NASA's Juno Spacecraft Refines its Path to Jupiter

PASADENA, Calif. -- NASA's solar-powered Juno spacecraft successfully refined its flight path Wednesday with the mission's first trajectory correction maneuver. The maneuver took place on Feb. 1. It is the first of a dozen planned rocket firings that, over the next five years, will keep Juno on course for its rendezvous with Jupiter.

The trajectory correction maneuver, which adjusts the spacecraft's flight path, began at 10:10 a.m. PST (1:10 p.m. EST) on Feb. 1. The Juno spacecraft's thrusters fired for 25 minutes, consumed about 6.9 pounds (3.11 kilograms) of fuel and changed the spacecraft's speed by 3.9 feet, or 1.2 meters, per second. The next big maneuver for Juno will occur in late August of 2012 when Juno executes its first of two deep space maneuvers to set the stage for its Earth flyby – and gravity assist – on its way to Jupiter.

Launched on Aug. 5, 2011, Juno is 182 days and 279 million miles (449 million kilometers) into its five-year, 1,740-million-mile (2,800-million-kilometer) journey to Jupiter. Once in orbit, the spacecraft will orbit the planet's poles 33 times and use its collection of eight science instruments to probe beneath the gas giant's obscuring cloud cover to learn more about Jupiter's origins, structure, atmosphere and magnetosphere, and look for a potential solid planetary core.

Juno's name comes from Greek and Roman mythology. The god Jupiter drew a veil of clouds around himself to hide his mischief, and his wife, the goddess Juno, was able to peer through the clouds and reveal Jupiter's true nature. For more information about Juno is online at http://www.nasa.gov/juno and http://missionjuno.swri.edu.

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NASA's Dawn's Spacecraft Views Dark Side of Vesta

Dawn took this image over Vesta's northern hemisphere after the spacecraft completed its first passage over the dark side of the giant asteroid. It is northern hemisphere winter on Vesta now, so its north pole is in deep shadow.

The Dawn science team is working to determine the significance of the distinct features in this image, which include large grooves or ridges extending for great distances around Vesta.

This image was taken by Dawn's framing camera on July 23, from a distance of 3,200 miles (5,200 kilometers).

The Dawn mission to Vesta and Ceres is managed by NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, for NASA. The University of California, Los Angeles, is responsible for overall Dawn mission science. The Dawn framing cameras have been developed and built under the leadership of the Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany, with significant contributions by DLR German Aerospace Center, Institute of Planetary Research, Berlin, and in coordination with the Institute of Computer and Communication Network Engineering, Braunschweig. The Framing Camera project is funded by the Max Planck Society, DLR, and NASA/JPL.

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NASA's Jupiter-Bound Juno Spacecraft Mated to its Rocket

NASA's Juno spacecraft completed its last significant terrestrial journey today, July 27, with a 15-mile (25-kilometer) trip from Astrotech Space Operations in Titusville, Fla., to its launch pad at the Cape Canaveral Air Force Station. The solar-powered, Jupiter-bound spacecraft was secured into place on top of its rocket at 10:42 a.m. EDT (7:42 a.m. PDT).

Juno will arrive at Jupiter in July 2016 and orbit its poles 33 times to learn more about the gas giant's interior, atmosphere and aurora.

"We're about to start our journey to Jupiter to unlock the secrets of the early solar system," said Scott Bolton, the mission's principal investigator from the Southwest Research Institute in San Antonio. "After eight years of development, the spacecraft is ready for its important mission."

Now that the Juno payload is atop the most powerful Atlas rocket ever made -- the United Launch Alliance Atlas V 551 -- a final flurry of checks and tests can begin and confirm that all is go for launch. The final series of checks begins Wednesday with an on-pad functional test. The test is designed to confirm that the spacecraft is healthy after the fueling, encapsulation and transport operations.

