Return-path: X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson Received: from beak.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl@andrew.cmu.edu (->+dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl) (->ota+space.digests) ID ; Tue, 1 May 90 01:43:14 -0400 (EDT) Message-ID: Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Tue, 1 May 90 01:42:42 -0400 (EDT) Subject: SPACE Digest V11 #336 SPACE Digest Volume 11 : Issue 336 Today's Topics: NASA Prediction Bulletins: Space Shuttle Re: Re: Dyson spheres? Magellan Update - 04/30/90 Galileo Update - 04/30/90 Antenna Re: Radar Re: Sex in space NASA Prediction Bulletin Format Re: Not-so-Silent Running (Was Re: a bunch of other irrelvant things) ---------------------------------------------------------------------- Date: 28 Apr 90 03:41:24 GMT From: ncis.tis.llnl.gov!blackbird!tkelso@lll-winken.llnl.gov (TS Kelso) Subject: NASA Prediction Bulletins: Space Shuttle The most current orbital elements from the NASA Prediction Bulletins are carried on the Celestial RCP/M, (513) 427-0674, and are updated several times weekly. Documentation and tracking software are also available on this system. As a service to the satellite user community, the most current elements for the current shuttle mission are provided below. The Celestial RCP/M may be accessed 24 hours/day at 300, 1200, or 2400 baud using 8 data bits, 1 stop bit, no parity. STS 31 1 20579U 90 37 A 90117.10416666 .00002331 00000-0 25599-3 0 432 2 20579 28.4724 214.4778 0006679 321.4080 256.4255 14.84204124 381 HST 1 20580U 90 37 B 90115.92007935 -.00019413 00000-0 -22999-2 0 416 2 20580 28.4631 222.0038 0005784 272.7940 87.2151 14.84112255 202 -- Dr TS Kelso Assistant Professor of Space Operations tkelso@blackbird.afit.af.mil Air Force Institute of Technology ------------------------------ Date: Mon, 30 Apr 90 18:18:00 EDT From: John Roberts Disclaimer: Opinions expressed are those of the sender and do not reflect NIST policy or agreement. Subject: Re: Re: Dyson spheres? >From: usc!elroy.jpl.nasa.gov!aristotle!pjs@ucsd.edu (Peter Scott) >Subject: Re: Dyson spheres? >In article <9004271901.AA08396@cmr.ncsl.nist.gov>, >roberts@CMR.NCSL.NIST.GOV (John Roberts) writes: >> [...] >> Ignoring the infrared feedback, one can calculate the maximum mass of a >> nonreflecting, nonrotating sphere that can be supported by light pressure >> from the sun. [...] >> Incidentally, to the inhabitants of the sphere, the sun would be "down", >> with the local force of gravity about 1/3000 of that on earth. >? Are you saying that the gravitational attraction exerted on a particle >on the inner surface of the sphere is g/3000? I thought that gravitational >attraction inside a spherical shell was 0. Yeah, I know it's approximately >the same answer, but still... what gives? Patrick Brewer has it right - I'm talking about the gravitational attraction of the sun. Since the sphere is not rotating, you are subject to the pull of the sun, which is felt as weight. Picture a scene from the old Saturday morning cartoons - a character is held up by the stream from a geyser. The pressure of the flowing water holds him up, but he still feels weight. Similarly, if you live in a room on the Dyson sphere described, you will tend to drift toward the inner side. If you are in a space suit sunbathing on the inner surface, then fall asleep and lose your grip, in an hour you will have moved about 19km toward the sun (from sqrt(2) * 1AU). Eventually you will either fall into the sun or pass very close by - I forgot the formula to determine how long the fall will take. Note the conclusion: you could build a Dyson sphere held up by light pressure, but it would be a crummy, low-density one, and might adversely affect the center star. John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ Date: 1 May 90 00:12:54 GMT From: usc!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov!baalke@ucsd.edu (Ron Baalke) Subject: Magellan Update - 04/30/90 MAGELLAN STATUS REPORT April 30, 1990 The Magellan spacecraft is now 103 million miles from Earth and nearly 21 million miles from Venus as of Monday, April 30. The cruise continues with all subsystems performing well. The spacecraft is traveling at 66,824 mph relative to the sun. Cruise sequence 22 was uploaded and is being executed perfectly. It changed to a new star pair for star calibrations. They are now Beta Gruis and Alpha Aquilae. Five of the seven daily star calibrations were fully successful with an average attitude update of 0.05 degrees. Two of them, on Tuesday and Thursday, were partially successful, with only single star updates, due to the rejection of Beta Gruis on both occasions by the star scanner unit's foreground filter. The spacecraft team is analyzing the playback data for those events. Last week also saw the completion of memory readouts of all command data system redundant memories in both the A and B sides. No parity errors were found. SPACECRAFT Distance from Earth (mi) 102,942,136 Velocity Heliocentric 66,824 mph One-way light time 9 mins, 12.5 secs Ron Baalke | baalke@mars.jpl.nasa.gov Jet Propulsion Lab M/S 301-355 | baalke@jems.jpl.nasa.gov 4800 Oak Grove Dr. | Pasadena, CA 91109 | Go Lakers! ------------------------------ Date: 30 Apr 90 23:02:55 GMT From: sdd.hp.com!