Internet Surfer 2.0

home *** CD-ROM | disk | FTP | other *** search

/ Internet Surfer 2.0 / Internet Surfer 2.0 (Wayzata Technology) (1996).iso / pc / text / mac / faqs.511 < prev next >

Wrap

Text File | 1996-02-12 | 27.8 KB | 763 lines

Frequently Asked Questions (FAQS);faqs.511 AAS - American Astronautical Society AIAA - American Institute of Astronautics & Aeronautics World Space Foundation Other groups not mentioned above NEXT: FAQ #14/15 - How to become an astronaut Xref: bloom-picayune.mit.edu sci.astro:28930 sci.space:51984 news.answers:4371 Path: bloom-picayune.mit.edu!enterpoop.mit.edu!eff!sol.ctr.columbia.edu!emory!gatech!concert!borg!mahler!leech From: leech@mahler.cs.unc.edu (Jon Leech) Newsgroups: sci.astro,sci.space,news.answers Subject: Space FAQ 01/15 - Introduction Keywords: Frequently Asked Questions Message-ID: <intro_723318103@cs.unc.edu> Date: 2 Dec 92 17:41:48 GMT Expires: 6 Jan 93 17:41:43 GMT References: <diffs_723318039@cs.unc.edu> Sender: news@cs.unc.edu Followup-To: poster Organization: University of North Carolina, Chapel Hill Lines: 296 Approved: news-answers-request@MIT.Edu Supersedes: <intro_720641588@cs.unc.edu> Archive-name: space/intro Last-modified: $Date: 92/12/02 12:34:40 $ FREQUENTLY ASKED QUESTIONS ON SCI.SPACE/SCI.ASTRO INTRODUCTION This series of linked messages is periodically posted to the Usenet groups sci.space and sci.astro in an attempt to provide good answers to frequently asked questions and other reference material which is worth preserving. If you have corrections or answers to other frequently asked questions that you would like included in this posting, send email to leech@cs.unc.edu (Jon Leech). If you don't want to see the FAQ, add 'Frequently Asked Questions' to your KILL file for this group (if you're not reading this with a newsreader that can kill articles by subject, you're out of luck). The FAQ volume is excessive right now and will hopefully be trimmed down by rewriting and condensing over time. The FAQ postings are available in the Ames SPACE archive in FAQ/faq<#>. Good summaries will be accepted in place of the answers given here. The point of this is to circulate existing information, and avoid rehashing old answers. Better to build on top than start again. Nothing more depressing than rehashing old topics for the 100th time. References are provided because they give more complete information than any short generalization. Questions fall into three basic types: 1) Where do I find some information about space? Try your local public library first. The net is not a good place to ask for general information. Ask INDIVIDUALS (by email) if you must. There are other sources, use them, too. The net is a place for open ended discussion. 2) I have an idea which would improve space flight? Hope you aren't surprised, but 9,999 out of 10,000 have usually been thought of before. Again, contact a direct individual source for evaluation. NASA fields thousands of these each day. 3) Miscellanous queries. These are addressed on a case-by-case basis in the following series of FAQ postings. SUGGESTIONS FOR BETTER NETIQUETTE Read news.announce.newusers if you're on Usenet. Minimize cross references, [Do you REALLY NEED to?] Edit "Subject:" lines, especially if you're taking a tangent. Send mail instead, avoid posting follow ups. (1 mail message worth 100 posts). Internet mail readers: send requests to add/drop to SPACE-REQUEST not SPACE. Read all available articles before posting a follow-up. (Check all references.) Cut down attributed articles (leave only the points you're responding to; remove signatures and headers). Summarize! Put a