Posted on by Fraser Cain

Mediterranean Heat Map Produced from Space

Image credit: ESA
This ultra high-resolution sea surface temperature map of the Mediterranean could only have been made with satellites. Any equivalent ground-based map would need almost a million and a half thermometers placed into the water simultaneously, one for every two square kilometres of sea.

This most detailed ever heat map of all 2 965 500 square kilometres of the Mediterranean, the world’s largest inland sea is being updated on a daily basis as part of ESA’s Medspiration project.

With sea surface temperature (SST) an important variable for weather forecasting and increasingly seen as a key indicator of climate change, the idea behind Medspiration is to combine data from multiple satellite systems to produce a robust set of sea surface data for assimilation into ocean forecasting models of the waters around Europe and also the whole of the Atlantic Ocean.

For the Mediterranean Sea, the Medspiration product is being created to an unprecedented spatial resolution of two square kilometres, as Ian Robinson of the Southampton Oceanography Centre, managing the Medspiration Project explains: “The surface temperature distribution in the Mediterranean contains many finely detailed features that reveal eddies, fronts and plumes associated with the dynamics of water circulation. A resolution as fine as this is needed to allow these features to be properly tracked.”

The remaining ocean products are intended to have a still impressive spatial resolution of ten square kilometres. Overall results from the Medspiration project also feed into an even more ambitious scheme to combine all available SST data into a worldwide high-resolution product, known as the Global Ocean Data Assimilation Experiment (GODAE) High-Resolution Sea Surface Temperature Pilot Project (GHRSST-PP).

Its aim is to deliver to the user community a new generation of highly accurate worldwide SST products with a space resolution of less than ten kilometres every six hours.

As an important step towards achieving this goal, ESA has not only initiated Medspiration as the European contribution to the overall GHRSST-PP effort, but the Agency funded a GHRSST International Project Office, located at the Hadley Centre for Climate Prediction and Research, a part of the UK Met Office located in Exeter.

“Medspiration is at the forefront of the GHRSST-PP effort and is driving the operational demonstration of GHRSST-PP as an international system,” says Craig Donlon, head of the GHRSST Office. “GHRSST has developed with a ‘system of systems’ approach, demanding stable interfaces and comprehensive data handling and processing systems.

“Medspiration is ready to deliver the European component of GHRSST-PP. Over the next 12 months Medspiration will play a fundamental role in partnership with other operational groups in the USA, Australia and Japan as the GHRSST-PP system begins the operational delivery of a new generation of SST data products to European and international user communities in near real time.”

The temperature of the surface of the ocean is an important physical property that strongly influences the transfer of heat energy, momentum, water vapour and gases between the ocean and the atmosphere.

And because water takes a long time to warm up or cool down the sea surface functions as an enormous reservoir of heat: the top two metres of ocean alone store all the equivalent energy contained in the atmosphere.

The whole of their waters store more than a thousand times this same value ? climatologists sometimes refer to the oceans as the ‘memory’ of the Earth’s climate, and measuring SST on a long-term basis is the most reliable way to establish the rate of global warming.

Like thermometers in the sky, a number of different satellites measure SST on an ongoing basis. For example, the Advanced Along-Track Scanning Radiometer (AATSR) aboard ESA’s Envisat uses infrared wavelengths to acquire SST for a square kilometre of ocean to an accuracy of 0.2 ?C. In fact, thanks to its high accuracy, AATSR is helping to calibrate other sensors employed by the Medspiration project.

Other satellites may have decreased accuracy or resolution, but potentially make up for it with cloud-piercing microwave abilities or much larger measuring ‘footprints’. Combine all available satellite data together ? along with localised measurements from buoys and research ships – and you can achieve daily monitoring of the temperature of all the oceans covering 71% of the Earth’s surface. This information is then prepared for input into the relevant ‘virtual ocean’ ? a sophisticated computer model of the genuine article.

The combination of satellite and also available in-situ observations with numerical modelling ? a technique known as ‘data assimilation’ ? is an extremely powerful one. It has revolutionised atmospheric weather forecasting and is now being applied to the oceans.

Near real time observational inputs keep an ocean model from diverting too much from reality, while the outputs from the model make up for any gaps in coverage. With maximised coupling between actual observations and the numerical model, output data can be credibly used for operational tasks such as sea state and algal bloom forecasting, and predicting the path of oil spills. And these models can also be used to look deeper than just the ocean surface.

“The time is coming for operational monitoring and forecasting of three-dimensional global ocean structure,” comments Jean-Louis Fellous, Director for Ocean Research at France’s IFREMER, the French Research Institute for Exploitation of the Sea, a Medspiration project partner. “A project like Medspiration is a key contribution to this endeavour.

