sábado, 9 de febrero de 2013
Small near-Earth asteroid 2012 DA14 will pass very close to Earth on February 15, so close that it will pass inside the ring of geosynchronous weather and communications satellites. NASA's Near-Earth Object Program Office can accurately predict the asteroid's path with the observations obtained, and it is therefore known that there is no chance that the asteroid might be on a collision course with Earth. Nevertheless, the flyby will provide a unique opportunity for researchers to study a near-Earth object up close. Here are the facts about the safe flyby of Earth of asteroid 2012 DA14 -- a record close approach for a known object of this size.
Update Feb. 7, 2013
Asteroid 2012 DA14 Flyby Preview
NASA held a media teleconference on Thursday, Feb. 7, to discuss asteroid 2012 DA14 which will have a very close, but safe, flyby of Earth on Feb. 15, 2013. Also discussed are NASA's efforts to find potentially hazardous near-Earth objects.
To watch a recording of the teleconference, visit: http://www.ustream.tv/recorded/29104663 .
The Flyby of Asteroid 2012 DA14 - A Discussion with Don Yeomans of NASA's Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, Calif.
An animation depicting the trajectory of asteroid 2012 DA14 as it travels within the Earth-moon system on Feb. 15, 2013.
An overview of near-Earth objects with emphasis on the upcoming close approach of asteroid 2012 DA14.
Graphic depicts the trajectory of asteroid 2012 DA14 on Feb 15, 2013. In this view, we are looking down from above Earth's north pole. Image credit: NASA/JPL-Caltech
› Larger view
Graphic depicts the trajectory of asteroid 2012 DA14 during its close approach, as seen edge-on to Earth's equatorial plane. The graphic demonstrates why the asteroid is invisible to northern hemisphere observers until just before close approach: it is approaching from "underneath" our planet. On the other hand, after close approach it will be favorably placed for observers in the northern hemisphere. Image credit: NASA/JPL-Caltech
Q: What is asteroid DA14
A: Asteroid 2012 DA14 is a small near-Earth object – approximately 150 feet (45 meters) in diameter. On Feb. 15, 2013, the asteroid will pass by our planet at a remarkably close distance, but the asteroid’s path is understood well enough that there is no chance of a collision with the Earth.
Q: What date and what time will the asteroid be closest to Earth?
A: Asteroid 2012 DA14 will be closest to Earth on Feb. 15 at approximately 19:24 UTC (2:24 p.m. EST/11:24 a.m. PST). This time may change by a minute or two as the asteroid is tracked on its approach and predictions are refined.
At the time of closest approach, the asteroid will be over the eastern Indian Ocean, off Sumatra -- approx. latitude: -6 deg South. / longitude: 97.5 deg East.
Q: How far away will asteroid 2012 DA14 be at time of closest approach?
A: Asteroid 2012 DA14 will be only about 17,200 miles (27,700 kilometers) above Earth's surface at the time of closest approach on Feb 15, 2013. This distance is well outside Earth's atmosphere, but it is inside the belt of satellites in geostationary orbit, which is located 22,200 miles (35,800 kilometers) above Earth’s surface. The close-approach distance is only about one-tenth the distance between Earth and moon. Another way to express the distance between asteroid and Earth at time of closest approach is 4.4 Earth radii from Earth’s surface – or about twice the diameter of the Earth.
Q: Could asteroid DA14 impact Earth?
A: No. The orbit of asteroid 2012 DA14 is well understood – it will not come any closer than 17,150 miles (27,650 kilometers) above Earth's surface during its flyby on Feb 15, 2013.
The asteroid’s orbit around the sun is roughly similar to that of Earth, and it makes relatively close approaches to our planet’s orbit twice per orbit. But, the 2013 flyby is by far the closest the asteroid will approach our planet for many decades. The next notable close approach to Earth will be on February 16, 2046, when the asteroid will pass no closer than 620,000 miles (1,000,000,000 kilometers) from the center-point of Earth.
Q: What makes 2012 DA14 special?
A: The flyby of asteroid 2012 DA14 is the closest ever predicted Earth approach for an object this large.
Q: How long will asteroid 2012 DA14 be within the Earth/moon system?
A: Asteroid 2012 DA14's will be within the Earth/moon system for about 33 hours. Its orbit will bring it within the Earth/moon system (approach within one lunar distance, 237,000 miles of the Earth) on Feb. 15 at about 0300 UTC (7 p.m. PST on Thursday, Feb. 14). The asteroid will exit the Earth/moon system on Feb. 16 at about 1200 UTC (4 a.m. PST).
Q: Is there a chance that asteroid 2012 DA14 could be eclipsed by Earth?
A: Because of its trajectory, there is no chance that asteroid 2012 DA14 will pass through Earth’s shadow.
