March 21, 2007, 4:53 AM CT

Glimpse Of Future Sentinel-1 Images Over Ice

It is perhaps fitting that at the beginning of the International Polar Year, an ambitious airborne campaign is now underway and realising excellent results in the extreme north of Europe. The IceSAR campaign is in support of ESA's Sentinel-1 mission - which amongst other application areas will contribute to ice monitoring.

Carrying a Synthetic Aperture Radar (SAR), the images that.

Sentinel-1 will provide are especially well suited for applications based on mapping sea ice. High-resolution ice charts, monitoring icebergs and forecasting ice conditions are examples of important application areas that are expected to benefit greatly from Sentinel-1, which is being developed by ESA in support of GMES (Global Monitoring for Environment and Security).

Developing the mission to meet the users' needs in a variety of application areas is of utmost importance. A major challenge for Sentinel-1 is to ensure that the satellite will yield data with the quality and timeliness that users truly need. It is not surprising therefore, that airborne campaigns play an important role in helping with the design of these missions as the experiments carried out simulate satellite data long before the actual launch of the mission.

"ESA is putting a tremendous effort into the design and implementation of the Sentinel-1 mission," says Malcolm Davidson, Sentinel-1 Mission Scientist. "While this effort might be invisible to future users of Sentinel-1 products, it is critical that we validate the modes of operation and quality of data products ahead of launch. The IceSAR campaign is allowing us to simulate Sentinel-1 radar images over ice well before launch in 2011, and better prepare for the mission"......... Posted by: Sean      Read more         Source

March 19, 2007, 9:29 PM CT

Most Energetic Form Of Light

n 2002, when astronomers first detected cosmic gamma rays - the most energetic form of light known - coming from the constellation Cygnus they were surprised and perplexed. The region lacked the extreme electromagnetic fields that they thought were mandatory to produce such energetic rays. But now a team of theoretical physicists propose a mechanism that can explain this mystery and may also help account for another type of cosmic ray, the high-energy nuclei that rain down on Earth in the billions.

The new mechanism is described in a Physical Review Letters paper published online on March 20. The theoretical study was headed by Thomas Weiler, professor of physics at Vanderbilt, working with Luis Anchordoqui at the University of Wisconsin-Milwaukee; John Beacom at Ohio State University; Haim Goldberg at Northeastern University; and Sergio Palomares-Ruiz at the University of Durham.

Existing methods for producing cosmic gamma rays require the ultra-strong electromagnetic fields found only in some of the most extreme conditions in the universe, such as stellar explosions and regions surrounding the massive black holes found at the core of a number of galaxies. So they couldn't explain how a "starburst" region in the Cygnus galaxy dominated by young, hot, bright stars could produce such energetic rays. The newly proposed mechanism, however, shows how two constituents present in such an area - fast-moving nuclei found in stellar winds and ultraviolet light - can interact to produce cosmic gamma rays......... Posted by: Sean      Read more         Source

March 15, 2007, 9:15 PM CT

Water Quantity Around Mars South Pole

The amount of water trapped in frozen layers over Mars' south polar region is equivalent to a liquid layer about 11 metres deep covering the planet.

This new estimate comes from mapping the thickness of the dusty ice by the Mars Express radar instrument that has made more than 300 virtual slices through layered deposits covering the pole. The radar sees through icy layers to the lower boundary, which in places is as deep as 3.7 kilometres below the surface.

"The south polar layered deposits of Mars cover an area as wide as a big portion of Europe. The amount of water they contain has been estimated before, but never with the level of confidence this radar makes possible," said Dr. Jeffrey Plaut of NASA's Jet Propulsion Laboratory, Pasadena (California), co-Principal Investigator for the radar and lead author of the study.

The instrument, named the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS), is also mapping the thickness of similar layered deposits at the north pole of Mars.

Our radar is doing its job extremely well, said Prof. Giovanni Picardi of the University of Rome La Sapienza, Principal Investigator for the instrument. MARSIS is showing to be a very powerful tool to probe underneath the Martian surface, and its showing how our teams goals such as probing the polar layered deposits - are being successfully achieved, he continued. Not only MARSIS is providing us with the first ever views of Mars subsurface at those depths, but the details we are seeing are truly amazing. We are expecting even greater results when we will have concluded an on-going, sophisticated fine-tuning of our data processing methods. These should enable us to understand even better the surface and subsurface composition......... Posted by: Sean      Read more         Source

March 14, 2007, 10:30 PM CT

THEMIS Weighs In On The Northern Lights

Instruments known as solid-state telescopes (SSTs), built with detectors fabricated at Lawrence Berkeley National Laboratory and carried aboard the recently launched THEMIS mission, have delivered their first data on how charged particles in the solar wind interact with Earth's magnetic field to shape the planet's magnetosphere.

