by Paul Gilster | Sep 21, 2004 | Exoplanetary Science |
A network of robotic telescopes called RoboNet-1.0 will soon join the hunt for Earth-like planets around other stars. RoboNet will look for the effects of gravitational micro-lensing, where distant light is bent around an unseen foreground object. A star whose light is undergoing such lensing would, if it had a planet, show a blip in its detected light which RoboNet should be able to follow-up. “The network,” says a press release from the Particle Physics and Astronomy Research Council, which funded the project, “stands the best chance of any existing facility of actually finding another Earth due to the large size of the telescopes, their excellent sites and sensitive instrumentation.”
The globally distributed RoboNet offers astronomers the chance to search anywhere in the sky without regard to local light conditions by passing observations from one telescope to the next. The Liverpool Telescope (Canary Islands), Faulkes North (Maui) and Faulkes South (New South Wales) telescopes make up the network. Software for RoboNet was developed by the Liverpool John Moores University eStar project.
Image: The Liverpool Telescope with its distinctive clamshell dome. Credit: Astrophysics Research Institute, Liverpool JMU
Says Dr Iain Steele of the eSTAR project:
“We have been able to use and develop new Grid technologies, which will eventually be the successor to the World Wide Web, to build a network of intelligent agents that can detect and respond to the rapidly changing universe much faster than any human. The agents act as “virtual astronomers” collecting, analysing and interpreting data 24 hours a day, 365 days a year, alerting their flesh-and-blood counterparts only when they make a discovery.”
Observations on demand are also critical for studying sudden changes in astronomical objects such as violent Gamma Ray Bursts, which can last from milliseconds to a few minutes before fading away to a long afterglow. Scientists hoping to track Gamma Ray Bursts (GRBs) would have to point their telescopes at the right point in the sky almost instantly to make useful observations. But NASA’s Swift satellite, to be launched in October, will help pinpoint the explosions of GRBs, relaying the coordinates of each burst to the RoboNet network within seconds.
by Paul Gilster | Sep 20, 2004 | Outer Solar System
The European Space Agency has announced that the Huygens probe has passed its second to last in-flight checkout, in preparation for deployment to Titan in December. The critical Mission Timer Unit is in good health, a must given the fact that Huygens will coast for several weeks after being released by the Cassini Saturn orbiter. The MTU will be charged with waking Huygens up just before entry into Titan’s atmosphere. ESA’s coverage is here.
by Paul Gilster | Sep 20, 2004 | Deep Sky Astronomy & Telescopes
A team of Australian researchers has built an unmanned observatory high on an Antarctic plateau that may provide images nearly the equal of Hubble’s. That’s the word from Nature, where University of New South Wales associate professor Michael Ashley, co-author of the paper, described the capabilities of the new viewing site. The paper’s lead author is Dr. Jon S. Lawrence, a postdoctoral fellow at the University of New South Wales.
The location is known as Dome C, 3250 meters above sea level on the Antarctic Plateau, at latitude 75 degrees south. Among its favorable characteristics are low infrared sky emission, dry and extremely cold air, few clouds and low dust and aerosol content. The upshot: much less ‘star jitter.’ All of these factors make the site, which is 400 meters higher than the South Pole, far better for viewing than the location of instruments currently in place in Chile, Hawaii and the Canary Islands.
Having established the superiority of Dome C, the team now argues for larger apertures at the site that could deliver Hubble-style images at a cost far below that of much larger Earth-bound telescopes. “The discovery means that a telescope at Dome C on the Antarctic plateau could compete with a telescope two to three times larger at the best mid-latitude observatories, with major cost-saving implications,” Ashley said. “Dome C could become an important ‘test-bed’ for experiments and technologies that will later be flown as space missions. Indeed, for some projects, the site might be an attractive alternative to space based astronomy.”
At the site currently is an automated station called AASTINO (Automated Site Testing International Laboratory), which the duo established in January of 2004. The entire experiment was subsequently run by remote control. “When we left there in February,” said Ashley, “we said goodbye to it knowing all that we could do was communicate with it by the phone and the Internet. If we’d needed to press a reset button on a computer or something, there was no way to do so, and the entire experiment could have failed.” A news release from the University of New South Wales provides more information.
What may come next at Dome C makes for fascinating conjecture. At the SPIE Astronomical Telescopes and Instrumentation conference last June in Glasgow, Dr. Will Saunders of the Anglo-Australian Observatory presented a telescope concept built around icecrete — compressed snow in blocks as hard as concrete — that could be built at the site. According to Saunders, as quoted in this press release from the Anglo-Australian Observatory in Sydney: “With this simple telescope you could do the exquisite imaging that the extremely large telescopes plan to do, at a fraction of their cost. But, unlike them, this telescope would also be a great survey instrument, able to map the whole sky with Hubble-like clarity.”