“With the capabilities offered by spaceborne SST sensors, by satellite altimeters and by the 1,500 profiling floats measuring temperature and salinity in the deep ocean ? and all this data being fed in near-real time to global ocean models, this vision is becoming a reality.”

Although the new map of the Mediterranean represents an important step forward, both Medspiration and GODAE GHRSST-PP remain works in progress at this point.

The main problem with monitoring high-resolution SST of the Mediterranean is cloud cover. To compensate the team has available a near real time data stream from four separate satellites ? two European, one American and one Japanese. Also applied is a technique called ‘objective analysis’ that minimises cloud effects by interpolating values from just outside the obscured area or from that area measured at times before or after cloud covered it.

Mixing satellite data together on a routine basis is fraught with difficulty because the thermal structure of the upper ocean is actually extremely complex, and different sensors may be measuring different values. There is also considerable day-to-night variability, with daytime temperatures varying with depth much more than those during the night.

Part of the aim of Medspiration is to fully account for this diurnal cycle, in order to improve the overall effectiveness of its data assimilation into ocean forecasting models.

Original Source: ESA News Release

Posted on by Fraser Cain

High Bandwidth Communications With Mars

It would be a planetary scientist?s dream to peer through the eyes of a distant rover?s lenses in real-time, looking around an alien landscape as if she were actually on the planet?s surface, but current radio transmitters can?t handle the bandwidth necessary for a video feed across several million miles. New technology recently patented by scientists at the University of Rochester, however, may make applications like a Mars video feed possible, using lasers instead of radio technology. Special gratings inside the glass of a fiber laser virtually eliminate detrimental scattering, the main hurdle in the quest for high-powered fiber lasers.

?We use lasers in everything from telecommunications to advanced weaponry, but when we need a high-powered laser, we had to fall back on old, inefficient methods,? says Govind Agrawal, professor of optics at the University of Rochester. ?We?ve now shown an incredibly simple way to make high-power fiber lasers, which have enormous potential.?

By removing one of the main limitations of fiber lasers and fiber amplifiers, Agrawal has allowed them to replace traditionally more powerful, but less efficient and poorer quality, traditional lasers. Currently, industries use carbon dioxide and diode-pumped solid-state crystal lasers for welding or cutting metal and machining tiny parts, but these kinds of lasers are bulky and hard to cool. In contrast, the newest alternative, fiber lasers, are efficient, easy to cool, more compact, and more precise. The problem with fiber lasers, however, is that as their wattage increases, the fiber itself begins to create a backlash that effectively shuts down the laser.

Agrawal worked on a way to eliminate the backlash caused by a condition called stimulated Brillouin scattering. When light of high enough power travels down a fiber, the light itself changes the composition of the fiber. The light waves cause areas of the glass fiber to become more and less dense, much as a traveling caterpillar scrunches up and expands its body as it moves along. As the laser light passes from an area of high density to one of low density, it is diffracted the same way the image of a straw bends as it passes between the air and water in a glass. As the power of the laser increases, the diffraction increases until it is reflecting much of the laser light backward, toward the laser itself, instead of properly down the fiber.

In a discussion with, Hojoon Lee, a visiting professor from Korea, Agrawal wondered if gratings etched inside the fiber might help stop the reflection problem. The gratings can be designed to act as a kind of two-way mirror, working almost exactly the same way as the initial problem, only reflecting light forward instead of backward. With the new, simple design, the laser light fires down the fiber through the gratings, and some of it again creates the density changes that reflect some of the light backward?but this time the series of gratings simply bounces that backward reflection forward again. The net result is that the fiber laser can deliver higher wattages than ever before, rivaling conventional lasers and making possible applications that conventional lasers cannot perform, such as high-bandwidth laser communication with a planetary rover several million miles away.

As a laser beam travels between planets, it spreads out and diffracts so much that by the time a beam from Mars reaches us, its width would be larger than 500 miles, making it incredibly difficult to extract the information encoded on the beam. A fiber laser, with its ability to deliver more power, would help by giving receiving stations a more intense signal to work with. In addition, Agrawal is now working with NASA to develop a laser communications system that would spread less to begin with. ?It?s our hope that instead of having a beam that spreads out 500 miles, maybe we can get one that only spreads out a mile or so,? says Agrawal. That concentration of the laser?s power would make it much easier for us to receive high-bandwidth signals from a distant rover.

Many people are using fiber lasers to replace conventional lasers, from the military to the University of Rochester?s own Omega laser in the Laboratory for Laser Energetics (LLE), which is the most powerful ultraviolet laser in the world. Agrawal will be working with scientists at LLE to possibly implement the new grating system into the Omega?s new fiber laser system.

Original Source: University of Rochester News Release

Posted on by Fraser Cain

Ariane Lofts 7 Satellites at Once

Arianespace has successfully launched the Helios IIA observation satellite for the French, Belgian and Spanish ministries of defense.

