FW: Centauri Dreams - Solar Sail Mission to the Sun’s High Latitudes

[LARRY KLAES]

>From: Centauri Dreams <gilster at mindspring.com>
>Reply-To: Centauri Dreams <gilster at mindspring.com>
>Subject: Centauri Dreams
>Date: Thu, 12 Jun 2008 14:02:38 -0500 (CDT)
>
>Centauri Dreams
>
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>Solar Sail Mission to the Suns High Latitudes
>
>Posted: 12 Jun 2008 12:35 PM CDT

>http://www.centauri-dreams.org/?p=1921
>
>
>Every now and then, someone writes to point out that when I write about the 
>nearest star, I am actually talking about the Sun. True enough, and despite 
>our interstellar focus in these pages, I dont want to neglect the 
>contribution of missions like SOHO, Ulysses, Hinode, STEREO and others to 
>our understanding of how stars work. What we now need to deepen that 
>knowledge further is a polar mission like POLARIS, which is being designed 
>to make high-latitude studies of the Sun.
>
>For we have no extended studies of these regions, which will set up 
>observations impossible to make from the ecliptic. Nor does the proposed 
>Solar Orbiter mission offer a wide enough view of the polar regions. A new 
>study of the POLARIS mission notes its purpose: to determine the relation 
>between the magnetism and dynamics of the Suns polar regions and the solar 
>cycle. Indeed, the spacecraft would map the solar magnetic field in 3-D as 
>well as helping us understand its origins.
>
>But you knew there had to be more of an interstellar hook here. POLARIS 
>(Polar Investigation of the Sun) would use a combination of a Venus gravity 
>assist and solar sail propulsion to reach its 0.48 AU orbit around the Sun, 
>with an inclination to the solar equator of 75 degrees. Two reference 
>studies depict a sail varying in weight from 195 to 408 kilograms, with 
>sail side length of, respectively, 153 meters or 179. Significant issues 
>arise in considering these studies, one being the question of whether the 
>sail should be deployed before or after the Venus gravity assist (if after, 
>stowing the sail for six months could cause later problems).
>
>
>
>Paulette Liewer (JPL), Thierry Appourchaux (Institut dAstrophysique 
>Spatiale) and colleagues run through the options in a recent paper, with 
>the significant note that the major challenge for the entire mission is the 
>development and use of the sail. We need advancements in sail material, 
>deployment, attitude and orbit control, the sail jettisoning mechanism and 
>communications, which is why this mission catches the eye. Can an earlier 
>GeoSail mission, a small 250-kg spacecraft with a 50 X 50 meter sail 
>provide the essential shakedown to move some of these technologies forward?
>
>Image: A view of the spacecraft with the sail deployed on its mast. The 
>sail size is a square of 180 m while the spacecraft fits into a 2-m on a 
>side cube. Credit: J.-C.Leclec’h.
>
>Ultimately, of course, those of us who believe in sail technology hope to 
>see sails taking us throughout the inner Solar System and used as an early 
>boost for fast missions to the outer planets as well. Take the engineering 
>to an extreme and we might someday envision sundiver missions deploying a 
>sail at close approach to the Sun for the kind of accelerations we can 
>today only dream about. And there are, of course, those lightsail ideas 
>using beamed propulsion to get us to the stars.
>
>All of which depends upon getting a sail, any kind of sail, operational in 
>space for further study. No insurmountable difficulties stand between us 
>and implementation of early sail missions, if we have the will to proceed 
>with the necessary funding. So keep an eye on mission concepts like 
>POLARIS, discussed in Appourchaux et al., POLAR Investigation of the Sun - 
>POLARIS, accepted by Experimental Astronomy and now available online. Nor 
>are we through with the Sun  I want to discuss Solar Probe+, a mission that 
>will reach into the Suns corona, next week.
>
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>Low Frequency Musings on Extraterrestrial Life
>
>Posted: 11 Jun 2008 03:24 PM CDT
>http://www.centauri-dreams.org/?p=1919
>
>
>When it comes to SETI investigations, the Low Frequency Array (LOFAR) being 
>built in Europe offers intriguing possibilities. With a plan to encompass 
>roughly 25,000 small antennae, arranged in clusters spread out over an area 
>350 kilometers in diameter, LOFAR may prove sensitive enough to detect the 
