Date: Sat, 31 Oct 92 05:03:58 From: Space Digest maintainer Reply-To: Space-request@isu.isunet.edu Subject: Space Digest V15 #362 To: Space Digest Readers Precedence: bulk Space Digest Sat, 31 Oct 92 Volume 15 : Issue 362 Today's Topics: Galileo High Gain Antenna Update Gore Blames George Bush for Big Bang Re: Swift-Tuttle Comet a threat to earth? re HRMS for ETI Smith-Tuttle Comet a threat to earth? Welcome to the Space Digest!! Please send your messages to "space@isu.isunet.edu", and (un)subscription requests of the form "Subscribe Space " to one of these addresses: listserv@uga (BITNET), rice::boyle (SPAN/NSInet), utadnx::utspan::rice::boyle (THENET), or space-REQUEST@isu.isunet.edu (Internet). ---------------------------------------------------------------------- Date: 31 Oct 92 06:48:38 GMT From: Cameron Newham Subject: Galileo High Gain Antenna Update Newsgroups: sci.space In article <16459@umd5.umd.edu> jjk@astro.umd.edu writes: > > I've had a question and I don't know who to ask, so I'll do it here. > This question really doesn't require an answer to me, I'm just > wondering if the High Gain Antenna problem could be helped... > > So the question 1) does HST have the capability of imaging Galileo > when it gets close to earth? and 2) would this help the engineers at > all? > I don't think HST has the ability to slew fast enough to image Galileo. -cameron. ------------------------------ Date: 30 Oct 92 21:12:24 GMT From: Tim Stevens Subject: Gore Blames George Bush for Big Bang Newsgroups: talk.politics.space,sci.space In article <24OCT199219520543@judy.uh.edu>, wingo%cspara.decnet@Fedex.Msfc.Nasa.Gov writes: |> In article <92297.221907U56503@uicvm.uic.edu>, writes... |> > The Florida Institute of Technology is the first school in the |> > country to offer a degree in space technology. Many of its graduates |> > go on to work at NASA, Grumman, Lockheed, and Martin Marietta. The |> > school is located about 25 miles south of Cape Canaveral. Gore |> > echoed his remarks in Florida during a visit later in the day to the |> > U.S. Space and Rocket Center in Huntsville, Alabama. |> |> There was a large contingent from the University of Alabama in Huntsville at |> this little party carrying Bush/Quayle posters. Too bad it did not get on TV. |> Sorry Gore baby but it was the University of South Dakota that did it first. ^^^^^ Sorry Dennis baby but it was the University of *North* Dakota that 'did it first.' ----- David Webb started the 'Space Studies' program ~'87 (not sure of the exact year.) BTW it's an excellent program. |> David Webb has also put the program in place at Emery Riddle University in |> Florida. The University of Alabama in Huntsville continues in its efforts |> to train the real space professionals of the twentyfirst century. These |> students can read write and see propaganda when it is put out. Your |> talk is just talk. |> |> The Clinton/Gore Campaign is like a man trying to bed a beautiful virgin. They |> promise anything that they think can woo her to bed. What usually happens is |> that after the conquest the virgin is discarded as trash. Let this not happen |> to our nation. |> |> Dennis, University of Alabama in Huntsville -- Tim Stevens, (formerly of) University of North Dakota at Grand Forks [Always a NoDak] ------ Tim Stevens tjs@freddie.udev.cdc.com Control Data Systems Inc. (612) 482-3570 ------------------------------ Date: Sat, 31 Oct 1992 06:26:10 GMT From: Dave Tholen Subject: Re: Swift-Tuttle Comet a threat to earth? Newsgroups: sci.astro,sci.space Thorsten Altenkirch writes: > I understand that it is pretty unlikely that Swift-Tuttle will hit > earth in 2126. However, I would like to know what would happen in the > case such a big object would collide with our planet? I am not sure > whether my memory is right but in the discussion about the > disappearance of the dinosaurs an object of a size like 200m was > mentioned. Now, Swift-Tuttle is supposed to be much bigger (10 km?)... Your memory is partly in error. The disappearance of the dinosaurs involved an object about 10 km in diameter. 