by Paul Gilster | Oct 19, 2005 | Interstellar Medium, Missions, Outer Solar System
With liftoff scheduled for January, the New Horizons mission to Pluto and Charon (and, if we are lucky, at least one flyby of a more distant Kuiper Belt object) continues to generate excitement in the scientific community. The spacecraft is now at the Kennedy Space Center and will be moved to the launch pad in December, with liftoff planned for January 11. Major testing on the science payload is complete. The next round of major instrument calibrations and testing won’t occur until the early months of the journey as New Horizons moves toward a 2007 flyby of Jupiter for a gravity assist to Pluto.
How do you package enough instrumentation for good science at the edge of the Solar System into a payload that draws only 28 watts of power? The science payload work was led by the Southwest Research Institute (SwRI), whose recent news release lists the seven instruments that will explore these icy worlds:
Alice, an ultraviolet imaging spectrometer that will probe the atmospheric composition and structure of Pluto. (Led by SwRI; PI Dr. Alan Stern)
Ralph, a visible and infrared camera that will obtain high-resolution color maps and surface composition maps of the surfaces of Pluto and Charon. (Led by Ball Aerospace and SwRI; PI Dr. Alan Stern)
LORRI, or Long Range Reconnaissance Imager, will image Pluto’s surface at football-field sized resolution, resolving features as small approximately 50 yards across. (Led by APL; PI Dr. Andrew Cheng)
SWAP, or Solar Wind Around Pluto, will measure charged particles from the solar wind near Pluto to determine whether it has a magnetosphere and how fast its atmosphere is escaping. (Led by SwRI; PI Dr. David McComas)
PEPSSI, or Pluto Energetic Particle Spectrometer Science Investigation, will search for neutral atoms that escape the planet’s atmosphere and subsequently become charged by their interaction with the solar wind. (Led by APL; PI Dr. Ralph McNutt)
SDC, or Student Dust Counter, will count and measure the masses of dust particles along the spacecraft’s entire trajectory, covering regions of interplanetary space never before sampled. (Led by the University of Colorado; PI Dr. Mihaly Horanyi)
REX, or Radio Science Experiment, a circuit board containing sophisticated electronics that has been integrated with the spacecraft’s radio telecommunications system, will study Pluto’s atmospheric structure, surface thermal properties, and make measurements of the mass of Pluto and Charon and KBOs. (Led by Stanford University and APL; PI Dr. Len Tyler)
Centauri Dreams‘ take: a critical part of New Horizons mission will take be the continuous operation, during the ten-year cruise to Pluto, of a dust counter that will trace the distribution of dust particles throughout the Solar System. We’ve had some data on this already — Voyager 2 measured dust impact on the spacecraft’s skin with its plasma wave instrument as it moved past Uranus and Neptune. But the Voyager measurements were taken with a device designed specifically to measure charged particles inside the magnetic fields of these gas giant planets, not one optimized for dust.
Learning how much dust can affect spacecraft will become more and more significant as the speed of our missions increases. At 10 percent of light speed, a grain of sand could destroy an interstellar probe, so a thorough analysis of dust out past the Kuiper Belt and eventually into the Oort Cloud will one day be needed to see what kind of shielding such vehicles would demand.
For more on the problems of interplanetary dust, see see Eberhard Grun, Harald Kruger, and Markus Landgraf, “Dust Measurements in the Outer Solar System,” available at the arXiv site. The specifics on Voyager’s dust measurements are examined in D. A. Gurnett et al., “Micron-sized Dust Particles Detected in the Outer Solar System by the Voyager 1 and 2 Plasma Wave Instruments,” Geophysical Research Letters Vol. 24 (1997): pp. 3125-28.
by Paul Gilster | Oct 18, 2005 | Autonomy and Robotics
As we saw in yesterday’s post on microbots, one of the problems of robotic exploration is that we put our equipment into relatively smooth terrain. That makes sense, given the time and cost of getting rovers to Mars, for example; what a shame it would be to see a priceless instrument package slam into a mountainside as it touches down. But rugged terrains, those places where water and volcanic activity have changed a landscape, may tell us much about a planet’s history and the possible existence of life on it.
