home *** CD-ROM | disk | FTP | other *** search
- Date: Sat, 18 Jul 92 05:02:19
- From: Space Digest maintainer <digests@isu.isunet.edu>
- Reply-To: Space-request@isu.isunet.edu
- Subject: Space Digest V15 #012
- To: Space Digest Readers
- Precedence: bulk
-
-
- Space Digest Sat, 18 Jul 92 Volume 15 : Issue 012
-
- Today's Topics:
- Antimatter (was propulsion questions) (5 msgs)
- apollo 10
- FOR ALL MANKIND on TBS Sunday, July 19 (APOLLO lunar missions)
- Galileo Update - 07/17/92
- How to find limiting magnitude? (was Re: Solar Power Satellites)
- Looking gif horse in mouth
- Now, where at last ? (Re: apollo 10)
- Pathogens and the Orbiting Quarantine Facility
- Space Transportation Infrastructure Costs
- THE DIGEST IS BACK!!!!
-
- Welcome to the Space Digest!! Please send your messages to
- "space@isu.isunet.edu". Please do **NOT** send (un)subscription
- requests to that address! Instead, send a message of the form
- "Subscribe Space <your name>" 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: 17 Jul 92 14:32:00 GMT
- From: Jim Carr <jac@ds8.scri.fsu.edu>
- Subject: Antimatter (was propulsion questions)
- Newsgroups: sci.space,sci.physics
-
- In article <1992Jul17.123315.28475@inmos.co.uk> nick@inmos.co.uk () writes:
- >
- > I have brought this question over into sci.physics
- > because I think this question belongs there, and
- > re-directed followups back there.
-
- I put this answer on sci.physics too, but put the followup on sci.space
-
- > On sci.space there is a discussion about spacecraft
- > propulsion systems, in particular ones using antimatter
- > annihilation to generate the power source. Can anyone
-
- > tell me just how much energy (Joules please) would
- > be generated if 0.5 grams of X is annihilated with
- > 0.5 grams of anti-X.
-
- Gee, if you want Joules you should use MKS units, but no matter. ;-)
-
- When you annihilate matter and anti-matter, you get neutral bosons,
- usually photons, carrying off the energy. The energy is E=mc^2 if
- we assume the matter is essentially at rest (otherwise you must add
- in pc in quadrature to get the total energy available, and worry
- about the transformation between to the center-of-momentum frame).
-
- So given 0.5 gm + 0.5 gm = 1.0 gm = 0.001 kg, we get 9x10^{13} Joules.
-
- You will note for future reference that kg*(m/s)^2 = kg*m^2/s^2 = Joules.
-
- Also note that you could look this conversion up in the Appendix of
- Halliday and Resnick if you do not trust your memory of c or whatever.
-
- Remember that you have to expend several times this amount to create
- the anti-matter in the first place (since you effectively lose energy
- in making the boost from the lab to the center of momentum where the
- particles are created, and then you have to collect and cool the products),
- but the cost is probably worth it because of the concentrated form the
- energy is stored in.
-
- > With the different products
- > generated in the process does it make a defference
- > what we pick for X ( protons, electrons, whatever ).
-
- The physics is simplest with an elementary particle like an electron,
- since it just annihilates to two photons. A proton is a composite
- particle, and the actual annihilation takes place between a quark
- and anti-quark in each -- hence you get a wide variety of products
- possible, mostly pions I think, from the spectators. If you are
- considering this for propulsion, this choice would affect how you
- would go about using and directing this energy (which comes out
- isotropically if the matter is at rest) to effect propulsion.
-
- --
- J. A. Carr | "The New Frontier of which I
- jac@gw.scri.fsu.edu | speak is not a set of promises
- Florida State University B-186 | -- it is a set of challenges."
- Supercomputer Computations Research Institute | John F. Kennedy (15 July 60)
-
- ------------------------------
-
- Date: Fri, 17 Jul 92 15:53:29 GMT
- From: Ed Gruberman <cary@carina.unm.edu>
- Subject: Antimatter (was propulsion questions)
- Newsgroups: sci.space
-
- In article <1992Jul17.123315.28475@inmos.co.uk> nick@inmos.co.uk () writes:
- > Hi
- >
- > I have brought this question over into sci.physics
- > because I think this question belongs there, and
- > re-directed followups back there.
- >
- > On sci.space there is a discussion about spacecraft
- > propulsion systems, in particular ones using antimatter
- > annihilation to generate the power source. Can anyone
- > tell me just how much energy (Joules please) would
- > be generated if 0.5 grams of X is annihilated with
- > 0.5 grams of anti-X. with the different products
- > generated in the process does it make a defference
- > what we pick for X ( protons, electrons, whatever ).
- >
- > Nick
- Nick,
-
- It's fairly easy. E=mc^2. m=.001 kg, c=3x10^8 m/s, => E=9x13 J.
- All in gamma rays unfortuately. The big problema are a) how to convert
- all the gamma rays into kinetic energy for your ship or whatever and b)
- how to keep your cargo from getting fried. Tough problems since gamma
- rays are _very_ penetrating. Have fun. :-)
-
-
- Ed Gruberman
-
- cary@mplode.lampf.lanl.gov (VMS)
- cary@dsirae.lampf.lanl.gov (unix)
-
-
- XXXXX XX XX XXXXX XX XX XX XX XXXXX
- X X X X XXX XX XX XX X
- X XXX X XX XXX XX XX XX XXXXX
- X X X X XX XXX XX XX X
- XXXXX X XXXXX XX XX XXXXXX XXXXX
-
- An Extensive Air Shower Array at the Meson Physics Facility
- Los Alamos National Labs
-
- ____________________________________________________________________________
-
- My opinions are my own, don't you dare give someone else credit for them!