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov!baalke@ucsd.edu (Ron Baalke) Subject: Galileo Update - 04/30/90 GALILEO MISSION STATUS April 30, 1990 The Galileo spacecraft is almost 92 million miles from Earth today, so that a radio signal takes 16 1/2 minutes to go up to the spacecraft and return. Its speed in orbit around the Sun is 71,230 mph, and it has traveled almost 341 million miles since launch. Two weeks of spacecraft tracking have confirmed that the four-day trajectory correction maneuver completed April 12 went extremely well. The next maneuver, currently being designed, will start May 11 and take two days. The spacecraft health countinues to be generally excellent. Normal cruise activities this week have included Sun-pointing turns, propulsion system maintenance, and science observations by the magnetometer, dust and ultraviolet instruments. These activities are governed by a new operating sequence, transmitted to the spacecraft last Friday and covering the period from April 23 through June 10. Ron Baalke | baalke@mars.jpl.nasa.gov Jet Propulsion Lab M/S 301-355 | baalke@jems.jpl.nasa.gov 4800 Oak Grove Dr. | Pasadena, CA 91109 | Go Lakers! ------------------------------ Date: Mon, 30 Apr 1990 8:22:17 EDT From: KLUDGE@AGCB8.LARC.NASA.GOV Subject: Antenna X-Vmsmail-To: SMTP%"space+@andrew.cmu.edu" Yes, radar does just fall off as the square of the distance. You can't just plug the transmitter power into the inverse square law and get a valid number, that's true. You multiply the transmitter power by the antenna gain, and plug THAT into the inverse square law. Nothing fancy at all; the stuff radiated from a directional antenna is the same as the stuff radiated by an omni. It's just that more is radiated in some directions than others (and if you know the beam width, it's pretty easy to calculate the antenna gain, which will be left as an excercise to the reader). I am a EE. I really am. This stuff is a lot easier than you think. --scott (Engineer-In-Charge, Radio Techwood International) ------------------------------ Date: 30 Apr 90 14:57:06 GMT From: att!cbnewsl!moss!feg@ucbvax.Berkeley.EDU (Forrest Gehrke,2C-119,7239,ATTBL) Subject: Re: Radar In article , UD186413@VM1.NODAK.EDU (John Nordlie) writes: > A lot of discussion is going on about the power dissapation of > radar signals over distance. One fact that I have not seen > mentioned is that the inverse square law is being applied > to radar signals as if they were point sources, radiating energy > equally in all directions. This is not the case with radar (or > just about any other radio transmission). Radar is radiated from > an antenna in a highly directional beam. Simply plugging in the > transmitter power and distance into the inverse square equation will > not give you an accurate estimation of signal strength. > The width and shape of the beam must also be taken into consideration. > I am not an EE, so I don't know what equations you need to solve > this problem. Any radio-types out there know? All that has changed when a radio signal is emitted from an array (whether this is a parabolic dish or whatever) is the effective radiated power has been raised in the chosen direction, (often referred to as the gain of the array). This gives us a signal which will reach out further for a given power source than we would have been able if the the source had been isotropic. The inverse square law still holds, (especially so in space). But you are correct in thinking that the shape of the beam must be taken into account. Columnation at radar frequencies is nothing like achievable with lasers. As a result polarization effects must be taken into account when estimating the distance a detectable signal might reach. Calculating this is a bit sticky. Forrest Gehrke feg@dodger.ATT.COM ------------------------------ Date: 30 Apr 90 16:00:47 GMT From: sdd.hp.com!