May 3 2011
From The Space Library
RELEASE: 11-133 NASA DAWN SPACECRAFT REACHES MILESTONE APPROACHING ASTEROID
WASHINGTON -- NASA's Dawn spacecraft has reached its official approach phase to the asteroid Vesta and will begin using cameras for the first time to aid navigation for an expected July 16 orbital encounter. The large asteroid is known as a protoplanet - a celestial body that almost formed into a planet. At the start of this three-month final approach to this massive body in the asteroid belt, Dawn is 752,000 miles (1.21 million kilometers) from Vesta, or about three times the distance between the Earth and the moon. During the approach phase, the spacecraft's main activity will be thrusting with a special, hyper-efficient ion engine that uses electricity to ionize and accelerate xenon to generate thrust. The 12-inch-wide ion thrusters provide less thrust than conventional engines, but will provide propulsion for years during the mission and provide far greater capability to change velocity. "We feel a little like Columbus approaching the shores of the New World," said Christopher Russell, Dawn principal investigator, based at the University of California in Los Angeles (UCLA). "The Dawn team can't wait to start mapping this Terra Incognita." Dawn previously navigated by measuring the radio signal between the spacecraft and Earth, and used other methods that did not involve Vesta. But as the spacecraft closes in on its target, navigation requires more precise measurements. By analyzing where Vesta appears relative to stars, navigators will pin down its location and enable engineers to refine the spacecraft's trajectory. Using its ion engine to match Vesta's orbit around the sun, the spacecraft will spiral gently into orbit around the asteroid. When Dawn gets approximately 9,900 miles (16,000 kilometers) from Vesta, the asteroid's gravity will capture the spacecraft in orbit. "After more than three and a half years of interplanetary travel, we are finally closing in on our first destination," said Marc Rayman, Dawn's chief engineer, at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif. "We're not there yet, but Dawn will soon bring into focus an entire world that has been, for most of the two centuries scientists have been studying it, little more than a pinpoint of light." Scientists will search the framing camera images for possible moons around Vesta. None of the images from ground-based and Earth-orbiting telescopes have seen any moons, but Dawn will give scientists much more detailed images to determine whether small objects have gone undiscovered. The gamma ray and neutron detector instrument also will gather information on cosmic rays during the approach phase, providing a baseline for comparison when Dawn is much closer to Vesta. Simultaneously, Dawn's visible and infrared mapping spectrometer will take early measurements to ensure it is calibrated and ready when the spacecraft enters orbit around Vesta. Dawn's odyssey, which will take it on a 3-billion-mile journey, began on Sept. 27, 2007, with its launch from Cape Canaveral Air Force Station in Florida. It will stay in orbit around Vesta for one year. After another long cruise phase, Dawn will arrive at its second destination, an even more massive body in the asteroid belt called Ceres, in 2015. These two icons of the asteroid belt will help scientists unlock the secrets of our solar system's early history. The mission will compare and contrast the two giant asteroids, which were shaped by different forces. Dawn's science instrument suite will measure surface composition, topography and texture. In addition, the Dawn spacecraft will measure the tug of gravity from Vesta and Ceres to learn more about their internal structures. The Dawn mission to Vesta and Ceres is managed by JPL for NASA's Science Mission Directorate (SMD) in Washington. Dawn is a project of SMD's Discovery Program, which is managed by NASA's Marshall Space Flight Center in Huntsville, Ala. UCLA is responsible for overall Dawn mission science. Orbital Sciences Corp. of Dulles, Va., designed and built the Dawn spacecraft. The framing cameras have been developed and built under the leadership of the Max Planck Institute for Solar System Research in Katlenburg-Lindau in Germany, with significant contributions by the German Aerospace Center (DLR) Institute of Planetary Research in Berlin, and in coordination with the Institute of Computer and Communication Network Engineering in Braunschweig. The framing camera project is funded by NASA, the Max Planck Society and DLR.
