Posted on by Fraser Cain

What’s Creating the Methane, Life or Volcanoes?

Image credit: ESA
Considered suggestive of life, an atmosphere of methane on another planet is considered one of the four best candidates for detecting habitable conditions using remote sensing and telescope spectrographs. While methane can be made both by biological and non-biological processes, it is also degraded by non-biological means, so a high concentration often is interpreted as requiring a source to replenish it. If metabolism is that source, then some of the prerequisites for a steady-state ecosystem may be in play.

On Earth there are four gases linked to the presence of life and habitable conditions: water vapor, carbon dioxide, methane and molecular oxygen (O2, or its proxy, ozone O3). Water is essential to all biology we understand today, while the exchange of carbon dioxide and oxygen constitute the collective respirator for photosynthesis and breathable worlds. The dominant gas on Mars today is by far carbon dioxide.

With methane, there are some methanogenic organisms that require consumption of this gas for their subsistence. Methanogenesis converts carbon dioxide to methane. Since strong chemical reactions quickly destroy (oxidize) methane at the Martian surface, if methane is found today, there must be some replenishment that gives a clue to active biology. Such biosynthesis leaves a ubiquitous signature of life even in specimens where there are no fossils visible.

Michael J. Mumma of Goddard Space Flight Center first reported in a poster at a recent planetary conference [DPS] that his preliminary search for methane with both of two ground-based infrared telescopes had found something interesting. His survey turned up intriguing signs of what may be methane’s spectral line in the Martian atmosphere.

These hints have now been confirmed by the European orbiter, Mars Express. Using an instrument called the Planetary Fourier Spectrometer (PFS), the work reported in Nature magazine identified the characteristic spectral fingerprint of methane. “We have detected methane at concentrations of ten parts per billion,” said Vittorio Formisano of the Institute of Physics of Interplanetary Space in Rome and the principal investigator in the PFS team.

The current martian atmosphere is 99% thinner than the Earth’s. The surface temperature averages -64 F (-53 C), but varies between 200 below zero during polar nights to 80 F (27 C) at midday peaks near the equator. The global picture of Mars is sometimes compared terrestrially to Antarctic dry regions, only colder.

Carbon, nitrogen and methane would be the gaseous precursors to what would be required to sustain or transform Mars from its current inhospitable state to a warmer, microbe-friendly planet. Because researchers believe that methane can persist in the Martian atmosphere for less than 300 years, any methane they find can be assumed to arise from recent biological processes, produced, for example, by methane-producing bacteria. This close link gives methne its less scientific name of swamp gas.

The European Mars Express mission is capable of detecting methane in the martian atmosphere. As Agustin Chicarro, Mars Express Project Scientist said, these “investigations will provide clues as to why the north of the planet is so smooth and the south so rugged, how the Tharsis and Elysium mounds were lifted up and whether active volcanoes exist on Mars today.”

There are some problems with trying to understand the history of methane and other greenhouse gases on Mars. There is no evidence on Mars of large limestone deposits from the first billion years, which would be directly linked to large amounts of C02, a greenhouse gas.

Methane — which can be created naturally by volcanic eruptions or produced by primitive life — thus may be a missing piece of the puzzle to finding out if organic remnants might once have sustained a primordial Mars. The last period of active volcanism on Mars is well before the last 300 years that methane can survive in the martian atmosphere of today. University of Buffalo volcanologist, Tracy Gregg, told Astrobiology Magazine, “the youngest surficial activity discovered to date (and it’s probably 1 million years old, which would be considered quite young, and possibly “active” on Mars) is in a region that contains no large volcanic structures of any kind.” Mars’ gigantic volcano Mons Olympus was active until 100 million years ago.

Earlier observations had speculated on methane concentrations as high as 50-70 parts per million, not what Mars Express detected as ten parts per billion. This low level could not likely sustain a global pattern suggestive of a biosphere, but might support local ecologies if methane has some underground source. Whatever the final concentration might be, its appearance in such an unstable atmosphere has taken on importance to unravel the mysteries of a martian biosphere. The most frequently mentioned example of a martian methane economy centers on a deep biosphere of methane rich biochemistry, or anerobic methanogens.