Now a team of scientists is proposing a fundamental change to our existing paradigm of robotic exploration. In addition to orbiters, the team (scientists from the California Institute of Technology, the University of Arizona, and the U.S. Geological Survey) has focused on airborne instrument packages (think ‘blimps’), complemented by the kind of small, robotic explorers that could work their way into even the most hostile landscapes.
“We’re not trying to take anything away from the successful landings on Mars, Venus, and Titan, nor the orbital-based successes to most of the planetary bodies of the solar system,” says Wolfgang Fink, a physicist who is serving a multiyear appointment as a visiting associate at Caltech. “But we think our tier-scalable mission concept will afford greater opportunity and freedom to identify and home in on geological and potential astrobiological ‘sweet spots.'”
Note a key part of this strategy: a unified communications structure that integrates air and space assets with ground robots. It becomes more and more clear how vital the Interplanetary Internet Project is, an ambitious attempt to provide a communications backbone for the Solar System. Such an infrastructure could maximize information return by networking spacecraft through a set of protocols specifically designed for deep space exploration.
Image (click to enlarge): An artist’s conception of multi-tiered planetary missions. Credit: California Institute of Technology.
What could we learn from applying such tools to a new suite of robot explorers? Consider Mars, where, despite outstanding work by orbiting spacecraft, we still don’t know whether the mountains we’re seeing contain anything other than volcanic rock, or whether what looks like hydrothermal activity in the Martian past can be proven just that. The multi-tiered strategy is an ambitious way to solve these problems, as witness this comment by James Dohm, a planetary geologist in the Department of Hydrology and Water Resources at the University of Arizona:
“Ideally, you’d want to look at remote-based geological information while you walked with a rock hammer in hand along the margin that separates a lava flow from putative marine deposits, exploring possible water seeps and moisture embankments within the expansive canyon system of Valles Marineris that would extend from Los Angeles to New York, characterizing the sites of potential ancient and present hydrothermal activity, climbing over the ancient mountain ranges, gathering diverse rock types for lab analysis, and so on.
“We think we’ve devised a way to perform the geologic approach on other planets in more or less the way geologists do here on Earth.”
If Dohm is right, planetary exploration would become more flexible and more focused, identifying targets of scientific interest and migrating resources in their direction, a game plan that grows and shifts as further information is gathered. Stationary sensors could transmit details about targets of interest, while small and relatively expendable rovers would take on rocky and steep terrain to explore them. Airships would be particularly useful in environments like Titan, where autonomous systems would come into their own due to the long time lag with Earth.
Centauri Dreams‘ take: Clearly, as we move further out into the Solar System and beyond, concentrating all our instrumentation into a single package for exploration on a planetary surface makes less and less sense. That places the burden on autonomous systems to respond and adapt to a wide range of environments. Flexible, responsive machines are thus a critical element in the networking of the planets; they point toward the kind of systems that will be necessary for our first interstellar missions as we push into the Kuiper Belt.
A paper covering this work, “Next-generation robotic planetary reconnaissance missions: A paradigm shift,” will appear in an upcoming issue of Planetary and Space Science. A Caltech news release is available online.
by Paul Gilster | Oct 17, 2005 | Autonomy and Robotics
One way to explore a planetary surface is by rover, much as we are doing now on Mars with Spirit and Opportunity. The amount of data we’ve received from these missions has been nothing short of sensational, but as we look to the future, a key problem looms: rovers can sample only small areas of the surface. They’re a precious commodity that has to be targeted to high-value destinations, meaning they’re not adaptable to broad, general surveys.
But a new robotic approach may come to the rescue, and it’s one that has just received Phase II funding from NASA’s Institute for Advanced Concepts. Under the supervision of principal investigator Steven Dubowsky (Massachusetts Institute of Technology), the work focuses on ‘microbots’ to enable large-scale explorations. Microbots are spherical robots that could be dropped by the thousands, perhaps through air-bags deployed from orbiter spacecraft. They would be able to hop, bounce and roll their way to sites in the most rugged terrain, equipped with miniature imagers, spectrometers and a variety of sampling devices. Collectively, such microbots would pool their information to analyze vast areas of a planetary surface.