Q: How big is asteroid 2012 DA14?
A: Asteroid 2012 DA14 is currently estimated to be about 150 feet (45 meters) across and has an estimated mass of about 130,000 metric tons. If radar observations of this asteroid are successful, we might have a more accurate estimate of the asteroid’s size after its close approach.
Q: How fast will the asteroid be traveling at closest approach?
A: Asteroid 2012 DA 14 is traveling at about 17,450 miles per hour (28,100 kilometers per hour), or 4.8 miles per second (7.82 kilometers per second) relative to Earth.
Q: Who discovered asteroid DA14?
A: Asteroid 2012 DA14 was discovered by the La Sagra Sky Survey operated by the Astronomical Observatory of Mallorca in Spain on Feb. 23, 2012. The asteroid was about 2.7 million miles (4.3 million kilometers) distant when it was detected. Their observations were reported to the NASA funded Minor Planet Center, operated by the Smithsonian Astrophysical Observatory for the International Astronomical Union, where all observations from observatories worldwide are combined to maintain the database on all known asteroids and comets in our solar system.
Q: How many asteroids are out there similar in size to asteroid DA14?
A: Scientists believe there are approximately 500,000 near-Earth asteroids the size of 2012 DA14. Of those, less than one percent have been discovered.
Q: How many times do asteroids the size of DA14 fly this close?
A: Scientists at NASA's Near-Earth Object Program Office in Pasadena, Calif. estimate that an asteroid the size of 2012 DA14 flies this close every 40 years on average and that one will impact Earth, on average, about once in every 1,200 years.
Q: Is there a chance that asteroid DA14 will collide with one or more satellites?
A: There is very little chance that asteroid 2012 DA14 will impact a satellite or spacecraft. Because the asteroid is approaching from below Earth, it will pass between the outer constellation of satellites located in geosynchronous orbit (22,245 miles/35,800 kilometers) and the large concentration of satellites orbiting much closer to Earth. (The International Space Station, for example, orbits at the close-in altitude of 240 miles/386 kilometers.). There are almost no satellites orbiting at the distance at which the asteroid will pass.
Q: What will asteroid DA14’s close pass do to Earth’s rotation/tides/fault lines/etc.
A: The gravitational influence upon Earth and its inhabitants by the flyby of asteroid 2012 DA14 will be infinitesimally small.
Q: What would happen if DA14 were to impact Earth?
A: Asteroid 2012 DA14 will not impact Earth, but if another asteroid of a size similar to that of 2012 DA14 (about 150 feet across) were to impact Earth, it would release approximately 2.5 megatons of energy in the atmosphere and would be expected to cause regional devastation.
A comparison to the impact potential of an asteroid the size of 2012 DA14 could be made to the impact of a near-Earth object that occurred in 1908 in Tuguska, Siberia. Known in the asteroid community as the "Tunguska Event," this impact of an asteroid just slightly smaller than 2012 DA14 (approximately 100 – 130 feet/30-40 meters across) is believed to have flattened about 750 square miles (1,200 square kilometers) of forest in and around the Podkamennaya Tunguska River in what is now Krasnoyarsk Krai, Russia.
Q: Can I see the asteroid during its close approach?
A: Asteroid 2012 DA14 is small, so even though it will make a close flyby of Earth, the asteroid's apparent magnitude is expected to peak at about only 7.4 – too dim to be viewed by the naked eye. To view the asteroid, you will need a good pair of binoculars, or even better, a moderately powered telescope.
During the closest approach, and dependant on local weather, the asteroid will be visible from parts of Europe, Africa and Asia. The asteroid will appear to be moving relatively quickly as it crosses the sky from the south to the north.
Q: What is NASA doing about asteroid 2012 DA14?
A: As there is no chance of impact, there is nothing that needs to be done about the asteroid. However, the flyby of 2012 DA14 is a great opportunity for science. NASA's Goldstone Solar System Radar, located in California's Mojave Desert, will observe the asteroid on Feb. 16, 18, 19 and 20. Due to the asteroid's small size, the radar images generated are expected to be no more than a few pixels across. It will also be observed by numerous optical observatories worldwide to attempt to determine its spin rate and composition.
Q: What is NASA doing about Near-Earth Objects?
A: NASA has several ongoing programs regarding asteroid discovery and science.
The NASA Near Earth Object Observation (NEOO) Program detects and tracks asteroids and comets passing close to Earth using both ground- and space-based telescopes. The network of projects supported by this program, commonly called "Spaceguard," discovers these objects, characterizes a subset of them and plots their orbits to determine if any could be potentially hazardous to our planet.