Original Source: Astrobiology Magazine

Posted on by Fraser Cain

Landing on a Comet

Image credit: ESA
Rosetta?s lander Philae will do something never before attempted: land on a comet. But how will it do this, when the kind of surface it will land on is unknown?

With the surface composition and condition largely a mystery, engineers found themselves with an extraordinary challenge; they had to design something that would land equally well on either solid ice or powder snow, or any state in between.

In the tiny gravitational field of a comet, landing on hard icy surface might cause Philae to bounce off again. Alternatively, hitting a soft snowy one could result in it sinking. To cope with either possibility, Philae will touch as softly as possible. In fact, engineers have likened it more to docking in space.

Landing on a comet is nothing like landing on a large planet, you do not have to fight against the pull of the planet?s gravity, and there is no atmosphere.

The final touching velocity will be about one metre per second. That is near a walking pace. However, as anyone who has walked into a wall by mistake will tell you, it is still fast enough to do some damage. So, two other strategies have been implemented.

Firstly, to guard against bouncing off, Philae will fire harpoons upon contact to secure itself to the comet.

Secondly, to prevent Philae from disappearing into a snowy surface, the landing gear is equipped with large pads to spread its weight across a broad area ? which is how snowshoes work on Earth, allowing us to walk on powdery falls of snow.

When necessity forced Rosetta?s target comet to be changed in Spring 2003 from Comet Wirtanen to Comet 67P/Churyumov-Gerasimenko, the landing team re-analysed Philae?s ability to cope. Because Comet Churyumov-Gerasimenko is larger than Wirtanen, three times the radius, it will have a larger gravitational field with which to pull down Philae.

In testing it was discovered that the landing gear is capable of withstanding a landing of 1.5 metres per second ? this was better than originally assumed.

In addition, Rosetta will gently push out the lander from a low altitude, to lessen its fall. In the re-analysis, one small worry was that Philae might just topple, if it landed on a slope at high speed. So the lander team developed a special device called a ?tilt limiter?, and attached it to the lander before lift-off, to prevent this happening.

In fact, the unknown nature of the landing environment only serves to highlight why the Rosetta mission is vital in the first place. Astronomers and planetary scientists need to learn more about these dirty snowballs that orbit the Sun.

Original Source: ESA News Release

Posted on by Fraser Cain

Mars Express Confirms Methane Discovery

Image credit: ESA
During recent observations from the ESA Mars Express spacecraft in orbit around Mars, methane was detected in its atmosphere.

Whilst it is too early to draw any conclusions on its origin, exciting as they may be, scientists are thinking about the next steps to take in order to understand more.

From the time of its arrival at Mars, the Mars Express spacecraft started producing stunning results. One of the aims of the mission is analysing in detail the chemical composition of the Martian atmosphere, known to consist of 95% percent carbon dioxide plus 5% of minor constituents. It is also from these minor constituents, which scientists expect to be oxygen, water, carbon monoxide, formaldehyde and methane, that we may get important information on the evolution of the planet and possible implications for the presence of past or present life.

The presence of methane has been confirmed thanks to the observations of the Planetary Fourier Spectrometer (PFS) on board Mars Express during the past few weeks. This instrument is able to detect the presence of particular molecules by analysing their ?spectral fingerprints? – the specific way each molecule absorbs the sunlight it receives.

The measurements confirm so far that the amount of methane is very small ? about 10 parts in a thousand million, so its production process is probably small. However, the exciting question ?where does this methane come from?? remains.

Methane, unless it is continuously produced by a source, only survives in the Martian atmosphere for a few hundreds of years because it quickly oxidises to form water and carbon dioxide, both present in the Martian atmosphere. So, there must be a mechanism that refills the atmosphere with methane.

?The first thing to understand is how exactly the methane is distributed in the Martian atmosphere,? says Vittorio Formisano, Principal Investigator for the PFS instrument. ?Since the methane presence is so small, we need to take more measurements. Only then we will have enough data to make a statistical analysis and understand whether there are regions of the atmosphere where methane is more concentrated?.

