA and ESA's Hubble and Spitzer space telescopes. VIMS scientists are particularly interested in investigating atmospheric data - such as signatures of methane - from far-off star systems in near-infrared wavelengths.

The pointing has to be very accurate to get one of those extrasolar planets in VIMS's viewfinder, but the instrument has had lots of practice pointing at other stars.

Earlier this year, VIMS obtained its first successful observation of a transit by the exoplanet HD 189733b. Scientists want to improve these observations by reducing the amount of noise in the signal.

NASA Dawn Reveals Secrets of Giant Asteroid Vesta - 3D

This set of images from NASA's Dawn mission shows topography of the southern hemisphere of the giant asteroid Vesta and a map of Vesta's gravity variations that have been adjusted to account for Vesta's shape. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

Findings from NASA's Dawn spacecraft reveal new details about the giant asteroid Vesta, including its varied surface composition, sharp temperature changes and clues to its internal structure.

The findings were presented at the European Geosciences Union meeting in Vienna, Austria, and will help scientists better understand the early solar system and processes that dominated its formation.

Images from Dawn's framing camera and visible and infrared mapping spectrometer, taken 420 miles (680 kilometers) and 130 miles (210 kilometers) above the surface of the asteroid, show a variety of surface mineral and rock patterns.

Coded false-colour images help scientists better understand Vesta's composition and enable them to identify material that was once molten below the asteroid's surface.

Researchers also see breccias, which are rocks fused during impacts from space debris. Many of the materials seen by Dawn are composed of iron- and magnesium-rich minerals, which often are found in Earth's volcanic rocks.

Images also reveal smooth pond-like deposits, which might have formed as fine dust created during impacts settled into low regions.

"Dawn now enables us to study the variety of rock mixtures making up Vesta's surface in great detail," said Harald Hiesinger, a Dawn participating scientist at Munster University in Germany. "The images suggest an amazing variety of processes that paint Vesta's surface."

At the Tarpeia crater near the south pole of the asteroid, Dawn imagery revealed bands of minerals that appear as brilliant layers on the crater's steep slopes. The exposed layering allows scientists to see farther back into the geological history of the giant asteroid.

The layers closer to the asteroid's surface bear evidence of contamination from space rocks bombarding Vesta. Layers below preserve more of their original characteristics. Frequent landslides on the slopes of the craters also have revealed other hidden mineral patterns.

"These results from Dawn suggest Vesta's 'skin' is constantly renewing," said Maria Cristina De Sanctis, lead of the visible and infrared mapping spectrometer team based at Italy's National Institute for Astrophysics in Rome.

Dawn has given scientists a near 3-D view into Vesta's internal structure. By making ultra-sensitive measurements of the asteroid's gravitational tug on the spacecraft, Dawn can detect unusual densities within its outer layers.

Data now show an anomalous area near Vesta's south pole, suggesting denser material from a lower layer of Vesta has been exposed by the impact that created a feature called the Rheasilvia basin. The lighter, younger layers coating other parts of Vesta's surface have been blasted away in the basin.

Dawn obtained the highest-resolution surface temperature maps of any asteroid visited by a spacecraft. Data reveal temperatures can vary from as warm as minus 10 degrees Fahrenheit (minus 23 degrees Celsius) in the sunniest spots to as cold as minus 150 degrees Fahrenheit (minus 100 degrees Celsius) in the shadows.

This is the lowest temperature measurable by Dawn's visible and infrared mapping spectrometer. These findings show the surface responds quickly to illumination with no mitigating effect of an atmosphere.

"After more than nine months at Vesta, Dawn's suite of instruments has enabled us to peel back the layers of mystery that have surrounded this giant asteroid since humankind first saw it as just a bright spot in the night sky," said Carol Raymond, Dawn deputy principal investigator at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

"We are closing in on the giant asteroid's secrets."

Launched in 2007, Dawn began its exploration of the approximately 330-mile-wide (530-kilometers) asteroid in mid-2011. The spacecraft's next assignment will be to study the dwarf planet Ceres in 2015. These two icons of the asteroid belt have been witness to much of our solar system's history.

NASA Wise Image: The latest infra-red map of the Universe

The map of the whole sky was compiled by NASA's infrared space telescope, WISE, and is made up of 560 million stars, galaxies and other objects.

The Milky Way's disk and central bulge are traced out in blue, representing infrared light with a wavelength of 3.4 micrometres, which mainly comes from stars.

