samedi 2 août 2014

United Launch Alliance Successfully Launches Two Rockets in Just Four Days















ULA - Atlas V / GPS IIF-7 Launch poster.


Aug. 2, 2014


Image above: A United Launch Alliance (ULA) Atlas V rocket carrying the seventh Global Positioning System (GPS) IIF (GPS IIF-7) satellite.

A United Launch Alliance (ULA) Atlas V rocket carrying the seventh Global Positioning System (GPS) IIF (GPS IIF-7) satellite for the U.S. Air Force launched at 11:23 p.m. EDT yesterday from Space Launch Complex-41. This is the second successful ULA launch in just four days.

“Congratulations to the U.S. Air Force and all of our mission partners on the successful launch of the Atlas V carrying the GPS IIF-7 satellite,” said Jim Sponnick, ULA vice president, Atlas and Delta Programs. “ULA launch vehicles have delivered all of the current generation of GPS satellites, which are providing ever-improving capabilities for users around the world.”

video
Atlas V GPS IIF-7 Launch Highlights

This mission was launched aboard an Atlas V Evolved Expendable Launch Vehicle (EELV) 401 configuration vehicle, which includes a 4-meter-diameter payload fairing.  The Atlas booster for this mission was powered by the RD AMROSS RD-180 engine, and the Centaur upper stage was powered by a single Aerojet Rocketdyne RL10A engine.

“This launch marks the third time this year ULA has successfully launched two missions within a week,” said Sponnick “The ULA team’s focus on mission success, one launch at a time, allows us to be ready when our customers are ready to launch.”

GPS IIF-7 is the seventh in a series of next-generation GPS satellites and will join a worldwide timing and navigation system utilizing 24 satellites in six different planes, with a minimum of four satellites per plane positioned in orbit approximately 11,000 miles above the Earth’s surface. The GPS IIF series provides improved accuracy and enhanced performance for GPS users.

GPS satellite

ULA's next launch is the Atlas V WorldView-3 mission for DigitalGlobe scheduled for Aug. 13 from Space Launch Complex-3 at Vandenberg Air Force Base, California.

The EELV program was established by the United States Air Force to provide assured access to space for Department of Defense and other government payloads. The commercially developed EELV program supports the full range of government mission requirements, while delivering on schedule and providing significant cost savings over the heritage launch systems. 

With more than a century of combined heritage, United Launch Alliance is the nation’s most experienced and reliable launch service provider. ULA has successfully delivered more than 80 satellites to orbit that provide critical capabilities for troops in the field, aid meteorologists in tracking severe weather, enable personal device-based GPS navigation and unlock the mysteries of our solar system. ULA – Bringing rocket science down to Earth.

For more information on ULA, visit the ULA website at http://www.ulalaunch.com

Images, Video, Text, Credits: ULA / The Gunter Space Page.

Greetings, Orbiter.ch

vendredi 1 août 2014

NASA’s MESSENGER Spacecraft: 10 Years in Space












NASA - MESSENGER Mission to Mercury patch.

August 1, 2014

Ten years ago, on August 3, 2004, NASA’s MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) spacecraft blasted off from Cape Canaveral, Florida, for a risky mission that would take the small satellite dangerously close to Mercury’s surface, paving the way for an ambitious study of the planet closest to the Sun.

The spacecraft traveled 4.9 billion miles (7.9 billion kilometers) — a journey that included 15 trips around the Sun and flybys of Earth once, Venus twice, and Mercury three times — before it was inserted into orbit around its target planet in 2011.

video
MESSENGER Flies Over Mercury

Video above: In celebration of the 10th anniversary of its launch, the MESSENGER team released this movie showing a flyover of Mercury. The movie is sped up by a factor of seven for ease of viewing. Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory.

“We have operated successfully in orbit for more than three Earth years and more than 14 Mercury years as we celebrate this amazing 10th anniversary milestone,” said MESSENGER Mission Operations Manager Andy Calloway, of the Johns Hopkins University Applied Physics Laboratory (APL). “The MESSENGER spacecraft operates in one of the most challenging and demanding space environments in our Solar System, and we have met that challenge directly through innovation and hard work, as exemplified by the stunning discoveries and data return achievements. Our only regret is that we have insufficient propellant to operate another 10 years, but we look forward to the incredible science returns planned for the final eight months of the mission.”

MESSENGER is only the second spacecraft sent to Mercury. Mariner 10 flew past it three times in 1974 and 1975 and gathered detailed data on less than half the surface. MESSENGER took advantage of an ingenious trajectory design, lightweight materials, and miniaturization of electronics, all developed in the three decades since Mariner 10 flew past Mercury.


Image above: MESSENGER captured the images in the flyover movie during this flight path over Mercury's north polar region. Image Credit: NASA.

“It was quite challenging to design and execute a trajectory that could culminate in Mercury orbit,” said Mission and Spacecraft Systems Engineer Dan O’Shaughnessy, of APL. “Designing an attendant spacecraft that was light enough to carry the necessary propellant to execute such a trajectory with enough room left over for a payload capable of global characterization of the planet is an impressive accomplishment.”

Additionally, he said, “the team’s concept of operations that streamlines planning while optimizing the use of our payload — despite substantial thermal and power constraints — is an amazing feat.”

MESSENGER Deputy Principal Investigator Larry Nittler, of the Carnegie Institution of Washington, said that the mission has rewritten scientists’ understanding of the planet “and given us plenty of surprises.”

“Geochemical measurements have revealed a surface poor in iron, but rich in moderately volatile elements such as sulfur and sodium,” said Nittler. “These results rule out some long-standing theories put forward to explain Mercury’s anomalously high density compared with the other planets in the inner solar system,” he explained. “Maps of elemental abundances show that the interior is highly chemically heterogeneous, providing important clues to the early geological history of the planet.”


Image above: A closeup view from the 50 meters per pixel strip of images MESSENGER took during it's flyover of Mercury's north polar region. Image Credit: NASA.

View Full Flyover Image Strip: http://www.nasa.gov/sites/default/files/files/MESSENGER_flyover_movie_mosaicstrip_50mpp.jpg

“MESSENGER observations have also shown that Mercury’s surface was shaped by volcanic activity, identified unique landforms shaped by loss of volatile materials, and confirmed the presence of large amounts of water ice protected from the Sun’s heat within permanently shadowed impact craters near the planet’s poles,  said Nittler.

“We have found that the complex interplay of the interplanetary magnetic field with that of Mercury results in a remarkably dynamic electromagnetic environment surrounding the planet, including unexplained bursts of electrons and highly variable distributions of different elements in the thin exosphere,” Nittler added. “Over the next few months, MESSENGER will observe Mercury at lower altitudes and thus smaller spatial scales than ever before, and this is sure to result both in exciting scientific discoveries and new puzzles about our solar system’s enigmatic innermost planet.”

In celebration of the 10th anniversary of its launch, the MESSENGER team has released a movie acquired during an early stage of MESSENGER’s low-altitude campaign. The movie provides a bird’s-eye view of what the spacecraft sees as it flies over the planet at close range and was assembled from 214 images taken by the narrow-angle camera (NAC) on June 8, 2014. The NAC’s field of view looked toward the horizon along the direction of MESSENGER's motion as the probe crossed the terminator into night.


