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The Challenge of Spacecraft Robotics

by Paul Gilster | Nov 30, 2004 | Autonomy and Robotics | 3 Comments

Is any unmanned spacecraft a robotic probe? You might think so, given the tasks the hardware has to perform to accomplish a given scientific mission, but a more precise definition came out of the European Space Agency's ASTRA 2004 workshop, held in the Netherlands early in November. Says Gianfranco Visentin, head of ESA's Automation and Robotics Section, a space robot is "...a system having mobility and the ability to manipulate objects plus the flexibility to perform any combination of these tasks autonomously or by remote control." And according to this ESA press release, spacecraft robotics should be able to achieve the following: withstand a launch operate under difficult environmental conditions often in remote locations weigh as little as possible as any mass is expensive to launch use little power and have a long operational life operate autonomously be extremely reliable We're gaining a lot of experience with robots through the use of machines like NASA's Mars rovers Spirit...

Three Space Pioneers Discuss Their Trade

by Paul Gilster | Nov 29, 2004 | Culture and Society | 0 Comments

I've run into a fascinating discussion on American Enterprise Online titled "Look Heavenward?" -- it's a collection of articles whose description on the magazine's table of contents, "The pros and cons of spending more on manned space exploration," is wildly insufficient to describe its range. The most interesting of the pieces here consists of three thought-provoking conversations with space and astronomy pioneers. Bill Kauffman interviews comet hunter David Levy; David Isaac talks to Mars Society president Robert Zubrin; and Frederick Turner (University of Texas at Dallas poet and sometime interstellar theorist), interviews Freeman Dyson. I'll run just a few snippets, but at some point be sure to read the whole piece here. From the Zubrin interview, discussing terraforming and how humans may adapt to other worlds: ZUBRIN: I can elaborate by analogy. Human beings are not native to the Earth. We're native to East Africa. We're tropical animals. We have long, thin arms with no fur on...

On Colonizing the Galaxy

by Paul Gilster | Nov 27, 2004 | Breakthrough Propulsion, Culture and Society | 1 Comment

From the polymath Freeman Dyson, in an essay called "Extraterrestrials," which appears in his collection Disturbing the Universe (New York: Harper & Row, 1979, pp. 210-211): "Given plenty of time, there are few limits to what a technological society can do. Take first the question of colonization. Interstellar distances look forbiddingly large to human colonists, since we think in terms of our short human lifetime. In one man's lifetime we cannot go very far. But a long-lived society will not be limited by a human lifetime. If we assume only a modest speed of travel, say one hundredth of the speed of light, an entire galaxy can be colonized from end to end within ten million years. A speed of one percent of light velocity could be reached by a spaceship with nuclear propulsion, even using our present primitive technology. So the problem of colonization is a problem of biology and not of physics. The colonists may be long-lived creatures in whose sight a thousand years are but as...

Proto-Earths May Be Abundant

by Paul Gilster | Nov 26, 2004 | Exoplanetary Science | 0 Comments

New infrared studies of the dust around three young stars lend credence to the idea that Earth-like planets may circle other stars. Using the European Southern Observatory's Very Large Telescope Interferometer (VLTI), a team of astronomers studied the proto-planetary disks around the stars, homing in on the inner region of the discs. The results: the inner discs, in the area analogous to that swept out by the Earth around the Sun, are loaded with crystalline silicate grains -- sand -- with an average diameter of about 0.001 mm. Much smaller grains (about 0.0001 mm in size) would have contributed to the creation of this material, being heated in the inner system near the young star and coagulating into larger grains in this dense region. From an ESO press release: An important conclusion from the VLTI observations is therefore that the building blocks for Earth-like planets are present in circumstellar discs from the very start. This is of great importance as it indicates that planets...

Tracking Near-Earth Asteroids

by Paul Gilster | Nov 25, 2004 | Missions, Outer Solar System | 0 Comments

An asteroid called 2004 TP1 came within 13 LD of Earth on November 2 -- LD stands for 'lunar distance,' and is the average distance between the Earth and the Moon (238,855 miles, or 384,401 kilometers). Asteroid 2004 RZ164 will come even closer, at 7 LD on December 8. Both objects are considered Potentially Hazardous Asteroids (PHAs, as acronym-obsessed scientists like to call them). That means they are larger than 100 meters in diameter and come too close to Earth for comfort. 653 Potentially Hazardous Asteroids are now known. We've discussed such objects as perhaps the most significant reason for building up a space-based infrastructure that could ward off a potential strike. A good place to track them is the NASA-sponsored site Spaceweather.com, which bills itself as 'News and Information about the Sun-Earth Environment.' The site likewise tracks solar wind conditions (currently moving at 493.7 kilometers per second, based on data transmitted from the Advanced Composition Explorer...