return address in the body (signature) of your message (mail or article), state your institution, etc. Don't assume the 'reply' function of mailers will work. Use absolute dates. Post in a timely way. Don't post what everyone will get on TV anyway. Some editors and window systems do character count line wrapping: keep lines under 80 characters for those using ASCII terminals (use carriage returns). INDEX TO LINKED POSTINGS I've attempted to break the postings up into related areas. There isn't a keyword index yet; the following lists the major subject areas in each posting. Only those containing astronomy-related material are posted to sci.astro (indicated by '*' following the posting number). # Contents 1* Introduction Suggestions for better netiquette Index to linked postings Notes on addresses, phone numbers, etc. Contributors 2* Network resources Overview Mailing lists Periodically updated information Warning about non-public networks 3* Online (and some offline) sources of images, data, etc. Introduction Viewing Images Online Archives NASA Ames NASA Spacelink National Space Science Data Center Space And Planetary Image Facility Space Telescope Science Institute Electronic Info. Service Astronomical Databases Astronomy Programs Orbital Element Sets SPACE Digest Landsat & NASA Photos Planetary Maps Cometary Orbits 4* Performing calculations and interpreting data formats Computing spacecraft orbits and trajectories Computing planetary positions Computing crater diameters from Earth-impacting asteroids Map projections and spherical trignometry Performing N-body simulations efficiently Interpreting the FITS image format Sky (Unix ephemeris program) Three-dimensional star/galaxy coordinates 5* References on specific areas Publishers of space/astronomy material Careers in the space industry DC-X single-stage to orbit (SSTO) program LLNL "great exploration" Lunar science and activities Spacecraft models Rocket propulsion Spacecraft design Esoteric propulsion schemes (solar sails, lasers, fusion...) Spy satellites Space shuttle computer systems SETI computation (signal processing) Amateur satellies & weather satellites Tides 6* Constants and equations for calculations 7* Astronomical Mnemonics 8 Contacting NASA, ESA, and other space agencies/companies NASA Centers / Arianespace / ESA / NASDA / Soyuzkarta / Space Camp / Space Commerce Corporation / Spacehab / SPOT Image Other commercial space businesses 9 Space shuttle answers, launch schedules, TV coverage Shuttle launchings and landings; schedules and how to see them How to receive the NASA TV channel, NASA SELECT Dial-A-Shuttle and how to use it Amateur radio frequencies for shuttle missions Solid Rocket Booster fuel composition 10 Planetary probes - Historical Missions US planetary missions Mariner (Venus, Mars, & Mercury flybys and orbiters) Pioneer (Moon, Sun, Venus, Jupiter, and Saturn flybys and orbiters) Ranger (Lunar lander and impact missions) Lunar Orbiter (Lunar surface photography) Surveyor (Lunar soft landers) Viking (Mars orbiters and landers) Voyager (Outer planet flybys) Soviet planetary missions Soviet Lunar probes Soviet Venus probes Soviet Mars probes Japanese planetary missions Planetary mission references 11 Upcoming planetary probes - missions and schedules Cassini Galileo Magellan Mars Observer TOPEX/Poseidon Ulysses Other space science missions Proposed missions 12 Controversial questions What happened to the Saturn V plans Why data from space missions isn't immediately available Risks of nuclear (RTG) power sources for space probes Impact of the space shuttle on the ozone layer How long can a human live unprotected