Image above: Infographic with statistics on the MESSENGER mission. Image Credit: NASA.

“This view is what a traveler on the MESSENGER spacecraft might see during low-altitude operations in the coming year,” noted MESSENGER Co-Investigator Scott Murchie of APL. “During the final phase of its mission, MESSENGER's science instruments will use low-altitude operations like this to explore the surface and subsurface of Mercury at unprecedented resolution.”

The image frames were taken once per second while MESSENGER was at altitudes ranging from 115 to 165 kilometers, traveling at a speed of 3.7 kilometers per second relative to the surface. The movie is sped up by a factor of six for ease of viewing.

The images have resolutions ranging from 21 to 45 meters/pixel. Higher-resolution images of Mercury’s surface are possible if the camera is pointed directly below the spacecraft rather than looking to the horizon, and such operations will be the routine approach for low-altitude imaging in the coming year. The movie starts in the far north, east of the large crater Gaudí, passes over two unnamed craters just north of the crater Yoshikawa, over the large impact basin Lismer, north of the crater Van Dijck, and ends in the plains between the craters Nizami and Jókai. Many craters in this polar region are believed to host water ice in their permanently shadowed interiors.

“Our spacecraft team is delighted to celebrate the 10th anniversary of MESSENGER’s launch,” adds MESSENGER Principal Investigator Sean Solomon, of Columbia University’s Lamont-Doherty Earth Observatory. “In the past decade, observations by our resilient probe have deepened our understanding of both rocky planets and the dynamics of the inner heliosphere. As the new video demonstrates, however, some of the most exciting observations from the mission are still to come. We can expect new surprises as we view the innermost planet and its environment from closer range than ever before achieved by spacecraft.”

For more information about MESSENGER Mission, visit: http://www.nasa.gov/mission_pages/messenger/main/

Images, Video, Text, Credits: NASA/Johns Hopkins University Applied Physics Laboratory.

Greetings, Orbiter.ch

Rosetta’s Comet: Imaging the Coma









ESA - Rosetta Mission logo.

1 August 2014

Less than a week before Rosetta's rendezvous with comet 67P/Churyumov-Gerasimenko, images obtained by OSIRIS, the spacecraft's onboard scientific imaging system, show clear signs of a coma surrounding the comet's nucleus.

A new image from July 25, 2014, clearly reveals an extended coma shrouding 67P's nucleus. "Our coma images cover an area of 150 by 150 square kilometers (90 by 90 square miles)," said Luisa Lara from the Institute of Astrophysics in Andalusia, Spain. Most likely these images show only the inner part of the coma, where particle densities are highest. Scientist expect that 67P's full coma actually reaches much farther.


Image above: The nucleus of comet 67P/Churyumov-Gerasimernko as seen by Rosetta's OSIRIS instrument from a distance of 1,210 miles (1,950 kilometers) on July 29, 2014. Image Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM.

In the current image, the hazy, bright, circular structure to the right of the comet's nucleus is an artifact of the OSIRIS optical system. The center of the image located around the position of the nucleus is overexposed here.

Other new images of the comet's nucleus confirm the collar-like appearance of the neck region, which appears brighter than most parts of the comet's body and head. Possible explanations range from differences in material or grain size to topological effects.


Image above: This Rosetta OSIRIS image of the coma of comet 67P/Churyumov-Gerasimenko was taken on July 25, 2014. It covers an area about 90 miles (150 kilometers) across. Image Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM.

Rosetta is a European Space Agency mission with contributions from its member states and NASA.

The scientific imaging system, OSIRIS, was built by a consortium led by the Max Planck Institute for Solar System Research (Germany) in collaboration with Center of Studies and Activities for Space, University of Padua (Italy), the Astrophysical Laboratory of Marseille (France), the Institute of Astrophysics of Andalusia, CSIC (Spain), the Scientific Support Office of the European Space Agency (Netherlands), the National Institute for Aerospace Technology (Spain), the Technical University of Madrid (Spain), the Department of Physics and Astronomy of Uppsala University (Sweden) and the Institute of Computer and Network Engineering of the TU Braunschweig (Germany). OSIRIS was financially supported by the national funding agencies of Germany (DLR), France (CNES), Italy (ASI), Spain, and Sweden and the ESA Technical Directorate.

Rosetta's Philae lander is provided by a consortium led by DLR, Max Planck Institute for Solar System Research, CNES and ASI. Rosetta will be the first mission in history to rendezvous with a comet, escort it as it orbits the sun, and deploy a lander to its surface.

NASA's Jet Propulsion Laboratory, Pasadena, California, a division of the California Institute of Technology, also in Pasadena, manages the U.S. participation in the Rosetta mission for NASA's Science Mission Directorate in Washington. Rosetta carries three NASA instruments in its 21-instrument payload.

For more information on the U.S. instruments aboard Rosetta, visit: http://rosetta.jpl.nasa.gov

More information about Rosetta is available at: http://www.esa.int/rosetta

Images (mentioned), Text, Credits: NASA / Dwayne Brown / JPL / Preston Dyches / European Space Agency / Markus Bauer / Max Planck Institute for Solar System Research / Birgit Krummheuer.

Best regards, Orbiter.ch

Transport cargo ship Progress M-23M has completed its mission











ROSCOSMOS - Russian Vehicles patch.

01.08.2014

August 1 at 02:42 MSK in a predetermined area of the Pacific Ocean produced flooding incombustible residue cargo vehicle (THC) Progress M-23M. In accordance with the program laid down in the ship's on-board computer specialists Mission Control Center (MCC) FSUE TsNIIMash on "space truck" was included on the inhibition of the propulsion system, and then began a controlled reduction of THC from orbit.

Rocket Soyuz-U with (THC) Progress M-23M was launched from the Baikonur cosmodrome April 9, 2014 at 19 hours 26 minutes Moscow time. April 10, 2014 in 1 hour 20 minutes Moscow time was out docking the cargo spacecraft Progress M-23M from the International Space Station. Docked to the docking bay, Pierce (DC1) of the Russian segment of the ISS the undocking was performed in automatic mode.

Progress M-23M

Cargo spaceship delivered to the ISS more than 2.5 tonnes of goods: fuel, food, send the crew, equipment, water and other consumable materials necessary for the operation of the station in manned mode. In the ISS (TGC) Progress M-23M was docked 104 days.

Undocking TGC to the ISS on July 22, 2014 at 01:44 MSK. After her Progress for 10 days in the free flight, during which the experiment was conducted Radar-Progress. The purpose of this experiment is to determine the spatial and temporal dependencies of density, temperature, ionic composition local ionospheric inhomogeneities resulting from the on-board liquid-propellant rocket engines. The experiment has been involved full-time equipment: propulsion, radio VHF (TORU), as well as ground-based radio observations of the complex.

ROSCOSMOS Press Release: http://www.federalspace.ru/20811/

Image, Text, Credits: Roscosmos press service / ROSCOSMOS / NASA / Translation: Orbiter.ch Aerospace.

Rosetta takes comet’s temperature












ESA - Rosetta Mission patch.

1 August 2014

ESA’s Rosetta spacecraft has made its first temperature measurements of its target comet, finding that it is too hot to be covered in ice and must instead have a dark, dusty crust.

