- Dawn Spacecraft Arrives at Ceres, Becomes First to Orbit a Dwarf Planet
- Use of Curiosity Rover Arm Expected to Resume in a Few Days
- Hubble Sees Multiple Images of a Supernova for the Very First Time
- Thermonuclear Supernova Ejects Galaxy’s Fastest Star
- Air Force's Space Wing Unveils Multi-Vehicle Launch Support Center
- Opportunity Rover Examining Odd Mars Rocks at Valley Overlook
- Orion's Launch Abort System Motor Exceeds Expectations
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Posted: 06 Mar 2015 02:41 PM PST
NASA's Dawn spacecraft has become the first mission to achieve orbit around a dwarf planet. The spacecraft was approximately 38,000 miles (61,000 kilometers) from Ceres when it was captured by the dwarf planet’s gravity at about 4:39 a.m. PST (7:39 a.m. EST) Friday. Mission controllers at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California received a signal from the spacecraft at 5:36 a.m. PST (8:36 a.m. EST) that Dawn was healthy and thrusting with its ion engine, the indicator Dawn had entered orbit as planned. "Since its discovery in 1801, Ceres was known as a planet, then an asteroid and later a dwarf planet," said Marc Rayman, Dawn chief engineer and mission director at JPL. "Now, after a journey of 3.1 billion miles (4.9 billion kilometers) and 7.5 years, Dawn calls Ceres, home."
In order for Dawn to be captured by Ceres' gravitational field, the spacecraft started using its ion engines from a distance of 61,000 km to slow the spacecraft down. During this process, no image acquisition with the German-built Framing Camera on board the spacecraft was possible. "The solar arrays, which are a total of almost 20 metres across, had to be aligned with the Sun during this manoeuvre; therefore, the camera could not be pointed in the direction of Ceres," explained Ralf Jaumann from the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR). The planetary scientist is a member of the camera team, and is waiting anxiously for the next images, which will be acquired in April at distances of 33,000 and 22,000 kilometres. Prior to this, the Dawn spacecraft will disappear behind the dark, Sun-opposed side of the dwarf planet until mid-April.
Dawn, designed and built by Orbital ATK, reached Ceres with the innovative use of solar electric ion propulsion, the world's most advanced and efficient space propulsion technology. "Orbital ATK's flight-proven technology and extensive experience played key roles in integrating the ion propulsion system provided by the Jet Propulsion Laboratory," said Frank Culbertson, Orbital ATK Space Systems Group president. "This technology is revolutionizing solar system exploration and made Dawn's historic journey to two planetary bodies possible. We were committed to developing this spacecraft in an innovative way that was reliable and affordable. To see the Dawn flight system enter into this complex science phase fully functional is quite a testament to the design and workmanship."
In addition to being the first spacecraft to visit a dwarf planet, Dawn also has the distinction of being the first mission to orbit two extraterrestrial targets. From 2011 to 2012, the spacecraft explored the giant asteroid Vesta, delivering new insights and thousands of images from that distant world. Ceres and Vesta are the two most massive residents of our solar system’s main asteroid belt between Mars and Jupiter.
The most recent images received from the spacecraft, taken on March 1 show Ceres as a crescent, mostly in shadow because the spacecraft's trajectory put it on a side of Ceres that faces away from the sun until mid-April. When Dawn emerges from Ceres' dark side, it will deliver ever-sharper images as it spirals to lower orbits around the planet.
"We feel exhilarated," said Chris Russell, principal investigator of the Dawn mission at the University of California, Los Angeles (UCLA). "We have much to do over the next year and a half, but we are now on station with ample reserves, and a robust plan to obtain our science objectives."
From April, the camera will be observing Ceres from a distance of 13,500 kilometres from the surface and will explore the dwarf planet from this altitude for 20 days. "Then, we will be able to see much more detail and better interpret what is being observed," said Jaumann. "With the 'third dimension', that is, a topographic relief map of the surface, we will be able to perform an increasingly accurate analysis of the surface features." At this point the DLR Institute of Planetary Research will also be able to create the first complete, three-dimensional digital terrain model of Ceres. By the end of 2015, Dawn will close in to just 375 kilometres above Ceres. Three instruments on the spacecraft will spend a total of 18 months exploring the dwarf planet.
Ceres was discovered in 1801 and designated as a planet. It was later classified as an asteroid and finally placed in the newly defined class of dwarf planets in 2006. With its orbit around the Sun, its spherical shape and a diameter of 950 kilometres, Ceres was in the process of becoming a planet during the formation of the Solar System. However, the gravitational field of Jupiter probably thwarted this, so Ceres remained only partially developed. This makes it of interest to planetary scientists: "It embodies a stage of planet formation that can provide us with information about what happened 4.6 billion years ago," said Jaumann.