Following a flight lasting 60 minutes and 8 seconds, the Ariane 5 launch vehicle accurately injected Helios IIA into Sun-synchronous polar orbit. The mission also deployed six auxiliary payloads: four Essaim micro-satellites and two other small spacecraft, Parasol and Nanosat.

Sixteenth successful launch
With its 16th successful mission, the standard Ariane 5G (“Generic”) launcher continues to confirm its technical and operational maturity. The launcher also showed its ability to handle a complete range of missions, from government launches into Sun-synchronous orbit to huge commercial satellites into geostationary orbit and scientific spacecraft into special orbits.

The launch was from Europe’s Spaceport in Kourou, French Guiana, on Saturday, December 18, at 1:26 p.m. local time in Kourou (1626 GMT, and 5:26 pm in Paris).

A Boost for Defense
The Ariane 5 launcher is a key to the development of a common European defense and security policy, which must include space capability. Helios IIA is the 23rd military payload to be carried by Europe’s Ariane launcher.

Arianespace covers the spectrum of missions needed by European armed forces:

# Optical observation, including launches of Helios 1A in July 1995 and Helios 1B in December 1999 (for France, Italy, Spain).
# Telecommunications, with Syracuse I, II and II (France), Sicral 1 (Italy), Skynet 4 (U.K.), Hispasat 1A and 1B (Spain), Turksat 1A, 1B, 1C and Eurasiasat (Turkey).

Helios IIA
Helios IIA is the initial satellite in France’s second-generation defense and security spaceborne observation system, being conducted in conjunction with Belgium and Spain. France’s DGA defense procurement agency (D?l?gation G?n?rale pour l’Armement), which is part of the French MoD, is in charge of the program. It has assigned overall responsibility for the space segment to the French space agency, CNES (Centre National d’Etudes Spatiales).

Helios IIA weighed approximately 4,200 kg. at launch. It was built by EADS Astrium as prime contractor, leading a large team of European subcontractors, including Alcatel Space, in charge of the high resolution imaging instrument.

Essaim
The Essaim program is designed to demonstrate the feasibility of space-based detection of electromagnetic transmitters, and evaluate the performance of this type of system. EADS Astrium is prime contractor for the Essaim program.

Parasol
The Parasol microsat aims to characterize the radiation and microphysical properties of clouds and aerosols. French space agency CNES is prime contractor for the Parasol microsat.

Nanosat
Nanosat will provide an in-orbit demonstration of several telecommunications nano-technologies, as well as solar and magnetic sensors. It was developed and built by INTA of Spain.

Original Source: Arianespace News Release

Posted on by Fraser Cain

What’s Up This Week – Dec 20 – Dec 26, 2004

Image credit: NOAO
Season’s Greetings, fellow SkyWatchers! Take the time from your busy holiday schedule to relax with some astronomy. There will be three minor meteor showers this week: the Coma Berenicids, Delta Arietid and the Ursids. The waxing Moon will become our guide as we locate historic variable Mira. Mare Humorum and Crater Gassendi are great features to learn about on the lunar surface and we’ll travel to the outer arm of our own galaxy to study a multiple star system – Sigma Orionis. Not enough? Then I have a special and very challenging surprise for you on Christmas Day! Although the Moon goes full during this seven-day period, those who are just beginning with new telescopes will appreciate its presence as an easy “pointer” to Saturn. So lift your eyes toward the heavens and enjoy the bright stars of Winter…

Because here’s what’s up!

Monday, December 20 – If you’re up early this morning, take a few minutes to watch the skies for the peak of the Coma Berenicid meteor shower. Although the activity for this one is fairly weak, with an average fall rate of about seven per hour, it still warrants study.

So what makes this particular shower of interest? Noted first in 1959, the stream was eventually tied in 1973 to another minor shower bearing the same orbit known as the December Leo Minorids. As we know, meteoroid streams are traditionally tied to the orbit of a comet, and in this case the comet was unconfirmed! Observed in 1912 by B. Lowe, an Australian amateur astronomer, the comet was officially designated as 1913 I and was only seen four times before losing it to sunrise. Using Lowe’s observations, independent researchers computed the comet’s orbit and it was basically forgotten about until 1954. At that time, Fred Whipple was studying meteoroid orbits and made the association between his photographic studies and the enigmatic comet Lowe. By continuing to observe the annual shower, it was derived that the orbital period of the comet was about 75 years, but the two major streams occurred about 27 and 157 years apart. Thanks to the uneven dispersion of material, it may be another decade before we see some real activity from this shower, but even one meteor can make your day!