The observations of comet 67P/Churyumov–Gerasimenko were made by Rosetta’s visible, infrared and thermal imaging spectrometer, VIRTIS, between 13 and 21 July, when Rosetta closed in from 14 000 km to the comet to just over 5000 km.

Rosetta measures comet’s temperature. Image Credit: ESA

At these distances, the comet covered only a few pixels in the field of view and so it was not possible to determine the temperatures of individual features. But, using the sensor to collect infrared light emitted by the whole comet, scientists determined that its average surface temperature is about –70ºC.

The comet was roughly 555 million kilometres from the Sun at the time – more than three times further away than Earth, meaning that sunlight is only about a tenth as bright.

Although –70ºC may seem rather cold, importantly, it is some 20–30ºC warmer than predicted for a comet at that distance covered exclusively in ice.

“This result is very interesting, since it gives us the first clues on the composition and physical properties of the comet’s surface,” says VIRTIS principal investigator Fabrizio Capaccioni from INAF-IAPS, Rome, Italy.

Indeed, other comets such as 1P/Halley are known to have very dark surfaces owing to a covering of dust, and Rosetta’s comet was already known to have a low reflectance from ground-based observations, excluding an entirely ‘clean’ icy surface.

The temperature measurements provide direct confirmation that much of the surface must be dusty, because darker material heats up and emits heat more readily than ice when it is exposed to sunlight.


Animation above: mages of comet 67P/Churyumov-Gerasimenko taken on July 14, 2014, by the OSIRIS imaging system aboard the European Space Agency's Rosetta spacecraft have allowed scientists to create this three-dimensional shape model of the nucleus. Image Credit: ESA/Rosetta/MPS for OSIRIS Team/MPS/UPD/LAM/IAA/SSO/INTA/UPM.

“This doesn’t exclude the presence of patches of relatively clean ice, however, and very soon, VIRTIS will be able to start generating maps showing the temperature of individual features,” adds Dr Capaccioni.

In addition to global measurements, the sensor will study the variation of the daily surface temperature of specific areas of the comet, in order to understand how quickly the surface reacts to solar illumination.

In turn, this will provide insight into the thermal conductivity, density and porosity of the top tens of centimetres of the surface. This information will be important in selecting a target site for Rosetta’s lander, Philae.

It will also measure the changes in temperature as the comet flies closer to the Sun along its orbit, providing substantially more heating of the surface.

“Combined with observations from the other 10 science experiments on Rosetta and those on the lander, VIRTIS will provide a thorough description of the surface physical properties and the gases in the comet’s coma, watching as conditions change on a daily basis and as the comet loops around the Sun over the course of the next year,” says Matt Taylor, ESA’s Rosetta project scientist.

“With only a few days until we arrive at just 100 km distance from the comet, we are excited to start analysing this fascinating little world in more and more detail.”

More about Rosetta:

Rosetta is an ESA mission with contributions from its member states and NASA. Rosetta’s Philae lander is provided by a consortium led by DLR, MPS, CNES and ASI. Rosetta will be the first mission in history to rendezvous with a comet, escort it as it orbits the Sun, and deploy a lander.

Comets are time capsules containing primitive material left over from the epoch when the Sun and its planets formed. By studying the gas, dust and structure of the nucleus and organic materials associated with the comet, via both remote and in-situ observations, the Rosetta mission should become the key to unlocking the history and evolution of our Solar System, as well as answering questions regarding the origin of Earth’s water and perhaps even life.

Related links:

Rosetta’s visible, infrared and thermal imaging spectrometer (VIRTIS): http://www.esa.int/Our_Activities/Space_Science/S

More about VIRTIS: http://www.esa.int/Our_Activities/Space_Science/Rosetta/More_about_VIRTIS

Europe's comet chaser: http://www.esa.int/Our_Activities/Space_Science/Rosetta/Europe_s_comet_chaser

Rosetta at Astrium: http://www.astrium.eads.net/en/programme/rosetta-1go.html

Rosetta at DLR: http://www.dlr.de/dlr/en/desktopdefault.aspx/tabid-10394/

Ground-based comet observation campaign: http://www.rosetta-campaign.net/home

Rosetta Blog: http://blogs.esa.int/rosetta/

Images (mentioned), Text, Credit: ESA.

Cheers, Orbiter.ch

jeudi 31 juillet 2014

New NASA Research Shows Giant Asteroids Battered Early Earth










NASA / AMES Research Center logo.

July 30, 2014

New research shows that more than four billion years ago the surface of Earth was heavily reprocessed – or melted, mixed, and buried – as a result of giant asteroid impacts. A new terrestrial bombardment model, calibrated using existing lunar and terrestrial data, sheds light on the role asteroid collisions played in the evolution of the uppermost layers of the early Earth during the geologic eon called the "Hadean" (approximately 4 to 4.5 billion years ago).


Image above: An artistic conception of the early Earth, showing a surface pummeled by large impact, resulting in extrusion of deep seated magma onto the surface. At the same time, distal portion of the surface could have retained liquid water. Image Credit: Simone Marchi.

An international team of researchers from academic and government institutions, including NASA's Solar System Exploration Research Virtual Institute (SSERVI) at NASA's Ames Research Center in Moffett Field, California, published their findings in a paper, "Widespread Mixing and Burial of Earth's Hadean Crust by Asteroid Impacts" in the July 31, 2014 issue of Nature.

"A large asteroid impact could have buried a substantial amount of Earth's crust with impact-generated melt," said Yvonne Pendleton, SSERVI Director at Ames. "This new model helps explain how repeated asteroid impacts may have buried Earth's earliest and oldest rocks."

Terrestrial planet formation models indicate Earth went through a sequence of major growth phases: initially accretion of planetesimals – planetary embryos – over many tens of millions of years, then a giant impact by a large proto-planet that led to the formation of our moon, followed by the late bombardment when giant asteroids several tens to hundreds of miles in size periodically hit ancient Earth, dwarfing the one that killed the dinosaurs (estimated to be six miles in size) only 65 million years ago.

Researchers estimate accretion during the late bombardment contributed less than one percent of Earth's present-day mass, but the giant asteroid impacts still had a profound effect on the geological evolution of early Earth. Prior to four billion years ago Earth was resurfaced over and over by voluminous impact-generated melt. Furthermore, large collisions as late as about four billion years ago may have repeatedly boiled away existing oceans into steamy atmospheres. Despite the heavy bombardment, the findings are compatible with the claim of liquid water on Earth's surface as early as about 4.3 billion years ago based on geochemical data.

The new research reveals that asteroidal collisions not only severely altered the geology of the Hadean eon Earth, but likely also played a major role in the subsequent evolution of life on Earth as well.

"Prior to approximately four billion years ago, no large region of Earth's surface could have survived untouched by impacts and their effects," said Simone Marchi, SSERVI senior researcher at the Southwest Research Institute in Boulder, Colorado, and the paper's lead author. "The new picture of the Hadean Earth emerging from this work has important implications for its habitability."


Image above: Spatial distribution and sizes of craters formed on the early Earth. Each circle indicates the final estimated crater size. Color-coding indicates the time of impact. Image Credit: Simone Marchi et al. 2014.