Image: Design of a microbot. Dubowsky’s team thinks these tiny explorers would be about 10 centimeters in diameter and weigh 100 grams or less. Credit: Steven Dubowsky, MIT.
And microbots might be useful for targets below the surface as well, reaching deep underground by means of lava tubes, ice caves and boreholes. From a recent paper discussing the concept as part of an earlier NIAC study:
These targets are valuable since natural caves and other subsurface voids can provide a radically different set of conditions than the overlying surface. Such areas can serve as a repository for trapped materials from a planet’s past, and can yield materials that may shed light on past climate history and past solar activity. They can also provide a suite of environments for an enormous diversity of extremophile organisms, and have been suggested as the last refuge of life on planets like Mars where surface conditions have become significantly less hospitable to life over geological time.
Microbots turn out to be surprisingly mobile, using lightweight polymer materials to create actuators that allow a kind of directional hopping motion. After one cycle of bouncing and rolling, the microbot will return to a base posture, a method that has been demonstrated by working prototype. Powering the tiny robots would be micro fuel cells that create a high energy to weight ratio, allowing long distance travel over rough terrain. Current studies show that a microbot could leap 1.5 meters high and 1 meter horizontally under conditions like those on the surface of Mars, thus clearing boulders that might otherwise impede forward motion.
A variety of strategies for landing and deploying such microbots are examined in Dubowsky, Iagnemma, Liberatore et al., “A Concept Mission: Microbots for Large-Scale Planetary Surface and Subsurface Exploration.” This is the report on Dubowsky’s Phase I work on the concept, which will now receive a more detailed investigation in the Phase II study that runs from September 1, 2005 to August 31, 2007. All NIAC’s funded studies are available at its Web site.
by Paul Gilster | Oct 15, 2005 | Exoplanetary Science
It was in 1999 that former NASA administrator Dan Goldin spoke to the American Astronomical Society about what future telescopes might be able to see around distant stars. He imagined a classroom filled with images of exoplanets. “When you look on the walls, you see a dozen maps detailing the features of Earth-like planets orbiting neighboring stars,” Goldin said. “Schoolchildren can study the geography, oceans, and continents of other planets and imagine their exotic environments, just as we studied the Earth and wondered about exotic sounding places like Banghok and Istanbul . . . or, in my case growing up in the Bronx, exotic far-away places like Brooklyn.”
Is a telescope that could take such pictures remotely conceivable? The most innovative proposal I’ve heard to achieve these goals is Webster Cash’s New Worlds Imager concept. The University of Colorado at Boulder astronomer knows how tricky the project would be. As astronomer looking at the Earth from Alpha Centauri would face the problem that the planet would appear 10 to 20 billion times fainter than the Sun, depending on the Earth’s position in its orbit.
Cash hopes to get around such problems by placing a kilometer-wide sheet of plastic into space, a sheet with a hole meters-across in the middle. A spacecraft tens of thousands of kilometers away would be equipped with a standard telescope with an aperture the same size as the hole in the sheet. The result: a celestial pinhole camera, one that would spread the image of a distant planetary system across the sky as seen by the properly aligned secondary spacecraft and its telescope.
Image: An artist’s rendition of a single starshade-collector pair searching a star system for Earth-like planets. From bottom to top: collector spacecraft, starshade, and star system under study. The Earth is shown in the background. Credit: Webster Cash et al.
From a NASA story on New Worlds Imager by Ronald Toland at Goddard Space Flight Center:
The basic building block of the New Worlds Imager is a pair of spacecraft, a starshade and a collector, that function together as a single pinhole camera. The starshade serves as the pinhole for the camera, though the entire shade will be a kilometer (0.6 miles) or more in diameter, with a hole about 10 meters (10 yards) across punched in the center. The collector holds a telescope with a primary mirror the same size as the pinhole: 10 meters. To guarantee the best images, the starshade and collector need to be separated by about 200,000 km, or about half the distance from the Earth to the Moon. Two starshade-collector pairs, their images combined in a central combiner spacecraft, form the New Worlds Imager.