in space Using the shuttle beyond Low Earth Orbit The "Face on Mars" 13 Space activist/interest/research groups and space publications Groups Publications Undocumented Groups 14 How to become an astronaut 15 Orbital and Planetary Launch Services NOTES ON ADDRESSES, PHONE NUMBERS, ETC. Unless otherwise specified, telephone numbers, addresses, and so on are for the United States of America. Non-US readers should remember to add the country code for telephone calls, etc. CREDITS Eugene Miya started a series of linked FAQ postings some years ago which inspired (and was largely absorbed into) this set. Peter Yee and Ron Baalke have and continue to spend a lot of their own time setting up the SPACE archives at NASA Ames and forwarding official NASA announcements. Many other people have contributed material to this list in the form of old postings to sci.space and sci.astro which I've edited. Please let me know if corrections need to be made. Contributors I've managed to keep track of are: 0004847546@mcimail.com (Francis Reddy) - map projections akerman@bill.phy.queensu.CA (Richard Akerman) - crater diameters alweigel@athena.mit.edu (Lisa Weigel) - SEDS info aoab314@emx.utexas.edu (Srinivas Bettadpur) - tides awpaeth@watcgl.waterloo.edu (Alan Wm Paeth) - map projections aws@iti.org (Allen W. Sherzer) - Great Exploration baalke@kelvin.jpl.nasa.gov (Ron Baalke) - planetary probe schedules bankst@rata.vuw.ac.nz (Timothy Banks) - map projections, variable star analysis archive bern@uni-trier.de (Jochen Bern) - German mnemonic translation brosen@pioneer.arc.nasa.gov (Bernie Rosen) - Space Camp bschlesinger@nssdca.gsfc.nasa.gov (Barry Schlesinger) - FITS format cew@venera.isi.edu (Craig E. Ward) - space group contact info chapin@cbnewsc.att.com (Tom Chapin) - planetary positions cunnida@tenet.edu (D. Alan Cunningham) - NASA Spacelink cyamamot@kilroy.Jpl.Nasa.Gov (Cliff Yamamoto) - orbital elements datri@convex.com (Anthony Datri) - PDS/VICAR viewing software daver@sjc.mentorg.com (Dave Rickel) - orbit formulae dlbres10@pc.usl.edu (Phil Fraering) - propulsion eder@hsvaic.boeing.com (Dani Eder) - Saturn V plans, SRBs eugene@eos.arc.nasa.gov (Eugene N. Miya) - introduction, NASA contact info, started FAQ postings g@telesoft.com (Gary Morris) - amateur radio info gaetz@uwovax.uwo.ca (Terry Gaetz) - N-body calculations, orbital dynamics grandi@noao.edu (Steve Grandi) - planetary positions greer%utd201.dnet%utadnx@utspan.span.nasa.gov (Dale M. Greer) - constants henry@zoo.toronto.edu (Henry Spencer) - survival in vacuum, astronaut how-to, publication refs, DC-X higgins@fnal.bitnet (William Higgins) - RTGs, publishers, shuttle landings, spysats, propulsion, "Face on Mars" hmueller@cssun.tamu.edu (Hal Mueller) - map projections, orbital dynamics jbh55289@uxa.cso.uiuc.edu (Josh Hopkins) - launch services jim@pnet01.cts.com (Jim Bowery) - propulsion, launch services jscotti@lpl.arizona.edu (Jim Scotti) - planetary positions kcarroll@zoo.toronto.edu (Kieran A. Carroll)- refs for spacecraft design ken@orion.bitnet (Kenneth Ng) - RTGs klaes@verga.enet.dec.com (Larry Klaes) - planetary probe history leech@cs.unc.edu (Jon Leech) - crater diameters lfa@vielle.cray.com (Lou Adornato) - orbital dynamics maury.markowitz@egsgate.fidonet.org (Maury Markowitz) - propulsion mbellon@mcdurb.Urbana.Gould.COM - N-body calculations mcconley@phoenix.Princeton.edu (Marc Wayne Mcconley) - space careers msb@sq.com (Mark Brader) - Mariner 1 info. mwm@cmu.edu (Mark Maimone) - SPACE Digest nickw@syma.sussex.ac.uk (Dr. Nick Watkins) - models, spysats opus@pioneer.unm.edu (Colby Kraybill) - SPIF data archive panama@cup.portal.com (Kenneth W Durham) - cometary orbits, IAU paul.blase@nss.fidonet.org (Paul Blase) - propulsion pjs@plato.jpl.nasa.gov (Peter Scott) - RTGs pschleck@unomaha.edu (Paul W. Schleck) - AMSAT, ARRL contact info rdb@mel.cocam.oz.au (Rodney Brown) - propulsion refs rja7m@phil.cs.virginia.edu (Ran Atkinson) - FTPable astro. programs rjungcla@ihlpb.att.com (R. Michael Jungclas)- models roelle@sigi.jhuapl.edu (Curt Roelle) - German mnemonic translation seal@leonardo.jpl.nasa.gov (David Seal) - Cassini mission schedule shafer@skipper.dfrf.nasa.gov (Mary Shafer) - photos, shuttle landings smith@sndpit.enet.dec.com (Willie Smith) - photos stephen@gpwd.gp.co.nz (Stephen Dixon) - shuttle audio frequencies sterner@warper.jhuapl.edu (Ray Sterner) - planetary positions stooke@vaxr.sscl.uwo.ca (Phil Stooke) - planetary maps ted_anderson@transarc.com (Ted Anderson) - propulsion terry@astro.as.utexas.edu (Terry Hancock) - NASA center info thorson@typhoon.atmos.coloState.edu (Bill Thorson) - FITS info tm2b+@andrew.cmu.edu (Todd L. Masco) - SPACE Digest tom@ssd.csd.harris.com (Tom Horsley) - refs for algorithms veikko.makela@helsinki.fi (Veikko Makela) - orbital element sets wayne@csri.utoronto.ca (Wayne Hayes) - constants weemba@libra.wistar.upenn.edu (Matthew P Wiener) - Voyager history yamada@yscvax.ysc.go.jp (Yoshiro Yamada) - ISAS/NASDA missions yee@ames.arc.nasa.gov (Peter Yee) - AMES archive server, propulsion In Net memoriam: Ted Flinn NEXT: FAQ #2/15 - Network Resources Xref: bloom-picayune.mit.edu sci.space:51997 news.answers:4383 Path: bloom-picayune.mit.edu!enterpoop.mit.edu!eff!sol.ctr.columbia.edu!emory!gatech!concert!borg!mahler!leech From: leech@mahler.cs.unc.edu (Jon Leech) Newsgroups: sci.space,news.answers Subject: Space FAQ 15/15 - Orbital and Planetary Launch Services Keywords: Frequently Asked Questions Message-ID: <launchers_723318298@cs.unc.edu> Date: 2 Dec 92 17:45:02 GMT Expires: 6 Jan 93 17:44:58 GMT References: <diffs_723318039@cs.unc.edu> Sender: news@cs.unc.edu Followup-To: poster Organization: University of North Carolina, Chapel Hill Lines: 195 Approved: news-answers-request@MIT.Edu Supersedes: <launchers_720641966@cs.unc.edu> Archive-name: space/launchers Last-modified: $Date: 92/12/02 12:34:41 $ ORBITAL AND PLANETARY LAUNCH SERVICES The following data comes from _International Reference Guide to Space Launch Systems_ by Steven J. Isakowitz, 1991 edition. Notes: * Unless otherwise specified, LEO and polar paylaods are for a 100 nm orbit. * Reliablity data includes launches through Dec, 1990. Reliabity for a familiy of vehicles includes launches by types no longer built when applicable * Prices are in millions of 1990 $US and are subject to change. * Only operational vehicle families are included. Individual vehicles which have not yet flown are marked by an asterisk (*) If a vehicle had first launch after publication of my data, it may still be marked with an asterisk. Vehicle | Payload kg (lbs) | Reliability | Price | Launch Site (nation) | LEO Polar GTO | | | (Lat. & Long.) -------------------------------------------------------------------------------- Ariane 35/40 87.5% Kourou (ESA) (5.2 N, 52.8 W) AR40 4,900 3,900 1,900 1/1 $65m (10,800) (8,580) (4,190) AR42P 6,100 4,800 2,600 1/1 $67m (13,400) (10,600) (5,730) AR44P 6,900 5,500 3,000 0/0 ? $70m (15,200) (12,100) (6,610) AR42L 7,400 5,900 3,200 0/0 ? $90m (16,300) (13,000) (7,050) AR44LP 8,300 6,600 3,700 6/6 $95m (18,300) (14,500) (8,160) AR44L 9,600 7,700 4,200 3/4 $115m (21,100) (16,900) (9,260) * AR5 18,000 ??? 