Large impacts had particularly severe effects on existing ecosystems. Researchers found that on average, Hadean Earth more than four billion years ago could have been hit by one to four impactors that were more than 600 miles wide and capable of global sterilization, and by three to seven impactors more than 300 miles wide and capable of global ocean vaporization.

"During that time, the lag between major collisions was long enough to allow intervals of more clement conditions, at least on a local scale," said Marchi. "Any life emerging during the Hadean eon likely needed to be resistant to high temperatures, and could have survived such a violent period in Earth’s history by thriving in niches deep underground or in the ocean’s crust.”

The research was an international effort led by Marchi and William Bottke from the Southwest Research Institute in Boulder; Linda Elkins-Tanton from Carnegie Institution for Science in Washington; Michael Bierhaus and Kai Wünnemann from the Museum fur Naturkunde in Berlin, Germany; Alessandro Morbidelli from Observatoire de la Côte d'Azur in Nice, France, and David Kring from the Universities Space Research Association and Lunar and Planetary Institute in Houston.

The research was supported in part by SSERVI, a virtual institute that, with international partnerships, brings science and exploration researchers together in a collaborative virtual setting. SSERVI is funded by the Science Mission Directorate and Human Exploration and Operations Mission Directorate at NASA Headquarters in Washington.

For more information about SSERVI and selected member teams, visit: http://sservi.nasa.gov

Images (mentioned), Text, Credits: NASA / Ames Research Center / Rachel Hoover.

Best regards, Orbiter.ch

NASA's Fermi Space Telescope Reveals New Source of Gamma Rays











NASA - Fermi Gamma-ray Space Telescope logo.

July 31, 2014

Observations by NASA's Fermi Gamma-ray Space Telescope of several stellar eruptions, called novae, firmly establish these relatively common outbursts almost always produce gamma rays, the most energetic form of light.


Image above: These images show Fermi data centered on each of the four gamma-ray novae observed by the LAT. Colors indicate the number of detected gamma rays with energies greater than 100 million electron volts (blue indicates lowest, yellow highest). Image Credit: NASA/DOE/Fermi LAT Collaboration.

"There's a saying that one is a fluke, two is a coincidence, and three is a class, and we're now at four novae and counting with Fermi," said Teddy Cheung, an astrophysicist at the Naval Research Laboratory in Washington, and the lead author of a paper reporting the findings in the Aug. 1 edition of the journal Science.

A nova is a sudden, short-lived brightening of an otherwise inconspicuous star caused by a thermonuclear explosion on the surface of a white dwarf, a compact star not much larger than Earth. Each nova explosion releases up to 100,000 times the annual energy output of our sun. Prior to Fermi, no one suspected these outbursts were capable of producing high-energy gamma rays, emission with energy levels millions of times greater than visible light and usually associated with far more powerful cosmic blasts.

Fermi's Large Area Telescope (LAT) scored its first nova detection, dubbed V407 Cygni, in March 2010. The outburst came from a rare type of star system in which a white dwarf interacts with a red giant, a star more than a hundred times the size of our sun. Other members of the same unusual class of stellar system have been observed "going nova" every few decades.


Image above: The white dwarf star in V407 Cygni, shown here in an artist's concept, went nova in 2010. Scientists think the outburst primarily emitted gamma rays (magenta) as the blast wave plowed through the gas-rich environment near the system's red giant star. Image Credit: NASA's Goddard Space Flight Center/S. Wiessinger.

In 2012 and 2013, the LAT detected three so-called classical novae which occur in more common binaries where a white dwarf and a sun-like star orbit each other every few hours.

"We initially thought of V407 Cygni as a special case because the red giant's atmosphere is essentially leaking into space, producing a gaseous environment that interacts with the explosion's blast wave," said co-author Steven Shore, a professor of astrophysics at the University of Pisa in Italy. "But this can't explain more recent Fermi detections because none of those systems possess red giants."

Fermi detected the classical novae V339 Delphini in August 2013 and V1324 Scorpii in June 2012, following their discovery in visible light. In addition, on June 22, 2012, the LAT discovered a transient gamma-ray source about 20 degrees from the sun. More than a month later, when the sun had moved farther away, astronomers looking in visible light discovered a fading nova from V959 Monocerotis at the same position.

Astronomers estimate that between 20 and 50 novae occur each year in our galaxy. Most go undetected, their visible light obscured by intervening dust and their gamma rays dimmed by distance. All of the gamma-ray novae found so far lie between 9,000 and 15,000 light-years away, relatively nearby given the size of our galaxy.


Image above: Novae typically originate in binary systems containing sun-like stars, as shown in this artist's rendering. A nova in a system like this likely produces gamma rays (magenta) through collisions among multiple shock waves in the rapidly expanding shell of debris. Image Credit: NASA's Goddard Space Flight Center/S. Wiessinger.

Novae occur because a stream of gas flowing from the companion star piles up into a layer on the white dwarf's surface. Over time -- tens of thousands of years, in the case of classical novae, and several decades for a system like V407 Cygni -- this deepening layer reaches a flash point. Its hydrogen begins to undergo nuclear fusion, triggering a runaway reaction that detonates the accumulated gas. The white dwarf itself remains intact.

One explanation for the gamma-ray emission is that the blast creates multiple shock waves that expand into space at slightly different speeds. Faster shocks could interact with slower ones, accelerating particles to near the speed of light. These particles ultimately could produce gamma rays.

"This colliding-shock process must also have been at work in V407 Cygni, but there is no clear evidence for it," said co-author Pierre Jean, a professor of astrophysics at the University of Toulouse in France. This is likely because gamma rays emitted through this process were overwhelmed by those produced as the shock wave interacted with the red giant and its surroundings, the scientists conclude.

NASA's Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership managed by the agency's Goddard Space Flight Center in Greenbelt, Maryland. It was developed in collaboration with the U.S. Department of Energy, with contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.

For more information about Fermi, visit: http://www.nasa.gov/fermi

Related Links:

Paper: "Fermi Establishes Classical Novae as a Distinct Class of Gamma-Ray Sources": http://www.sciencemag.org/content/345/6196/554.abstract

"Fermi Detects 'Shocking' Surprise from Supernova's Little Cousin" (08.12.2010): http://www.nasa.gov/mission_pages/GLAST/news/shocking-nova.html

Imagine the Universe! Cataclysmic Variables: http://imagine.gsfc.nasa.gov/docs/science/know_l2/cataclysmic_variables.html

Images (mentioned), Text, Credits: NASA / J.D. Harrington / Goddard Space Flight Center / Lynn Chandler.

Cheers, Orbiter.ch

NASA Announces Mars 2020 Rover Payload to Explore the Red Planet as Never Before











NASA logo.

July 31, 2014

The next rover NASA will send to Mars in 2020 will carry seven carefully-selected instruments to conduct unprecedented science and exploration technology investigations on the Red Planet.


Image above: An artist concept image of where seven carefully-selected instruments will be located on NASA’s Mars 2020 rover. The instruments will conduct unprecedented science and exploration technology investigations on the Red Planet as never before. Image Credit: NASA.