>radiation leakage of transmitters in the radio and television bands from 
>extraterrestrial civilizations. The array will operate between 10 and 240 
>MHz. When completed, it will offer not only myriad astronomical 
>possibilities but SETI opportunities with a difference.
>
>Michael Garrett (Leiden University) is general director of ASTRON, the 
>Netherlands Institute for Radio Astronomy, now involved in building the new 
>array. Garrett makes note of whats possible if LOFARs formidable resources 
>are turned to SETI:
>
>LOFAR can extend the search for extra-terrestrial intelligence to an 
>entirely unexplored part of the low-frequency radio spectrum, an area that 
>is heavily used for civil and military communications here on Earth. In 
>addition, LOFAR can survey large areas of the sky simultaneously - an 
>important advantage if SETI signals are rare or transient in nature.
>
>This story has a particular resonance for me. Back in the 1970s, I put 
>together a shortwave listening post that had it all  three receivers, 
>including radioteletype capability, and all sorts of filters and peripheral 
>equipment. I loved DXing the tropical bands, my specialty, looking for 
>faint Indonesian local stations that would drift into the eastern US 
>usually around sunrise for their brief window of receivability. In the 
>evenings, I would hunt unusual, low-power South American stations, 
>including the holy grail for shortwave listeners, the Falkland Islands, a 
>fabulous catch that only a few old hands had made (I never did log the 
>Falklands).
>
>Even harder to get was Tristan da Cunha  I knew of no one other than a few 
>South African DXers who could lay claim to that one. It occurred to me one 
>night as I was logging a new station in my book that the right kind of 
>equipment might catch a signal from another star. Back then, knowing little 
>about these matters, I just assumed that signal would be a radio or TV 
>signal, and that we would be listening in to the traffic of a civilization 
>not so different from our own. I pondered what kind of antenna it would 
>take, and wrote a speculative piece called Where the Real DX Is for Glenn 
>Hausers Review of International Broadcasting.
>
>LOFARs frequency range covers areas I used to scan, but no one today is as 
>naive as I was about expecting other civilizations to be like ours. But 
>whatever we find, a SETI attempt via LOFAR is worth doing. Sure, nearby 
>civilizations would be unlikely to be at the same level of electromagnetic 
>development  radio and TV  that we are. On the other hand, it seems 
>reasonable to search broadly through the spectrum in case were missing 
>something obvious. Its not as if SETI is LOFARs raison detre, but making 
>researchers aware of SETI possibilities is only common sense.
>
>
>
>So what is LOFAR about? The plan is to survey the universe with higher 
>resolution and sensitivity than any previous surveys at these wavelengths, 
>mapping everything from the reionization of hydrogen in the early universe 
>to the formation of galaxies and the clusters that house them. Throw in the 
>distribution of cosmic rays, the study of pulsars and transient events of 
>all descriptions and you have an observatory that deepens our understanding 
>in these frequency ranges and is certain to make serendipitous discoveries.
>
>Image: A typical galaxy like the Milky Way contains as many stars as there 
>are grains of sand on all the worlds beaches. Most of these stars have 
>planetary systems and many will have the right conditions for life to 
>flourish. LOFAR can potentially search for artificial radio signals from 
>intelligent civilizations in nearby stellar systems. Credit: LOFAR.
>
>Serendipity as in the discovery of ETI? LOFARs SETI potential has been 
>under discussion in the Netherlands this past week at a workshop held in 
>Dwingeloo. With stations spread throughout northern Europe, the observatory 
>will be inspiring various SETI observing proposals as the projects Phase I 
>progresses to full capability. Prepare for the unexpected, even if its not 
>the signature of an extraterrestrial transmitter. Every time we push into 
>higher-resolution instrumentation or look at the universe in less studied 
>wavelengths, something unusual tends to happen. Who knows what LOFARs 
>version of gamma-ray bursts may turn out to be?
>
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