Once this is done, scientists will try to establish a link between the planet-wide distribution of methane and possible atmospheric or surface processes that may produce it. ?Based on our experience on Earth, the methane production could be linked to volcanic or hydro-thermal activity on Mars. The High Resolution Stereo camera (HRSC) on Mars Express could help us identify visible activity, if it exists, on the surface of the planet?, continues Formisano. Clearly, if it was the case, this would imply a very important consequence, as present volcanic activity had never been detected so far on Mars.

Other hypotheses could also be considered. On Earth, methane is a by-product of biological activity, such as fermentation. ?If we have to exclude the volcanic hypothesis, we could still consider the possibility of life,? concludes Formisano.

?In the next few weeks, the PFS and other instruments on-board Mars Express will continue gathering data on the Martian atmosphere, and by then we will be able to draw a more precise picture,? says Agustin Chicarro, ESA Mars Express Project Scientist.

Thanks to the PFS instrument, scientists are also gathering precious data about isotopes in atmospheric molecules such as water and carbon dioxide – very important to understand how the planet was formed and to add clues on the atmospheric escape. The PFS also gives important hints about water-cloud formation on the top of volcanoes, and shows the presence of active photochemical processes in the atmosphere.

Original Source: ESA News Release

Posted on by Mark Mortimer

Book Review: Lost in Space

In Greg’s view NASA, the premiere space institute, is a government bureaucracy that is more concerned with preserving itself than in extending the space frontier. He alludes to conspiracies and to too close a relationship between NASA and their predominant suppliers Boeing and Lockheed Martin. Much of the source of this problem is the perceived current purpose of NASA which is to garner as many votes as possible for the party in power. One need only consider NASA’s inception. Here, when President Kennedy was looking for a means of countering the Soviets he considered space but he argued, “We shouldn’t be spending this kind of money because I’m not that interested in space”. Nonetheless soon after saying this he gave NASA the mandate to go to the moon. NASA then achieved this goal while at the same time ensuring contracts were provided to constituents in each of the 51 states. Ever since then NASA has not had the necessary political backing for a large scale enterprise or even the maintenance of the status quo. Sadly, without the political necessity nor an immediate economic benefit the dreamers are getting drenched with the reality of too high a cost to extend the frontier for too low an economic return.

The deciding factor for all this dreaming is the cost of accessing space. Usually quoted as a cost per pound (or kilogram), the current value is one or two orders of magnitude too high for establishing an industry. Further, according to Greg, established big business and government garner greater benefits from maintaining their control over all elements and they therefore don’t want to reduce the cost nor see anyone else reduce the cost. This doesn’t mean it won’t happen. There is the X-Prize and its front runner, Rutan’s White Knight aircraft that will launch the rocket ship SpaceShipOne into sub-orbital flight. Robert Zubrin has his Mars Society. The Mars Habitat analogue on Devon Island is conditioning people for an eventual presence on Mars. MirCorp was an endeavour to privatize the Mir space station thus annulling governments’ current monopoly on housing humans in space. Almost all the well known alternative access to space advocates have a reference. Yet, with all their brilliant engineering constructs and all their courtship of politicians somehow the feeling from reading the book is that there is just not enough of a reward to ever overcome the cost.

This book is about a dream not some academic juxtaposing of facts and issues for dissemination of automatons sitting around a boardroom table. It is an anguished cry as this dream is foundering, not because of inability, but in the belief of the short sightedness or incomprehension of bureaucracy. You can’t sit on the fence after reading this book, either you want things changed for the better or you want to give up altogether. If you are interested in advancing humans in space you will read of many other like minded people and their successes. You will also find many routes for pursuing your own preference for advocating space development most of which don’t involve a boardroom table.

As a view in the alternative access to space movement, this book is excellent. However as a view into the contributions of NASA and the space industry, this book is very one-sided. NASA the institute is given a very negative persona; a self interested, overpowering bore. Yet the individuals within NASA all seem to be exceptionally fine. Then in considering the people working on alternative accesses to space, this book seems to say that they can do no wrong. All their ideas are eminently favourable and worthy of public support and funding. A more balanced view would have been fairer, but likely less passionate.

