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Ongoing Space Missions(2)

(This is the second part of the series "Ongoing Space Missions" in which I will try to inform the readers all about the spacecrafts still travelling or operating beyond near-earth orbit)

Chandra X-ray Observatory

Launched 1999 July 23

The objective -

To explore the hot turbulent regions in space with images 25 times sharper than previous x-ray pictures.

Mission Basics-

Chandra is the third of NASA’s Great Observatories, after the Hubble Space Telescope and the Compton Gamma Ray Observatory. Chandra is designed to observe X-rays from high-energy regions of the universe, such as the remnants of exploded stars.Chandra’s improved sensitivity make it possible to perform detailed studies of black holes, supernovas, and dark matter, and increase our understanding of the origin, evolution, and destiny of the universe.

Chandra’s unusual orbit, which has the shape of an ellipse, takes the spacecraft more than a third of the way to the moon before returning to its closest approach to the Earth of 16,000 kilometers (9,942 miles). The time to complete an orbit is 64 hours and 18 minutes.

Mission Cost-

The breakdown for Chandra Costs is $1.65 billion for Development. Operations and Data Analysis for the first five years are budgeted to be $0.75 billion. Launch costs were approximately $350 million. Operations and Data Analysis for the years 5-10 are budgeted to be $245 million

End of Mission

The scientific mission should last 5-15 years but the spacecraft should stay aloft for 25 - 50 years.

posted by: kyawoo at 22:14 | link | comments |
astronomy, unmanned missions

Ongoing Space Missions(1)

(This is the first part of the series "Ongoing Space Missions" in which I will try to inform the readers all about the spacecrafts still travelling or operating beyond near-earth orbit)

The Advanced Composition Explorer(ACE)

Launched 1997 August 25

The objective -

to observe particles of solar, interplanetary, interstellar, and galactic origins.

Mission Basics-

The Earth is constantly bombarded with a stream of accelerated particles arriving from the Sun and interstellar and galactic sources. Study of these energetic particles will contribute to our understanding of the formation and evolution of the solar system as well as the astrophysical processes involved. ACE spacecraft is carrying six high-resolution sensors and three monitoring instruments.

When reporting space weather ACE can provide an advance warning (about one hour) of geomagnetic storms that can overload power grids, disrupt communications on Earth, and present a hazard to astronauts.

ACE orbits the L1 libration point which is a point of Earth-Sun gravitational equilibrium about 1.5 million km from Earth and 148.5 million km from the Sun.

End of mission

The spacecraft has enough propellant on board to maintain an orbit at L1 until 2019.

posted by: kyawoo at 01:03 | link | comments |
unmanned missions

New "super Earth" detected

 European astronomers have found one of the smallest planets known outside our solar system, a world about 14 times the mass of our own around a star much like the Sun. It could be a rocky planet with a thin atmosphere, a sort of "super Earth," the researchers said today. But this is no typical Earth. It completes its tight orbit in less than 10 days, compared to the 365 required for our year. Its daytime face would be scorched.

No planet so small has ever been detected around a normal star. And the finding reveals a solar system more similar to our own than anything found so far.

The star is like our Sun and just 50 light-years away.

Most of the more than 120 planets found beyond our solar system are gaseous worlds as big or larger than Jupiter, mostly in tight orbits that would not permit a rocky planet to survive.

posted by: kyawoo at 22:27 | link | comments |
astronomy

Spacewalk

Humans have made more than 250 spacewalks, 142 of them by NASA astronauts.

The very first U.S. spacewalk was done by Ed White outside Gemini 4 in June 1965. The most recent spacewalk was by International Space Station crewmembers on Aug. 3.

There have been 55 spacewalks at the ISS — 25 from Space Shuttles and 30 based from the Station itself. Total time of ISS spacewalks is 332 hours and 56 minutes. That’s about 14 days.

The Russians have done 111 spacewalks, including the first. Cosmonaut Alexei Leonov stepped out of the Voshkod 2 spacecraft in March 1965. He traveled about 3,500 miles during his 12-minute outing.

posted by: kyawoo at 12:56 | link | comments |

Understanding the planets' interiors

The basic structure and composition of Earth and the other planets in our solar system can be determined from routine astronomical observations. Measurements of surface chemical composition, either by direct sampling (as has been done on Earth, the moon, and Mars) or through spectroscopic observations, can be used to estimate elemental abundances and the degree of chemical differentiation that occurred as the planets condensed from the solar nebula. Remote observations of the gravitational field can be used to understand how a planet's mass is distributed, whereas the strength and shape of the magnetic field provides some constraint on the structure of a metallic core.