All observations from observatories worldwide are sent to the NASA funded Minor Planet Center, operated by the Smithsonian Astrophysical Observatory for the International Astronomical Union, where they are combined to maintain the database on all known asteroids and comets in our solar system. The Near-Earth Object Program Office at JPL manages the technical and scientific activities for NASA's Near-Earth Object Program of the Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology in Pasadena. The NEO Program Office performs more precise orbit determination on the objects, and predicts whether any will become an impact hazard to the Earth, or any other planet in the solar system. The NEOO Program also performs orbit analysis on the discovered Near Earth Asteroids (NEAs) at Goddard Space Flight Center to determine which ones may become good robotic or human spaceflight destinations in the near future.
NASA's 70-meter (230-foot) Goldstone antenna, located about 35 miles north of Barstow on the Ft. Irwin Military Base, is part of NASA's Deep Space network. The antenna is one of only two facilities capable of imaging asteroids with radar. The other is the National Science Foundation's 1,000-foot-diameter (305 meters) Arecibo Observatory in Puerto Rico. The capabilities of the two instruments are complementary, and NASA’s NEOO Program supports the radar capability at both these facilities. The Arecibo radar is about 20 times more sensitive, can see about one-third of the sky, and can detect asteroids about twice as far away. Goldstone is fully steerable, can see about 80 percent of the sky, can track objects several times longer per day, and can image asteroids at finer spatial resolution. JPL manages the Goldstone Solar System Radar and the Deep Space Network for NASA.
NASA has also started serveral basic research and technology demonstration projects to better understand the nature of asteroids and how they might best be deflected from an Earth impacting trajectory, or to develop the space technology required to do this. This development work includes improved Solar Electric Propulsion (SEP) systems that could push or pull an asteroid for an extended time, and close proximity operations and grappling mechanisms to work in and around asteroids and manipulate their surfaces. This technology will also be useful for future robotic and human missions to these objects, and even potentially resource mining operations.
Q: What current/future NASA missions are targeting asteroids and near-Earth objects?
A: NASA has one asteroid mission underway and another slated for launch in 2016.
Launched in 2007, NASA’s Dawn spacecraft has just finished orbiting the giant asteroid Vesta and is on its way to the dwarf planet Ceres. These two worlds are the two most massive objects in the main asteroid belt. The main asteroid belt is the likely region of origin for most NEAs. At each target, Dawn will acquire color photographs, compile a topographic map, map the elemental and mineralogical composition, measure the gravity field and search for moons. The data gathered by Dawn will enable scientists to understand the conditions under which these objects formed, determine the nature of the building blocks from which the terrestrial planets formed and contrast the formation and evolution of Vesta and Ceres. Dawn’s quest to understand the conditions that existed when our solar system formed provides context for the understanding of the observation of planetary systems around other stars.
The Dawn mission is managed by the Jet Propulsion Laboratory, for NASA’s Science Mission Directorate, Washington, D.C. It is a project of the Discovery Program managed by NASA’s Marshall Space Flight Center, Huntsville, Ala. The principal investigator resides at UCLA, and is responsible for overall Dawn mission science. Orbital Sciences Corporation of Dulles, designed and built the Dawn spacecraft. Other partners include the Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany, the German Aerospace Center, Berlin, the Italian Space Agency, Rome, Italy’s National Institute for Astrophysics, Rome, Los Alamos National Laboratory, N.M., and the Planetary Science Institute, Tucson, Ariz.
For more information about the Dawn mission, please visit: http://dawn.jpl.nasa.gov/mission/
NASA will launch a spacecraft to an asteroid in 2016 and use a robotic arm to pluck samples from an Near Earth Asteroid (NEA) that could better explain our solar system's formation and how life began. The mission, called Origins-Spectral Interpretation-Resource Identification-Security-Regolith Explorer, or OSIRIS-REx, will be the first U.S. mission to carry samples from an asteroid back to Earth. After traveling two years, OSIRIS-REx will approach the primitive Near Earth Asteroid designated 1999 RQ36 in 2018, discovered by the NEOO Program back in 1999. Once within three miles of the asteroid, the spacecraft will begin six months of comprehensive surface mapping. The spacecraft gradually will move closer to the site, and the arm will extend to collect more than two ounces of material for return to Earth in 2023.
Dante Lauretta from the University of Arizona is the mission’s principal investigator. NASA's Goddard Space Flight Center provides overall mission management, systems engineering and safety and mission assurance for NASA’s Science Mission Directorate, Washington, D.C. It is a project of the New Frontiers Program managed by NASA’s Marshall Space Flight Center, Huntsville, Ala. Lockheed Martin Space Systems of Denver is constructing the spacecraft.
For more information on OSIRIS-REx, visit: http://osiris-rex.lpl.arizona.edu/
NASA is sending the OSIRIS-REx spacecraft to asteroid 1999 RQ36 to better understand the evolution of its orbit and to retrieve a pristine sample for study on Earth.