"The on-pad functional test is the first of seven tests and reviews that Juno and its flight team will undergo during the spacecraft's last 10 days on Earth," said Jan Chodas, Juno's project manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "There are a number of remaining pre-launch activities that we still need to focus on, but the team is really excited that the final days of preparation, which we've been anticipating for years, are finally here. We are ready to go."

The launch period for Juno opens Aug. 5, 2011, and extends through Aug. 26. For an Aug. 5 liftoff, the launch window opens at 11:34 a.m. EDT (8:34 a.m. PDT) and remains open through 12:43 p.m. EDT (9:43 a.m. PDT).

JPL manages the Juno mission for principal investigator Scott Bolton. The Juno mission is part of the New Frontiers Program managed at NASA's Marshall Space Flight Center in Huntsville, Ala. Lockheed Martin Space Systems of Denver built the spacecraft. Launch management for the mission is the responsibility of NASA's Launch Services Program at the agency's Kennedy Space Center in Florida. JPL is a division of the California Institute of Technology in Pasadena.

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Dawn Nears Start of Year-Long Stay at Giant Asteroid

NASA's Dawn spacecraft is on track to begin the first extended visit to a large asteroid. The mission expects to go into orbit around Vesta on July 16 and begin gathering science data in early August. Vesta resides in the main asteroid belt and is thought to be the source of a large number of meteorites that fall to Earth.

"The spacecraft is right on target," said Robert Mase, Dawn project manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "We look forward to exploring this unknown world during Dawn's one-year stay in Vesta's orbit."

After traveling nearly four years and 1.7 billion miles (2.7 billion kilometers), Dawn is approximately 96,000 miles (155,000 kilometers) away from Vesta. When Vesta captures Dawn into its orbit on July 16, there will be approximately 9,900 miles (16,000 kilometers) between them. When orbit is achieved, they will be approximately 117 million miles (188 million kilometers) away from Earth.

After Dawn enters Vesta's orbit, engineers will need a few days to determine the exact time of capture. Unlike other missions where a dramatic, nail-biting propulsive burn results in orbit insertion around a planet, Dawn has been using its placid ion propulsion system to subtly shape its path for years to match Vesta's orbit around the sun.

Images from Dawn's framing camera, taken for navigation purposes, show the slow progress toward Vesta. They also show Vesta rotating about 65 degrees in the field of view. The images are about twice as sharp as the best images of Vesta from NASA's Hubble Space Telescope, but the surface details Dawn will obtain are still a mystery.

"Navigation images from Dawn's framing camera have given us intriguing hints of Vesta, but we're looking forward to the heart of Vesta operations, when we begin officially collecting science data," said Christopher Russell, Dawn principal investigator, at UCLA. "We can't wait for Dawn to peel back the layers of time and reveal the early history of our solar system."

Dawn's three instruments are all functioning and appear to be properly calibrated. The visible and infrared mapping spectrometer, for example, has started to obtain images of Vesta that are larger than a few pixels in size. During the initial reconnaissance orbit, at approximately 1,700 miles (2,700 kilometers), the spacecraft will get a broad overview of Vesta with color pictures and data in different wavelengths of reflected light. The spacecraft will move into a high-altitude mapping orbit, about 420 miles (680 kilometers) above the surface to systematically map the parts of Vesta's surface illuminated by the sun; collect stereo images to see topographic highs and lows; acquire higher-resolution data to map rock types at the surface; and learn more about Vesta's thermal properties.

Dawn then will move even closer, to a low-altitude mapping orbit approximately 120 miles (200 kilometers) above the surface. The primary science goals of this orbit are to detect the byproducts of cosmic rays hitting the surface and help scientists determine the many kinds of atoms there, and probe the protoplanet's internal structure. As Dawn spirals away from Vesta, it will pause again at the high-altitude mapping orbit. Because the sun's angle on the surface will have progressed, scientists will be able to see previously hidden terrain while obtaining different views of surface features.