The specifics of structure and composition, however, are much more debatable. And it is these details that tell us a much more extensive and ultimately more interesting story about the internal dynamics of the planets and their evolution. As a result, trying to determine them is frontier research in almost all fields of earth and planetary science.

Even on Earth, many of these details have to be inferred from remote observations. Because we cannot sample the deep Earth, we must deduce its composition either by looking at the clues hidden in igneous and metamorphic rocks, or by examining proxies for composition and structure such as the three-dimensional variation of the velocity of seismic waves produced by earthquakes and sampled by networks of seismometers on the surface. The late Francis Birch, the eminent Harvard geophysicist, and his colleagues and students worked out the basic methodology that brings these distinct observations together. Birch showed how the stiffness of rocks changes under the extreme conditions of pressure and temperature deep within planets, as well as with chemical composition. Because the speed of seismic waves depends on the stiffness of the medium through which they propagate, it is possible to calculate temperature and composition from maps of seismic velocity. Most current research is based on Birch's work and it has even been extended to the most extreme temperature and pressure conditions of the Earth's core. For example, much of our understanding of the large- and small-scale convection patterns driving plate tectonics has come about by using Birch-type proxies for temperature and composition.

Birch knew, however, that such interpretations should be made cautiously. Birch provided a small Rosetta stone that enabled future workers to interpret the results his methodology made possible. Thus, when talking about the chemical composition of planetary interiors, “certain” should be replaced by “dubious,” “positive proof” by “vague suggestions,” and, when talking about the Earth's core, “pure iron” should be replaced by “uncertain mixture of all the elements.” We obviously know more today than we did fifty years ago, but Birch's words resonate in every classroom and laboratory.

How can we improve our understanding of the other planets? Manned and unmanned missions to the moon and Mars deployed seismometers, which provided tantalizing but ultimately limited information before they stopped operating (although the Spirit and Opportunity rovers continue to transmit chemical analyses and pictures of the red planet back to Earth). Almost all planetary landing missions now in the design stage include seismological instrumentation and some even include sample return. Hopefully the best science is yet to come. But even on Earth, where thousands of seismometers have been deployed and new experiments, such as the National Science Foundation's “EarthScope,” are now being conducted, each new observation raises as many questions as it answers. The Earth's story has been written, but we're only on the first few chapters.

posted by: kyawoo at 22:15 | link | comments |
planets

Remnants of the collision of Jupiter and a comet

From July 16 through July 22, 1994, Comet P/Shoemaker-Levy 9 collided with Jupiter sending hot gases into the Jovian atmosphere. Dark scars lasted for weeks.

Shocks created by the impacts led to high-temperature chemical reactions that produced hydrogen cyanide, which remains in the air but has been spread around a bit in the years since. The comet also delivered carbon monoxide and water, which through an interaction with sunlight, scientists suspect, was converted to carbon dioxide.

The hydrogen cyanide has diffused some both north and south, mixed by wave activity. Jupiter’s cloud bands carry material around the planet swiftly, but the bands do not mix easily. Not surprisingly, hydrogen cyanide is most abundant in a belt at the latitude where the comet was absorbed.

The highest concentration of carbon dioxide, however, has shifted away from the latitude of the impact. It is most prevalent poleward of 60 degrees south and decreases abruptly, toward the equator, north of 50 degrees south. Another smaller spike in its presence occurs at high northern latitudes, around 70 to 90 degrees north.

Perhaps the two chemicals got distributed at different altitudes, and are being moved around by different currents. Or maybe the formation of the carbon dioxide was more complex than thought. He said it might have involved carbon monoxide first moving away from the impact area and then interacting with other substances at higher latitudes before being converted to carbon dioxide.

These findings are the result of the Cassini spacecraft, now at Saturn, as it examined Jupiter in 2000 and 2001.

posted by: kyawoo at 22:39 | link | comments |
comets, jupiter

Gravity assist to Messenger

It's easy to fly by a planet. It can be done by pointimg a spacecraft in the right direction to pass by the planet as it orbits the Sun

But inserting a craft into a planet's orbit is a different story. Too slow, the probe will drop into the planet's atmosphere and burn up. Too fast, it will fly off into space, stuck helpless in a solar orbit for billions of years.

