Return-path: X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson Received: from corsica.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr1/ota/space/space.dl@andrew.cmu.edu (->+dist+/afs/andrew.cmu.edu/usr1/ota/space/space.dl) (->ota+space.digests) ID ; Wed, 30 Aug 89 00:35:11 -0400 (EDT) Message-ID: Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Wed, 30 Aug 89 00:34:55 -0400 (EDT) Subject: SPACE Digest V10 #3 SPACE Digest Volume 10 : Issue 3 Today's Topics: Voyager link calculations Re: Galileo's RTG's. Voyager Disc (was Re: voyager audio) Re: SPACE Digest V9 #616 Re: deep space dishes Re: Hipparchos (Was Re: European Space Agency) STS-34 background briefings set (Forwarded) Re: NSS Hotline Update ---------------------------------------------------------------------- Date: 24 Aug 89 03:33:46 GMT From: ka9q.bellcore.com!karn@bellcore.com (Phil Karn) Subject: Voyager link calculations Here's another link calculation for Voyager 2 at Neptune. I got some more precise figures, and the result looks pretty reasonable. My references to "Yuen" are to the book "Deep Space Telecommunications Systems Engineering", edited by Joseph H. Yuen and published by Plenum (ISBN 0-306-41489-9). 8415 MHz transmitter power +11.04 dBW (12.7 W - low power mode ref Yuen): 3.7 m spacecraft antenna gain (ref Yuen p 4): +48.13 dB EIRP: +59.17 dBW Path loss, 4.416e9 km, 8415 MHz: 303.85 dB = 20 log10(4*pi*d*f/c) Receive signal flux: -244.68 dBW 70m receive antenna gain: +73.8 dB = 10 log(4*pi*A/lambda^2) - N lambda = C/8415e6 = 3.56cm (assuming N = 2 dB illum loss) Receive signal power: -170.88 dBW = 8.16e-18 W = 8.16 attowatts = 8.16 nano nano watts Received energy per bit (Eb): -214.22 dBJ = 3.78e-22 J at 21.6 kb/s (43.34 dB-b/s) = .000378 attojoules = 0.378 piconanojoules Receive noise density (N0): -218.60 dBW-Hz = 10 log10(kT) T = 10 Kelvin (ref USENET) Eb/N0 ratio: 4.38 dB This is quite consistent with the performance of the concatenated rate 1/2 Reed Solomon + rate 1/2 convolutional coder, which according to Yuen (p 255) has a very steep "wall" or threshold just below 3 dB. However, this figure does not take into account miscellaneous losses (connectors, feedlines, etc) on board Voyager or at the receiving site, nor does it allow for atmospheric absorption or transmitter degradation below the nominal 12.7 watt figure. According to an interview carried tonight on NASA select, the arraying of the VLA to Goldstone effectively doubles the aperture of the receiver, so this should give another 3 dB of margin to compensate for these factors. As you can see, attention to detail is all-important here! Phil ------------------------------ Date: 23 Aug 89 15:46:04 GMT From: mailrus!jarvis.csri.toronto.edu!utgpu!utzoo!henry@tut.cis.ohio-state.edu (Henry Spencer) Subject: Re: Galileo's RTG's. In article <3216@scolex.sco.COM> hiramc@sco.COM (Hiram Clawson) writes: >Why can't fuel cells be used for power generation in deep space? >I assume there is a good reason they can't. No, they were, on Project Apollo. The trouble with fuel cells is that they run out of fuel when you start talking about missions lasting years. Getting even a modest power output that lasts years requires either an outside source -- which means sunlight (assuming that it is bright enough where the mission is going), since a space probe can't trail an extension cord behind it -- or an *extremely* high energy density in a self-contained power supply. The energy density of chemical fuels is just too low; nuclear power sources are the only viable method. -- V7 /bin/mail source: 554 lines.| Henry Spencer at U of Toronto Zoology 1989 X.400 specs: 2200+ pages. | uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ Date: 23 Aug 89 16:17:04 GMT From: ncspm!jay@ncsuvx.ncsu.edu (Jay C. Smith) Subject: Voyager Disc (was Re: voyager audio) In article <563@mit-amt.MEDIA.MIT.EDU> adam@mit-amt.MEDIA.MIT.EDU (Adam Glass) writes: >I would like to get a copy of the audio from the voyager's gold LP (you know, >the one with the pictures of the man and woman, and the sounds of earth?) >Where can I get a tape (preferred medium) of the "sondes of earth"? Actually the entire contents of the discs sent with the Voyager spacecraft seem like a good commercial laser videodisc release. Has this been done? -- "Good. For a minute I thought we were in trouble." --------------------------------------------------------------------- Jay C. Smith uucp: ...!mcnc!ncsuvx!ncspm!jay Domain: jay@ncspm.ncsu.edu internet: jay%ncspm@ncsuvx.ncsu.edu ------------------------------ Date: Wed, 23 Aug 89 09:57:44 EDT From: Leonard Abbey Subject: Re: SPACE Digest V9 #616 To: Henry Spencer Mr. Spencer, we could do it again. You couldn't. Leonard Abbey Georgia Tech Research Institute labbey@gtri01.gatech.edu ------------------------------ Date: 23 Aug 89 17:09:30 GMT From: tekbspa!optilink!cramer@lll-winken.llnl.gov (Clayton Cramer) Subject: Re: deep space dishes