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NASA Probe Sees Solar Wind Decline

The 33-year odyssey of NASA's Voyager 1 spacecraft has reached a distant point at the edge of our solar system where there is no outward motion of solar wind. Now hurtling toward interstellar space some 17.4 billion...

Super-Earth Atmosphere

A team of astronomers, including two NASA Sagan Fellows, has made the first characterizations of a super-Earth's atmosphere, by using a ground-based telescope...

Kepler Discovers

NASA's Kepler spacecraft has discovered the first confirmed planetary system with more than one planet crossing in front of, or transiting, the same star...

Pulverized Planet

Tight double-star systems might not be the best places for life to spring up, according to a new study using data from NASA's Spitzer Space Telescope....

Dark Asteroids

NASA is set to launch a sensitive new infrared telescope to seek out sneaky things in the night sky -- among them, dark asteroids that could pose a threat to Earth....

Archive for October 2011

An instrument on NASA's Mars rover Curiosity can check for any water that might be bound into shallow underground minerals along the rover's path.

"If we conclude that there is something unusual in the subsurface at a particular spot, we could suggest more analysis of the spot using the capabilities of other instruments," said this instrument's principal investigator, Igor Mitrofanov of the Space Research Institute, Russia.

The Mars Science Laboratory mission will use 10 instruments on Curiosity to investigate whether the area selected for the mission has ever offered environmental conditions favorable for life and favorable for preserving evidence about life.

"The strength of Mars Science Laboratory is the combination of all the instruments together," Mitrofanov added.

The Dynamic Albedo of Neutrons instrument, or DAN, will scout for underground clues to a depth of about 20 inches (50 centimeters). The Russian Federal Space Agency contributed it to NASA as part of a broad collaboration between the United States and Russia in the exploration of space. Sergey Saveliev, deputy head of the Russian Federal Space Agency, emphasized that the cooperation on this project serves as a continuation of the joint activities associated with the study of Mars to enhance the scientific return to the international community in the areas of Mars exploration and Mars knowledge. The accommodation and integration of the Russian DAN in the U.S. Mars Science Laboratory flight and mission systems give evidence of strengthening cooperation between the two countries in space endeavors.

DAN will bring to the surface of Mars an enhancement of nuclear technology that has already detected Martian water from orbit. "Albedo" in the instrument's name means reflectance -- in this case, how original high-energy neutrons injected into the ground bounce off atomic nuclei in the ground. Neutrons that collide with hydrogen atoms bounce off with a characteristic decrease in energy, similar to how one billiard ball slows after colliding with another. By measuring the energies of the neutrons leaking from the ground, DAN can detect the fraction that was slowed in these collisions, and therefore the amount of hydrogen.

Oil prospectors use this technology in instruments lowered down exploration holes to detect the hydrogen in petroleum. Space explorers have adapted it for missions to the moon and Mars, where most hydrogen is in water ice or in water-derived hydroxyl ions.

Mitrofanov is the principal investigator for a Russian instrument on NASA's Mars Odyssey orbiter, the high-energy neutron detector (HEND), which measures high energy of neutrons coming from Mars. In 2002, it and companion instruments on Odyssey detected hydrogen interpreted as abundant underground water ice close to the surface at high latitudes. That discovery led to NASA's Phoenix Mars Lander going to far northern Mars in 2008 and confirming the presence of water ice.

"You can think of DAN as a reconnaissance instrument," Mitrofanov said. Just as Phoenix investigated what Odyssey detected, Curiosity can use various tools to investigate what DAN detects. The rover has a soil scoop and can also dig with its wheels. Its robotic arm can put samples into instruments inside the rover for thorough analyses of ingredients. Rock formations that Curiosity's cameras view at the surface can be traced underground with DAN, enhancing the ability of scientists to understand the geology.

The neutron detectors on Odyssey rely on galactic cosmic rays hitting Mars as a source of neutrons. DAN can work in a passive mode relying on cosmic rays, but it also has its own pulsing neutron generator for an active mode of shooting high-energy neutrons into the ground. In active mode, it is sensitive enough to detect water content as low as one-tenth of one percent in the ground beneath the rover.

The neutron generator is mounted on Curiosity's right hip. A module with two neutron detectors is mounted on the left hip. With pulses lasting about one microsecond and repeated as frequently as 10 times per second, key measurements by the detectors are the flux rate and delay time of moderated neutrons with different energy levels returning from the ground. The generator will be able to emit a total of about 10 million pulses during the mission, with about 10 million neutrons at each pulse.

"We have a fixed number of about 10 million shots, so one major challenge is to determine our strategy for how we will use them," said Maxim Litvak, leading scientist of the DAN investigation from the Space Research Institute.

Operational planning anticipates using DAN during short pauses in drives and while the rover is parked. It will check for any changes or trends in subsurface hydrogen content, from place to place along the traverse. Because there is a low possibility for underground water ice at Curiosity's Gale crater landing site, the most likely form of hydrogen in the ground of the landing area is hydrated minerals. These are minerals with water molecules or hydroxyl ions bound into the crystalline structure of the mineral. They can tenaciously retain water from a wetter past when all free water has gone.

"We want a better understanding of where the water has gone," said Alberto Behar, DAN investigation scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "DAN fits right into the follow-the-water strategy for studying Mars."