6,800 0/0 $105m (39,600) (15,000) [300nm] Atlas 213/245 86.9% Cape Canaveral (USA) (28.5 N, 81.0W) Atlas E -- 820 -- 15/17 $45m Vandeberg AFB (1,800) (34.7 N, 120.6W) Atlas I 5,580 4,670 2,250 1/1 $70m (12,300) (10,300) (4,950) Atlas II 6,395 5,400 2,680 0/0 $75m (14,100) (11,900) (5,900) Atlas IIA 6,760 5,715 2,810 0/0 $85m (14,900) (12,600) (6,200) * Atlas IIAS 8,390 6,805 3,490 0/0 $115m (18,500) (15,000) (7,700) Delta 189/201 94.0% Cape Canaveral (USA) Vandenberg AFB Delta 6925 3,900 2,950 1,450 14/14 $45m (8,780) (6,490) (3,190) Delta 7925 5,045 3,830 1,820 1/1 $50m (11,100) (8,420) (2,000) Energia 2/2 100% Baikonur (Russia) (45.6 N 63.4 E) Energia 88,000 80,000 ??? 2/2 $110m (194,000) (176,000) H series 22/22 100% Tangeshima (Japan) (30.2 N 130.6 E) * H-2 10,500 6,600 4,000 0/0 $110m (23,000) (14,500) (8,800) Kosmos 371/377 98.4% Plestek (Russia) (62.8 N 40.1 E) Kosmos 1100 - 1350 (2300 - 3000) $??? Kapustin Yar [400 km orbit ??? inclination] (48.4 N 45.8 E) Long March 23/25 92.0% Jiquan SLC (China) (41 N 100 E) * CZ-1D 720 ??? 200 0/0 $10m Xichang SLC (1,590) (440) (28 N 102 E) Taiyuan SLC CZ-2C 3,200 1,750 1,000 12/12 $20m (41 N 100 E) (7,040) (3,860) (2,200) CZ-2E 9,200 ??? 3,370 1/1 $40m (20,300) (7,430) * CZ-2E/HO 13,600 ??? 4,500 0/0 $??? (29,900) (9,900) CZ-3 ??? ??? 1,400 6/7 $33m (3,100) * CZ-3A ??? ??? 2,500 0/0 $???m (5,500) CZ-4 4,000 ??? 1,100 2/2 $???m (8,800) (2,430) Pegasus/Taurus 2/2 100% Peg: B-52/L1011 (USA) Taur: Canaveral Pegasus 455 365 125 2/2 $10m or Vandenberg (1,000) (800) (275) * Taurus 1,450 1,180 375 0/0 $15m (3,200) (2,600) (830) Proton 164/187 87.7% Baikonour (Russia) Proton 20,000 ??? 5,500 164/187 $35-70m (44,100) (12,200) SCOUT 99/113 87.6% Vandenberg AFB (USA) Wallops FF SCOUT G-1 270 210 54 13/13 $12m (37.9 N 75.4 W) (600) (460) (120) San Marco (2.9 S 40.3 E) * Enhanced SCOUT 525 372 110 0/0 $15m (1,160) (820) (240) Shavit 2/2 100% Palmachim AFB (Israel) ( ~31 N) Shavit ??? 160 ??? 2/2 $22m (350) Space Shuttle 37/38 97.4% Kennedy Space (USA) Center Shuttle/SRB 23,500 ??? 5,900 37/38 $248m (28.5 N 81.0 W) (51,800) (13,000) [FY88] * Shuttle/ASRM 27,100 ??? ??? 0/0 (59,800) SLV 2/6 33.3% SHAR Center (India) (400km) (900km polar) (13.9 N 80.4 E) ASLV 150 ??? ??? 0/2 $???m (330) * PSLV 3,000 1,000 450 0/0 $???m (6,600) (2,200) (990) * GSLV 8,000 ??? 2,500 0/0 $???m (17,600) (5,500) Titan 160/172 93.0% Cape Canaveral (USA) Vandenberg Titan II ??? 1,905 ??? 2/2 $43m (4,200) Titan III 14,515 ??? 5,000 2/3 $140m (32,000) (11,000) Titan IV/SRM 17,700 14,100 6,350 3/3 $154m-$227m (39,000) (31,100) (14,000) Titan IV/SRMU 21,640 18,600 8,620 0/0 $???m (47,700) (41,000) (19,000) Vostok 1358/1401 96.9% Baikonur (Russia) [650km] Plesetsk Vostok 4,730 1,840 ??? ?/149 $14m (10,400) (4,060) Soyuz 7,000 ??? ??? ?/944 $15m (15,400) Molniya 1500kg (3300 lbs) in ?/258 $???M Highly eliptical orbit Zenit 12/13 92.3% Baikonur (Russia) Zenit 13,740 11,380 4,300 12/13 $65m (30,300) (25,090) (9,480) Xref: bloom-picayune.mit.edu sci.astro:28932 sci.space:51986 news.answers:4373 Path: bloom-picayune.mit.edu!enterpoop.mit.edu!eff!sol.ctr.columbia.edu!emory!gatech!concert!borg!mahler!leech From: leech@mahler.cs.unc.edu (Jon Leech) Newsgroups: sci.astro,sci.space,news.answers Subject: Space FAQ 04/15 - Calculations Keywords: Frequently Asked Questions Message-ID: <math_723318189@cs.unc.edu> Date: 2 Dec 92 17:43:15 GMT Expires: 6 Jan 93 17:43:09 GMT References: <diffs_723318039@cs.unc.edu> Sender: news@cs.unc.edu Followup-To: poster Organization: University of North Carolina, Chapel Hill Lines: 353 Approved: news-answers-request@MIT.Edu Supersedes: <math_720641672@cs.unc.edu> Archive-name: space/math Last-modified: $Date: 92/12/02 12:34:43 $ PERFORMING CALCULATIONS AND INTERPRETING