NASA announced the selected Mars 2020 rover instruments Thursday at the agency's headquarters in Washington. Managers made the selections out of 58 proposals received in January from researchers and engineers worldwide. Proposals received were twice the usual number submitted for instrument competitions in the recent past. This is an indicator of the extraordinary interest by the science community in the exploration of the Mars. The selected proposals have a total value of approximately $130 million for development of the instruments.

The Mars 2020 mission will be based on the design of the highly successful Mars Science Laboratory rover, Curiosity, which landed almost two years ago, and currently is operating on Mars. The new rover will carry more sophisticated, upgraded hardware and new instruments to conduct geological assessments of the rover's landing site, determine the potential habitability of the environment, and directly search for signs of ancient Martian life.

"Today we take another important step on our journey to Mars," said NASA Administrator Charles Bolden.” While getting to and landing on Mars is hard, Curiosity was an iconic example of how our robotic scientific explorers are paving the way for humans to pioneer Mars and beyond. Mars exploration will be this generation’s legacy, and the Mars 2020 rover will be another critical step on humans' journey to the Red Planet."


Image above: Planning for NASA's 2020 Mars rover envisions a basic structure that capitalizes on the design and engineering work done for the NASA rover Curiosity, which landed on Mars in 2012, but with new science instruments selected through competition for accomplishing different science objectives. Mars 2020 is a mission concept that NASA announced in late 2012 to re-use the basic engineering of Mars Science Laboratory to send a different rover to Mars, with new objectives and instruments, launching in 2020. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, manages NASA's Mars Exploration Program for the NASA Science Mission Directorate, Washington. Image Credit: NASA/JPL-Caltech.

Scientists will use the Mars 2020 rover to identify and select a collection of rock and soil samples that will be stored for potential return to Earth by a future mission. The Mars 2020 mission is responsive to the science objectives recommended by the National Research Council's 2011 Planetary Science Decadal Survey.

“The Mars 2020 rover, with these new advanced scientific instruments, including those from our international partners, holds the promise to unlock more mysteries of Mars’ past as revealed in the geological record,” said John Grunsfeld, astronaut and associate administrator of NASA's Science Mission Directorate in Washington. “This mission will further our search for life in the universe and also offer opportunities to advance new capabilities in exploration technology.”

The Mars 2020 rover also will help advance our knowledge of how future human explorers could use natural resources available on the surface of the Red Planet. An ability to live off the Martian land would transform future exploration of the planet. Designers of future human expeditions can use this mission to understand the hazards posed by Martian dust and demonstrate technology to process carbon dioxide from the atmosphere to produce oxygen. These experiments will help engineers learn how to use Martian resources to produce oxygen for human respiration and potentially oxidizer for rocket fuel.

"The 2020 rover will help answer questions about the Martian environment that astronauts will face and test technologies they need before landing on, exploring and returning from the Red Planet," said William Gerstenmaier, associate administrator for the Human Exploration and Operations Mission Directorate at NASA Headquarters in Washington. "Mars has resources needed to help sustain life, which can reduce the amount of supplies that human missions will need to carry. Better understanding the Martian dust and weather will be valuable data for planning human Mars missions. Testing ways to extract these resources and understand the environment will help make the pioneering of Mars feasible."

The selected payload proposals are:

-   Mastcam-Z, an advanced camera system with panoramic and stereoscopic imaging capability with the ability to zoom. The instrument also will determine mineralogy of the Martian surface and assist with rover operations. The principal investigator is James Bell, Arizona State University in Phoenix.

-   SuperCam, an instrument that can provide imaging, chemical composition analysis, and mineralogy. The instrument will also be able to detect the presence of organic compounds in rocks and regolith from a distance. The principal investigator is Roger Wiens, Los Alamos National Laboratory, Los Alamos, New Mexico. This instrument also has a significant contribution from the Centre National d’Etudes Spatiales,Institut de Recherche en Astrophysique et Plane’tologie (CNES/IRAP) France.

-   Planetary Instrument for X-ray Lithochemistry (PIXL), an X-ray fluorescence spectrometer that will also contain an imager with high resolution to determine the fine scale elemental composition of Martian surface materials. PIXL will provide capabilities that permit more detailed detection and analysis of chemical elements than ever before. The principal investigator is Abigail Allwood, NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California.

-   Scanning Habitable Environments with Raman & Luminescence for Organics and Chemicals (SHERLOC), a spectrometer that will provide fine-scale imaging and uses an ultraviolet (UV) laser to determine fine-scale mineralogy and detect organic compounds. SHERLOC will be the first UV Raman spectrometer to fly to the surface of Mars and will provide complementary measurements with other instruments in the payload. The principal investigator is Luther Beegle, JPL.

-   The Mars Oxygen ISRU Experiment (MOXIE), an exploration technology investigation that will produce oxygen from Martian atmospheric carbon dioxide. The principal investigator is Michael Hecht, Massachusetts Institute of Technology, Cambridge, Massachusetts.

-   Mars Environmental Dynamics Analyzer (MEDA), a set of sensors that will provide measurements of temperature, wind speed and direction, pressure, relative humidity and dust size and shape. The principal investigator is Jose Rodriguez-Manfredi, Centro de Astrobiologia, Instituto Nacional de Tecnica Aeroespacial, Spain.

The Radar Imager for Mars' Subsurface Exploration (RIMFAX), a ground-penetrating radar that will provide centimeter-scale resolution of the geologic structure of the subsurface. The principal investigator is Svein-Erik Hamran, Forsvarets Forskning Institute, Norway.

"We are excited that NASA's Space Technology Program is partnered with Human Exploration and the Mars 2020 Rover Team to demonstrate our abilities to harvest the Mars atmosphere and convert its abundant carbon dioxide to pure oxygen," said James Reuther, deputy associate administrator for programs for the Space Technology Mission Directorate. "This technology demonstration will pave the way for more affordable human missions to Mars where oxygen is needed for life support and rocket propulsion."

Instruments developed from the selected proposals will be placed on a rover similar to Curiosity, which has been exploring Mars since 2012. Using a proven landing system and rover chassis design to deliver these new experiments to Mars will ensure mission costs and risks are minimized as much as possible, while still delivering a highly capable rover.

Curiosity recently completed a Martian year on the surface -- 687 Earth days -- having accomplished the mission's main goal of determining whether Mars once offered environmental conditions favorable for microbial life.

The Mars 2020 rover is part the agency's Mars Exploration Program, which includes the Opportunity and Curiosity rovers, the Odyssey and Mars Reconnaissance Orbiter spacecraft currently orbiting the planet, and the MAVEN orbiter, which is set to arrive at the Red Planet in September and will study the Martian upper atmosphere.

In 2016, a Mars lander mission called InSight will launch to take the first look into the deep interior of Mars. The agency also is participating in the European Space Agency's (ESA’s) 2016 and 2018 ExoMars missions, including providing "Electra" telecommunication radios to ESA's 2016 orbiter and a critical element of the astrobiology instrument on the 2018 ExoMars rover.

NASA's Mars Exploration Program seeks to characterize and understand Mars as a dynamic system, including its present and past environment, climate cycles, geology and biological potential. In parallel, NASA is developing the human spaceflight capabilities needed for future round-trip missions to Mars.