"This is the world's first chance to get an up close look at two bodies which date back to the formation of the solar system, but evolved very differently," said Mike Miller, Orbital ATK vice president, Science and Environmental Programs, Civil and Defense Division. "Ceres is thought to contain substantial water, perhaps up to 27 percent of its mass, a quantity roughly equivalent to the fresh water on Earth. It's expected to be mostly in the form of ice, but there may also be a liquid subsurface ocean. The Dawn detailed image and compositional data will help us understand this very exciting prospect."
Dawn's mission 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, Alabama. UCLA is responsible for overall Dawn mission science. Orbital ATK Inc., in Dulles, Virginia, designed and built the spacecraft. The German Aerospace Center, Max Planck Institute for Solar System Research, Italian Space Agency and Italian National Astrophysical Institute are international partners on the mission team.
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Posted: 06 Mar 2015 02:07 PM PST
Managers of NASA's Curiosity Mars rover mission expect to approve resumption of rover arm movements as early as next week while continuing analysis of what appears to be an intermittent short circuit in the drill. A fluctuation in current on Feb. 27 triggered a fault-protection response that immediately halted action by the rover during the mission's 911th Martian day, or sol. Since then, the rover team has avoided driving Curiosity or moving the rover's arm, while engineers have focused on diagnostic tests. Science observations with instruments on the rover's mast have continued, along with environmental monitoring by its weather station.
"Diagnostic testing this week has been productive in narrowing the possible sources of the transient short circuit," said Curiosity Project Manager Jim Erickson of NASA's Jet Propulsion Laboratory, Pasadena, California. "The most likely cause is an intermittent short in the percussion mechanism of the drill. After further analysis to confirm that diagnosis, we will be analyzing how to adjust for that in future drilling."
The sample-collection drill on Curiosity's robotic arm uses both rotation and hammering, or percussion, to penetrate into Martian rocks and collect pulverized rock material for delivery to analytical instruments inside the rover.
The short on Sol 911 occurred while the rover was transferring rock-powder sample from the grooves of the drill into a mechanism that sieves and portions the powder. The percussion action was in use, to shake the powder loose from the drill.
Engineers received results Thursday, March 5, from a test on Curiosity that similarly used the drill's percussion action. During the third out of 180 up-and-down repeats of the action, an apparent short circuit occurred for less than one one-hundredth of a second. Though small and fleeting, it would have been enough to trigger the fault protection that was active on Sol 911 under the parameters that were in place then.
The rover team plans further testing to characterize the intermittent short before the arm is moved from its present position, in case the short does not appear when the orientation is different.
After those tests, the team expects to finish processing the sample powder that the arm currently holds and then to deliver portions of the sample to onboard laboratory instruments. Next, Curiosity will resume climbing Mount Sharp.
NASA's Mars Science Laboratory Project is using Curiosity to assess ancient habitable environments and major changes in Martian environmental conditions. JPL, a division of the California Institute of Technology in Pasadena, built the rover and manages the project for NASA's Science Mission Directorate in Washington.
Credit: NASA
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Posted: 06 Mar 2015 01:47 PM PST
Three-leaf clover plants abound everywhere: on lawns, in gardens, and in forests. But spotting a four-leaf clover is a rare, lucky find. Astronomers using the Hubble Space Telescope have found the equivalent of a four-leaf clover with the discovery of four images of the same supernova. The images are arranged around a giant foreground elliptical galaxy embedded in a cluster of galaxies. The arrangement forms a cross-shaped pattern called an Einstein Cross. The powerful gravity from both the elliptical galaxy and its galaxy cluster magnifies the light from the supernova behind them in an effect called gravitational lensing. The elliptical galaxy and its galaxy cluster, MACS J1149.6+2223, are 5 billion light-years away from Earth. The supernova behind it is 9.3 billion light-years away.
Although astronomers have discovered dozens of multiply imaged galaxies and quasars, they have never seen a stellar explosion resolved into several images. "It really threw me for a loop when I spotted the four images surrounding the galaxy — it was a complete surprise," said Patrick Kelly of the University of California, Berkeley, a member of the Grism Lens Amplified Survey from Space (GLASS) collaboration. The GLASS group is working with the Frontier Field Supernova (FrontierSN) team to analyze the exploding star. Kelly is also the lead author on the science paper, which appeared on March 6 in a special issue of the journal Science celebrating the centenary of Albert Einstein's Theory of General Relativity.