In summary, if you want to know where NASA has gone wrong or of the many ideas that individuals have been and are expounding for space access, Lost in Space is the book. Perhaps unexpectedly it also contains an interesting view of the power of individuals within a large democracy. Just be ready for passion about a dream as this book has lots of it.

Review by Mark Mortimer

More information from Amazon.com

Posted on by Fraser Cain

Researchers Find Methane in Mars Atmosphere

Researchers from both NASA and the European Space Agency are reported to have independently found evidence of methane in the Martian atmosphere – on Earth, methane is a by-product of life. Methane gas would be destroyed by the Sun’s radiation, so something would need to be replenishing it in the atmosphere. Neither agency has gone public with their findings yet; however, as they’re working to confirm their results with other instruments.

Posted on by Fraser Cain

X-43A Goes Hypersonic

Image credit: NASA
NASA’s second X-43A hypersonic research aircraft flew successfully today, the first time an airbreathing scramjet powered aircraft has flown freely.

The unpiloted vehicle’s supersonic combustion ramjet, or scramjet, ignited as planned and operated for the duration of its hydrogen fuel supply, which lasted about 10 seconds. The X-43A reached its test speed of Mach 7.

“It’s been a great, record-breaking day,” said Larry Huebner, NASA Langley Research Center’s Hyper-X propulsion lead. “We achieved positive acceleration of the vehicle while we were climbing, and maintained outstanding vehicle control. This was a world-record speed for air-breathing flight,” Huebner said.

The flight, originating from NASA’s Dryden Flight Research Center, began at 12:40 p.m. PST, as NASA’s B-52B launch aircraft carrying the X-43A lifted off the runway. The X-43A, mounted on a modified Pegasus booster rocket, was launched from the B-52B just before 2 p.m. The rocket boosted the X-43A up to its test altitude of about 95,000 ft. over the Pacific Ocean, where the X-43A separated from the booster and flew freely for several minutes following scramjet engine operation, in order to gather aerodynamic data.

“Today was a grand-slam in the bottom of the 12th,” said Joel Sitz, NASA Dryden Flight Research Center’s X-43A project manager. “It was fun all the way to Mach 7. We separated the research vehicle from the launch vehicle, as well as separating the real from the imagined,” Sitz said.

NASA’s Langley Research Center, Hampton, Va., and Dryden Flight Research Center, Edwards, Calif., jointly conduct the Hyper-X program. ATK GASL (formerly MicroCraft, Inc.) in Tullahoma, Tenn., built both the vehicle and the engine, and Boeing Phantom Works in Huntington Beach, Calif., designed the thermal protection and onboard systems. The booster is a modified Pegasus rocket built by Orbital Sciences Corp. Chandler, Ariz.

Original Source: NASA News Release

Posted on by Fraser Cain

Spirit Begins its Journey to Columbia Hills

Image credit: NASA/JPL
NASA’s Spirit will begin trekking toward hills on its eastern horizon in the next few days, entering a new phase of the rover’s exploration of Mars just before its prime three-month mission ends and its extended mission begins, rover team members said today.

The range of peaks named “Columbia Hills” is an island of older rock surrounded by a younger volcanic layer which surfaces the plain that Spirit has been crossing, said Dr. Ray Arvidson of Washington University, St. Louis. He is deputy principal investigator for the science payload on both Spirit and its twin rover, Opportunity.

Older rocks may hold evidence of an ancient body of water thought to have once filled Gusev Crater. Spirit landed inside that 150-kilometer-wide (95-mile-wide) crater 12 weeks ago, and the rover’s main task is to find geological clues about whether the region ever had a wet environment. Spirit has spent much of its time since landing driving toward a 200-meter-wide (660-foot-wide) crater nicknamed “Bonneville.” Rover scientists had anticipated that the impact that excavated Bonneville might have ejected rocks old enough to hold clues about whether Gusev held water.

“The ejecta from Bonneville didn’t get excavated from deep enough to get below the volcanic layer,” Arvidson said. So, after finishing an examination of a light-colored rock on the crater’s rim, Spirit will head for the hills.