THEMIS's principal investigator is Vassilis Angelopoulos of the University of California at Berkeley's Space Sciences Laboratory (SSL), which is leading the mission for NASA and which designed and built the instruments in collaboration with agencies in Gera number of, France, and Austria.

The first NASA mission comprised of five different coordinated spacecraft, all five THEMIS spacecraft were launched from Cape Canaveral together aboard a single rocket on February 17, 2007. Eventually the five will study the mysterious eruptions in Earth's Northern and Southern Lights known as "substorms," but first they must achieve widely separated orbits, a process that will take several months.

An acronym for Time History of Events and Macroscopic Interactions during Substorms, THEMIS will obtain the evidence needed to solve what principal investigator Angelopoulos calls "a nagging question that the field has to resolve" - namely, competing theories about where auroral substorms originate in the magnetosphere......... Posted by: Sean      Read more         Source

February 27, 2007, 8:45 PM CT

Successful Rosetta swing

The European Space Agency's (ESA) Rosetta spacecraft successfully completed a swing-by of Mars in the early hours of Sunday morning (25th February 2007). Not only did this mark an important milestone on the spacecraft's 7.1 billion km journey to comet Churyumov Gerasimenko but it provided a unique opportunity to gather further scientific data and images from the Red Planet.

INTA/UPM/DASP/IDAThe critical gravity assist manoeuvre around Mars has helped Rosetta change direction putting it on the correct track towards Earth its next destination planet whose gravitational energy Rosetta will exploit in November this year to gain acceleration and continue on its ten-year journey to the comet which it will reach in 2014.

At 2.57 GMT mission controllers at ESA's Space Operations Centre (ESOC) in Gera number of confirmed that Rosetta had successfully completed the swing-by manoeuvre. At its closest approach (around 2.15 GMT) Rosetta passed the surface of Mars at a distance of 250 km (155 miles) travelling at a mere 10.1 km/second relative to the centre of the planet.

During the swing by there was a 25 minute period when Rosetta passed into the shadow of Mars denying the probe the ability to generate power using its solar arrays. At this time the spacecraft was put into "eclipse mode" with no science operations taking place on the orbiter instruments......... Posted by: Sean      Read more         Source

February 27, 2007, 8:01 PM CT

About The Extrasolars

So far, astronomers have discovered about 200 planets outside our solar system, known as "extrasolar" planets. Very little is known about most of them, but for the first time, scientists have obtained new information about the atmospheres of two such planets by splitting apart the light emitted from them.

Sara Seager, MIT associate professor of earth, atmospheric and planetary sciences, is part of a research group based at Goddard Space Flight Center that studied a planet about 904 trillion miles from Earth, known as HD 209458b. The researchers used NASA's Spitzer Space Telescope to capture the most detailed information yet about an extrasolar planet.

Seager's team is one of three that are reporting spectral observations of extrasolar planets this week. Two groups studied HD 209458b, and one studied another planet in a different solar system. The work by Seager's team is reported in the Feb. 22 issue of Nature.

Astronomers often learn about distant objects, such as stars and galaxies, by studying the composition of light emitted by them, Seager said. But extrasolar planets are much dimmer than stars and thus far more difficult to study.

Light from extrasolar planets is "very, very hard to measure because the stars are so bright and the planets are faint. This planet is right at the edge of what we can detect with this telescope," said Seager, who arrived at MIT in January to start a program devoted to studying extrasolar planets......... Posted by: Sean      Read more         Source

February 26, 2007, 7:10 PM CT

South Pole Telescope achieves first light

Scientists aimed the South Pole Telescope at Jupiter on the evening of Feb. 16 and successfully collected the instrument's first test observations. Soon, far more distant quarry will fall under the SPT's sights as a team from nine institutions tackles one of the.

biggest mysteries of modern cosmological research. That mystery: What is dark energy, the force that dominates the universe?

"The telescope, camera and optics are all working as.

designed," said John Carlstrom, the S. Chandrasekhar Distinguished Service Professor in Astronomy & Astrophysics at the University of.