NASA's Jet Propulsion Laboratory will build and manage operations of the Mars 2020 rover for the NASA Science Mission Directorate at the agency’s headquarters in Washington.

Related link:

Mars 2020 Rover and Beyond News Teleconference from NASA Headquarters in Washington DC: https://www.youtube.com/watch?v=1cRhU6bMLis&list=UULA_DiR1FfKNvjuUpBHmylQ

For more information about NASA's Mars programs, visit: http://www.nasa.gov/mars

Images (mentioned), Text, Credits: NASA / Dwayne Brown.

Best regards, Orbiter.ch

Hubble Shows Farthest Lensing Galaxy Yields Clues to Early Universe











NASA - Hubble Space Telescope patch.

July 31, 2014

Astronomers using NASA's Hubble Space Telescope have unexpectedly discovered the most distant galaxy that acts as a cosmic magnifying glass. Seen here as it looked 9.6 billion years ago, this monster elliptical galaxy breaks the previous record-holder by 200 million years.


Image above: The farthest cosmic lens yet found, a massive elliptical galaxy, is shown in the inset image at left. The galaxy existed 9.6 billion years ago and belongs to the galaxy cluster, IRC 0218. Image Credit: NASA and ESA.

These "lensing" galaxies are so massive that their gravity bends, magnifies, and distorts light from objects behind it, a phenomenon called gravitational lensing.  Finding one in such a small area of the sky is so rare that you would normally have to survey a region hundreds of times larger to find just one.

The object behind the cosmic lens is a tiny spiral galaxy undergoing a rapid burst of star formation. Its light has taken 10.7 billion years to arrive here and seeing this chance alignment at such a great distance from Earth is a rare find. Locating more of these distant lensing galaxies will offer insight into how young galaxies in the early universe build themselves up into the massive dark-matter-dominated galaxies of today. Dark matter cannot be seen, but it accounts for the bulk of the universe's matter.

"When you look more than 9 billion years ago in the early universe, you don't expect to find this type of galaxy lensing at all," explained lead researcher Kim-Vy Tran of Texas A&M University in College Station. "It's very difficult to see an alignment between two galaxies in the early universe. Imagine holding a magnifying glass close to you and then moving it much farther away. When you look through a magnifying glass held at arm's length, the chances that you will see an enlarged object are high. But if you move the magnifying glass across the room, your chances of seeing the magnifying glass nearly perfectly aligned with another object beyond it diminishes."

Team members Kenneth Wong and Sherry Suyu of Academia Sinica Institute of Astronomy & Astrophysics (ASIAA) in Taipei, Taiwan, used the gravitational lensing from the chance alignment to measure the giant galaxy's total mass, including the amount of dark matter, by gauging the intensity of its lensing effects on the background galaxy's light. The giant foreground galaxy weighs 180 billion times more than our sun and is a massive galaxy for its time. It is also one of the brightest members of a distant cluster of galaxies, called IRC 0218.

"There are hundreds of lens galaxies that we know about, but almost all of them are relatively nearby, in cosmic terms," said Wong, first author on the team's science paper. "To find a lens as far away as this one is a very special discovery because we can learn about the dark-matter content of galaxies in the distant past. By comparing our analysis of this lens galaxy to the more nearby lenses, we can start to understand how that dark-matter content has evolved over time."

video
Hubble orbiting Earth

The team suspects the lensing galaxy continued to grow over the past 9 billion years, gaining stars and dark matter by cannibalizing neighboring galaxies. Tran explained that recent studies suggest these massive galaxies gain more dark matter than stars as they continue to grow. Astronomers had assumed dark matter and normal matter build up equally in a galaxy over time, but now know the ratio of dark matter to normal matter changes with time. The newly discovered distant lensing galaxy will eventually become much more massive than the Milky Way and will have more dark matter, too.

Tran and her team were studying star formation in two distant galaxy clusters, including IRC 0218, when they stumbled upon the gravitational lens. While analyzing spectrographic data from the W.M. Keck Observatory in Hawaii, Tran spotted a strong detection of hot hydrogen gas that appeared to arise from a giant elliptical galaxy. The detection was surprising because hot hydrogen gas is a clear signature of star birth. Previous observations showed that the giant elliptical, residing in the galaxy cluster IRC 0218, was an old, sedate galaxy that had stopped making stars a long time ago. Another puzzling discovery was that the young stars were at a much farther distance than the elliptical galaxy. Tran was very surprised, worried and thought her team made a major mistake with their observations.

The astronomer soon realized she hadn't made a mistake when she looked at the Hubble images taken in blue wavelengths, which revealed the glow of fledgling stars. The images, taken by Hubble's Advanced Camera for Surveys and the Wide Field Camera 3, revealed a blue, eyebrow-shaped object next to a smeared blue dot around the massive elliptical. Tran recognized the unusual features as the distorted, magnified images of a more distant galaxy behind the elliptical galaxy, the signature of a gravitational lens.

To confirm her gravitational-lens hypothesis, Tran's team analyzed Hubble archival data from two observing programs, the 3D-HST survey, a near-infrared spectroscopic survey taken with the Wide Field Camera 3, and the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, a large Hubble deep-sky program. The data turned up another fingerprint of hot gas connected to the more distant galaxy.

The distant galaxy is too small and far away for Hubble to determine its structure. So, team members analyzed the distribution of light in the object to infer its spiral shape. In addition, spiral galaxies are more plentiful during those early times. The Hubble images also revealed at least one bright compact region near the center. The team suspects the bright region is due to a flurry of star formation and is most likely composed of hot hydrogen gas heated by massive young stars. As Tran continues her star-formation study in galaxy clusters, she will be hunting for more signatures of gravitational lensing.

The team's results appeared in the July 10 issue of The Astrophysical Journal Letters.

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington.

For images and more information about Hubble, visit: http://www.nasa.gov/hubble and http://hubblesite.org/news/2014/33 and http://www.spacetelescope.org/

Image (mentioned), Video, Text, Credits:  NASA / J.D. Harrington / Space Telescope Science Institute / Donna Weaver/Ray Villard / ESA.

Greetings, Orbiter.ch

mercredi 30 juillet 2014

ALMA Finds Double Star with Weird and Wild Planet-forming Discs












ESO - European Southern Observatory logo.

30 July 2014

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have found wildly misaligned planet-forming gas discs around the two young stars in the binary system HK Tauri. These new ALMA observations provide the clearest picture ever of protoplanetary discs in a double star. The new result also helps to explain why so many exoplanets — unlike the planets in the Solar System — came to have strange, eccentric or inclined orbits. The results will appear in the journal Nature on 31 July 2014.

Artist’s impression of the discs around the young stars HK Tauri A and B

Unlike our solitary Sun, most stars form in binary pairs — two stars that are in orbit around each other. Binary stars are very common, but they pose a number of questions, including how and where planets form in such complex environments.

“ALMA has now given us the best view yet of a binary star system sporting protoplanetary discs  — and we find that the discs are mutually misaligned!” said Eric Jensen, an astronomer at Swarthmore College in Pennsylvania, USA.

The two stars in the HK Tauri system, which is located about 450 light-years from Earth in the constellation of Taurus (The Bull), are less than five million years old and separated by about 58 billion kilometres — this is 13 times the distance of Neptune from the Sun.