And if you want to make your “night” an early one, why not trying looking for another odd meteor shower? Tonight will be the peak of the Delta Arietids! These unusual meteors also bear a resemblance to last week’s Geminids, for the source of the stream appears to be a sun-grazing asteroid named Icarus. The hourly fall rate will be about 12 fast and bright “shooting stars”, but the Moon will interfere since it is so close to the radiant. Be sure to watch early as the constellation of Aries will be in the best position for only a few hours after dark. Have a telescope? Then be sure to visit with Madam Selene while out, because the “Straight Wall” will be making its one night stand parallel to the terminator. Look for its thread-thin black shadow just north of the emerging Tycho.

Tuesday, December 21 – This morning marks the point of winter solstice for the northern hemisphere – the time of year where the Sun appears furthest south. For parents, educators or just those who appreciate physically observing the wonders of astronomy, today would be a good time to start a very simple – and very pleasing – experiment. By placing a stake into the ground, or using a stationery object like a fence or sign post, measure the length of the shadow at noon. Write down your measurements, or cut and tag a piece of string with the date. Around every two weeks or so, repeat the process and enjoy the results!

Mira, Mira on the wall… Who’s the strangest star of all? You are, Omicron Ceti. Tonight we’re going to use the nine day old Moon to help guide us to one of the most interesting stars in the sky – Mira! Over 400 years ago, David Fabricus identified Mira, a.k.a. “the Beautiful One”, to be the very first variable star. But what exactly is it? At the time of its discovery, it was thought to be a nova. Cataloged by Bayer seven years later as 4th magnitude Omicron Ceti, imagine the surprise as it “disappeared” from unaided eye visibility! At minimum Mira is around magnitude 9, but within 331 days can flux as high as 3rd or 4th magnitude and has been known to even reach the brightness of Aldeberan.

As a binary system, Mira A is a red giant that goes through some intense changes during its cycle. As one of the coolest of the red stars at minimum, its hot, blue, sub-dwarf companion actually has twice the mass of the primary star. Is it possible that this tiny companion’s extreme gravitation and heat could affect Mira? As Omicron continues to deplete its hydrogen, the interior “pulses” causing it to become more than 100 times brighter and expand more than 700 times the size of our own Sun. In late 1997, Mira became the second star to be resolved by the Hubble Space Telescope and showed a very strange extension towards its companion star.

So how bright will it be tonight? Ah, my friends… That is the joy of discovery!

Wednesday, December 22 – Up early? Fantastic! In the pre-dawn hours of this morning, we have two treats for you – the return of Mercury and the Ursid meteor shower! Cruising around the Sun about every thirteen and a half years, Comet 8P/Tuttle sheds a little skin. Although it never passes inside of Earth’s orbit, some six years later we pass through its debris stream. Not so unusual? Then think again, because it takes as much as six centuries before the meteoroid trail is effected enough by Jupiter’s gravitation to pass into our atmosphere.

Although the Moon will interfere with watching this circumpolar meteor shower, the hours before dawn could see activity of up to 12 per hour. By keeping watch on the constellation of Ursa Major, you just might spot one of these slow moving, 600 year old travelers that make their path only halfway between us and the Moon!

Before dawn this morning, take a look down low on the horizon and say welcome back to Mercury. Above it, and leading the way is bright Venus. For telescopic observers, the real treat will be to see how differently each planet is phased. Venus will appear highly gibbous, while Mercury will only be about one-third illuminated. Keep watch on this pair in the days ahead as they swap places in the sky!

Thursday, December 23 – Tonight exploring the Moon will be in order as one of the most graceful and recognizable lunar features will be prominent – Gassendi. As an ancient mountain walled plane that sits proudly at the northern edge of Mare Humorum, Gassendi sports a bright ring and a triple central mountain peak that are within the range of binoculars. Telescopic viewers will appreciate Gassendi at high power to view how its southern border has been eroded by lava flow and the many riles and ridges that exist inside the crater and the presence of the younger Gassendi A on north wall. While viewing the Mare Humorum area, keep in mind that we are looking at an area about the size of the state of Arkansas. It is believed that a planetoid collision originally formed Mare Humorum. The incredible impact crushed the surface layers of the Moon resulting in a concentric “anticline” that can be traced twice the size of the original impact area. The floor of this huge crater then filled in with lava and was once thought to have a greenish appearance but in recent years have more accurately been described as reddish. That’s one mighty big crater!

Friday, December 24 – Twas the night before Christmas and all through the house, not a creature was stirring… Except for the mouse with the telescope who wants to see a multiple star system! Why don’t we join him tonight and have a look at a very nice and easily resolved, Sigma Orionis.

This particular system is easily found without a map. By identifying the three “belt” stars of Orion, go to the easternmost – Alnitak – and Sigma is the first star south of it. In the telescope you will find a beautiful combination of four stars. The 3.8 magnitude white primary commands attention. With a designation of A/B, this super-massive and extremely bright pair are far too close (about 100 AU apart) to be split with a small scope. Looking 11″ to the southwest, you will discover the 10th magnitude white “C” star and you will see the 7.2 magnitude red “D” star 13″ to the east. Further away yet at a distance of 42″ to the east/northeast is the 6.5 magnitude blue “E” star.