A New Tool for Researchers

by Paul Gilster | Nov 24, 2004 | Administrative | 1 Comment

Searching the Internet has always been dicey, given the wide range of sites you're likely to pull up on any topic, and the varying degrees of quality each may bring. Google has done good work in restricting Web results -- its 'site-specific search,' for example, allows you to search within a universe of sites related to a particular topic. Now the company has gone one better with a new engine called Google Scholar, a test version of which is available. The beauty of Google Scholar is that your search is limited to journal articles, books, preprints, technical reports and theses, the kind of material serious researchers need to uncover without having to sift out all the chaff. As this article in Nature makes clear, the new service does a fine job at finding the relevant articles on your topic, using variations on the familiar Google algorithms that study the linking that takes place between Web pages and offer a key to their utility. But instead of studying links to other pages,...

An Anomaly from the Edge of the Solar System

by Paul Gilster | Nov 23, 2004 | Missions | 0 Comments

Those of us with still fresh memories of Voyager 2's encounter with Neptune in 1989 find it gratifying that both Voyager probes are still returning good science. It's even more remarkable that the Pioneer 10 and 11 probes are still in the thick of things, but anomalies in their journeys beyond the orbit of Pluto offer tantalizing clues of some unexplained phenomenon in the far ranges of the Solar System. As this article in Nature points out, since 1980 the Pioneers have been returning radio signals that have kept shifting to shorter and shorter wavelengths. The implication: both spacecraft are decelerating, even if only by the slightest amount. Some are calling this the 'Pioneer anomaly,' and it may just point to a new principle in physics, perhaps involving exotic forces or undiscovered forms of matter. On the other hand, it may have a much more mundane explanation, such as a fuel leak that could be affecting the probes' progress. Either way, engineers faced with designing...

By the Light of a Passing Star

by Paul Gilster | Nov 22, 2004 | Exoplanetary Science | 0 Comments

Microlensing Planet Finder is a proposed mission that would use the gravitational lensing effect to achieve extraordinary detection capabilities. As presented in The Microlensing Planet Finder: Completing the Census of Extrasolar Planets in the Milky Way (PDF warning), MPF could find planets down to 0.1 Earth mass, in locations as close as 0.7 AU to their parent stars. And unlike any other planet-finding technology, MPF would be able to find free-floating planetary bodies unassociated with any star. Gravitational microlensing is perhaps the most exotic planet-finding technique. A star or planet can act as a kind of lens, magnifying a more distant bright star behind it. It is the gravitational field of the foreground star that, as Einstein predicted, focuses the light of the distant star, just as a glass lens focuses light in a telescope. By analyzing the light produced by such an event, astronomers can find telltale anomalies that indicate the presence of planets around the...

A Quote for the Weekend

by Paul Gilster | Nov 20, 2004 | Culture and Society | 0 Comments

From the remarkable H. G. Wells, in a 1902 lecture at London's Royal Institution: "It is conceivable that some great unexpected mass of matter should presently rush upon us out of space, whirl sun and planets aside like dead leaves before the breeze, and collide with and utterly destroy every spark of life upon this earth... It is conceivable, too, that some pestilence may presently appear, some new disease, that will destroy not 10 or 15 or 20 per cent of the earth's inhabitants as pestilences have done in the past, but 100 per cent, and so end our race... And finally there is the reasonable certainty that this sun of ours must some day radiate itself toward extinction... There surely man must end. That of all such nightmares is the most insistently convincing. And yet one doesn't believe it. At least I do not. And I do not believe in these things because I have come to believe in certain other things--in the coherency and purpose in the world and in the greatness of human destiny....

Finding Planets in the Datastream

by Paul Gilster | Nov 19, 2004 | Exoplanetary Science | 1 Comment

A new project called PlanetQuest will soon offer a way to get involved personally with the hunt for extrasolar planets. The idea is to use the power of distributed computing, as the hugely influential SETI@home project has already done, letting people run data analysis software as a screensaver that operates whenever their computer is idle. PlanetQuest will be designed to hunt for planets by studying high-density star regions looking for occlusions -- in other words, for evidence that an extrasolar planet has moved between us and its star. Laurance Doyle, an astrophysicist at the SETI Institute, notes that while occlusions may be rare (after all, the stellar system must be lined up with ours so that planetary orbits cross our line of vision), the hunt will also yield dividends in terms of our knowledge of variable stars, as well as broader issues like stellar stability and evolution. But even as we accumulate new data, we still have the problem of managing what we have. Consider the...