"We've packed our year at Vesta chock-full of science observations to help us unravel the mysteries of Vesta," said Carol Raymond, Dawn's deputy principal investigator at JPL. Vesta is considered a protoplanet, or body that never quite became a full-fledged planet.

Dawn launched in September 2007. Following a year at Vesta, the spacecraft will depart for its second destination, the dwarf planet Ceres, in July 2012. Dawn's mission to Vesta and Ceres is managed by JPL for NASA's Science Mission Directorate in Washington. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Ala.

UCLA is responsible for overall Dawn mission science. Orbital Sciences Corp. of Dulles, Va., designed and built the spacecraft. The German Aerospace Center, the Max Planck Institute for Solar System Research, the Italian Space Agency and the Italian National Astrophysical Institute are part of the mission team. JPL is managed for NASA by the California Institute of Technology in Pasadena

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MESSENGER Provides New Data about Mercury

After nearly three months in orbit about Mercury, MESSENGER's payload is providing a wealth of new information about the planet closest to the Sun, as well as a few surprises.

The spacecraft entered orbit around Mercury on March 18, 2011 UTC, becoming the first spacecraft ever to do so. Tens of thousands of images of major features on the planet — previously seen only at comparatively low resolution — are now available in sharp focus. Measurements of the chemical composition of Mercury's surface are providing important clues to the origin of the planet and its geological history. Maps of the planet's topography and magnetic field are revealing new clues to Mercury's interior dynamical processes. And scientists now know that bursts of energetic particles in Mercury's magnetosphere are a continuing product of the interaction of Mercury's magnetic field with the solar wind.

This week, MESSENGER completed is first perihelion passage from orbit, its first superior solar conjunction from orbit, and its first orbit-correction maneuver. "Those milestones provide important context to the continuing feast of new observations that MESSENGER has been sending home on nearly a daily basis,” offers MESSENGER Principal investigator Sean Solomon of the Carnegie Institution of Washington.

A Surface Revealed in Unprecedented Detail

Among the fascinating features seen in MESSENGER flyby images of Mercury were bright, patchy deposits on some crater floors. Without high-resolution images to obtain a closer look, these features remained a curiosity. New targeted Mercury Dual Imaging System images at up to 10 meters per pixel reveal these patchy deposits to be clusters of rimless, irregular pits varying in size from hundreds of meters to several kilometers. These pits are often surrounded by diffuse halos of higher-reflectance material, and they are found associated with central peaks, peak rings, and rims of craters.

"The etched appearance of these landforms is unlike anything we've seen before on Mercury or the Moon," says Brett Denevi, a staff scientist at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., and a member of the MESSENGER imaging team. "We are still debating their origin, but they appear to have a relatively young age and may suggest a more abundant than expected volatile component in Mercury's crust."


Mercury's Surface Composition

The X-ray Spectrometer (XRS) — one of two instruments on MESSENGER designed to measure the abundances of many key elements on Mercury — has made several important discoveries since the orbital mission began. The magnesium/silicon, aluminum/silicon, and calcium/silicon ratios averaged over large areas of the planet's surface show that, unlike the surface of the Moon, Mercury's surface is not dominated by feldspar-rich rocks.

XRS observations have also revealed substantial amounts of sulfur at Mercury's surface, lending support to prior suggestions from ground-based telescopic spectral observations that sulfide minerals are present. This discovery suggests that the original building blocks from which Mercury was assembled may have been less oxidized than those that formed the other terrestrial planets, and it has potentially important implications for understanding the nature of volcanism on Mercury.


Mapping of Mercury's Topography and Magnetic Field

MESSENGER's Mercury Laser Altimeter has been systematically mapping the topography of Mercury's northern hemisphere. After more than two million laser-ranging observations, the planet's large-scale shape and profiles of geological features are both being revealed in high detail. The north polar region of Mercury, for instance, is a broad area of low elevations. The overall range in topographic heights seen to date exceeds 9 kilometers.

