The animation depicts a mapping of the positions of known near-Earth objects (NEOs) at points in time over the past 20 years, and finishes with a map of all known asteroids as of January 2018. Asteroid search teams supported by NASA's NEO Observations Program have found over 95 percent of near-Earth asteroids currently known. There are now over 18,000 known NEOs and the discovery rate averages about 40 per week. Image credit: NASA/JPL-Caltech
https://www.jpl.nasa.gov/images/asteroid/20180723/main-animation-16.gifNASA's Center for Near-Earth Object Studies Enters Third Decade.
On March 11, 1998, asteroid astronomers around the world received an ominous message: new observational data on the recently discovered asteroid 1997 XF11 suggested there was a chance that the half-mile-wide (nearly one kilometer) object could hit Earth in 2028.
The message came from the Minor Planet Center, in Cambridge, Massachusetts, the worldwide repository for such observations and initial determination of asteroid orbits. And although it was intended to alert only the very small astronomical community that hunts and tracks asteroids to call for more observations, the news spread quickly.
Most media outlets did not know what to make of the announcement, and mistakenly highlighted the prospect that Earth was doomed.
The animation depicts a mapping of the positions of known near-Earth objects (NEOs) at points in time over the past 20 years, and finishes with a map of all known asteroids as of January 2018. Asteroid search teams supported by NASA's NEO Observations Program have found over 95 percent of near-Earth asteroids currently known. There are now over 18,000 known NEOs and the discovery rate averages about 40 per week. Image credit: NASA/JPL-Caltech
Fortunately, it turned out that Earth was never in danger from 1997 XF11. After performing a more thorough orbit analysis with the available asteroid observations, Don Yeomans, then the leader of the Solar System Dynamics group at NASA's Jet Propulsion Laboratory in Pasadena, California, along with his colleague Paul Chodas, concluded otherwise. "The 2028 impact was essentially impossible," said Chodas, who is now director of NASA's Center for Near-Earth Object Studies (CNEOS), located at JPL.
"To this day we still get queries on the chances of XF11 impacting in 2028," Chodas said. "There is simply no chance of XF11 impacting our planet that year, or for the next 200 years."
Chodas knows this thanks to CNEOS' precise orbit calculations using observation data submitted to the Minor Planet Center by observatories all over the world that detect and track the motion of asteroids and comets. For the past two decades, CNEOS calculations have enabled NASA to become the world leader in these efforts, keeping close watch on all nearby asteroids and comets -- especially those that can cross Earth's orbit.
"We compute high-precision orbits for all asteroids and comets and map their positions in the Solar System, both forward in time to detect potential impacts, and backward to see where they've been in the sky," Chodas said. "We provide the best map of orbits for all known small bodies in the Solar System."
The chart depicts the cumulative number of known Near-Earth asteroids (NEAs) versus time
The chart depicts the cumulative number of known Near-Earth asteroids (NEAs) versus time. The area in red depicts the number of known NEAs larger than 0.6 miles (1 kilometer). The area in orange depicts the quantity of known NEAs larger than 460 feet (140 meters). The area in blue depicts the number of known NEAs in all sizes. Image credit: NASA/JPL-Caltech
Larger view
Mapping the Celestial Hazard
Near-Earth Objects (NEOs) are asteroids and comets in orbits that bring them into the inner solar system, within 121 million miles (195 million kilometers) of the Sun, and also within roughly 30 million miles (50 million kilometers) of Earth's orbit around the Sun.
The media frenzy around NEO 1997 XF11 demonstrated the need for clarity and precision in communicating with the public about the close passes by Earth of these objects, as well as "the importance of peer review before public statements like these are made," Chodas said.
NASA's original intent was to fulfill a 1998 Congressional request to detect and catalogue at least 90 percent of all NEOs larger than one kilometer in size (roughly two-thirds of a mile) within 10 years. To help reach the Congressional goal, NASA Headquarters requested that JPL establish a new office to work with the data provided by the International Astronomical Union-sanctioned Minor Planet Center for submission of all observations of asteroids and comets, and to coordinate with observatories operated by academic institutions around the United States, as well as U.S. Air Force space surveillance assets.
In the summer of 1998, NASA established the Near-Earth Object Observations Program and JPL became the home for the agency's research data and analysis on NEOs, the "Near-Earth Object Program Office." (To view the announcement regarding the creation of the Near-Earth Object Program Office, see:
https://www.jpl.nasa.gov/news/news.php?feature=5134)In 2016, the office was renamed the Center for Near-Earth Object Studies (CNEOS) in conjunction with the establishment of the Planetary Defense Coordination Office (PDCO) at NASA Headquarters in Washington.
For about 20 years, CNEOS has been NASA's central hub for accurately mapping the orbits of all the known NEOs, predicting their upcoming close approaches, reliably assessing their chances of impact to our planet, and delivering that information to both astronomers worldwide and the general public.