The young double star HK Tauri in the constellation of Taurus

The fainter star, HK Tauri B, is surrounded by an edge-on protoplanetary disc that blocks the starlight. Because the glare of the star is suppressed, astronomers can easily get a good view of the disc by observing in visible light, or at near-infrared wavelengths.

The companion star, HK Tauri A, also has a disc, but in this case it does not block out the starlight. As a result the disc cannot be seen in visible light because its faint glow is swamped by the dazzling brightness of the star. But it does shine brightly in millimetre-wavelength light, which ALMA can readily detect.

Using ALMA, the team were not only able to see the disc around HK Tauri A, but they could also measure its rotation for the first time. This clearer picture enabled the astronomers to calculate that the two discs are out of alignment with each other by at least 60 degrees. So rather than being in the same plane as the orbits of the two stars at least one of the discs must be significantly misaligned.

Wide-field view of part of the Taurus star formation region

“This clear misalignment has given us a remarkable look at a young binary star system,” said Rachel Akeson of the NASA Exoplanet Science Institute at the California Institute of Technology in the USA. “Although there have been earlier observations indicating that this type of misaligned system existed, the new ALMA observations of HK Tauri show much more clearly what is really going on in one of these systems.”

Stars and planets form out of vast clouds of dust and gas. As material in these clouds contracts under gravity, it begins to rotate until most of the dust and gas falls into a flattened protoplanetary disc swirling around a growing central protostar.

Composite views of HK Tauri from Hubble and ALMA

But in a binary system like HK Tauri things are much more complex. When the orbits of the stars and the protoplanetary discs are not roughly in the same plane any planets that may be forming can end up in highly eccentric and tilted orbits [1].

“Our results show that the necessary conditions exist to modify planetary orbits and that these conditions are present at the time of planet formation, apparently due to the formation process of a binary star system,” noted Jensen. “We can’t rule other theories out, but we can certainly rule in that a second star will do the job.”

The motions of material in the discs around the young double star HK Tauri

Since ALMA can see the otherwise invisible dust and gas of protoplanetary discs, it allowed for never-before-seen views of this young binary system. “Because we’re seeing this in the early stages of formation with the protoplanetary discs still in place, we can see better how things are oriented,” explained Akeson.

Looking forward, the researchers want to determine if this type of system is typical or not. They note that this is a remarkable individual case, but additional surveys are needed to determine if this sort of arrangement is common throughout our home galaxy, the Milky Way.

video
Zooming in on the young double star HK Tauri

Jensen concludes: “Although understanding this mechanism is a big step forward, it can’t explain all of the weird orbits of extrasolar planets — there just aren’t enough binary companions for this to be the whole answer. So that’s an interesting puzzle still to solve, too!”

Notes:

[1] If the two stars and their discs are not all in the same plane, the gravitational pull of one star will perturb the other disc, making it wobble or precess, and vice versa. A planet forming in one of these discs will also be perturbed by the other star, which will tilt and deform its orbit.

More information:

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Southern Observatory (ESO), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan. ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

This research was presented in a paper entitled “Misaligned Protoplanetary Disks in a Young Binary Star System”, by Eric Jensen and Rachel Akeson, to appear in the 31 July 2014 issue of the journal Nature.

The team is composed of Eric L. N. Jensen (Dept. of Physics & Astronomy, Swarthmore College, USA) and Rachel Akeson (NASA Exoplanet Science Institute, IPAC/Caltech, Pasadena, USA).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning the 39-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links:

Research paper: http://www.eso.org/public/archives/releases/sciencepapers/eso1423/eso1423a.pdf

NRAO press release about HK Tauri results: https://public.nrao.edu/news/pressreleases/young-binary-star-system-form-planets-with-weird-orbits

Image of HK Tauri from the NASA/ESA Hubble Space Telescope: http://www.spacetelescope.org/images/opo9905m/

More about ALMA: http://www.eso.org/public/teles-instr/alma/

Photos of ALMA: http://www.eso.org/public/images/archive/category/alma/

Videos of ALMA: http://www.eso.org/public/videos/archive/category/alma/

ALMA brochure: http://www.eso.org/public/products/brochures/alma_brochure_en/

The movie ALMA — In Search of our Cosmic Origins: http://www.eso.org/public/videos/eso1312a/

The ALMA Photo Book In Search of our Cosmic Origins – The Construction of the Atacama Large Millimeter/submillimeter Array: http://www.eso.org/public/products/books/alma-photobook/

More press releases with ALMA: http://www.eso.org/public/news/archive/search/?adv=&facility=36

Images, Text, Credits: ESO/ALMA/R. Hurt (NASA/JPL-Caltech/IPAC)/IAU and Sky & Telescope/Digitized Sky Survey 2. Acknowledgement: Davide De Martin/B. Saxton (NRAO/AUI/NSF); K. Stapelfeldt et al. (NASA/ESA Hubble)/NASA/JPL-Caltech/R. Hurt (IPAC)/Video: ESO/Digitized Sky Survey 2/N. Risinger (skysurvey.org). Music: movetwo.

Best regards, Orbiter.ch

Gaia: ‘Go’ for science












ESA - Gaia Mission patch.

29 July 2014

Following extensive in-orbit commissioning and several unexpected challenges, ESA’s billion-star surveyor, Gaia, is now ready to begin its science mission.

The satellite was launched on 19 December 2013, and is orbiting a virtual location in space 1.5 million kilometres from Earth.

Gaia’s goal is to create the most accurate map yet of the Milky Way. It will make extremely accurate measurements of the positions and motions of about 1% of the total population of roughly 100 billion stars in our home Galaxy to help answer questions about its origin and evolution.

Inside Gaia’s billion-pixel camera

Repeatedly scanning the sky, Gaia will observe each of its billion stars an average of 70 times each over five years. Small apparent motions in the positions of the stars will allow astronomers to determine their distances and movements through the Milky Way.

In addition, Gaia will also measure key physical properties of each star, including its brightness, temperature and chemical composition.

Gaia spins slowly once every six hours, sweeping its two telescopes across the sky and focusing the light from their separate fields simultaneously onto a single focal plane – the largest digital camera ever flown in space, with nearly a billion pixels.

As the stars drift across the camera, the relative positions of all detected stars are measured and downlinked to Earth. Over time, a complete network of positions of stars covering the whole sky is built up, before being analysed to yield a highly accurate 3D map.

The accuracy required is astonishing: Gaia must be able to measure positions to a level equivalent to the width of a human hair seen at 2000 km. In turn, these measurements demand a very rigorous calibration of the satellite and its instruments, a painstaking procedure that has taken the first part of the year to complete.

Gaia is now ready to begin its five-year science phase, but the commissioning also uncovered some unexpected anomalies.

One problem detected early in the commissioning was associated with water freezing on some parts of the optics, causing a temporary reduction in transmission of the telescopes.

This water was likely trapped in the spacecraft before launch and emerged once it was in a vacuum. Heating the affected optics to remove the ice has now largely solved this problem, but it is likely that one or two more ‘decontamination’ cycles will be required during the mission to keep it in check.

Another problem is associated with ‘stray light’ reaching Gaia’s focal plane at a level higher than predicted before launch. This appears to be a mixture of light from the Sun finding its way past Gaia’s 10 m-diameter sunshield and light from other astronomical objects, both making their way to the focal plane as a diffuse background.