NASA’s Jet Propulsion Laboratory, Pasadena, Calif., built each of the two Mars Exploration Rovers for a prime mission of 90 martian days of operation. Both rovers are healthy and could operate for several additional months, said JPL’s Matt Wallace, mission manager. A martian day, or sol, lasts about 40 minutes longer than an Earth day, and Spirit’s 82nd sol began on Friday. “Spirit will start driving toward the hills on sol 84 or a little after that,” Wallace said.

Scientists have examined the terrain between Bonneville Crater and Columbia Hills in photographs taken from orbit by NASA’s Mars Global Surveyor and found several features to inspect along the route. These include some small craters and a dark streak apparently left by a whirlwind that removed dust.

Science team member Dr. Larry Crumpler of New Mexico Museum of Natural History, Albuquerque, said, “It won’t be a continuous drive, like a bad road trip. We’ll actually get out and do some touristy things along the way.”

With stops for “traverse science” along the way, the trip of about 2.3 kilometers (1.3 miles) to the near edge of Columbia Hills will probably take 60 to 90 sols, Arvidson said.

Beginning next week and continuing into the extended mission, Spirit’s controllers will switch from working on Mars time – with schedules set to coincide with day or night at Gusev crater – to an Earth time schedule easier to maintain for the long haul. The Opportunity team will shift the following week, Wallace said.

Opportunity is also at the start of a trek. This week, it climbed out of the small impact crater informally named “Eagle Crater” that it had been examining since it landed nine weeks ago. Rocks in an outcrop within the crater have provided evidence that the site was once under flowing water. In coming weeks, Opportunity will drive about 750 meters (nearly half a mile) to a crater nicknamed “Endurance,” where scientists hope to find and examine a thicker set of bedrock layers to learn more about the duration of the region’s wet history.

Before leaving Eagle Crater, Opportunity inspected the soil at five sites in the opposite half of the crater from the outcrop. The target patches show a diversity of particle sizes and shapes on the surface. “We’re seeing the effects of differences in wind speed,” said Bethany Ehlmann, a science team collaborator from the University of Washington, St. Louis. In some patches more than others, winds have removed small particles and left large particles behind, she said.

Spherical gray particles that have been fancifully called blueberries are plentiful in some soil patches higher on the inner slope of the crater than near the center of the crater. A reading by Opportunity’s Moessbauer spectrometer on one of the higher patches found the highest concentration of hematite seen so far in the mission, reported Dr. Goestar Klingelhoefer of the University of Mainz, Germany. He is the lead scientist for that instrument, which is used for identifying iron-containing minerals. The type of hematite Opportunity has been finding usually forms on Earth under wet environmental conditions. JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover project for NASA’s Office of Space Science, Washington, D.C. Images and additional information about the project are available from JPL at http://marsrovers.jpl.nasa.gov and from Cornell University, Ithaca, N.Y., at http://athena.cornell.edu .

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Gregory Olsen Will Be the Next Space Tourist

Image credit: Space Adventures
Space Adventures?, Ltd., the world’s leading space experiences company, announced today that American technology entrepreneur Gregory Olsen, Ph.D. will be the next private space explorer client. The company which organized the space flights for the world’s first private space explorers, American businessman Dennis Tito in 2001, and the first African in space, Mark Shuttleworth, in 2002, disclosed Dr. Olsen’s identity and his mission objectives during a press conference today in New York City.

The mission continues Space Adventures? ongoing effort to open the space frontier to more than just career astronauts and cosmonauts. Dr. Olsen is set to begin cosmonaut training next month at the Yuri Gagarin Cosmonaut Training Center in Star City, Russia, with the launch date for the expedition currently planned for April 2005.

Dr. Olsen, CEO of Sensors Unlimited, Inc., Princeton, N.J., commented, ?I hope that by traveling to the International Space Station I can help inspire today’s youth to dream big and to realize that education hard work and a desire to achieve your vision is the magic of America. If I can do it, so can you!?