Predicting Close Approaches and Impacts: Sentry and Scout
The first and most important step in assessing the impact risk of an asteroid or comet is to determine whether any given object's orbit will cross Earth's orbit -- and then how close it will actually get to our planet. JPL was determining high-precision orbits for a few NEOs even before NASA launched its NEO Observations Program, and has since upgraded its orbit models to provide the most accurate assessment available for asteroid positions and orbits.
Observatories around the world take digital images of the sky to detect moving points of light (the asteroid or comet) over days, weeks, months (and even decades!), and then report the positions of these moving objects relative to the static background of stars to the Minor Planet Center. See "How a Speck of Light Becomes an Asteroid".The CNEOS scientists then use all this observation data to more precisely calculate an NEO's orbit and predict its motion forward in time for many years, looking for close approaches and potential impacts to the Earth, its Moon, and other planets.
A CNEOS system called "Sentry" searches ahead for all potential future Earth impact possibilities over the next hundred years -- for every known NEO. Sentry's impact monitoring runs continually using the latest CNEOS generated orbit models, and the results are stored online.In most cases so far, the probabilities of any potential impacts are extremely small, and in other cases, the objects themselves are so small -- less than 20 meters in size, or nearly 66 feet -- that they would almost certainly disintegrate even if they did enter Earth's atmosphere.
"If Sentry finds potential impacts for an object, we add it to our online 'impact risk' table, and asteroid observers can then prioritize that object for further observation," said Steve Chesley of JPL, a member of the CNEOS team who was the main developer of the Sentry system. "The more measurementsmade of the object's position over time, the better we can predict its future path."
"In most cases, the new measurements mean the object can be removed from the risk list because the uncertainties in the orbital path are reduced and the possibility of impact is ruled out," Chesley said.
More recently, CNEOS also developed a system called Scout to provide more immediate and automatic trajectory analyses for the most recently discovered objects, even before independent observatories confirm their discovery. Operating around the clock, the Scout system not only notifies observers of the highest priority objects to observe at any given time, it also immediately alerts the Planetary Defense Coordination Office of any possible imminent impacts within the next few hours or days.A recent example is the Scout-predicted impact of the small asteroid 2018 LA over Botswana, Africa.
More Hunting to Do
With the addition of more capable NASA-funded asteroid surveys over the years, NASA's NEO Observations Program is responsible for over 90 percent of near-Earth asteroid and comet discoveries. There are now over 18,000 known NEOs and the discovery rate averages about 40 per week.
Although the original Congressional goal from 1998 has been exceeded and much progress has been made in asteroid discovery and tracking over the past two decades, the work isn't over. In 2005, Congress established a new, much more ambitious goal for the NEO Observations Program -- to discover 90 percent of the NEOs down to the much smaller size of 450 feet (140 meters), and to do so by the year 2020 (https://www.congress.gov/congressional-report/109th-congress/house-report/158/1).
These smaller asteroids may not present a threat of global catastrophe if they impact Earth, but they could still cause massive regional devastation and loss of life, especially if they occur near a metropolitan area. CNEOS continues to make improvements to its orbital analysis tools, image and graphic presentation capabilities, and updates of its websites to quickly and accurately provide the very latest information on NEOs to PDCO, the astronomical community and the public.
JPL hosts the Center for Near-Earth Object Studies for NASA's Near-Earth Object Observations Program, an element of the Planetary Defense Coordination Office within the agency's Science Mission Directorate.
More information about CNEOS, asteroids and near-Earth objects can be found at:
https://cneos.jpl.nasa.govhttps://www.jpl.nasa.gov/asteroidwatchFor more information about NASA's Planetary Defense Coordination Office, visit:
https://www.nasa.gov/planetarydefenseFor asteroid and comet news and updates, followAsteroidWatchon Twitter:
twitter.com/AsteroidWatch
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L'éclipse lunaire du 27 juillet 2018 est la seconde éclipse de Lune de l'année 2018. Il s'agit d'une éclipse totale ; elle est la deuxième éclipse totale d'une série de trois, se produisant à environ 6 mois d'intervalle. C'est aussi une éclipse totale centrale, la Lune passant par le centre de l'ombre de la Terre. C'est la première éclipse lunaire centrale depuis celle du 15 juin 2011.
Puisqu'elle se produit lorsque la Lune est proche de l'apogée, cette éclipse sera aussi la plus longue éclipse lunaire totale du XXIe siècle, avec une phase de totalité de près de 103 minutes1.
Cette simulation animée montre l'apparence approximative de la Lune passant dans l'ombre de la Terre durant cette éclipse. La Lune passe par le centre de l'ombre durant cette éclipse totale centrale.
Sommaire
1 Visibilité
2 Notes et références
3 Voir aussi
3.1 Articles connexes
3.2 Liens externes
Visibilité
L'éclipse est visible depuis la totalité de l'Océan Indien, qui est tourné vers la Lune lors de cette éclipse. L'Afrique centrale et orientale ainsi que l'Asie centrale assisteront à l'intégralité de l'éclipse.
L'Amérique du Sud, le Nord-Ouest de l'Afrique et l'Europe verront les différentes phases de cette éclipse après le coucher du Soleil.
Les premières phases de l'éclipse seront visibles depuis l'Asie du Sud-Est et l'Australie, aux premières heures du matin (local), avant le lever du Soleil.