Sharp-eyed observers will also note another multiple system in the same field of view to the northwest. This is Struve 761. As an “all white” system of similar magnitudes, you will see two residing east/west of each other and the third companion to the north. What we are looking at is a system that is about 1,500 light years away from us in the rich, star-forming region of Orion. Give that mouse a piece of cheese!

Saturday, December 25 – In keeping with the season, tonight’s astronomical object is a celebration of both starlight and asterism. Located 10 degrees east of Betelgeuse, the NGC 2264 will be a challenging object thanks to tonight’s near-full Moon, but the results will be quite worth it! Also known as “the Christmas Tree” cluster, this bright asterism of approximately 20 bright stars and over a 100 fainter ones is embroiled in a faint nebula that will be lost to bright skies, leaving only the delightful “Christmas Tree” shape adorned with stars. The very brightest of these stars, S Monoceros, is fifth magnitude and will show clearly in the finder scope and as a double at magnification. Steady skies will reveal that the “star” and the top of our “tree” is also a visual double and home to the beautiful “Cone Nebula”! Many of the stars will also appear to have companions, as well as tints of silver as gold. The visual effect of this splendid open cluster (as seen in this sketch by Jeff Barbour) is well worth the challenge it presents. Happy Holidays!

Sunday, December 26 – Did you get a new telescope? Then enjoy tonight’s full Moon! Although it is very bright, it is also the easiest of astronomical targets and will show many prominent features, bright rays and expansive plains of maria. If you are itching to explore, but unfamiliar with the sky, the Moon will offer to be your guide to one of the most exciting planets for the beginner – Saturn!

With the Moon in the constellation of Gemini tonight, you will see three “stars” gathered to the east. Point your telescope at the southern-most of this trio and enjoy the “Lord of the Rings”. Even small telescopes can appreciate the broad ring system, but there is also a treat tonight as well. Appearing to “follow” Saturn across the sky is its easily spotted moon, Titan!

I would like to thank all of you who have taken the time to write! Your observations of Comet Macholz have been wonderful, so please continue to observe it despite the Moon. I deeply appreciate all the kind words I have received. Do not be afraid to ask questions or share an observation. This column is all about you! Until next week? I wish you the very best of the season. Keep looking up and enjoying the wonders of our Universe! Light speed… ~Tammy Plotner

Posted on by Fraser Cain

Lighting Storms on Saturn

As NASA’s Cassini spacecraft approached Saturn last July, it found evidence that lightning on Saturn is roughly one million times stronger than lightning on Earth.

That’s just one of several Cassini findings that University of Iowa Space Physicist Don Gurnett will present in a paper to be published Thursday, Dec. 16, in Science Express, an online version of the journal Science, and in a talk to be delivered Friday, Dec. 17, at a meeting of the American Geophysical Union in San Francisco.

Other findings include:
–Cassini impacted dust particles as it traversed Saturn’s rings.
–Saturn’s radio rotation rate varies.

The comparison between Saturn’s enormously strong lightning and Earth’s lightning began several years ago as the Cassini spacecraft prepared for its journey to Saturn by swinging past the Earth to receive a gravitational boost. At that time, Cassini started detecting radio signals from Earth’s lightning as far out as 89,200 kilometers from the Earth’s surface. In contrast, as Cassini approached Saturn, it started detecting radio signals from lightning about 161 million kilometers from the planet. “This means that radio signals from Saturn’s lightning are on the order of one million times stronger than Earth’s lightning. That’s just astonishing to me!” says Gurnett, who notes that some radio signals have been linked to storm systems observed by the Cassini imaging instrument.

Earth’s lightning is commonly detected on AM radios, a technique similar to that used by scientists monitoring signals from Cassini.

Regarding Saturn’s rings, Gurnett says that the Cassini Radio and Plasma Wave Science (RPWS) instrument detected large numbers of dust impacts on the spacecraft. Gurnett and his science team found that as Cassini approached the inbound ring plane crossing, the impact rate began to increase dramatically some two minutes before the ring plane crossing, then reached a peak of more than 1,000 per second at almost exactly the time of the ring plane crossing, and finally decreased to pre-existing levels about two minutes later. Gurnett notes that the particles are probably quite small, only a few microns in diameter, otherwise they would have damaged the spacecraft.