Dr Brad Tucker from The Australian National University (ANU) says it's a dream discovery for the team. "It's perfectly set up, you couldn't have designed a better experiment," Tucker said. "You can test some of the biggest questions about Einstein's theory of relativity all at once - it kills three birds with one stone."
When the four images fade away, astronomers predict they will have a rare opportunity to catch a rerun of the supernova. This is because the current four-image pattern is only one part of the lensing display. The supernova may have appeared as a single image some 20 years ago elsewhere in the cluster field, and it is expected to reappear once more within the next five years.
“We observe the light from a distant supernova, but what we see here is a strange and rare sight. The enormous mass has deflected the light from the underlying supernova, so the light is seen in four images configured like a cross around the elliptical galaxy. It is called an Einstein Cross after Albert Einstein, who first predicted the phenomenon of gravitational lensing 100 years ago,” explains Anja von der Linden, postdoc at the Dark Cosmology Centre at the Niels Bohr Institute at the University of Copenhagen.
This prediction is based on computer models of the cluster, which describe the various paths the supernova light is taking through the maze of clumpy dark matter in the galactic grouping. Each image takes a different route through the cluster and arrives at a different time, due, in part, to differences in the length of the pathways the light follows to reach Earth. The four supernova images captured by Hubble, for example, appeared within a few days or weeks of each other.
“It’s a wonderful discovery,” said Alex Filippenko, a UC Berkeley professor of astronomy and a member of Kelly’s team. “We’ve been searching for a strongly lensed supernova for 50 years, and now we’ve found one. Besides being really cool, it should provide a lot of astrophysically important information.”
The supernova's various light paths are analogous to several trains that leave a station at the same time, all traveling at the same speed and bound for the same location. Each train, however, takes a different route, and the distance for each route is not the same. Some trains travel over hills. Others go through valleys, and still others chug around mountains. Because the trains travel over different track lengths across different terrain, they do not arrive at their destination at the same time. Similarly, the supernova images do not appear at the same time because some of the light is delayed by traveling around bends created by the gravity of dense dark matter in the intervening galaxy cluster.
"Our model for the dark matter in the cluster gives us the prediction of when the next image will appear because it tells us how long each train track is, which correlates with time," said Steve Rodney of the Johns Hopkins University in Baltimore, Maryland, leader of the FrontierSN team. "We already missed one that we think appeared about 20 years ago, and we found these four images after they had already appeared. The prediction of this future image is the one that is most exciting because we might be able to catch it. We hope to come back to this field with Hubble, and we'll keep looking to see when that expected next image appears."
Measuring the time delays between images offers clues to the type of warped-space terrain the supernova's light had to cover and will help the astronomers fine-tune the models that map out the cluster's mass. "We will measure the time delays, and we'll go back to the models and compare them to the model predictions of the light paths," Kelly said. "The lens modelers, such as Adi Zitrin (California Institute of Technology) from our team, will then be able to adjust their models to more accurately recreate the landscape of dark matter, which dictates the light travel time."
While making a routine search of the GLASS team's data, Kelly spotted the four images of the exploding star on Nov. 11, 2014. The FrontierSN and GLASS teams have been searching for such highly magnified explosions since 2013, and this object is their most spectacular discovery. The supernova appears about 20 times brighter than its natural brightness, due to the combined effects of two overlapping lenses. The dominant lensing effect is from the massive galaxy cluster, which focuses the supernova light along at least three separate paths. A secondary lensing effect occurs when one of those light paths happens to be precisely aligned with a specific elliptical galaxy within the cluster. "The dark matter of that individual galaxy then bends and refocuses the light into four more paths," Rodney explained, "generating the rare Einstein Cross pattern we are currently observing."
The two teams spent a week analyzing the object's light, confirming it was the signature of a supernova. They then turned to the W.M. Keck Observatory on Mauna Kea, in Hawaii, to measure the distance to the supernova's host galaxy.
The astronomers nicknamed the supernova Refsdal in honor of Norwegian astronomer Sjur Refsdal, who, in 1964, first proposed using time-delayed images from a lensed supernova to study the expansion of the universe. "Astronomers have been looking to find one ever since," said Tommaso Treu of the University of California, Los Angeles, the GLASS project's principal investigator. "The long wait is over!"
The Frontier Fields survey is a three-year program that uses Hubble and the gravitational-lensing effects of six massive galaxy clusters to probe not only what is inside the clusters but also what is beyond them. The three-year FrontierSN program studies supernovae that appear in and around the galaxy clusters of the Frontier Fields and GLASS surveys. The GLASS survey is using Hubble's spectroscopic capabilities to study remote galaxies through the cosmic telescopes of 10 massive galaxy clusters, including the six in the Frontier Fields.