Lunar eclipse from moon-2018Jul27.png
La Terre vue de la Lune lors du maximum de l'éclipse. Visibility Lunar Eclipse 2018-07-27.png
Carte de visibilité.
Notes et références
(en) Cet article est partiellement ou en totalité issu de l’article de Wikipédia en anglais intitulé « July 2018 lunar eclipse » (voir la liste des auteurs).
↑ (en)In 2018 the longest lunar eclipse will take place in 100 years [archive] En 2018 la plus longue éclipse lunaire qui aura lieu en 100 ans.
Voir aussi
Articles connexes
2018 en astronomie
Liste d'éclipses lunaires (en)
Liste d'éclipses lunaires se produisant au XXIe siècle (en)
Liens externes
Sur les autres projets Wikimedia :
Éclipse lunaire du 27 juillet 2018, sur Wikimedia Commons
(en)[PDF]Carte de l'éclipse générale et informations sur l'éclipse [archive] Eclipse Predictions by Fred Espenak, NASA/GSFC
(en)Hermit eclipse: 2018-07-27 [archive]
Éclipse lunaire du 27 juillet 2018
Précédée par Suivie par
31 janvier 2018
(totale)
27 juillet 2018
(totale)
21 janvier 2019
(totale)
https://fr.wikipedia.org/wiki/%C3%89clipse_lunaire_du_27_juillet_2018--------------------------
ECOSTRESS acquired this image the night of July 9 over Egypt. Yellow and red indicate generally higher temperatures. The River Nile is visible as a thin blue line on the main image. The black-and-white inset shows the level of detail available from ECOSTRESS, with the relatively cool Nile River and surrounding vegetation appearing darker. Credit: NASA/JPL-Caltech
https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA22590Just days after its successful installation on the International Space Station, NASA's newest Earth-observing mission, the ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS), has collected its first science data on Earth's surface temperature.
ECOSTRESS will measure the temperature of plants from space, enabling researchers to determine how much water plants use and to study how droughts affect plant health.
The instrument was launched June 29 from Florida's Cape Canaveral Air Force Station on a SpaceX cargo resupply mission. It rode to orbit in the "trunk" of SpaceX's Dragon spacecraft, which berthed at the station on July 2. On July 5, ground controllers at NASA's Johnson Space Center in Houston extracted ECOSTRESS from the trunk, robotically transferred it to the station's Japanese Experiment Module - Exposed Facility (JEM-EF) and installed it. After a few days of testing and start-up activities, ECOSTRESS acquired its first-light image on July 9.
"Often satellite missions require weeks or months to produce data of the quality that we are already getting from ECOSTRESS," said the mission's principal investigator, Simon Hook of NASA's Jet Propulsion Laboratory in Pasadena, California. ECOSTRESS is one of a new class of low-cost, rapid-development NASA science instruments. The ECOSTRESS instrument was launched less than four years after the project was started.
The ECOSTRESS team is now checking out the instrument and acquiring preliminary science data, a process expected to take about a month. They have completed an initial calibration of the science data and are now validating the data by comparing them with similar measurements made at ground control sites. When this process is complete, ECOSTRESS will be ready to begin its one-year science mission.
JPL built and manages the ECOSTRESS mission for NASA's Earth Science Division in the Science Mission Directorate at NASA Headquarters in Washington. ECOSTRESS is an Earth Venture Instrument mission; the program is managed by NASA's Earth System Science Pathfinder program at NASA's Langley Research Center in Hampton, Virginia.
For more information on ECOSTRESS, visit:
https://ecostress.jpl.nasa.govFor more information on science activities aboard the space station, visit:
https://www.nasa.gov/mission_pages/station/research/benefits/research_by_com_campaignNews Media Contact
Esprit Smith
Jet Propulsion Laboratory, Pasadena, California
818-354-4269
Esprit.Smith@jpl.nasa.gov2018-172
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These two images of Lake Superior and the surrounding area are the first data downlinked from the CubeSat Multispectral Observation System (CUMULOS) cameras. Credit: NASA/Aerospace Corporation
https://www.jpl.nasa.gov/images/cubesat/20180703/cumulos-16.jpgThese two images of Lake Superior and surrounding area show the first data downlinked from the CubeSat Multispectral Observation System (CUMULOS) cameras. The image on the left, taken by a short-wavelength infrared camera, captures a larger area of the lake and shows strong contrast between land and water features. The narrower field of view image on the right taken by the payload's long-wavelength infrared camera indicates a difference in water temperature between the lake's center and the water in the bays and inlets.
CUMULOS is testing the performance of commercial sensors for weather and environmental monitoring missions. The cameras are designed for point-and-stare imaging and allow nearly simultaneous coverage of Earth regions from an orbital altitude of 280 miles (452 kilometers).
CUMULOS is hosted as a demonstration of an experimental payload on NASA's Integrated Solar Array and Reflectarray Antenna (ISARA), which is managed by NASA's Jet Propulsion Laboratory in Pasadena, California, and operated by The Aerospace Corporation.
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