Mars Science Laboratory Project Scientist John Grotzinger of the California Institute of Technology in Pasadena said, "DAN will provide the ability to detect hydrated minerals or water ice in the shallow subsurface, which provides immediate clues as to how the geology of the subsurface might guide exploration of the surface. In addition, DAN can tell us how the shallow subsurface may differ from what the rover sees at the surface. None of our other instruments have the ability to do this. DAN measurements will tell us about the habitability potential of subsurface rocks and soils -- whether they contain water -- and as we drive along, DAN may help us understand what kinds of rocks are under the soils we drive across."

Information from DAN will also provide a ground-truth calibration for the measurements that the gamma-ray and neutron detectors on Odyssey have made and continue to make, all around the planet, enhancing the value of that global data set. The team leader of Odyssey's gamma-ray spectrometer suite, William Boynton of the University of Arizona in Tucson, is a co-investigator on the DAN investigation, with the major responsibility to provide DAN data products to NASA's Planetary Data System for usage by scientists everywhere.

The distorted shapes in the cluster are distant galaxies from which the light is bent by the gravitational pull of an invisible material called dark matter within the cluster of galaxies. This cluster is an early target in a survey that will allow astronomers to construct the most detailed dark matter maps of more galaxy clusters than ever before.

These maps are being used to test previous, but surprising, results that suggest that dark matter is more densely packed inside clusters than some models predict. This might mean that galaxy cluster assembly began earlier than commonly thought.
The multi-wavelength survey, called the Cluster Lensing And Supernova survey with Hubble (CLASH), probes, with unparalleled precision, the distribution of dark matter in 25 massive clusters of galaxies. So far, the CLASH team has observed six of the 25 clusters.

Dark matter makes up the bulk of the universe’s mass, yet it can only be detected by measuring how its gravity tugs on visible matter and warps space like a fun house mirror so that the light from distant objects is distorted.

Galaxy clusters like MACS 1206 are perfect laboratories for studying dark matter’s gravitational effects because they are the most massive structures in the universe. Because of their heft, the clusters act like giant cosmic lenses, magnifying, distorting and bending any light that passes through them – an effect known as gravitational lensing.

Lensing effects can also produce multiple images of the same distant object, as evident in this Hubble picture. In particular, the apparent numbers and shapes of distant galaxies far beyond a galaxy cluster become distorted as the light passes through, yielding a visible measurement of how much mass is in the intervening cluster, and how it is distributed. The substantial lensing distortions seen are proof that the dominant component of clusters is dark matter. The distortions would be far weaker if the clusters’ gravity came only from the visible galaxies in the clusters.

MACS 1206 lies 4 billion light-years from Earth. Hubble’s keen vision helped CLASH astronomers uncover 47 multiple images of 12 newly identified faraway galaxies. Finding so many multiple images in a cluster is a unique capability of Hubble, and the CLASH survey is optimized to find them. The new observations build on earlier work by Hubble and ground-based telescopes.

Taking advantage of two of Hubble’s powerful cameras, the Advanced Camera for Surveys and the Wide Field Camera 3, the CLASH survey covers a broad wavelength range, from ultraviolet to near infrared. Astronomers need the diverse colors to estimate the distances to lensed galaxies and study them in more detail. Hubble’s unique capabilities allow astronomers to estimate distances to galaxies that are four times fainter than ground-based telescopes can see.

The era when the first clusters formed is not precisely known, but is estimated to be at least 9 billion years ago and possibly as far back as 12 billion years ago. If most of the clusters in the CLASH survey are found to have excessively high accumulations of dark matter in their central cores, then it may yield new clues to the early stages in the origin of structure in the universe.

Future telescopes like NASA’s James Webb Space Telescope, a space-based infrared observatory now being built, will be able to study the fainter lensed galaxies in clusters like MACS 1206 in greater detail. The Webb will be powerful enough to the spectra of some of the magnified galaxies to study their early chemical composition.

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

A fleet of spacecraft including NASA's Hubble Space Telescope has uncovered unprecedented details in the surroundings of a supermassive black hole. Observations reveal huge bullets of gas being driven away from the gravitational monster and a corona of very hot gas hovering above the disk of matter that is falling into the black hole.

A team led by Jelle Kaastra of SRON Netherlands Institute for Space Research made use of data from ESA's XMM-Newton and INTEGRAL spacecraft (which study X-rays and gamma rays, respectively), the Hubble Space Telescope (for ultraviolet observations with the COS instrument), and NASA's Chandra (X-ray) Observatory and Swift (gamma-ray) satellites.

The black hole that the team chose to study lies at the heart of the galaxy Markarian 509 (Mrk 509), nearly 500 million light-years away. This black hole is colossal, containing 300 million times the mass of the Sun, and is growing more massive every day as it continues to feed on surrounding matter, which glows brightly as it forms a rotating disk around the black hole. Mrk 509 was chosen because it is known to vary in brightness, which indicates that the flow of matter is turbulent.

The above image of Mrk 509 was taken in April 2007 with Hubble's Wide Field Planetary Camera 2. But using a large number of telescopes that are sensitive to different wavelengths of light gave astronomers unprecedented coverage running from the infrared, through the visible, ultraviolet, X-rays, and into the gamma-ray band.