Two decades ago, Earth-based radar images showed that around both Mercury's north and south poles are deposits characterized by high radar backscatter. These polar deposits are thought to consist of water ice and perhaps other ices preserved on the cold, permanently shadowed floors of high-latitude impact craters. MESSENGER's altimeter is testing this idea by measuring the floor depths of craters near Mercury's north pole. To date, the depths of craters hosting polar deposits are consistent with the idea that those deposits occupy areas in permanent shadow.

Energetic Particle Events at Mercury

One of the major discoveries made by Mariner 10 during the first of its three flybys of Mercury in 1974 were bursts of energetic particles in Mercury's Earth-like magnetosphere. Four bursts of particles were observed on that flyby, so it was puzzling that no such strong events were detected by MESSENGER during any of its three flybys of the planet in 2008 and 2009. With MESSENGER now in near-polar orbit about Mercury, energetic events are being seen almost like clockwork.

"We are assembling a global overview of the nature and workings of Mercury for the first time,” adds Solomon, "and many of our earlier ideas are being cast aside as new observations lead to new insights. Our primary mission has another three Mercury years to run, and we can expect more surprises as our solar system's innermost planet reveals its long-held secrets."

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STEREO Sees Complete Far Side

The far side unveiled! This is the first complete image of the solar far side, the half of the sun invisible from Earth. Captured on June 1, 2011, the composite image was assembled from NASA's two Solar TErrestrial RElations Observatory (STEREO) spacecraft. STEREO-Ahead's data is shown on the left half of image and STEREO-Behind's data on the right.

The STEREO spacecraft reached opposition (180° separation) on February 6 but part of the sun was inaccessible to their combined view until June 1. This image represents the first day when the entire far side could be seen.

The image is aligned so that solar north is directly up. The seam between the two images is inclined because the plane of Earth’s -- and STEREO's -- orbit, known as the "ecliptic", is inclined with respect to the sun's axis of rotation. The data was collected by STEREO's Extreme Ultraviolet Imagers in the SECCHI instrument suites.

STEREO was built and is operated for NASA by the Applied Physical Laboratory of the Johns Hopkins University; the spacecraft were launched on October 25, 2006 aboard a Delta II. The SECCHI instrument suite is a collaboration led by the Naval Research Laboratory, and the EUVI instruments were built by the Lockheed Martin Solar and Astrophysics Laboratory.

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Cassini and Telescope See Violent Saturn Storm

NASA's Cassini spacecraft and a European Southern Observatory ground-based telescope tracked the growth of a giant early-spring storm in Saturn's northern hemisphere that is so powerful it stretches around the entire planet. The rare storm has been wreaking havoc for months and shooting plumes of gas high into the planet's atmosphere.

Cassini's radio and plasma wave science instrument first detected the large disturbance, and amateur astronomers tracked its emergence in December 2010. As it rapidly expanded, its core developed into a giant, powerful thunderstorm. The storm produced a 3,000-mile-wide (5,000-kilometer-wide) dark vortex, possibly similar to Jupiter's Great Red Spot, within the turbulent atmosphere.

The dramatic effects of the deep plumes disturbed areas high up in Saturn's usually stable stratosphere, generating regions of warm air that shone like bright "beacons" in the infrared. Details are published in this week's edition of Science Magazine.

"Nothing on Earth comes close to this powerful storm," says Leigh Fletcher, the study's lead author and a Cassini team scientist at the University of Oxford in the United Kingdom. "A storm like this is rare. This is only the sixth one to be recorded since 1876, and the last was way back in 1990."

This is the first major storm on Saturn observed by an orbiting spacecraft and studied at thermal infrared wavelengths, where Saturn's heat energy reveals atmospheric temperatures, winds and composition within the disturbance.

Temperature data were provided by the Very Large Telescope (VLT) on Cerro Paranal in Chile and Cassini's composite infrared spectrometer (CIRS), operated by NASA's Goddard Space Flight Center in Greenbelt, Md.