Finally, variations in Saturn’s radio rotation rate came as a surprise. Based upon more than one year of Cassini measurements, the rate is 10 hours 45 minutes and 45 seconds, plus or minus 36 seconds. That’s about six minutes longer than the value recorded by the Voyager 1 and 2 flybys of Saturn in 1980-81. Scientists use the rotation rate of radio emissions from the giant gas planets such as Saturn and Jupiter to determine the rotation rate of the planets themselves because the planets have no solid surfaces and are covered by clouds that make direct visual measurements impossible.

Gurnett suggests that the change in the radio rotation rate is difficult to explain. “Saturn is unique in that its magnetic axis is almost exactly aligned with its rotational axis. That means there is no rotationally induced wobble in the magnetic field, so there must be some secondary effect controlling the radio emission. We hope to nail that down during the next four to eight years of the Cassini mission.”

One possible scenario was suggested nearly 20 years ago. Writing in the May 1985 issue of “Geophysical Research Letters,” Alex J. Dessler, a senior research scientist at the Lunar and Planetary Laboratory, University of Arizona, argued that the magnetic fields of gaseous giant planets, such as Saturn and Jupiter, are more like that of the sun than of the Earth. The sun’s magnetic field does not rotate as a solid body. Instead, its rotation period varies with latitude. Commenting earlier this year on the work of Gurnett and his team, Dessler said, “This finding is very significant because it demonstrates that the idea of a rigidly rotating magnetic field is wrong. Saturn’s magnetic field has more in common with the sun than the Earth. The measurement can be interpreted as showing that the part of Saturn’s magnetic field that controls the radio emissions has moved to a higher latitude during the last two decades.”

The radio sounds of Saturn’s rotation — resembling a heartbeat — and other sounds of space can be heard by visiting Gurnett’s Web site at: http://www-pw.physics.uiowa.edu/space-audio

Cassini, carrying 12 scientific instruments, on June 30, 2004, became the first spacecraft to orbit Saturn and begin a four-year study of the planet, its rings and its 31 known moons. The $1.4 billion spacecraft is part of the $3.3 billion Cassini-Huygens Mission that includes the Huygens probe, a six-instrument European Space Agency probe, scheduled to land on Titan, Saturn’s largest moon, in January 2005.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology, Pasadena, Calif. manages the Cassini-Huygens mission for NASA’s Office of Space Science, Washington, D.C. JPL designed, developed and assembled the Cassini orbiter. For the latest images and information about the Cassini-Huygens mission, visit: http://www.nasa.gov/cassini.

Original Source: UI News Release

Posted on by Fraser Cain

Saturn’s Environment is Driven By Ice

Ice particles are key players in the ever-changing panorama at Saturn, according to a new study led by a University of Colorado at Boulder professor using an instrument on the Cassini-Huygens spacecraft now at the ringed planet.

Larry Esposito of the Laboratory for Atmospheric and Space Physics said data from the Ultraviolet Imaging Spectrometer, or UVIS, indicates much of Saturn’s system is filled with ice, as well as atoms derived from water. Esposito is the principal investigator for the $12.5 million UVIS instrument riding on the craft.

Esposito said hydrogen and oxygen atoms are widely distributed in the planetary system, which extends millions of miles outward from Saturn. Cassini researchers are seeing large fluctuations in the amount of oxygen in the Saturn system, he said.

“A possible explanation for the fluctuation in oxygen is that small, unseen icy moons have been colliding with Saturn’s E ring,” said Esposito. “The collisions may have produced small grains of ice, which yielded oxygen atoms when struck by energetic, charged particles in Saturn’s magnetosphere. UVIS is able to identify these glowing atoms.”

A paper on the subject authored by Esposito and colleagues appears in the Dec. 16 issue of Science Express, the online version of Science magazine. Esposito also will give a presentation on the new results from the Cassini-Huygens mission at the Fall Meeting of the American Geophysical Union, being held this week through Friday in San Francisco.

Saturn’s ring particles may have formed originally from pure ice, Esposito said. But they have since been subjected to continual bombardment by meteorites, which has contaminated the ice and caused the rings to darken.

Over time, incessant meteorite bombardment has likely spread the dirty material resulting from the collisions widely among the ring particles, he said. But instead of uniformly dark rings, the UVIS instrument is recording “radial variations” that show brighter and darker bands in the individual rings.

“The evidence indicates that in the last 10 million to 100 million years, fresh material probably was added to the ring system,” he said. The research team proposed that such “renewal events” are from the fragmentation of small moons, each probably about 20 kilometers (12 miles) across.

“The interiors of the tiny moonlets, which have been shielded from contamination by the continual collisions with each other, are the source of purer water ice,” he said. “Both the oxygen fluctuation and the spectral variation in Saturn’s rings support a model of ring history in which small moons are continually destroyed to produce new rings.”

The ice grains released by the continual moonlet collisions are bathed by Saturn’s radiation belt, liberating the oxygen atoms that are seen by UVIS in the ultraviolet as they reflect sunlight in the immense cloud surrounding Saturn, said Esposito.