The bluish blobs to the bottom right are our two largest satellite galaxies, the Large and Small Magellanic clouds, more than 150,000 light years away. Andromeda forms a small blue streak to the lower left, and the image is dotted with more distant galaxies.

Longer-wavelength radiation, coloured green and red, comes from dust clouds. Just above the galactic disk near the centre of the image is the Rho Ophiuchi cloud complex, only 130 light years away, where new stars are forming.

Among the discoveries made by WISE are many near-Earth asteroids, as well as a new class of super-cool stars called Y-dwarfs.

NASA Cassini Double Play: Enceladus And Titan

On the left, Saturn's moon Enceladus is backlit by the sun, showing the fountain-like sources of the fine spray of material that towers over the south polar region.

On the right, is a composite image of Titan. Image credit: NASA/JPL/SSI and NASA/JPL/University of Arizona

About a month and a half after its last double flyby, NASA's Cassini spacecraft will be turning another double play this week, visiting the geyser moon Enceladus and the hazy moon Titan.

The alignment of the moons means that Cassini can catch glimpses of these two contrasting worlds within less than 48 hours, with no detours in between.

Cassini will make its closest approach to Enceladus late at night on May 17 Pacific time, which is in the early hours of May 18 UTC. The spacecraft will pass within about 435 kilometers (270 miles) of the moon's surface.

The main scientific goal at Enceladus will be to watch the sun play peekaboo behind the water-rich plume emanating from the moon's south polar region. Scientists using the ultraviolet imaging spectrograph will be able to use the flickering light to measure whether there is molecular nitrogen in the plume.

Ammonia has already been detected in the plume and scientists know heat can decompose ammonia into nitrogen molecules. Determining the amount of molecular nitrogen in the plume will give scientists clues about thermal processing in the moon's interior.

The second of Cassini's two flybys is an encounter with Titan. The closest approach will take place in the late evening May 19 Pacific time, which is in the early hours of May 20 UTC. The spacecraft will fly to within 1,400 kilometers (750 miles) of the surface.

Cassini will primarily be doing radio science during this pass to detect the subtle variations in the gravitational tug on the spacecraft by Titan, which is 25 percent larger in volume than the planet Mercury.

Analyzing the data will help scientists learn whether Titan has a liquid ocean under its surface and get a better picture of its internal structure. The composite infrared spectrometer will also get its southernmost pass for thermal data to fill out its temperature map of the smoggy moon.

Cassini has made four previous double flybys and one more is planned in the years ahead.

Cassini and Amateur Astronomers Chase massive Storm On Saturn

With the help of amateur astronomers, the composite infrared spectrometer instrument aboard NASA's Cassini spacecraft has taken its first look at a massive blizzard in Saturn's atmosphere. The instrument collected the most detailed data to date of temperatures and gas distribution in that planet's storms.

The data showed a large, turbulent storm, dredging up loads of material from the deep atmosphere and covering an area at least five times larger than the biggest blizzard in this year's Washington, D.C.-area storm front nicknamed "Snowmageddon."

"We were so excited to get a heads-up from the amateurs," said Gordon Bjoraker, a composite infrared spectrometer team member based at NASA's Goddard Space Flight Center in Greenbelt, Md. Normally, he said, "Data from the storm cell would have been averaged out."

Cassini's radio and plasma wave instrument and imaging cameras have been tracking thunder and lightning storms on Saturn for years in a band around Saturn's mid-latitudes nicknamed "storm alley." But storms can come and go on a time scale of weeks, while Cassini's imaging and spectrometer observations have to be locked in place months in advance.

The radio and plasma wave instrument regularly picks up electrostatic discharges associated with the storms, so team members have been sending periodic tips to amateur astronomers, who can quickly go to their backyard telescopes and try to see the bright convective storm clouds.

Amateur astronomers including Anthony Wesley, Trevor Barry and Christopher Go got one of those notices in February and were able to take dozens of pictures over the next several weeks.

In late March, Wesley, an amateur astronomer from Australia who was actually the first person to detect the new dark spot caused by an impact on Jupiter last summer, sent Cassini scientists an e-mail with a picture of the storm.

"I wanted to be sure that images like these were being seen by the Cassini team just in case this was something of interest to be imaged directly by Cassini or the Hubble Space Telescope," Wesley wrote.