"Our new observations show that the storm had a major effect on the atmosphere, transporting energy and material over great distances, modifying the atmospheric winds -- creating meandering jet streams and forming giant vortices -- and disrupting Saturn's slow seasonal evolution," said Glenn Orton, a paper co-author, based at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

The violence of the storm -- the strongest disturbances ever detected in Saturn's stratosphere -- took researchers by surprise. What started as an ordinary disturbance deep in Saturn's atmosphere punched through the planet's serene cloud cover to roil the high layer known as the stratosphere.

"On Earth, the lower stratosphere is where commercial airplanes generally fly to avoid storms which can cause turbulence," says Brigette Hesman, a scientist at the University of Maryland in College Park who works on the CIRS team at Goddard and is the second author on the paper. "If you were flying in an airplane on Saturn, this storm would reach so high up, it would probably be impossible to avoid it."

Other indications of the storm's strength are the changes in the composition of the atmosphere brought on by the mixing of air from different layers. CIRS found evidence of such changes by looking at the amounts of acetylene and phosphine, both considered to be tracers of atmospheric motion. A separate analysis using Cassini's visual and infrared mapping spectrometer, led by Kevin Baines of JPL, confirmed the storm is very violent, dredging up larger atmospheric particles and churning up ammonia from deep in the atmosphere in volumes several times larger than previous storms. Other Cassini scientists are studying the evolving storm, and a more extensive picture will emerge soon.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The mission is managed by JPL for NASA's Science Mission Directorate in Washington. The European Southern Observatory in Garching, Germany operates the VLT in Chile. JPL is a division of the California Institute of Technology in Pasadena.

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Launching Balloons in Antarctica

They nicknamed it the "Little Balloon That Could." Launched in December of 2010 from McMurdo Station in Antarctica, the research balloon was a test run and it bobbed lower every day like it had some kind of leak. But every day for five days it rose back up in the sky to some 112,000 feet in the air.

Down on Earth, physicist Robyn Millan was cheering it on, hoping the test launch would bode well for the success of her grand idea: launches in 2013 and 2014 of 20 such balloons to float in the circular wind patterns above the South Pole. Each balloon will help track electrons from space that get swept up in Earth's magnetic field and slide down into our atmosphere. Such electrons are an integral part of the turbulent magnetic space weather system that extends from the sun to Earth.

A professor at Dartmouth College, Millan is the principal investigator for a project called BARREL, or Balloon Array for RBSP Relativistic Electron Losses. Millan's proposal will work hand in hand with NASA's Radiation Belt Space Probes (RBSP) mission, two NASA spacecraft due to launch in 2012 to study a mysterious part of Earth's magnetic environs called the Van Allen radiation belts. The radiation belts are made up of two regions, each one a gigantic donut of protons and electrons that surrounds Earth.

"We're both looking at the loss of particles from the radiation belts," says Millan. "RBSP sits in space near the equatorial plane and looks at the particles along magnetic field lines there. These particles come into our atmosphere – following magnetic field lines to their base at the Poles – and produce X-rays. BARREL measures those X-rays. Together we can combine measurements of the same set of particles."

Figuring out what causes this rain of electrons will do more than simply improve understanding of the physics behind what drives such high-energy particles. The charged particles within the radiation belts can damage sensitive electronics on spacecraft like those used for global positioning systems and communications, and can injure humans in space. (The electrons don't make it all the way to Earth, so pose no danger to those of us on the ground.) Experiments like BARREL and RBSP help us understand the processes and mitigate those risks.

Millan began working on balloons during her graduate work at University of California, Berkeley, where she studied physics. She worked on a balloon called MAXIS that focused on electron precipitation from the magnetosphere into the ionosphere. "Then," she says, "We got this idea. They launch these huge payloads in Antarctica, but before that they send up smaller test balloons to make sure conditions are right for the big launch. And we thought – what if you could put instruments on those? So we took our payload, and miniaturized it."