Chicago, who heads the SPT Team. "First light with the SPT is a major milestone for the project and is a fitting conclusion to a remarkably productive summer season for the South Pole Station. We now look.

forward to fully characterizing the instrument and beginning cosmological observations," he said.

The $19.2 million SPT is funded primarily by the National Science Foundation, with additional support from the Kavli Foundation of Oxnard, Calif., and the Gordon and Betty Moore Foundation of San Francisco.

The telescope stands 75 feet tall, measures 33 feet across and weighs 280 tons. It was test-built in Kilgore, Texas, then taken apart, shipped by boat to New Zealand, and flown to the South Pole. Since November, the SPT team under the guidance of project manager Steve Padin, Senior Scientist in Astronomy & Astrophysics at the University of Chicago, has worked furiously to reassemble and deploy the telescope......... Posted by: Sean      Read more         Source

February 21, 2007, 9:13 PM CT

Watching Sky Through Three Giant Eyes

The ESO Very Large Telescope Interferometer, which allows astronomers to scrutinise objects with a precision equivalent to that of a 130-m telescope, is proving itself an unequalled success every day. One of the latest instruments installed, AMBER, has led to a flurry of scientific results, an anthology of which is being published this week as special features in the research journal Astronomy & Astrophysics.

"With its unique capabilities, the VLT Interferometer (VLTI) has created itself a niche in which it provide answers to many astronomical questions, from the shape of stars, to discs around stars, to the surroundings of the supermassive black holes in active galaxies," says Jorge Melnick (ESO), the VLT Project Scientist. The VLTI has led to 55 scientific papers already and is in fact producing more than half of the interferometric results worldwide.

"With the capability of AMBER to combine up to three of the 8.2-m VLT Unit Telescopes, we can really achieve what nobody else can do," added Fabien Malbet, from the LAOG (France) and the AMBER Project Scientist.

Eleven articles will appear this week in Astronomy & Astrophysics' special AMBER section. Three of them describe the unique instrument, while the other eight reveal completely new results about the early and late stages in the life of stars......... Posted by: Sean      Read more         Source

February 20, 2007, 9:00 PM CT

Our View Of The Gamma-ray Sky

Integral's latest survey of the gamma-ray universe continues to change the way astronomers think of the high-energy cosmos. With over seventy percent of the sky now observed by Integral, astronomers have been able to construct the largest catalogue yet of individual gamma-ray-emitting celestial objects. And there is no end in sight for the discoveries.

Integral is the European Space Agency's latest orbiting gamma-ray observatory. Ever since Integral began scientific operations in 2003, the project team has been devoting a substantial proportion of its observing time to a survey of the gamma-ray universe.

"The gamma-ray sky is notoriously variable and extremely unpredictable," says Anthony Dean, University of Southampton, UK, one of the original proposers of the Integral mission. Hence, the need for Integral's constant vigilance and an accurate catalogue of all gamma-ray sources. With this, astronomers can target individual gamma-ray objects for more detailed, study.

For the past three and a half years, Integral has been collecting survey data. At the end of every year, the data has been turned into a catalogue of sources.

During the first year, it concentrated on the regions close to the centre of our galaxy and found more than 120 sources. During the following year, Integral broadened its reach and found almost 100 more sources......... Posted by: Sean      Read more         Source

February 20, 2007, 8:47 PM CT

Five Spacecraft To The Sun-earth Flotilla

The main scientific objective of THEMIS (Time History of Events and Macroscale Interactions during Substorms) is to find what triggers magnetic substorms. This phenomenon corresponds to periods of time during which violent changes happen within the Earth's magnetic environment or magnetosphere. It is triggered at distances from one tenth to half the Earth-Moon distance on the nightside of Earth and hurls energetic particles towards our planet. These particles are responsible for the very bright and colourful auroras and are commonly harmless. However, when the Sun unleashes massive clouds of charged particles towards Earth, a series of 10 or more substorms can occur in rapid succession. Such a series may be responsible for the failure of power grids and satellites observed during some of these events.

Six plus five equals eleven.

Cluster is the first space mission composed of four satellites flying in formation to study the Sun-Earth connection. Launched in 2000, this mission, originally planned for two years, has been extended to the end of 2009. It was joined in 2003 by the first Double Star spacecraft named TC-1 and in 2004 by TC-2, both partially equipped with spare instruments of the Cluster satellites. Double Star is the first Chinese scientific space mission in the Earth's magnetosphere......... Posted by: Sean      Read more         Source