DATA FORMATS COMPUTING SPACECRAFT ORBITS AND TRAJECTORIES References that have been frequently recommended on the net are: "Fundamentals of Astrodynamics" Roger Bate, Donald Mueller, Jerry White 1971, Dover Press, 455pp $8.95 (US) (paperback). ISBN 0-486-60061-0 NASA Spaceflight handbooks (dating from the 1960s) SP-33 Orbital Flight Handbook (3 parts) SP-34 Lunar Flight Handbook (3 parts) SP-35 Planetary Flight Handbook (9 parts) These might be found in university aeronautics libraries or ordered through the US Govt. Printing Office (GPO), although more information would probably be needed to order them. M. A. Minovitch, _The Determination and Characteristics of Ballistic Interplanetary Trajectories Under the Influence of Multiple Planetary Attractions_, Technical Report 32-464, Jet Propulsion Laboratory, Pasadena, Calif., Oct, 1963. The title says all. Starts of with the basics and works its way up. Very good. It has a companion article: M. Minovitch, _Utilizing Large Planetary Perubations for the Design of Deep-Space Solar-Probe and Out of Ecliptic Trajectories_, Technical Report 32-849, JPL, Pasadena, Calif., 1965. You need to read the first one first to realy understand this one. It does include a _short_ summary if you can only find the second. Contact JPL for availability of these reports. "Spacecraft Attitude Dynamics", Peter C. Hughes 1986, John Wiley and Sons. "Celestial Mechanics: a computational guide for the practitioner", Lawrence G. Taff, (Wiley-Interscience, New York, 1985). Starts with the basics (2-body problem, coordinates) and works up to orbit determinations, perturbations, and differential corrections. Taff also briefly discusses stellar dynamics including a short discussion of n-body problems. COMPUTING PLANETARY POSITIONS More net references: Van Flandern & Pullinen, _Low-Precision Formulae for Planetary Positions_, Astrophysical J. Supp Series, 41:391-411, 1979. Look in an astronomy or physics library for this; also said to be available from Willmann-Bell. Gives series to compute positions accurate to 1 arc minute for a period + or - 300 years from now. Pluto is included but stated to have an accuracy of only about 15 arc minutes. _Interactive Computer Ephemeris_ (from the US Naval Observatory) distributed on IBM-PC floppy disks, $35 (Willmann-Bell). Covers dates 1800-2049. "Planetary Programs and Tables from -4000 to +2800", Bretagnon & Simon 1986, Willmann-Bell. Floppy disks available separately. "Fundamentals of Celestial Mechanics" (2nd ed), J.M.A. Danby 1988, Willmann-Bell. A good fundamental text. Includes BASIC programs; a companion set of floppy disks is available separately. "Astronomical Formulae for Calculators" (4th ed.), J. Meeus 1988, Willmann-Bell. "Astronomical Algorithms", J. Meeus 1991, Willmann-Bell. If you actively use one of the editions of "Astronomical Formulae for Calculators", you will want to replace it with "Astronomical Algorithms". This new book is more oriented towards computers than calculators and contains formulae for planetary motion based on modern work by the Jet Propulsion Laboratory, the U.S. Naval Observatory, and the Bureau des Longitudes. The previous books were all based on formulae mostly developed in the last century. Algorithms available separately on diskette. "Practical Astronomy with your Calculator" (3rd ed.), P. Duffett-Smith 1988, Cambridge University Press. "Orbits for Amateurs with a Microcomputer", D. Tattersfield 1984, Stanley Thornes, Ltd. Includes example programs in BASIC. "Orbits for Amateurs II", D. Tattersfield 1987, John Wiley & Sons. "Astronomy / Scientific Software" - catalog of shareware, public