200 m would produce only local, not global, effects. But yes, if P/Swift-Tuttle shares the low albedo of other comets like P/Halley, then it could be 10 km in diameter as well. A direct hit on Earth would not be good news. ------------------------------ Date: Sat, 31 Oct 1992 01:57:53 GMT From: Alan McGowen Subject: re HRMS for ETI Newsgroups: sci.space Some speculations (what else is this thread, anyway?): P(life | suitable planet) ~ 1 (Check out recent evidence for multiple origins of coding. The person who said the "organic soup" theory was dead because of improbability should learn about the theory, due to Manfred Eigen, of the origin of coding by heterocyclic catalysis. Generating the negentropy is not a severe theoretical problem, and if coding actually had multiple origins it must have been a cakewalk for nature, however badly we might explain it.) P(multicellular life | life) ~ 0.5 (Within the lifespan of a biosphere. It might be lower. The estimate is based on nothing more than the fact that multicellularity appeared roughly midway through the main sequence lifespan of the sun.) P(smart life | multicellular life) ~ 0.01 (Smart life means e.g. birds and mammals. Check out Bonner's book _The Evolution of Complexity_, which might put this at ~1. That may be a major overestimate, however: there may be just one fundamental adaptation -- vertebrate sociality -- which drives the entire phyletic trend towards increasing "smartness" (encephalization). If that basic adaptation itself has a very low prior probability, this one is an overestimate. No similar phyletic trend apparently occurs outside the vertebrates. The justification for the number is that it is roughly the inverse of the number of animal phyla, only one of which exhibits encephalization.) P(symbolic intelligence | smart life) "1 e-12" (Specifically human intelligence is no more (really just some very small likely than is the specific adaptation number) pattern of any other species. The fact that it may open a new adaptive zone *if reached* is not relevant to its conditional probability, which has to do with how easy it is to arrive at an adaptation (preadaptation), not with how good it is to have it once it has been arrived at (fitness). By contrast to symbolic intelligence consider, e.g. eyes, which have evolved independently many different times. So has flight. There is also the Saganistic possibility that symbolic intelligence does *not* prove to be adaptive for very long: the evidence of its mounting effect on the biosphere makes this a more than abstruse possibility.) It interests me that many physical scientists seem to think either that Sagan: P(life) ~ 1 & P(radio telescopes | life) ~ 1 --> many civilizations or that Tipler: P(life) ~ 0 & P(radio telescopes | life) ~ 1 --> sparse civilizations while virtually all evolutionary biologists seem to think that Simpson: P(life) ~ 1 & P(radio telescopes | life) ~ 0 --> sparse civilizations. See Stephan Gould's essay about this in _Bully for Bronotosaurus_, and also see his book _Wonderful Life_ (which I understand has not been a favorite of the Seti crowd). [Some of the strange Cambrian critters Gould discusses in that book have recently been held to be fossilization artifacts -- hodgepodges of bits of other organisms -- or to be assignable to known groups after all.] ------------ Alan McGowen ------------------------------ Date: Sat, 31 Oct 1992 07:09:30 GMT From: Dave Tholen Subject: Smith-Tuttle Comet a threat to earth? Newsgroups: sci.space Jack Romachek writes: > Strange. I did a calculation using the orbital elements from IAU > Circular 5636 and had the comet returning to perihelion on 17 Dec. 2127, > when according to the circular should happen 11 July 2126. That > is approximately the same time difference encountered above. Will including > planetary perturbations cause the comet to arrive 17 months earlier than > a strictly two-body (comet+sun) calculation? Yes. That and whatever non-gravitational terms Marsden assumed for his extrapolation to the next perihelion passage. ------------------------------ Newsgroups: sci.astro,sci.space Subject: Re: Collision with Comet P/Swift-Tuttle Message-Id: <1992Oct31.043614.1120@cbnewsd.cb.att.com> From: "lewis.h.mammel..jr" Date: Sat, 31 Oct 1992 04:36:14 GMT Followup-To: sci.astro References: <1992Oct27.005235.42690@frodo.cc.flinders.edu.au> Organization: AT&T Summary: orbit calculations, questions Lines: 