In article <313@magic.UUCP>, jam@magic.UUCP (James A. Markevitch) writes: > Let's see... from some computations I did a few years ago the power for # Voyager's signal is as follows: # # 22W transmitter @ 8.5GHz 43 dBm # 3.7m parabolic antenna 55% efficient 38 dBi # free space path loss (29.6 AU) -303 dB # 70m antenna gain 73 dBi # -------- # -149 dBm # # 15 degree K receiver -187 dBm/Hz # # S/N 38 dB/Hz # # I can't remember, offhand, what the data rate from Voyager is, but 20kHz # comes to mind, so: # # BW 20kHz -43 dB # # S/N for a single 70m antenna -5 dB # # This sounds a little low, even given the arrays being used so maybe the # data rate is lower or there is a little slop in some of the above # numbers. # # Jamie The data rate is wrong, I think. My copy of _Mariner_Jupiter_Saturn_ 77_Mission_Test_And_Telemetry_System_Software_Planning_Document_ (before they changed the name to Voyager) dated May 18, 1976, shows: Three high rate streams: one at 57.6 KBPS, & two at 1200 BPS, & ESP input at 16 BPS. One low rate stream at 40 bps, & two high rate streams: one at 57.6 KBPS, & one at 67.2 KBPS, & ESP input at 16 bps. My vague recollection was that the 1200 bps stream was engineering and general science data, and the 57.6 kbps stream was general science and imaging data. (Everything was mixed together in the most peculiar arrangements, which required software to separate the various types of data out -- which is what I did -- badly -- on that project). -- Clayton E. Cramer {pyramid,pixar,tekbspa}!optilink!cramer A pacifist who calls the police isn't one; hired violence is still violence. ---------------------------------------------------------------------------- Disclaimer? You must be kidding! No company would hold opinions like mine! ------------------------------ Date: 23 Aug 89 13:41:46 GMT From: stsci!shireen@noao.edu (Giggles Gonzaga -- Prophetess of Wisdom and Truth) Subject: Re: Hipparchos (Was Re: European Space Agency) From article <132@castle.ed.ac.uk>, by bob@castle.ed.ac.uk (Bob Gray): > > Does anyone have more information about what orbit Hipparcos > is actualy in, and how long it is going to last there? > Bob. A guy named Peter Bunclark has been posting some very interesting information on HIPPARCOS in our local Space Telescope Science Institute bulletin board. Here are excerpts from his articles -- ------------------------------------------------------------------------ Date: 14 Aug 89 10:20:05 EDT "Hipparcos was successfully launched just after midnight on the 8/9 August. This placed the satellite into a transfer orbit with a perigee height of 800 km and an apogee height of 41,000 km. The satellite was successfully spun up and all systems were described as nominal. On Thursday 10 August at 1420 the apogee boost motor was supposed to fire and place Hipparcos into a geostationary orbit. It didn't. This was at the 4th apogee of the satellite. At the 6th apogee (Friday 11th 0930) another unsuccessful attempt occurred. Technical evaluations were being carried out." Date: 17 Aug 89 12:26:40 EDT "The cause of the problem that has led to the failure of the apogee boost motors has been traced to a short circuit. The spin rate of the satellite was halved to see if this would have any affect on the short circuit. A further attempt at firing the motors was tried at 1300 (BST) today (17th). This was unsuccessful. The next attempt will be on Monday 21st at 1110 (BST). If all attempts are unsuccessful the planned revised mission will take place in the current highly elliptical orbit (210km-36000km). It is possible that the perigee will be raised several hundred kms by using the hydrazine boosters. There are fears now that even this mission will not be as successful as first thought. Originally it should have lasted 6 months or more. Now the timescale is thought to be 3 to 4 months. This will mean that we will not even be able to get full sky coverage." Date: 21 Aug 89 10:27:16 EDT "It would seem that there are 2 faults in the firing systems of the satellite. With the 2nd firing system it seems that the first stage of the circuitry is working fine but it's not proceeding to the second stage. In addition to the 1110 attempt on Monday to fire the motor there will also be one on Tuesday. There are also more problems with the alternative observing programme than first thought. Due to the lack of continuous contact with the ground stations it makes it very difficult to work out the attitude of the satellite (needed to better than 1" accuracy) if it observes in a manner similar to the original mission. An alternative is that the spin axis points towards the Sun all the time. This leads to problems with the Solar panels overheating. Even if the ground station at Kourou is used we would only get ~70% coverage. There is also the problem that the detectors must be switched off when the satellite is below 10,000km. This is for about 2 hours every orbit. Another problem