domain, and commercial software for IBM and other PCs. Astronomy software includes planetarium simulations, ephemeris generators, astronomical databases, solar system simulations, satellite tracking programs, celestial mechanics simulators, and more. Andromeda Software, Inc. P.O. Box 605 Amherst, NY 14226-0605 COMPUTING CRATER DIAMETERS FROM EARTH-IMPACTING ASTEROIDS Astrogeologist Gene Shoemaker proposes the following formula, based on studies of cratering caused by nuclear tests. (1/3.4) D = S S c K W : crater diameter in km g p f n (1/6) S = (g /g ) : gravity correction factor for bodies other than g e t Earth, where g = 9.8 m/s^2 and g is the surface e t gravity of the target body. This scaling is cited for lunar craters and may hold true for other bodies. (1/3.4) S = (p / p ) : correction factor for target density p , p a t t p = 1.8 g/cm^3 for alluvium at the Jangle U a crater site, p = 2.6 g/cm^3 for average rock on the continental shields. C : crater collapse factor, 1 for craters <= 3 km in diameter, 1.3 for larger craters (on Earth). (1/3.4) K : .074 km / (kT TNT equivalent) n empirically determined from the Jangle U nuclear test crater. 3 2 19 W = pi * d * delta * V / (12 * 4.185 * 10 ) : projectile kinetic energy in kT TNT equivalent given diameter d, velocity v, and projectile density delta in CGS units. delta of around 3 g/cm^3 is fairly good for an asteroid. An RMS velocity of V = 20 km/sec may be used for Earth-crossing asteroids. Under these assumptions, the body which created the Barringer Meteor Crater in Arizona (1.13 km diameter) would have been about 40 meters in diameter. More generally, one can use (after Gehrels, 1985): Asteroid Number of objects Impact probability Impact energy diameter (km) (impacts/year) (* 5*10^20 ergs) 10 10 10^-8 10^9 1 1 000 10^-6 10^6 0.1 100 000 10^-4 10^3 assuming simple scaling laws. Note that 5*10^20 ergs = 13 000 tons TNT equivalent, or the energy released by the Hiroshima A-bomb. References: Gehrels, T. 1985 Asteroids and comets. _Physics Today_ 38, 32-41. [an excellent general overview of the subject for the layman] Shoemaker, E.M. 1983 Asteroid and comet bombardment of the earth. _Ann. Rev. Earth Planet. Sci._ 11, 461-494. [very long and fairly technical but a comprehensive examination of the subject] Shoemaker, E.M., J.G. Williams, E.F. Helin & R.F. Wolfe 1979 Earth-crossing asteroids: Orbital classes, collision rates with Earth, and origin. In _Asteroids_, T. Gehrels, ed., pp. 253-282, University of Arizona Press, Tucson. Cunningham, C.J. 1988 _Introduction to Asteroids: The Next Frontier_ (Richmond: Willman-Bell, Inc.) [covers all aspects of asteroid studies and is an excellent introduction to the subject for people of all experience levels. It also has a very extensive reference list covering essentially all of the reference material in the field.] MAP PROJECTIONS AND SPHERICAL TRIGNOMETRY Two easy-to-find sources of map projections are the "Encyclopaedia Brittanica", (particularly the older volumes) and a tutorial appearing in _Graphics Gems_ (Academic Press, 1990). The latter was written with simplicity of exposition and suitability of digital computation in mind (spherical trig formulae also appear, as do digitally-plotted examples). More than you ever cared to know about map projections is in John Snyder's USGS publication "Map Projections--A Working Manual", USGS Professional Paper 1395. This contains detailed descriptions of 32 projections, with history, features, projection formulas (for both spherical earth and ellipsoidal earth), and numerical test cases. It's a neat book, all 382 pages worth. This one's $20.