?We are excited to announce that Dr. Olsen will be the next private space explorer to visit the International Space Station,? said Eric Anderson, president and CEO, Space Adventures. ?He has such a passion for this flight and sees it as an investment in the future. Dr. Olsen not only is committed to motivating young people to study science and technology, but also plans to undertake several science and engineering projects during his flight. That he is paying for his mission privately, in addition to carrying out research and educational programs, makes him his own ?private space program.? We, at Space Adventures, are impressed by the quality and caliber of Dr. Olsen and his plans.?

In conjunction with the Federal Space Agency and the Rocket Space Corporation Energia, Space Adventures continues its commitment to opening the final frontier for private citizens. This innovative project secures the first of four seats made available exclusively to Space Adventures aboard the Soyuz TMA spacecraft traveling to the International Space Station through 2007.

Dr. Olsen, born in 1945 in Brooklyn, N.Y., was raised in a working class family. His father was an electrician and his mother a schoolteacher. He graduated from Fairleigh Dickinson University with a bachelor’s of science and master’s degree in physics. He then went on to graduate from the University of Virginia with a doctorate in materials science. From 1972 to 1983, he worked at RCA Laboratories, now known as the Sarnoff Corporation. In 1984 Dr. Olsen started his first company, Epitaxx and later sold it for $12 million (USD). He founded Sensors Unlimited, Inc. in 1992, later sold it for $700 million (USD) in 2000. Sensors Unlimited develops highly sensitive near-infrared cameras.

Space Adventures, the only U.S. company to have successfully launched private tourists to the International Space Station, headquartered in Arlington, Virginia with an office in Moscow, Russia. It offers a variety of programs such as Zero Gravity, MiG flights, cosmonaut training, space flight qualification programs and reservations on future sub-orbital spacecrafts. The company’s advisory board comprises Apollo 11 moonwalker Buzz Aldrin; shuttle astronauts Kathy Thomton, Robert (Hoot) Gibson, Charles Walker, Nom Thagard, Sam Durrance and Byron Lichtenber; and Skylab astronaut Owen Garriott. For more information, please visit www.spaceadventures.com.

Original Source: Space Adventures News Release

Posted on by Fraser Cain

Experiment Will Help Probe “Theory of Everything”

Image credit: NASA/JPL
Sooner or later, the reign of Einstein, like the reign of Newton before him, will come to an end. An upheaval in the world of physics that will overthrow our notions of basic reality is inevitable, most scientists believe, and currently a horse race is underway between a handful of theories competing to be the successor to the throne.

In the running are such mind-bending ideas as an 11-dimensional universe, universal “constants” (such as the strength of gravity) that vary over space and time and only remain truly fixed in an unseen 5th dimension, infinitesimal vibrating strings as the fundamental constituents of reality, and a fabric of space and time that’s not smooth and continuous, as Einstein believed, but divided into discrete, indivisible chunks of vanishingly small size. Experiment will ultimately determine which triumphs.

A new concept for an experiment to test the predictions of Einstein’s relativity more precisely than ever before is being developed by scientists at NASA’s Jet Propulsion Laboratory (JPL). Their mission, which effectively uses our solar system as a giant laboratory, would help narrow the field of vying theories and bring us one step closer to the next revolution in physics.

A House Divided
It may not weigh heavily on most people’s minds, but a great schism has long plagued our fundamental understanding of the universe. Two ways of explaining the nature and behavior of space, time, matter, and energy currently exist: Einstein’s relativity and the “standard model” of quantum mechanics. Both are extremely successful. The Global Positioning System (GPS), for instance, wouldn’t be possible without the theory of relativity. Computers, telecommunications, and the Internet, meanwhile, are spin-offs of quantum mechanics.

But the two theories are like different languages, and no one is yet sure how to translate between them. Relativity explains gravity and motion by uniting space and time into a 4-dimensional, dynamic, elastic fabric of reality called space-time, which is bent and warped by the energy it contains. (Mass is one form of energy, so it creates gravity by warping space-time.) Quantum mechanics, on the other hand, assumes that space and time form a flat, immutable “stage” on which the drama of several families of particles unfolds. These particles can move both forward and backward in time (something relativity doesn’t allow), and the interactions between these particles explain the basic forces of nature — with the glaring exception of gravity.