An early New Worlds Explorer system should be able to provide spectroscopic analyses that would help us understand the atmosphere of Earth-like worlds. Later generations, using numerous spacecraft that pool their data through interferometry, may be able to offer breathtaking closeups. “There is no necessary limitation on this optical system,” Cash told me during a 2003 interview. “We might create a view as close as a hundred kilometers, looking at weather systems, oceans, continents.” The only limitation would be the orbital inclination of the planet around its star; we would only see its surface as presented to us along our line of sight. But that limitation seems insignificant compared to the knowledge we would gain.
Cash’s concept is stunning, as was Goldin’s vision of that future classroom. Now comes the welcome news that New Worlds Imager has moved beyond its earlier Phase I work at NASA’s Institute for Advanced Concepts and has been granted a Phase II award, one of five proposals to receive such a grant for the period Sept. 1, 2005 to Aug. 31, 2007. Phase II funding means Cash’s earlier work, available at the NIAC site, is to be advanced through a longer and better funded grant of up to $400,000. You can see an overview of the project with useful background material here (PDF warning).
by Paul Gilster | Oct 14, 2005 | Breakthrough Propulsion |
What a pleasure to discover that Robert Freitas’ Kinematic Self-Replicating Machines is now available online. The 2004 book (from Landes Bioscience of Georgetown TX) is the most comprehensive study of nanotechnology yet written, a compendium of information on self-replicating systems both proposed and experimentally studied. Moreover, it contains a survey of the historical development of nanotechnology, 200 illustrations and over 3000 references to the technical literature.
That nanotechnology (and self-replicating systems in particular) could change our ideas of interstellar flight now seems obvious, but not so long ago ago the concept of one machine building another was studied only at the macro-level. Thus Freitas’ previous work on a self-reproducing spacecraft he called REPRO. The scientist wrote the concept up in a 1980 issue of the Journal of the British Interplanetary Society, conceiving of a mammoth Daedalus-style spacecraft built in orbit around Jupiter and, like Daedalus, using helium-3 from the giant planet’s atmosphere in its fusion engine.
REPRO was a vast and ambitious project, equipped with numerous smaller probes for planetary exploration, but its key purpose was to reproduce. Each REPRO probe would create an automated factory that would build a new probe every 500 years. Probe by probe, star by star, the galaxy would be explored.
Just 25 years later, Freitas still ponders galactic exploration, but he now concentrates on the world of the very small, studying nanotechnological methods that could allow space probes the size of sewing needles. Containing the computing power of thousands of human brains, such probes could be sent out by the millions. If just one of them reached a planet, moon or asteroid around a nearby star, it could begin to reproduce, and in much shorter time frames than allowed for the earlier REPRO probe.
When I interviewed him for Centauri Dreams in 2003, Freitas put it this way:
“The fastest known bacteria I’m aware of is e. coli that can replicate in fifteen minutes at ideal temperature with an excess of nutrients. It is approximately one to two microns in size, which is roughly the same size as the sophisticated assemblers that will one day manipulate matter at this level. If such assemblers landed on an asteroid that was a great distance away from the suns of the Alpha Centauri system, where perhaps there would not be the best energy density, and where materials would have to be scavenged, this would not be an ideal ‘petri dish’ kind of environment. So you might have to add two or three orders of magnitude of time. But you’re still looking at replication times on the order of weeks.”
So nanotechnology’s implications for interstellar flight may be profound, particularly as they enable the vision of a survey of the entire galaxy within a million-year time frame. Some (Frank Tipler among them) have argued that the lack of evidence for extraterrestrial probes within our own Solar System demonstrates that no technical civilizations exist in our part of the universe, but if probes are built with nanotechnology, they may have little trouble avoiding detection in the systems they survey.
We need, then, to give nanotechnology a good look as we plan an interstellar future. Freitas’ Kinematic Self-Replicating Machines is an essential reference for anyone hoping to see how breakthrough methods may make robotic probes possible not just to the nearby stars but throughout the Milky Way.
Freitas’ REPRO paper is “A Self-Reproducing Interstellar Probe,” Journal of the British Interplanetary Society 33 (1980): 251-64. Also available in revised form on the Web. See also F. Valdes and Robert A. Freitas Jr., “Comparison of Reproducing and Nonreproducing Starprobe Strategies for Galactic Exploration,” Journal of the British Astronomical Society 33 (1980): 402-406.