Other authors on the Science Express paper include LASP’s Joshua Colwell, Kristopher Larsen, William McClintock and Ian Stewart. Researchers from the University of Southern California, NASA’s Jet Propulsion Laboratory, Central Arizona University, the California Institute of Technology and the Max Planck Institute and Stuttgart University in Germany also co-authored the paper.

Launched in 1997, the Cassini-Huygens spacecraft achieved Saturn orbit June 30. During the spacecraft’s four-year tour of the Saturn system, the UVIS team will continue to track the dynamic interactions of the planet’s rings, moons and radiation belts, Esposito said.

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, Calif., manages the Cassini-Huygens mission for NASA’s Science Mission Directorate in Washington, D.C.

Original Source: UCB News Release

Posted on by Fraser Cain

Atlas V Launches AMC-16

Image credit: ILS
An Atlas V launch vehicle placed the AMC-16 satellite into orbit early this morning, marking the 10th and final mission of the year for International Launch Services (ILS).

This was the 74th consecutive successful launch for the Atlas vehicle family, as well as the fourth launch and fourth commercial mission for the Atlas V launcher.

The Atlas V vehicle lifted off at 7:07 a.m. EST (12:07 GMT), and an hour and 49 minutes later separated the satellite into a geosynchronous transfer orbit. Both the Atlas V launcher and the A2100 model satellite were built by Lockheed Martin Space Systems Co. ILS is a joint venture of Lockheed Martin (LMT), of Bethesda, Md., and Khrunichev State Research and Production Space Center of Moscow.

For the past year ILS has been launching nearly monthly with its two vehicles ? the Lockheed Martin Atlas and Khrunichev?s Proton. Not only was today?s launch the 10th of the year; it also was the sixth launch on an Atlas vehicle and the fourth launch this year for the same customer, SES AMERICOM. Atlas IIAS vehicles orbited AMC-10 and AMC-11 in February and May, respectively, and a Proton Breeze M vehicle lifted AMC-15 in October.

?This is record-setting in the number of times we have launched for a single customer in a calendar year,? said ILS President Mark Albrecht. ?SES AMERICOM is a ?platinum customer,? one with which we have a long-standing relationship and have seen many launches. We look forward to continuing our ties with the launch of WS-2 (AMC-12) in early 2005.?

The AMC-16 satellite, like its twin, AMC-15, is integral to AMERICOM2Home and its customer, EchoStar?s DISH Network. In its final orbital location of 85 degrees West, it will provide coverage to all 50 states.

Anders Johnson, senior vice president of strategic satellite initiatives for SES AMERICOM, said, ?We are delighted that AMC-16 has been successfully launched; our heartiest congratulations first to Lockheed Martin for delivering a great spacecraft and to ILS for this morning?s picture-perfect launch.?

ILS is the global leader in launch services, offering the industry?s two best launch systems: Atlas and Proton. With a remarkable launch rate of 69 missions since 2000, the Atlas and Proton launch vehicles have consistently demonstrated the reliability and flexibility that have made them preferred choice among satellite operators worldwide. Since the beginning of 2003, ILS has signed more new commercial contracts than all of its competitors combined.

Original Source: ILS News Release

Posted on by Fraser Cain

Titan’s Layered Atmosphere

Cassini’s second close flyby of Titan completes a ‘before’ and ‘after’ look at the fuzzy moon and provides the first direct evidence of changing weather patterns in the skies over Titan.

In images obtained less than two months ago, the Titan skies were cloud free, except for a patch of clouds observed over the moon’s south pole. In images taken Monday, Dec. 13, during Cassini’s second close flyby of Titan, several extensive patches of clouds have formed.

“We see for the first time discrete cloud features at mid-latitudes, which means we see direct evidence of weather, and we can get wind speeds and atmospheric circulation over a region we hadn?t been able to measure before,” said Dr. Kevin Baines, Cassini science-team member with the visual and infrared mapping spectrometer, from NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

The latest data and other results from Cassini’s close observations of Saturn’s moons Titan and Dione were presented today at a news conference during the American Geophysical Union fall meeting in San Francisco.

Cassini swept within 1,200 kilometers (750 miles) of Titan’s surface on Monday, and took a close look at the icy moon Dione just one day later. During the flyby, Cassini captured a stunning view of Titan’s night side with the atmosphere shimmering in its own glow. This allows scientists to study the detached haze layers, which extend some 400 kilometers (249 miles) above Titan.

Images from Cassini’s cameras show regions on Titan that had not been seen clearly before, as well as fine details in Titan?s intermittent clouds. The surface features may be impact related, but without information on their height, it is too soon to know for sure. No definitive craters have been seen in these images, though several bright rings or circular features are seen in dark terrain.