The stalemate between these two theories has gone on for decades. Most scientists assume that somehow, eventually, a unifying theory will be developed that subsumes the two, showing how the truths they each contain can fit neatly within a single, all-encompassing framework of reality. Such a “Theory of Everything” would profoundly affect our knowledge of the birth, evolution, and eventual fate of the universe.

Slava Turyshev, a scientist at JPL, and his colleagues have thought of a way to use the International Space Station (ISS) and two mini-satellites orbiting on the far side of the sun to test the theory of relativity with unprecedented accuracy. Their concept, developed in part through funding from NASA’s Office of Biological and Physical Research, would be so sensitive that it could reveal flaws in Einstein’s theory, thus providing the first hard data needed to distinguish which of the competing Theories of Everything agree with reality and which are merely fancy chalk-work.

The experiment, called Laser Astrometric Test Of Relativity (LATOR), would look at how the sun’s gravity deflects beams of laser light emitted by the two mini-satellites. Gravity bends the path of light because it warps the space through which the light is passing. The standard analogy for this warping of space-time by gravity is to imagine space as a flat sheet of rubber that stretches under the weight of objects like the sun. The depression in the sheet would cause an object (even a no-mass particle of light) passing nearby the sun to turn slightly as it went by.

In fact, it was by measuring the bending of starlight by the sun during a solar eclipse in 1919 that Sir Arthur Eddington first tested Einstein’s theory of general relativity. In cosmic terms, the sun’s gravity is fairly weak; the path of a beam of light skimming the edge of the sun would only be bent by about 1.75 arcseconds (an arcsecond is 1/3600 of a degree). Within the limits of accuracy of his measuring equipment, Eddington showed that starlight did indeed bend by this amount — and in doing so effectively impeached Newton.

LATOR would measure this deflection with a billion (109) times the precision of Eddington’s experiment and 30,000 times the precision of the current record-holder: a serendipitous measurement using signals from the Cassini spacecraft on its way to explore Saturn.

“I think [LATOR] would be quite an important advance for fundamental physics,” says Clifford Will, a professor of physics at Washington University who has made major contributions to post-Newtonian physics and is not directly involved with LATOR. “We should continue to try to press for more accuracy in testing general relativity, simply because any kind of deviation would mean that there’s new physics that we were not aware of before.”

Solar laboratory
The experiment would work like this: Two small satellites, each about one meter wide, would be launched into an orbit circling the sun at roughly the same distance as Earth. This pair of mini-satellites would orbit more slowly than Earth does, so about 17 months after launch, the mini-satellites and Earth would be on opposite sides of the sun. Even though the two satellites would be about 5 million km apart, the angle between them as viewed from Earth would be tiny, only about 1 degree. Together, the two satellites and Earth would form a skinny triangle, with laser beams along its sides, and one of those beams passing close to the sun.

Turyshev plans to measure the angle between the two satellites using an interferometer mounted on the ISS. An interferometer is a device that catches and combines beams of light. By measuring how waves of light from the two mini-satellites “interfere” with each other, the interferometer can measure the angle between the satellites with extraordinary precision: about 10 billionths of an arcsecond, or 0.01 ?as (micro-arcseconds). When the precision of the other parts of the LATOR design are considered, this gives an overall accuracy for measuring how much gravity bends the laser beam of about 0.02 ?as for a single measurement.

“Using the ISS gives us a few advantages,” Turyshev explains. “For one, it’s above the distortions of Earth’s atmosphere, and it’s also large enough to let us place the two lenses of the interferometer far apart (one lens on each end of the solar panel truss), which improves the resolution and accuracy of the results.”

The 0.02 ?as accuracy of LATOR is good enough to reveal deviations from Einstein’s relativity predicted by the aspiring Theories of Everything, which range from roughly 0.5 to 35 ?as. Agreement with LATOR’s measurements would be a major boost for any of these theories. But if no deviation from Einstein is found even by LATOR, most of the current contenders–along with their 11 dimensions, pixellated space, and inconstant constants–will suffer a fatal blow and “pass on” to that great dusty library stack in the sky.