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo!henry@ucsd.edu (Henry Spencer) Subject: Re: Sex in space In article <21753@dartvax.Dartmouth.EDU> ccmay@eleazar.dartmouth.edu (Chris May) writes: >... a friend and I are interested in knowing whether anyone has >had sexual intercourse while in orbit... Nobody has admitted to it. :-) I consider it rather unlikely: workloads are heavy, privacy is nonexistent, and the sponsoring agencies are prudish. (For example, there are married couples among the US astronauts, but they do *not* fly together.) It's just possible that it might have been tried on the US shuttle as a highly-unauthorized private venture. :-) >... Would the offending couple be booted from the >astronaut program if caught? Very probably. At the very least, their chances of flying again would be zero. Flight assignments are decided by office politics, and incurring the wrath of the higher-ups is bad news. -- If OSI is the answer, what is | Henry Spencer at U of Toronto Zoology the question?? -Rolf Nordhagen| uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ Date: 30 Apr 90 11:44:46 GMT From: ncis.tis.llnl.gov!blackbird!tkelso@lll-winken.llnl.gov (TS Kelso) Subject: NASA Prediction Bulletin Format As a service to the satellite user community, the following description of the NASA Prediction Bulletin's two-line orbital element set format is uploaded to sci.space on a monthly basis. The most current orbital elements from the NASA Prediction Bulletins are carried on the Celestial RCP/M, (513) 427-0674, and are updated several times weekly. Documentation and tracking software are also available on this system. The Celestial RCP/M may be accessed 24 hours/day at 300, 1200, or 2400 baud using 8 data bits, 1 stop bit, no parity. ============================================================================== Data for each satellite consists of three lines in the following format: AAAAAAAAAAA 1 NNNNNU NNNNNAAA NNNNN.NNNNNNNN +.NNNNNNNN +NNNNN-N +NNNNN-N N NNNNN 2 NNNNN NNN.NNNN NNN.NNNN NNNNNNN NNN.NNNN NNN.NNNN NN.NNNNNNNNNNNNNN Line 1 is a eleven-character name. Lines 2 and 3 are the standard Two-Line Orbital Element Set Format identical to that used by NASA and NORAD. The format description is: Line 2 Column Description 01-01 Line Number of Element Data 03-07 Satellite Number 10-11 International Designator (Last two digits of launch year) 12-14 International Designator (Launch number of the year) 15-17 International Designator (Piece of launch) 19-20 Epoch Year (Last two digits of year) 21-32 Epoch (Julian Day and fractional portion of the day) 34-43 First Time Derivative of the Mean Motion or Ballistic Coefficient (Depending on ephemeris type) 45-52 Second Time Derivative of Mean Motion (decimal point assumed; blank if N/A) 54-61 BSTAR drag term if GP4 general perturbation theory was used. Otherwise, radiation pressure coefficient. (Decimal point assumed) 63-63 Ephemeris type 65-68 Element number 69-69 Check Sum (Modulo 10) (Letters, blanks, periods = 0; minus sign = 1; plus sign = 2) Line 3 Column Description 01-01 Line Number of Element Data 03-07 Satellite Number 09-16 Inclination [Degrees] 18-25 Right Ascension of the Ascending Node [Degrees] 27-33 Eccentricity (decimal point assumed) 35-42 Argument of Perigee [Degrees] 44-51 Mean Anomaly [Degrees] 53-63 Mean Motion [Revs per day] 64-68 Revolution number at epoch [Revs] 69-69 Check Sum (Modulo 10) All other columns are blank or fixed. Example: NOAA 6 1 11416U 86 50.28438588 0.00000140 67960-4 0 5293 2 11416 98.5105 69.3305 0012788 63.2828 296.9658 14.24899292346978 Note that the International Designator fields are usually blank, as issued in the NASA Prediction Bulletins. -- Dr TS Kelso Assistant Professor of Space Operations tkelso@blackbird.afit.af.mil Air Force Institute of Technology ------------------------------ Date: 30 Apr 90 10:50:40 GMT From: mcsun!ukc!icdoc!syma!nickw@uunet.uu.net (Nick Watkins) Subject: Re: Not-so-Silent Running (Was Re: a bunch of other irrelvant things) In article <1990Apr30.014139.16820@uokmax.uucp> tom@uokmax.uucp (Tom Egelston) writes: >In article <2523@syma.sussex.ac.uk> nickw@syma.susx.ac.uk (Nick Watkins) writes: >>Have you heard of a Rocket called Saturn V ? There are 2 still available >>for your contemplation if you haven't ... > > Only two?!?!?!? Last I checked, there was one at Kennedy, Johnson, and >one at Huntsville. Has someone sprayed a fresh coat of paint on one and >"borrowed" it? ;-) One is an engineering mockup (Huntsville I think). Other two are Apollo 18's & 19's, with Apollo 20's going to launch Skylab (or some similar permutation). Good article by David Baker in an ancient copy of Spaceflight covered other Apollo hardware, perhaps a keen netter would like to revise it. Nick "Get your ticket for that wheel in space while there's time " - IGY, Donald Fagen -- Dr. Nick Watkins, Space & Plasma Physics Group, School of Mathematical & Physical Sciences, Univ. of Sussex, Brighton, E.Sussex, BN1 9QH, ENGLAND JANET: nickw@syma.sussex.ac.uk BITNET: nickw%syma.sussex.ac.uk@uk.ac ------------------------------ End of SPACE Digest V11 #336 *******************