RELEASE: 11-134 NASA'S GRAVITY PROBE B CONFIRMS TWO EINSTEIN SPACE-TIME THEORIES
WASHINGTON -- NASA's Gravity Probe B (GP-B) mission has confirmed two key predictions derived from Albert Einstein's general theory of relativity, which the spacecraft was designed to test. The experiment, launched in 2004, used four ultra-precise gyroscopes to measure the hypothesized geodetic effect, the warping of space and time around a gravitational body, and frame-dragging, the amount a spinning object pulls space and time with it as it rotates. GP-B determined both effects with unprecedented precision by pointing at a single star, IM Pegasi, while in a polar orbit around Earth. If gravity did not affect space and time, GP-B's gyroscopes would point in the same direction forever while in orbit. But in confirmation of Einstein's theories, the gyroscopes experienced measurable, minute changes in the direction of their spin, while Earth's gravity pulled at them. The findings are online in the journal Physical Review Letters. "Imagine the Earth as if it were immersed in honey. As the planet rotates, the honey around it would swirl, and it's the same with space and time," said Francis Everitt, GP-B principal investigator at Stanford University. "GP-B confirmed two of the most profound predictions of Einstein's universe, having far-reaching implications across astrophysics research. Likewise, the decades of technological innovation behind the mission will have a lasting legacy on Earth and in space." GP-B is one of the longest running projects in NASA history, with agency involvement starting in the fall of 1963 with initial funding to develop a relativity gyroscope experiment. Subsequent decades of development led to groundbreaking technologies to control environmental disturbances on spacecraft, such as aerodynamic drag, magnetic fields and thermal variations. The mission's star tracker and gyroscopes were the most precise ever designed and produced. GP-B completed its data collection operations and was decommissioned in December 2010. "The mission results will have a long-term impact on the work of theoretical physicists," said Bill Danchi, senior astrophysicist and program scientist at NASA Headquarters in Washington. "Every future challenge to Einstein's theories of general relativity will have to seek more precise measurements than the remarkable work GP-B accomplished." Innovations enabled by GP-B have been used in GPS technologies that allow airplanes to land unaided. Additional GP-B technologies were applied to NASA's Cosmic Background Explorer mission, which accurately determined the universe's background radiation. That measurement is the underpinning of the big-bang theory, and led to the Nobel Prize for NASA physicist John Mather. The drag-free satellite concept pioneered by GP-B made a number of Earth-observing satellites possible, including NASA's Gravity Recovery and Climate Experiment and the European Space Agency's Gravity field and steady-state Ocean Circulation Explorer. These satellites provide the most precise measurements of the shape of the Earth, critical for precise navigation on land and sea, and understanding the relationship between ocean circulation and climate patterns. GP-B also advanced the frontiers of knowledge and provided a practical training ground for 100 doctoral students and 15 master's degree candidates at universities across the United States. More than 350 undergraduates and more than four dozen high school students also worked on the project with leading scientists and aerospace engineers from industry and government. One undergraduate student who worked on GP-B became the first American woman in space, Sally Ride. Another was Eric Cornell who won the Nobel Prize in Physics in 2001. "GP-B adds to the knowledge base on relativity in important ways and its positive impact will be felt in the careers of students whose educations were enriched by the project," said Ed Weiler, associate administrator for the Science Mission Directorate at NASA Headquarters. NASA's Marshall Space Flight Center in Huntsville, Ala., managed the Gravity Probe-B program for the agency. Stanford University, NASA's prime contractor for the mission, conceived the experiment and was responsible for the design and integration of the science instrument, mission operations and data analysis. Lockheed Martin Corp. of Huntsville designed, integrated and tested the space vehicle and some of its major payload components.
RELEASE: 11-136 TWO NASA SITES WIN WEBBY AWARDS
WASHINGTON -- Two NASA websites have been recognized in the 15th Annual Webby Awards -- the leading international honor for the world's best Internet sites. NASA's main website, www.NASA.gov, received its third consecutive People's Voice Award for best government site. NASA's Global Climate Change site, which won last year's People's Voice Award for science, won the 2011 judges' award for best science site. "NASA is committed to sharing its compelling story with people everywhere and with every communication tool," said David Weaver, NASA's associate administrator for communications. "We are very grateful to the online community for its continued support of what we are doing, and are excited about our future." NASA recently posted new interactive pieces on the 30th anniversary of the Space Shuttle Program and the 50th anniversary of the first U.S. spaceflight. And in the last year, the agency has streamlined its online video presentation into a single player and deployed a version of the site optimized for mobile devices. "NASA has a very broad-based web team that can take content, literally the best raw material in the universe, and create compelling imagery, video and multimedia pieces to tell the agency's story," said Internet Services Manager Brian Dunbar in the Office of Communications at NASA Headquarters in Washington. NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif., manages the climate site for the agency's Science Mission Directorate. "NASA satellites take key measurements of our climate, and the Global Climate Change site gives the public access to that data as a visual, immersive experience," said Randal Jackson, JPL's Internet communications manager. "We're grateful for the high degree of interest the public has shown in Earth's vital signs." NASA has had a web presence almost since HTML was invented in the early 1990's, but the site's popularity skyrocketed after a 2003 redesign and relaunch focused on making it more usable and understandable for the general public. Since then, there have been more than 1.5 billion visits to the site, and its customer-satisfaction ratings are among the highest in government and comparable to popular commercial sites. Reaching beyond the web, NASA's online communications include a Facebook page with more than 368,000 "likes"; a Twitter feed with more than a million followers; and more than 160 accounts across a variety of social media platforms. Last fall, NASA placed first by a wide margin in the L2 Digital IQ Index for the Public Sector study that ranks 100 public sector organizations in the effectiveness of their websites, digital outreach, social media use and mobile sites. The Office of Communications and the Office of the Chief Information Officer, both at NASA Headquarters, manage the agency's website. Presented by the International Academy of Digital Arts and Sciences, the Webby Award recognizes excellence in technology and creativity. The academy created the awards in 1996 to help drive the creative, technical, and professional progress of the Internet and evolving forms of interactive media. While members of the International Academy of Digital Arts and Sciences select the Webby award winners, the online community determines the winners of the People's Voice Awards.
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