The spacecraft head into space with all the energy and speed it had when it left the Earth, and then have to slow down to meet up with a planet.

This means it has to burn off a lot of energy during its journey. One way is to carry a large amount of fuel and perform braking maneuvers during the trip. But fuel may accounts for more than half of the spacecraft's total launch weight; adding more would weigh down the spacecraft to the point where it wouldn't be practical to launch at all.

The other technique, which MESSENGER is going to undertake on its journey to Mercury, is called "gravity assist." Most people think of speeding up a spacecraft when they hear about this concept, but it can actually work to slow one down as well.

This is due to "angular momentum," the tremendous amount of energy a planet orbiting the Sun has because of its enormous size and speed. When a spacecraft flies past that giant body, it can tap into the planet's gravity to increase its speed. When a spacecraft flies along in front of it, the opposite happens: the vehicle gives up some of its energy to the planet.

Messenger will fly by Earth, Venus and Mercury several times to burn off energy before making its final approach to the inner planet on March 18, 2011.

posted by: kyawoo at 22:18 | link | comments |
unmanned missions, space science

Comet chaser and lander

The first space mission ever to land on a comet, European Space Agency’s Rosetta spacecraft is on its way to rendezvous with Comet 67P/Churyumov-Gerasimenko. When the craft reaches its target in 2014 the lander will touch down on the comet surface and the main spacecraft will follow the comet for many months as it heads towards the Sun. Ingenious instruments on board Rosetta will ‘smell’ the comet for different substances, analysing samples that have been ‘cooked’ in a set of miniature ovens. Rosetta will help us to understand if life on Earth began with the help of ‘comet seeding’.

The Rosetta mission will achieve many historic firsts:

· Rosetta will be the first spacecraft to orbit a comet’s nucleus.

· It will be the first spacecraft to fly alongside a comet as it heads towards the inner Solar System.

· Rosetta will be the first spacecraft to examine from close proximity how a frozen comet is transformed by the warmth of the Sun.

· Shortly after its arrival at the comet, the Rosetta lander will make the first controlled touchdown on a comet nucleus.

Please search and read other entry on Rosetta in this blog.

posted by: kyawoo at 23:31 | link | comments |
unmanned missions, comets

Mercury

A cosmic oddity.

Mercury is closer to the sun than any other planet, but its temperature 840°F is not quite the hottest. That distinction goes to nearby Venus, where the temperature climbs to 900°F, owing to the planet’s dense, heat-trapping atmosphere

Yet there may be water ice in permanently shadowed polar crate. At the poles, where the sun is low on the horizon, light may never shine inside some craters. That means water, delivered by a comet or left over from the formation of the planet, could remain frozen indefinitely.

Mercury spins so slowly and scoots around the sun so fast that a Mercury year — just 88 Earth days — is half as long as a Mercury day.

On the planet’s illuminated side — where the sun looks three times as big as it does from Earth and is 11 times as bright — temperatures climb to 840°F. When that side rotates into darkness, the thermometer plunges to —300°F. Reasons for Mercury’s wild temperature swings are its lack of any appreciable atmosphere and its reflective surface that bounces 90% of the sun’s heat back into space Eons of this rotisserie roll have cooked Mercury down to a nub with a metal core that represents three-quarters of its diameter.

High density

Because Mercury is extremely dense for its size — it’s comparable to Earth — researchers believe it has a large metallic, most likely iron core. But exactly how large the core is, whether its outer regions are molten, and whether it rotates to power the planet’s strong magnetic field, are still unknown.

Astronomers have put forward several theories to explain Mercury’s extreme density.

According to one version of events, denser elements, such as iron, were drawn closer to the sun in the region of space where Mercury formed when the solar system was created from a swirling cloud of gas and dust.

Other experts think that the younger and hotter sun vaporized a large part of the planet’s original rocky exterior, leaving behind the iron core.

And still others hypothesize that much of Mercury’s outer surface was blasted away in a collision with another planet-sized body at the dawn of the solar system.

Magnetic field

Scientists believe Earth’s magnetic field — which acts like a giant bar magnet at the poles — is generated by swirling motions of molten rock that surrounds the solid core. Mars, the moon and possibly Venus once had magnetic fields, but they apparently went dormant when the interiors of these celestial bodies cooled and solidified.

Mercury, from all appearances, also looks like a dormant planet. The half of the planet is pitted with ancient craters and there are no indications of recent volcanic activity. Huge escarpments stretch for hundreds of kilometres, giving the impression that Mercury cracked and shrank during a cooling process long ago. Even so, this odd little planet is somehow producing a magnetic field.