Gaia spacecraft

The effect on Gaia’s performance is negligible for brighter objects at magnitude 15 and above, and a slight degradation in the positional accuracy is seen for fainter stars, reaching 50% for stars at Gaia’s nominal faint limit of magnitude 20.

There is also some effect on the accuracy to which stellar brightnesses will be measured.

The impact of the stray light should, in principle, be more significant for faint stars seen by Gaia’s Radial Velocity Spectrometer (RVS).

“However, we are optimising the onboard software to mitigate as much as possible the impact caused by these higher background levels of light, and we are confident that we will not be far off our initial and somewhat conservative estimate of studying 150 million stars with RVS, as planned,” says Giuseppe Sarri, ESA’s Gaia Project Manager.

“We will still be able to analyse one billion – if not more – stars with the astrometry and photometry instruments, measuring each star's position and motion up to 100 times more accurately than Gaia’s predecessor Hipparcos and for a far larger number of stars.”

Further tests made during commissioning have shown that it may be possible to extend Gaia’s reach to stars even fainter than magnitude 20, while at the other end, software changes enable Gaia to measure almost all of the brightest stars in the sky, previously ruled out as being too bright for such a sensitive system. Both of these extensions will need further analysis before being implemented.

Finally, Gaia also contains a laser device called the ‘basic angle monitor’, designed to measure the angle of separation between Gaia’s two telescopes to an extremely high level of accuracy. This is necessary in order to correct for expected periodic variations in the separation angle caused by thermal changes in the payload as Gaia spins.

Although this system is working, the detected variations in the basic angle are larger than expected. Further efforts are being made to measure and accurately calibrate the variations, with the aim of largely eliminating them during the overall data analysis.

The commissioning has not only focused on the spacecraft performance, but also on the flow of data on the ground, testing procedures that will be used to process and analyse the vast amount of data that will be transmitted to Earth on a daily basis for the next five years.

Thus, after extensive testing and analysis of systems both in space and on the ground, Gaia is now in a position to begin routine operations.

“The commissioning phase has been challenging, and although some activities are ongoing, all in all Gaia is in good shape to fulfil its promise – all of the core scientific goals are still achievable, as hoped,” says Timo Prusti, ESA’s Project Scientist for Gaia.

“Given the somewhat longer-than-expected commissioning and taking into account the time needed to develop some new software, we anticipate that the first intermediate catalogue of science data will be released to scientists and the public in summer 2016.

“However, if rapidly-changing objects such as supernovas are detected, open alerts will be made as soon as possible – a service we hope to have up and running before the end of this year.”

For a full quantitative analysis of Gaia’s expected science performance based on the results of commissioning, see http://www.cosmos.esa.int/web/gaia/news_20140729.

For updates published during the commissioning period, please refer to the Gaia blog: http://blogs.esa.int/gaia/

Related articles

How many stars are there in the Universe?: http://www.esa.int/Our_Activities/Space_Science/Herschel/How_many_stars_are_there_in_the_Universe

Eye of Gaia: billion-pixel camera to map Milky Way: http://orbiterchspacenews.blogspot.ch/2011/07/eye-of-gaia-billion-pixel-camera-to-map.html

Related links:

Gaia’s Radial Velocity Spectrometer (RVS): http://www.esa.int/Our_Activities/Space_Science/Gaia/Science_instruments

Gaia spacecraft testing: http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=31544&farchive_objecttypeid=31&farchive_objectid=30928

Vodcast: Charting the Galaxy - from Hipparcos to Gaia: http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=45772&fattributeid=885

Little books of Gaia: http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=35010

Make a Gaia model: http://www.rssd.esa.int/index.php?project=Gaia&page=Gaia_model

Explore stellar neighbourhood in 3D: http://workshop.chromeexperiments.com/stars/

Gaia launch campaign photos: http://sci.esa.int/gaia-launch-campaign-photos/

Image, Video, Text, Credit: ESA / C. Carreau.

Greetings, Orbiter.ch

Lifetime of gravity measurements heralds new beginning









ESA - GOCE Mission logo.

30 July 2014

Although ESA’s GOCE satellite is no more, all of the measurements it gathered during its life skirting the fringes our atmosphere, including the very last as it drifted slowly back to Earth, have been drawn together to offer new opportunities for science.

Carrying the first 3D gravity sensor in space, this state-of-the-art satellite measured Earth’s gravity with unprecedented accuracy.

GOCE

GOCE’s four years in orbit resulted in a series of four gravity models, each more accurate than the last. These models have been used to generate corresponding ‘geoids’ – the surface of a global ocean moulded  by gravity alone.

Shaped by differences in gravity, the geoid is a crucial reference for understanding ocean circulation, sea-level change and ice dynamics.

From a mission that just keeps giving, a fifth model has now been produced. It incorporates data collected throughout the satellite’s 42-month operational life.

The previous geoid, released in March 2013, was based on 27 months of measurements.

2011 GOCE geoid

The satellite was designed to orbit at an extremely low altitude of 255 km to gain the best possible gravity measurements. At the end of 2012, low fuel consumption allowed operators to extend its life and start to lower the satellite a further 31 km for even more accurate measurements. This was at the very limit of its capability but maximised the return for science.

After more than doubling its planned life in orbit, the satellite ran out of fuel and drifted back into the atmosphere in November 2013.

The fifth gravity model and geoid, which ESA has recently made available, includes these final precious measurements, right up until the satellite finally stopped working and ironically succumbed to the force it was designed to measure.

GOCE reenters atmosphere

Although the satellite is no longer in orbit, scientists now have the best possible information to hand about Earth’s gravity, effectively a new beginning for the mission.

GOCE has already shed new light on different aspects of Earth and surpassed its original scope in a number of ways.

It is being used to understand how oceans carry huge quantities of heat around the planet and to develop a global height reference system.

It has provided information about atmospheric density and winds, mapped the boundary between Earth’s crust and upper mantle, and used to understand what is going on in these layers far below our feet.

Moho and lithosphere

And its achievements include mapping a scar in Earth’s gravity caused by the 2011 Japanese earthquake.

The ultimate geoid model and gravity data will be used for years to come for a deeper understanding of Earth.

ESA’s GOCE Mission Manager, Rune Floberhagen, said, “We are very happy with the results of the final, super-low altitude phase of our mission.

Gravity scar over Japan

“In fact, efforts made by the mission team and by scientists to secure flight operations at these extreme altitudes and to process the data have resulted in a doubling of the information content and a very significant increase in spatial resolution.

“Indeed, our new ‘Release 5 solutions’ go well beyond the ambitious objectives we had when the GOCE project started.

“Scientists worldwide now have a satellite-based gravity field model at hand that will remain the de facto standard for many years to come.”

For more information about GOCE mission, visit: http://www.esa.int/Our_Activities/Observing_the_Earth/GOCE/

Access GOCE data: http://earth.esa.int/GOCE/

Images, Text, Credits: ESA/AOES Medialab/HPF/DLR/Bill Chater/GeoExplore STSE GOCE+ study team/DGFI/TU Delft.

Best regards, Orbiter.ch