84 Sender: news@CRABAPPLE.SRV.CS.CMU.EDU Source-Info: Sender is really isu@VACATION.VENARI.CS.CMU.EDU In article <1992Oct27.005235.42690@frodo.cc.flinders.edu.au>, phacb@cc.flinders.edu.au () writes: > Circular No. 5636 > Central Bureau for Astronomical Telegrams > INTERNATIONAL ASTRONOMICAL UNION > Postal Address: Central Bureau for Astronomical Telegrams > Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. > > PERIODIC COMET SWIFT-TUTTLE (1992t) > Orbital computations by the undersigned, and also by S. Nakano, > Sumoto, Japan, have so far failed to link all the observations, even > when allowance is made for nongravitational forces. Although a > reasonable fit can be made to the 1862 (except October) and 1992 > observations, the resulting transverse nongravitational component is > so large that the resulting eighteenth-century perihelion time is 15 > months too late. Alternatively, although the three perihelion times > can be well represented without any consideration of nongravitational > forces at all, there are strong systematic errors, amounting to more > than 1', in 1862 and 1992. The gravitational orbital elements below > satisfy the observations in 1992 and in Oct. 1862 very well, and they > also represent the presumed 1737 perihelion time within 1 day. 1862 - 1737 = 125 1992 - 1862 = 130 2126 - 1992 = 134 By Kepler's law this corresponds to a continuing increase in the semimajor axis, which dynamically means that the comet is gaining energy ( per unit remaining mass ) on each orbit. Is this right? ( I don't see how it could be wrong. ) Is it unusual ? > Backward computation of this solution reveals few candidates for > earlier appearances of the comet, although the one of -68 fits within > 1 year (there being 15 revolutions between then and 1862), and the > comet of +60 may also belong. Future extrapolation gives the next > return to perihelion as 2126 July 11, although the problem with the > computation of the nongravitational forces must introduce some > uncertainty; a change by +15 days could cause the comet to hit the > earth on 2126 Aug. 14. It therefore seems prudent to attempt to > follow P/Swift-Tuttle for as long as possible after the present > perihelion passage, in the hope that an adequate independent orbit > determination, uncontaminated by nongravitational effects, can be made > from mid-1993 (at r = 3 AU and far to the south) to, say, 1998 (when r > = 15 AU and an assumed nuclear absolute magnitude of 14 yields an > apparent magnitude of 26). > > Epoch = 1992 Dec. 4.0 TT > T = 1992 Dec. 12.323 TT Peri. = 153.013 > e = 0.96359 Node = 139.456 2000.0 > q = 0.95812 AU Incl. = 113.430 > a = 26.31666 AU n = 0.007301 P = 135.00 years I don't understand why P is 135.00 NOW, given that it's been increasing, and that it's due back in 134 years. I fiddled with these numbers ( Thanks for posting them! ) and I found that, as given, they bring the comet to 1.03156 AU at its descending node at longitude 319.456. I calculate that the earth is at 1.01317 at this longitude, so it seems that we're dealing with a 2% variation to get a hit - that's about 230 earth diameters. ( Of course, the predicted perturbations may put it much closer. ) Now in 15 days, the earth moves about 3000 earth diameters, so I can see why you might get an elongated "footprint", where the major uncertainty is in arrival time. You can take a "spherical horse" approach, and put the earth in a target plane displaced from the bull's eye by 3000, 200. Then assume that the standard deviation is about the same along each axis as these displacements. Of course the earth has an area of about 1 in these units, so I get a probability of one in: 2*pi*e*3000*200 ~1e7 So I agree with whoever said 1 in 10,000 was way to pessimistic. I wonder if Marsden did an essentially 1-d estimation ? I get a one in 7300 chance that way ( 3000*sqrt(2*pi*e) ). Surely there must be SOME uncertainty in the transverse direction ? You know, a good unit of risk might be "decks", meaning how many shuffled decks you would have to cut simultaneously to the Ace of Spades to get a death sentence. Marsden's got us between 2 and 3 decks. Lew Mammel, Jr. ------------------------------ End of Space Digest Volume 15 : Issue 362 ------------------------------