All this at a fifth of the price of some of the large Earth-bound instruments now in planning stages. The Nature article is Jon S. Lawrence, Michael C. B. Ashley et.al., “Exceptional Astronomical Seeing Conditions Above Dome C in Antarctica.” Nature 431, pp. 278-81 (16 September 2004). Nature‘s online news site has a precis.
by Paul Gilster | Sep 17, 2004 | Communications and Navigation, Missions
Scottish minister Robert Stirling developed an engine in the 19th Century that used heated air instead of steam as the motive force for a piston engine. Now an acoustical version of the principle has emerged. As described in an article in a recent issue of Applied Physics Letters, a joint team from Los Alamos National Laboratory and Northrop Grumman Space Technology have created TASHE — the “thermoacoustic-Stirling heat engine.”
The work of LANL scientist Scott Backhaus and Emanuel Tward and Mike Petach from Northrop Grumman, TASHE would be used to generate electricity aboard spacecraft, and would be quite a step up from the thermoelectric devices now used, which convert roughly 7 percent of their heat energy into electricity using heat from the decay of a radioactive fuel.
By contrast, TASHE converts up to 18 percent of its heat source energy into usable electricity. The expansion of helium gas inside the engine drives the process, as described in a recent issue of Physics News Update:
In the TASHE system, intense, spontaneously generated sound waves (in the place of mechanical pistons in the 19th-century design) shuttle parcels of helium gas between a cold end and hot end. The hot and cold end temperatures are generated by connecting the engine to a high-temperature heat source and an ambient-temperature heat sink through the heat exchangers. Thermally driven expansion and contraction of the gas, in concert with pressure oscillations (induced by the temperature difference), intensify the power of the initial sound waves which become strong enough to drive a piston connected to the device. The motion of the piston vibrates a coil of copper wire that produces electricity as it moves relative to a permanent magnet.
The upshot: the size and power of instruments in deep space probes can be increased, a critical factor given the tight resources available to spacecraft designers. Evaluate TASHE in light of Project Prometheus, a scheme that would create compact reactors to fly on a new generation of robotic space probes, including the Jupiter Icy Moons Orbiter (JIMO), which would depart no earlier than 2012 and rendezvous with Europa, Ganymede, and Callisto.
Sources: Press release from DOE/Los Alamos National Laboratory via EurekAlert 16 Sept. 2004; “Acoustically powered deep-space electric generator,” by Phil Schewe and Ben Stein, in Physics News Update No. 695, August 4, 2004. The original paper is S. Backhaus, E. Tward and M. Petach, “Traveling-wave thermoacoustic electric generator” in Applied Physics Letters, Vol. 85, Issue 6, pp. 1085-87.
by Paul Gilster | Sep 16, 2004 | Communications and Navigation
Here’s an interesting observation from Joss Bland-Hawthorn, who is head of instrument science at the Anglo-Australian Observatory in Sydney: “Astronomers are losing vast amounts of data from recent satellite missions to Mars. We collect a hundred times more than we can transmit back.”
The comment appears in the current issue of New Scientist, in an article by Maggie McKee called “Mars Laser Will Beam Super-fast Data.” And the problem identified is one that will plague us more and more the farther we get from Earth. Radio signals are inherently less efficient than lasers, and not only because shorter wavelengths can carry more information in the same unit of time. A laser signal transmitted from a Mars orbiter, says New Scientist, will only spread to a width of a few hundred kilometers by the time it reaches the Earth. A radio signal, by contrast, diffuses rapidly with distance.
How rapidly? Well, JPL’s James Lesh told me in a telephone interview last year that the Mars Pathfinder mission returned a signal that had spread to hundreds of times the diameter of the Earth by the time it arrived. And because the data rate depends on the power of the signal, getting good information out of the ether can be quite a challenge. For an Alpha Centauri probe, the numbers become staggering: a radio signal from such a probe would reach Earth with 81 million times weaker a signal than the one the Voyager probe sent back from Neptune.
The good news is that the Mars Telecommunications Orbiter, to be launched in 2009, will include a laser communications package along with its more traditional radio equipment. The five-meter Hale Telescope in California and a still to be constructed array of smaller telescopes will be used to detect the Mars signals. Lasers are the future when it comes to communicating with the outer Solar System, not to mention the nearest star.
An excellent reference here is Lesh’s “Space Communications Technologies for Interstellar Missions,” Journal of the British Interplanetary Society 49 (1996): 7-14, which was written with C. J. Ruggier, and R. J. Cesarone.
And a final thought: why isn’t a bibliography of so essential a journal as JBIS available online? One of my great hopes for the Interstellar Flight Foundation is that it may be able to reintroduce an interstellar bibliography of the kind that Robert Forward and Eugene Mallove once edited.