The NEXT Generation of Ion Propulsion

by Paul Gilster | Nov 18, 2004 | Advanced Rocketry | 4 Comments

Can ion propulsion really lead the way to the outer planets? No one can know for sure, but recent advances in solar-electric propulsion surely make ion methods a prime candidate. Not only has SMART-1 conducted a thorough ion engine shakedown on its lengthy and circuitious route to the Moon, but a variety of new studies are showing the way to more powerful ion thrusters that will eventually lead to the nuclear-electric systems we'll need for deep space missions. Today's standard ion engine is called NSTAR (it's a short acronym for a long term: the NASA Solar Electric Propulsion Technology Application Readiness thruster). The agency used one of these on its highly successful Deep Space 1 mission. In tests at the Jet Propulsion Laboratory, an NSTAR thruster was operated for a continuous 30,352 hours. That's almost five years of operation for an engine whose design life was only 8,000 hours. You can read more about that test in this NASA news release (PDF warning). Image: This xenon ion...

Remembering ‘Far Centaurus’

by Paul Gilster | Nov 17, 2004 | Culture and Society | 7 Comments

Although it originally ran in the January, 1944 issue of Astounding, I first ran into A.E. Van Vogt's "Far Centaurus" in a collection of short stories called Destination: Universe (New York: Signet Books, 1952). It would be hard today to re-create the power of the story's opening, so imbued have we become with reality-stretching concepts, but "Far Centaurus" remains the ultimate illustration of the starship paradox: why send a slow ship when a faster one will surely be built that will one day overtake it? Van Vogt's crew arrives in Alpha Centauri space only to find that there is an inhabited planetary system waiting for them, one settled long after their departure from Earth by the much faster ships that were built later. The dialogue is a bit bumpy and the science occasionally awry (van Vogt seems to think there are four, rather than three Centauri stars, for example), but the story has retained its power to this day. Image: The first paperback edition of Destination: Universe....

To the Peak of Eternal Light

by Paul Gilster | Nov 16, 2004 | Advanced Rocketry | 0 Comments

It used to be said that the Sun never set on the British Empire. Those days may be long gone, but there is still a place where the Sun forever shines, and it's on the Moon. The Peak of Eternal Light is a mountain at the lunar south pole that is always in view of the Sun. Its year-round temperature is a comparatively mild (by lunar standards) -20C, making it possibly useful as a site for a future lunar base. The possibility of water ice in nearby craters, though not proven, could be an attractive bonus. No wonder the European Space Agency is fascinated with the Peak of Eternal Light. Fascinated enough to make it a prime survey target for SMART-1, the ion-powered spacecraft that entered lunar orbit on Monday. SMART-1's studies of the Moon's south pole will surely be fascinating, as will its look at the South Pole-Aitken Basin, a huge impact crater that punches deep into the Moon's mantle. At stake may be new theories about the Moon's formation. But for deep-space enthusiasts, the...

Cosmos 1 Launch Date Set

by Paul Gilster | Nov 15, 2004 | Sail Concepts | 0 Comments

The Planetary Society has announced that its Cosmos 1 solar sail is to be launched on March 1, 2005. A letter to members from executive director Louis Friedman, who worked on NASA sail designs for an aborted Halley's comet mission in the 1970s, called Cosmos 1 'the world's first solar sail spacecraft.' And indeed it is, if by 'spacecraft' we mean 'free-flying vehicle.' The first Russian Znamya experiments with sail deployment are over a decade old, and involved a 20-meter spinning sail-mirror. Although Znamya was intended to demonstrate the practicality of beaming solar energy to polar and subarctic settlements, the design pointed to a larger concept. When I talked to him last year at JPL, NASA sail expert 'Hoppy' Price showed me a photograph of the deployed sail-mirror, which had problems. "...there are these wrinkles in the sail, so it didn't really work quite the way it was supposed to work," Price said. "And it was a lot heavier than what we'd like to build. But the more we study...

Starlight Off an Alien Sea

by Paul Gilster | Nov 13, 2004 | Exoplanetary Science | 0 Comments

Terrestrial Planet Finder will one day help us detect Earth-like worlds around other stars, no matter which technologies are deployed (Centauri Dreams remains an advocate of Webster Cash's New Worlds Imager). But once we start finding such worlds, what sort of data signatures should we look for to help us identify habitable surface environments? That question has been addressed in a new way by Penn State Erie assistant professor of physics and astronomy Darren M. Williams. Working with the University of Hawaii's Eric Gaidos, Williams outlined a theory that planets with abundant water should show strong scattering of starlight from ocean surfaces and discussed ways of examining such data. From a summary of the presentation: "Here we simulate the specular reflection of starlight off the surface of Earth-like planets to calculate visible light curves for different viewing geometries, obliquities, and land-sea fractions. The amplitude and polarization of the reflected signal is found to...