She and her team, which includes scientists and students at UC Berkeley, UC Santa Cruz, and University of Washington, set about making payloads that weigh only 50 pounds for balloons that are some 90 feet in diameter. That still sounds fairly big unless you know that the typical balloons launched in Antarctica are the size of a football field and carry payloads of some 3,000 pounds. The team received funding from the National Science Foundation to fly a total of six small balloons in 2005, and shortly thereafter she learned that NASA had put out a call for experiments to support RBSP.

David Sibeck, the project scientist for RBSP at Goddard Space Flight Center in Greenbelt, Md., recalls that Millan's project proposal was well-tailored to RBSP's goals. "One of RBSP's main challenges will be to differentiate between the hordes of theories that try to explain why the belts wax and wane over time," Sibeck says. "The RBSP spacecraft will be equipped to distinguish between different options, but Millan's balloons have an advantage in one specific area: they can measure particles that break out of the belts and make it all the way to Earth's atmosphere."

The first test of BARREL -- funded by NASA and also supported by NSF's Office of Polar Programs that supports logistics of all research in Antarctica -- began in December of 2008. The final one began this past winter, when Millan left New Hampshire for Antarctica on Nov. 15. She arrived in McMurdo Station – after a transfer in Christ Church, New Zealand and a day lost due to crossing the date line – on Nov. 19. This flight needed to test travel and ease of launch capabilities as much as anything else, so Millan's team had shipped all the balloons ready to fly. Once in Antarctica, she and her colleague, Brett Anderson, a Dartmouth graduate student, got to work unpacking.

"It was great," she says. "We just had to pull them out of the box and turn them on. We mounted their solar panels and with just two people we were able to get things ready really fast, which isn't always the easiest thing to do when in Antarctica."

One reason to do such electron research at the Poles is that Earth's magnetic field lines touch down there. But equally important for this campaign are the slowly circling wind patterns that set up each summer. The BARREL project will release another balloon every 1-2 days and each should fall into line, consistently buoyed by the winds along the same circular path.

This past December – which is, of course, the summer in Antarctica – it took longer than normal for those winds, known as circumpolar winds, to set up. So when the first balloon was launched – a process spearheaded by the Columbia Scientific Balloon Facility -- it floated straight North towards Tasmania. This was the balloon that came to be known as The Little Balloon That Could, says Millan: "Perhaps it had a very small hole, but it didn't quite make it as high as it was supposed to – some 120,000 feet. It only ever got to 112,000 feet, but it maintained that height doggedly and even sent back some interesting data as it flew through an X-ray aurora.” A second balloon did hit the right wind current, successfully transmitting data. (The second balloon did, however, have to be cut down a little early due to an overheated battery.)

So now the BARREL team will begin work on preparing the real show – two campaigns of 20 balloons each that will be launched during the 2012 to 2014 time frame.

"Her balloons will work in conjunction with RBSP," says Sibeck. "She can let us know if they're seeing particles and RBSP can look for the events that might be scattering them out of the radiation belts down to Earth." In addition, since each balloon is meant to stay aloft for 10 days, they will cover a huge area in the sky. When RBSP spots an interesting phenomenon, BARREL can give feedback over a large area as to where the particles went. The team will be able to see how big that region is and measure the total amount of particles that get kicked out of the belts – and thus determine how big of an effect different phenomena have. "That's something we would have more trouble doing with the spacecraft," says Sibeck.

Once each balloon is launched it moves slowly by floating in the wind. Those on the ground cannot control it, other than the single command to terminate the mission. A small explosive detonates and cuts the cable to the payload, which then floats down to the ground on a parachute. This was the fate of the two test balloons in December 2010, though they were particularly sorry to cut down the Little Balloon That Could. "We really wanted to see how far it would go," says Millan. "But it was so far north that we were getting close to Australian air space and we had to cut it down."

So the team declared the test a success, packed up their gear and began the long trip home to New Hampshire to oversee the building of 45 more payloads.

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