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Posted: 06 Mar 2015 12:18 PM PST
Scientists using the W. M. Keck Observatory and Pan-STARRS1 telescopes on Hawaii have discovered a star that breaks the galactic speed record, traveling with a velocity of about 1,200 kilometers per second or 2.7 million miles per hour. This velocity is so high, the star will escape the gravity of our galaxy. In contrast to the other known unbound stars, the team showed that this compact star was ejected from an extremely tight binary by a thermonuclear supernova explosion. These results are published in the March 6 issue of Science.
Stars like the Sun are bound to our Galaxy and orbit its center with moderate velocities. Only a few so-called hypervelocity stars are known to travel with velocities so high that they are unbound, meaning they will not orbit the galaxy, but instead will escape its gravity to wander intergalactic space.
A close encounter with the supermassive black hole at the centre of the Milky Way is typically presumed the most plausible mechanism for kicking these stars out of the galaxy.
A team of astronomers led by Stephan Geier (European Southern Observatory, Garching) observed the known high-velocity star know as US 708 with the Echellette Spectrograph and Imager instrument on the 10-meter, Keck II telescope to measure its distance and velocity along our line of sight. By carefully combining position measurements from digital archives with newer positions measured from images taken during the course of the Pan-STARRS1 survey, they were able to derive the tangential component of the star's velocity (across our line of sight).
Putting the measurements together, the team determined the star is moving at about 1,200 kilometers per second – much higher than the velocities of previously known stars in the Milky Way galaxy. More importantly, the trajectory of US 708 means the supermassive black hole at the galactic center could not be the source of US 708's extreme velocity.
US 708 has another peculiar property in marked contrast to other hypervelocity stars: it is a rapidly rotating, compact helium star likely formed by interaction with a close companion. Thus, US 708 could have originally resided in an ultra compact binary system, transferring helium to a massive white dwarf companion, ultimately triggering a thermonuclear explosion of a type Ia supernova. In this scenario, the surviving companion, i.e. US 708, was violently ejected from the disrupted binary as a result, and is now travelling with extreme velocity.
These results provide observational evidence of a link between helium stars and thermonuclear supernovae, and is a step towards understanding the progenitor systems of these mysterious explosions.
The W. M. Keck Observatory operates the largest, most scientifically productive telescopes on Earth. The two, 10-meter optical/infrared telescopes near the summit of Mauna Kea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrographs and world-leading laser guide star adaptive optics systems.
ESI (Echellette Spectrograph and Imager) is a medium-resolution visible-light spectrograph that records spectra from 0.39 to 1.1 microns in each exposure. Built at UCO/Lick Observatory by a team led by Prof. Joe Miller, ESI also has a low-resolution mode and can image in a 2 x 8 arcmin field of view. An upgrade provided an integral field unit that can provide spectra everywhere across a small, 5.7 x 4.0 arcsec field. Astronomers have found a number of uses for ESI, from observing the cosmological effects of weak gravitational lensing to searching for the most metal-poor stars in our galaxy.
Keck Observatory is a private 501(c) 3 non-profit organization and a scientific partnership of the California Institute of Technology, the University of California and NASA.
Credit: keckobservatory.org
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Posted: 06 Mar 2015 11:59 AM PST
The 45th Space Wing held a Multi-Vehicle Launch Support Center grand opening ceremony March 4, 2015, at the Cape Canaveral Air Force Station (CCAFS) Headquarters Building. The renovated center is now equipped with 30 computers, 60 monitors, six projection screens and countdown clocks to provide video and data during launch countdowns. "We commemorate the history of the Cape in this facility, we celebrate our current partnerships and capabilities, and we contemplate the possibilities going forward, not only dreaming of the possibilities of the spaceport of the future, but actually taking concrete steps to make it happen together," said Krystkowiak.
He said the support center could be converted into a full launch control center if a new commercial customer wanted to use it for that purpose.
"The facility is primed and ready to support future customers," he said. "Its utilizations have the potential to expand with the future outlook of the Cape Canaveral Spaceport."
The 45th Space Wing currently operates a number of rockets and missiles, including the Delta IV and Atlas V, and provides support for the Department of Defense, NASA, and commercial manned and unmanned space programs.