Young Planet Confirmed Around Star in Taurus

by Paul Gilster | Nov 12, 2004 | Exoplanetary Science | 2 Comments

An extrasolar planet the size of Neptune is news, and when that planet is in an orbit roughly analagous to Neptune's in our own solar system, researchers take special note. After all, almost all the planets we've discovered around other stars are huge gas giants orbiting extremely close to their parent stars. And this extrasolar planet is more anomalous still. It was back in May that a team from the University of Rochester led by Drs. Dan Watson and William Forrest, using NASA's Spitzer Space Telescope, discovered a gap in the dust around the star CoKu Tau 4, one of five young stars they surveyed in the constellation Taurus. The central part of the dust disk around the star was missing, a 'hole' that can only be explained by the presence of a planet, and a young one, at that. In fact, this planet is assumed to be between 100,000 to half a million years old, a toddler by any astronomer's definition. CoKu Tau 4 is itself about one million years old; by contrast, Earth is approximately...

Icy Worlds Beyond Pluto

by Paul Gilster | Nov 11, 2004 | Outer Solar System | 0 Comments

Roughly 1,000 Kuiper Belt objects have been discovered orbiting beyond Neptune since the first was found in 1992. Now researchers are suggesting that these icy objects -- considered to be leftover building blocks of the solar system -- are much smaller than was originally thought. The key is albedo, a measure of how much light an object reflects. Using a presumed albedo of four percent, which is the figure for comets, astronomers had calculated the size of the Kuiper Belt objects, and believed there were more than 10,000 KBOs with diameters greater than 100 kilometers (62 miles), compared to 200 asteroids known to be that large in the main asteroid belt between Mars and Jupiter. But all these measurements depend on an accurate read on albedo. A higher albedo means a more reflective object, forcing a reassessment of how large the KBO objects really are. Image: Kuiper Belt Object 2002 AW197 (Image: NASA/JPL/John Stansberry, University of Arizona) And as reported at the ongoing meeting...

New Keck Images Show Power of Adaptive Optics

by Paul Gilster | Nov 10, 2004 | Deep Sky Astronomy & Telescopes, Exoplanetary Science | 0 Comments

We've talked about adaptive optics here recently, particularly in regard to the W.M. Keck observatory complex at Mauna Kea (Hawaii). Keck's new adaptive system essentially removes atmospheric distortion and improves data processing of the raw image. What you wind up with is a stunningly clear view, as has become apparent in new images of Uranus released by the observatory. The images show Uranus and its ring system, first with the adaptive optics system shut off, then with it on. You can see how much more visible the rings are in the second image, but notice too the deep atmospheric cloud structure in the images on the right. More images are available at the Keck site's article on these findings. Image Credit: Heidi Hammel, Space Science Institute, Boulder, CO/Imke de Pater, University of California, Berkeley/ W. M. Keck Observatory. From the Keck information, quoting a scientist who conducted a second set of observations of the planet: Dr. Lawrence Sromovsky, principal investigator...

Slingshot to the Outer Planets?

by Paul Gilster | Nov 9, 2004 | Advanced Rocketry, Sail Concepts | 0 Comments

The conference of the Division for Planetary Sciences of the American Astronomical Society continues in Louisville. Among the papers presented at today's Advanced Propulsion session were three of particular interest for interstellar advocates. Les Johnson, who heads up NASA's In-Space Propulsion Technology Program, gave an overview on the technology portfolio now being examined. "Some of the most promising technologies for achieving these goals use the environment of space itself for energy and propulsion and are generically called, 'propellantless' because they do not require on-board fuel to achieve thrust," Johnson wrote in a precis of the talk. "Propellantless propulsion technologies include scientific innovations such as solar sails, electrodynamic and momentum transfer tethers, aeroassist, and aerocapture." Both solar sails and aerocapture are candidates for flight validation as early as 2008. Two other presentations of particular note: "Solar Sail Propulsion: A Simple,...

Cassini and the Kuiper Belt

by Paul Gilster | Nov 8, 2004 | Missions, Outer Solar System | 0 Comments

When it comes to interstellar work, don't forget the Kuiper Belt. Although amateur astronomer Kenneth Edgeworth was the first to predict its existence, the Belt was named for Gerard Kuiper, who analyzed it in 1951. It is a region of thousands (and perhaps millions) of small, icy moons and cometary debris that exists from the orbit of Neptune well into deep space. Our first interstellar missions will be explorations of this area and the vast Oort cloud of comets that may extend as much as a light year out from the Sun. And yes, in a true sense, the Voyager probes could be considered interstellar missions, still reporting data as they move on toward the heliopause. But we may learn a good deal about Kuiper Belt objects by studying the findings of a spacecraft considerably closer, the Cassini Saturn orbiter. Cassini's Ultraviolet Imaging Spectrometer tells us that Phoebe, a tiny world about one-fifteenth the diameter of Earth's moon, is probably itself a Kuiper Belt object that was...

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In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For many years this site coordinated its efforts with the Tau Zero Foundation. It now serves as an independent forum for deep space news and ideas. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image courtesy of Marco Lorenzi).

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