is that the satellite will spend longer stretches of time in the Earth's shadow due to it being in the current orbit. These periods will be longer than the backup batteries can cope with, so that during the March/April eclipse season the satellite will have to be placed in a dormant state. It could be that the satellite will not recover from this. There will also be a delay of 2 months (plus) before this alternative mission gets started while ESOC ground control carrys out various reprogramming that has to be done." -- ______________________________________________________________________________ Shireen Gonzaga/Space Telescope Science Inst./3700 San Martin Dr., Baltimore, MD21218/tel301-338-4412/ARPA shireen@stsci.edu/SPAN SCIVAX::GONZAGA/sometimes you just have to give in to the absurd -- Picard in ST-TNG "Up the Long Ladder" ------------------------------ Date: 24 Aug 89 22:43:02 GMT From: trident.arc.nasa.gov!yee@ames.arc.nasa.gov (Peter E. Yee) Subject: STS-34 background briefings set (Forwarded) Sarah Keegan Headquarters, Washington, D.C. August 24, 1989 Steve Nesbitt Johnson Space Center, Houston N89-61 EDITORS NOTE: STS-34 BACKGROUND BRIEFINGS SET The background briefings and astronaut press conference for STS-34, the Oct. 12 flight of Space Shuttle Atlantis, are scheduled for Sept. 5 and 6 at the Johnson Space Center, Houston. STS-34 will deploy the Galileo spacecraft to study the planet Jupiter. A mission overview with the lead flight director and Galileo spacecraft mission manager will begin at 1:30 p.m. EDT, Sept. 5, followed at 3 p.m. by a briefing from the Galileo mission scientist of the scientific observations to the made by the planetary probe. Briefings on other STS-34 payloads and experiments will follow. The astronaut crew of STS-34 will hold a press conference at 11:15 a.m. EDT, Sept. 6. All briefings will be carried live on NASA Select television via Satcom F2R, transponder 13, 72 degrees west longitude. Two- way question and answer capability will be available at NASA Headquarters, Washington, D.C., the Jet Propulsion Laboratory, Pasadena, Calif., the Kennedy Space Center, Fla., and the Marshall Space Flight Center, Huntsville, Ala. ------------------------------ Date: 23 Aug 89 16:51:27 GMT From: mcsun!ukc!icdoc!syma!nickw@uunet.uu.net (Nick Watkins) Subject: Re: NSS Hotline Update In article <1989Aug14.170247.7161@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes: >In article <246900031@cdp> jordankatz@cdp.UUCP writes: >>A Soviet cosmonaut, Valeri Bykovsky, has written a book in which >>he states that he was slated to pilot a spacecraft to the Moon >>prior to the US Apollo 11, but that the death of a top Soviet >>rocket designer slowed the lunar program. [Deleted stuff] >Christ on a crutch! What microcephalic ignoramus wrote this?!? The >Soviets said openly, explicitly, and repeatedly that they had a lunar >program and that it was aimed at beating the US. They've gone sort >of quiet about it since it was cancelled, but it was never a secret, >and there is plenty of corroborating evidence for its existence. All true, BUT, official Soviet acknowledgements are useful, especially as Bykovsky had been speculated on as a lunar flyby or orbit cosmonaut (see e.g Phil Clark's "The Soviet Manned Space Programme"). The fact that the lunar programme was delayed by Korolev's death is not surprising, but as this was in 1966 one wonders how urgent the race was by 1969. Certainly the original Soyuz designs (c.f. Clark's book) had been heavily amended. >Incidentally, said ignoramus may also have jumped to incorrect conclusions. >Note that Bykovsky is said to have referred to "a lunar mission", not >necessarily a landing mission ... [stuff deleted] ... > but a lunar >flyby -- a la Apollo 8 -- was definitely possible and might have been >practical before Apollo 8 if things had gone right. The said Phil Clark is not sure about "definitely". He points out some interesting counter arguments, but along with most observers feels that the flurry of Zond activity before Apollo 8 did mean a lunar flyby was imminent. On a related point the current issue of "Spaceflight" carries a letter relating the disclosure by Cosmonaut Valentin Lebedev of the existence of the G1 booster, confirmation of the conical 1st stage design, and confirmation of the 3 launch failures. He then went on (in coversation with Mark Camp of Texas A&M) to deny "the existence of a Soviet manned lunar landing programme in the 1960s". Risking Henry's wrath I would say this is the first admission of the existence of the G1 and near conclusive proof that there WAS a manned lunar programme, unless the G1 was a long term space station related project. This of course doesn't prove the Russians were in any shape to land men on the moon though. -- 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 Voice: +44 273 678072 ------------------------------ End of SPACE Digest V10 #3 *******************