Credit: patrick.af.mil
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Posted: 06 Mar 2015 11:34 AM PST
.jpg "This map updates progress that NASA's Mars Exploration Rover Opportunity is making toward reaching a driving distance equivalent to a marathon footrace. It indicates the rover's position on March 5, 2015, relative to where it could surpass that distance. Credit: NASA/JPL-Caltech")
NASA's Mars Exploration Rover Opportunity climbed last month to an overlook for surveying "Marathon Valley," a science destination chosen because spectrometer observations from orbit indicate exposures of clay minerals. Near the overlook, it found blocky rocks so unlike any previously examined on Mars that the rover team has delayed other activities to provide time for a thorough investigation. "We drove to the edge of a plateau to look down in the valley, and we found these big, dark-gray blocks along the ridgeline," said Opportunity Project Scientist Matt Golombek of NASA's Jet Propulsion Laboratory, Pasadena, California. "We checked one and found its composition is different from any ever measured before on Mars. So, whoa! Let's study these more before moving on."
The first rock checked at the site has relatively high concentrations of aluminum and silicon, and an overall composition not observed before by either Opportunity or its twin rover, Spirit. This was determined by examining the rock, called "Jean-Baptiste Charbonneau," with the Alpha Particle X-ray Spectrometer instrument on the end of Opportunity's robotic arm. The next target rock at the site is called "Sergeant Charles Floyd." The team's target-naming theme in the area is from the Lewis and Clark expedition.
Although the rocks are gray, the visible-light spectrum of the Charbonneau type has more purple than most Mars rocks, and the spectrum of the Floyd type has more blue. Of the two types, the bluer rocks tend to lie higher on the ridge.
Actions to restore use of Opportunity's non-volatile flash file system will resume after inspection of the rocks on this ridge. Due to recurrent problems with the flash memory, including "amnesia events" and computer resets, Opportunity has been operating since late 2014 in a mode that avoids use of the flash memory.
Between the stops at Charbonneau and Floyd, the rover team uploaded to Opportunity a new version of the rover's flight software. The new version is designed to use only six of the rover's seven banks of flash memory. It will avoid the seventh bank, known to be a problem area.
The rover is using the new software, but a memory reformatting will be needed before resuming use of flash memory. After reformatting, the operations team will avoid use of the rover's arm for several days to make sure the flash file system is fixed and no longer causes resets. A reset during the use of the rover's arm would require a complex recovery effort.
As of March 5, Opportunity has driven 26.139 miles (42.067 kilometers) since it landed on Mars in January 2004. This brings it within 140 yards (128 meters) of reaching the distance of a marathon footrace.
NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover Project for NASA's Science Mission Directorate in Washington.
Credit: NASA
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Posted: 06 Mar 2015 11:17 AM PST
Three seconds. That’s all it took for the attitude control motor of NASA’s Orion Launch Abort System (LAS) to prove that its material can survive not only the intense temperatures, pressures, noise and vibrations experienced during a launch emergency but also 40 percent beyond. The LAS is being designed to bring a crew to safety should there be a problem in the launch pad or during ascent. "We tested over the maximum expected environments to assure the motor could withstand an abort emergency," explained LAS chief engineer Wayne Walters. On March 4, Orbital ATK, in collaboration with NASA and Lockheed Martin, completed its latest test of one of the most complex solid rocket systems ever built for the LAS.
"I am very proud of the team's successful test," Walters said. "This motor program is making great achievements due primarily to management support and a highly integrated engineering team. These boundary extending tests are paving the way to a successful qualification program for human space flight."
Built by Orbital ATK, the attitude control motor consists of a solid propellant gas generator, with eight proportional valves equally spaced around the outside of the three-foot diameter motor. Together, the valves can exert up to 7,000 pounds of steering force to the vehicle in any direction upon command from the Orion – the spacecraft that will one-day take humans to an asteroid and eventually Mars.
Despite being one of the last in line of a series, this test was the first of its kind.
"For the first time, the motor demonstrated capability far enough above what it would see in flight," said Kevin Rivers, deputy director for the Flight Projects Directorate at NASA's Langley Research Center in Virginia. "We can now have absolute confidence that the motor would perform flawlessly during a crewed mission."
Engineers at Orbital ATK’s facility in Elkton, Maryland, tested one of the valves of the attitude control motor during the test, which would be used to keep the LAS, with the crew module, on a controlled flight path if it needed to jettison and steer away from the launch vehicle in an emergency. It also reorients the module for parachute deployment and landing.
"Although we hope the system will never be needed, it is comforting to know we are designing a system that ensures our astronauts are safe when they go on missions beyond low-Earth orbit," said LAS flight dynamics lead John Davidson.
The LAS is managed out of Langley in collaboration with NASA’s Marshall Space Flight Center in Alabama and NASA contractor Lockheed Martin.
Credit: NASA
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