Because the mission requires only existing technologies, Turyshev says LATOR could be ready to fly as soon as 2009 or 2010. So it may not be too long before the stalemate in physics is broken and a new theory of gravity, space, and time takes the throne.

Original Source: NASA/Science Story

Posted on by Fraser Cain

ESA Tests Cargo Ship Tracking System

Image credit: ESA
For the first time, the ‘videometer’ (VDM), a new technology device to ensure very precise automatic rendezvous operations between the 20.7 tonne Jules Verne Automated Transfer Vehicle and the ISS, has been successfully tested this month.

State of the art
Based on the design of a star tracker, the Jules Verne videometer, which is the first automatic optical operational system ever used for spacecraft navigation, has been through extensive simulated rendezvous tests. This state of the art rendezvous technology is the crucial part of the new European cargo spaceship to which it gives its specific name of Automated Transfer Vehicle (ATV).

“For the first time, the ATV rendezvous sensors were used successfully in real conditions. And, within their operational domain, they worked exceptionally well,” said ESA ATV engineer Stein E. Strandmoe, who supervised a critical 10-day test campaign.

Precision
For the final rendezvous manoeuvres, the ATV will use its videometer eye-like sensors, combined with additional parallel measurement systems, which allow an automatic docking with an incredible centimetre precision while the spacecraft and the ISS are circling the Earth at 28 000 km/h. “The first European rendezvous spacecraft is expected to dock with ISS next year with the accuracy of the size of a one Euro coin”, said ESA astronaut Jean-Fran?ois Clervoy, senior advisor to the ATV programme.

These built-in automatic capabilities of the ATV must be compatible with the demanding requirements of human spaceflight safety, necessary for the permanently crewed ISS.

Target patterns
The videometer is able to analyse images of its emitted laser beam automatically reflected by passive retroreflectors serving as targets installed on the Station, next to the Russian docking port where the ATV will be attached.

During the last 200 metres of the orbital final approach manoeuvre, the videometer must automatically recognize the retroreflectors target patterns and then calculate the distance and direction to the docking port.

This precise tracking of the relative motion between the two spacecraft as they get closer ? starting at a speed of up to 3.6 km/h ? provides indispensable information to the on-board Guidance, Navigation and Control (GNC) system, which automatically pilots the bus-sized cylindrical ESA cargo ship towards the ISS.

Rendezvous testing
To realistically check the videometer capabilities ? in targeting and acquisition ? the tests were conducted in a hi-tech ship hull research facility at the French defence agency ‘D?l?gation G?n?rale pour l’Armement’ (DGA), located in Val-de-Reuil, 100 km west of Paris. A contract between ESA and DGA will allow further ATV rendezvous testing, including during the Jules Verne flight, if needed.

Inside an exceptional building, 600 metres in length, a 120 000 kg mobile platform, able to ride on 550 metre long rails, enabled the simulation of a continuous approach between the two space vehicles from a range of several hundred metres to within almost docking distance. On the platform, a set of passive rendezvous targets (retroreflectors), identical to the ones to be installed on ISS, were facing the videometer which was mounted on an articulated robotic arm (with six degrees of freedom) representing the ATV motion.

This seven metre high mobile arm was used to simulate the angular movements of the ATV to check if the videometer was still able to target the ISS retroreflectors and provide the information to the ATV control system necessary to adjust its trajectory accordingly.

First time success
The results of the test campaign showed that the whole videometer system ? that is to say the laser illuminator and the image analyser of the reflected laser beams ? was able to continuously track the simulated ISS platform from a distance of 313 metres, right up close to docking. “We have stable acquisition and tracking in its entire operating domain,” said Stein Strandmoe. At greater distances, Jules Verne will use a relative GPS reference system to get closer to the Station.

“The most surprising thing was that the sensors were almost undisturbed when we tried to fool them with other reflecting surfaces or other lights that could interfere with rendezvous targets in the ISS background,” said Strandmoe. “It’s amazing how the videometer, as a totally new development, proved to be such a robust system. I was quite surprised that it worked so well the first time it was tested!”

Original Source: ESA News Release