Under the shrinking surface theory, researchers believe that Mercury’s crust first formed over a gigantic molten core. As that core cooled, it led to a volume change causing the surface to buckle and break.

Unlike water, which actually expands as it cools, most materials tend to contract and the same goes for Mercury’s rocky crust. Based on observations of the planet’s known hemisphere, scientists estimate the planet’s surface has shrunk inward between less than one kilometer and three kilometers

Unlike Earth, Mercury does not spin on a tilted axis, which means a crater at its north or south pole would be in permanent shadow. And Mercury’s ultra-thin atmosphere does not transport heat from the equator to the poles, as Earth’s does.

The floor of a shadowed crater would never see the sun and would be cold enough — minus 300 degrees Fahrenheit or colder — to freeze water for the lifetime of the planet.

Previous mission - Mariner-10

Three decades ago, the NASA sent its Mariner 10 spacecraft to Mercury on a pioneering mission. Looping around Venus and the Sun, the craft made three swift flybys of Mercury during 1974 and 1975, sending back almost 1,000 pictures that mapped only 40 percent of the surface of the heavily cratered planet. Mariner found iron-laden Mercury to be the densest planet in the solar system and the only inner planet besides Earth with a global magnetic field, but left scientists wanting to know more.

Current mission - Messenger

Messenger is one of NASA’s lower-cost, rapidly executed Discovery Program robot missions designed to go from planning to flight in about three years. Pulling off the $427 million mission requires getting gravitational boosts from planetary flybys to get the spacecraft to Mercury and maneuver it into orbit.

Even though Mercury is 50 million miles from Earth at closest approach, Messenger will travel 5 billion miles to get there. It’s technologically infeasible to fly straight to Mercury and so the spacecraft must swing once past Earth, twice past Venus and thrice past Mercury before slowing down enough to slip into orbit around Mercury.

The technology for designing a spacecraft capable of withstanding harsh heat for prolonged periods was unavailable until recently. The main body of the spacecraft, made of a lightweight, heat-tolerant graphite composite material, is covered with multilayered insulation and peppered with radiators and heat pipes to channel heat away. The craft, powered by two electricity-generating solar panels, weighs 2,424 pounds at launching, half of that rocket fuel for its maneuvering engine and control thrusters.

The most distinctive feature of the spacecraft is a large, highly reflective, heat-resistant sunshade attached to the front on a titanium frame. Measuring eight feet tall and six feet across, the quarter-inch-thick shield is made of front and back layers of Nextel ceramic cloth surrounding inner layers of Kapton plastic insulation.

Temperatures on the front of the white shield could reach 700 degrees Fahrenheit when Mercury is closest to the Sun, engineers said, but the spacecraft on the shady side should operate at a room temperature of 68 degrees. Messenger is programmed to keep the shade between itself and the Sun at all times.

Messenger is to circle Mercury for one Earth year in an oval-shaped orbit that takes it 124 miles above the surface at the nearest point and 9,420 miles out at the farthest. Cameras will send back images showing features as small as 60 feet across; a battery of spectrometers will identify the elements and compounds on the surface; a laser altimeter will map landforms and distances; and other experiments will study variations in the planet’s gravity and magnetic field.

Once its mission is accomplished in 2012, Messenger will keep orbiting until it eventually crashes onto the surface.

posted by: kyawoo at 12:57 | link | comments |
mercury

2 new Saturn moons discovered

The Cassini-Huygens mission has discovered two new moons around Saturn.

The new discoveries take Saturn’s total tally of natural satellites to 33.

The moons are about 3km (2 miles) and 4km (2.5 miles) across and located 194,000km (120,000 miles) and 211,000 km (131,000 miles) from Saturn’s centre.

They are provisionally named S/2004 S1 and S/2004 S2.

S/2004 S1 and S/2004 S2 were first seen by Dr Sebastien Charnoz, a colleague of Cassini imaging team member Andre Brahic at the University of Paris, France.

Moons surrounding the giant planets are not generally found where they formed because tidal forces from the planet can cause them to drift from their original locations. In drifting, they may sweep through locations where other moons disturb them, making their orbits eccentric or inclined relative to the planet’s equator. One of the new moons might have undergone such an evolution.

posted by: kyawoo at 23:08 | link | comments |
saturn, unmanned missions