Cassini imaging scientists are intrigued by the complex braided structure of surface fractures on Dione. To the surprise of scientists, the wispy terrain features do not consist of thick ice deposits, but bright ice cliffs created by tectonic features. ?This is one of the most surprising results so far. It just wasn?t what we expected,? said Dr. Carolyn Porco, Cassini imaging team leader, Space Science Institute, Boulder, Colo.

Other Cassini results presented at the meeting included observations made by the ultraviolet imaging spectrograph instrument, which indicates that the nearby environment of the rings and moons in the Saturn system is filled with ice, and atoms derived from water. Cassini researchers are seeing large changes in the amount of oxygen atoms in the Saturn system. A possible explanation for the fluctuation in oxygen is that small, unseen icy moons have been colliding with Saturn’s E ring,” said Dr. Larry Esposito, principal investigator of the imaging spectrograph instrument, University of Colorado, Boulder, Colo. “These collisions may have produced small grains of ice, which yielded oxygen atoms.” Esposito presented these findings at the meeting, and a paper on the subject appears in the online version of the journal Science.

According to Esposito, Saturn’s ring particles may have formed originally from pure ice. But they have since been subjected to continual bombardment by meteorites, which has contaminated the ice and caused the rings to darken. Over time, continuous meteorite bombardment has likely spread the dirty material resulting from the collisions over a wide area in the rings. “The evidence indicates that in the last 10 to 100 million years, fresh material probably was added to the ring system,” said Esposito. These renewal events are from fragments of small moons, each probably about 20 kilometers (12 miles) across.

Images and more information about the Cassini mission are available at http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini .

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the Cassini mission for NASA’s Science Mission Directorate, Washington, D.C. JPL designed, developed and assembled the Cassini orbiter. The European Space Agency built and managed the development of the Huygens probe and is in charge of the probe operations. The Italian Space Agency provided the high-gain antenna, much of the radio system and elements of several of Cassini’s science instruments.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Cassini’s Approach to Dione

Cassini captured Dione against the globe of Saturn as it approached the icy moon for its close rendezvous on Dec. 14, 2004. This natural color view shows the moon has strong variations in brightness across its surface, but a remarkable lack of color, compared to the warm hues of Saturn’s atmosphere. Several oval-shaped storms are present in the planet’s atmosphere, along with ripples and waves in the cloud bands.

The images used to create this view were obtained with the Cassini spacecraft wide-angle camera at a distance of approximately 603,000 kilometers (375,000 miles) from Dione through a filter sensitive to wavelengths of ultraviolet light centered at 338 nanometers. The Sun-Dione-spacecraft, or phase, angle is 34 degrees. The image scale is about 32 kilometers (20 miles) per pixel.

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, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.

For more information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and the Cassini imaging team home page, http://ciclops.org.

Original Source: NASA/JPL/SSI News Release

Posted on by Fraser Cain

Sooty Nebula Around a Sun Like Star

The Coronagraphic Imager with Adaptive Optics (CIAO) on the Subaru telescope captured this near-infrared (wavelengths of 1.25 – 2.2 microns) image of a star at the end of its life. BD +303639 is a planetary nebula, similar to the Ring Nebula in the constellation Lyra, the Harp. It is about five thousand light years from Earth in the direction of the constellation Cygnus, the Swan. The surface of the star in the center of the nebula sizzles at a temperature of forty two thousand degrees Kelvin, and shines fifty thousand times brighter than our Sun.

At the end of their lives, comparatively lightweight stars like our Sun shed dust and gas which pile around the star. BD +303639 rapidly puffed off its outer layers about nine hundred years ago. This material, weighing almost a quarter of the Sun, has now expanded into a shell one hundred times more extended than the Solar System. The central star illuminates the material which looks like a life preserver from our point of view.

With visible light we can only see the light from the central star scattering off the dust. In infrared light, we can also see light emitted by the dust itself. CIAO used a technique called adaptive optics, which removes the twinkle of light due to turbulence in Earth’s atmosphere, to obtain an extraordinarily sharp image of the dust surrounding the star. (Note 1)

Spectra of the central star from the Subaru telescope’s High Dispersion Sepctrogrtaph indicates that the sizzling at the star’s surface is generating large quantities of carbon. This carbon is a likely ingredient of the dust surrounding the star.

Shedding of material is an integral part of the life of stars. “Although astronomers have been studying the dust and gas surrounding stars of different ages and types, we are only beginning to be able to observe and understand detailed structures such those in BD +303639,” says Dr. Koji Murakawa, an astronomer at the Netherlands Foundation for Research in Astronomy. Murakawa adds that “images like these give us precious insight into the last moments in a stars life.”

Note 1: The coronagraph, a device that blocks the light from a bright central star, was not used to obtain this image.

Original Source: Subaru Telescope News Release