-
- ----------------------------------------------------------------------------
-
- ------------------------------
-
- Date: 17 Jul 92 19:25:39 GMT
- From: Bill Higgins-- Beam Jockey <higgins@fnalc.fnal.gov>
- Subject: Antimatter (was propulsion questions)
- Newsgroups: sci.space
-
- In article <6y=mm0p@lynx.unm.edu>, cary@carina.unm.edu (Ed Gruberman) writes:
- > In article <1992Jul17.123315.28475@inmos.co.uk> nick@inmos.co.uk () writes:
- >> Can anyone
- >> tell me just how much energy (Joules please) would
- >> be generated if 0.5 grams of X is annihilated with
- >> 0.5 grams of anti-X. with the different products
- >> generated in the process does it make a defference
- >> what we pick for X ( protons, electrons, whatever ).
- >
- > It's fairly easy. E=mc^2. m=.001 kg, c=3x10^8 m/s, => E=9x13 J.
- > All in gamma rays unfortuately.
-
- Sorry, Ed. (boot to the head) *WHUMP!* Take a look at your Particle
- Properties book.
-
- If you interact eletrons and positrons, you get essentially 100% gamma
- rays.
-
- If you interact protons and antiprotons, or neutrons and antineutrons,
- etc., you get a mixture of stuff; for engineering purposes, it's all
- pions. About a third of these are pi-zeroes, 98.8% of which turn
- instantly to gammas.
-
- The rest of the output, positive and negative pions, decay to muons
- and neutrinos, and the muons decay to electrons and neutrinos. Since
- these are charged, you can in principle persuade them to go where you
- want them to go (out the engine exhaust) with big enough magnetic
- fields, if you grab them in the few dozen nanoseconds (pions) or
- microseconds (muons) of their existence. I do this for a living. (-:
-
- The correct statement is that, given enough time for everything to
- decay-- one second should do nicely-- the annihilation energy will be
- divided among gamma photons, electrons, and neutrinos, all of which
- are stable. A significant share of the energy (more than 1%) is
- carried by each species. I won't look up just what the partition is.
-
- Nick should go to the library and get *Mirror Matter* by Robert L.
- Forward and Joel Davis, which is fun to read and will proably answer
- most of his questions about antimatter. (It may cause him to think of
- new ones. I'm prepared to take that risk.)
-
- Jim Carr and Henry Spencer gave good answers to Nick's posting,
- although Henry also seems to think that everything winds up in gammas.
- (Don't feel bad, Henry-- Eugen Saenger made the same mistake in his
- book *Space Flight*, and he was a smart guy too.)
-
- I will resist giving Cary/Ed another Boot To The Head for having a
- long signature. Been guilty of that myself on occasion...
-
- [o]
- [|] /// Bill Higgins
- E H ///
- |8D:O: occc))))<)) Fermi National Accelerator Laboratory
- E H ///
- [|]// Bitnet: HIGGINS@FNAL.BITNET
- [|]
- Bumper sticker seen on a Soyuz: SPAN/Hepnet/Physnet: 43011::HIGGINS
- GOT HARD CURRENCY?
- TRY OUR MICROGRAVITY LAB! Internet: HIGGINS@FNAL.FNAL.GOV
-
- ------------------------------
-
- Date: 17 Jul 92 19:48:08 GMT
- From: SCOTT I CHASE <sichase@csa2.lbl.gov>
- Subject: Antimatter (was propulsion questions)
- Newsgroups: sci.space
-
- In article <9847@sun13.scri.fsu.edu>, jac@ds8.scri.fsu.edu (Jim Carr) writes...
- >In article <1992Jul17.123315.28475@inmos.co.uk> nick@inmos.co.uk () writes:
- >
- >> On sci.space there is a discussion about spacecraft
- >> propulsion systems, in particular ones using antimatter
- >> annihilation to generate the power source. Can anyone
- >> tell me just how much energy (Joules please) would
- >> be generated if 0.5 grams of X is annihilated with
- >> 0.5 grams of anti-X.
- >
- >Gee, if you want Joules you should use MKS units, but no matter. ;-)
-
- Well, if there is no matter, then the answer is zero Joules. :-)
-
- >When you annihilate matter and anti-matter, you get neutral bosons,
- >usually photons, carrying off the energy. The energy is E=mc^2 if
-
- When you take a chunk of matter and bring it near a chunk of antimatter,
- several processes happen. Electrons annihilate positrons, producing photons
- for the most part, but also neutrinos a small part of the time. But
- most of the energy comes from nuclear annihilation where the larger
- rest mass means that more channels are open even at rest. So, for
- example, I would expect some electrons and positrons to fly out of a
- gold + antigold nuclear annihilation. Muons, pions, kaons, etc., are
- also allowed.
-
- To be strictly fair, the existence, and consequent properties of antiatoms
- is still an entirely open experimental question for the most part, so this
- is really speculation. The properties of nucleon-antinucleon annihilation
- are well studied, of course, but entire antinuclei are an entirely different
- question.
-
- No one has ever produced even an antihelium nucleus. Antideuterons are
- doable, as are antitritons (typically with 10-3 yield relative to antideuterons)
- but more complex antinuclei are too tough to make.
-
- So no one has ever produced anything other than an isotope of antihydrogen.
- There is antimatter in the cosmic rays, but I don't know if anyone has ever
- seen complex antinuclei. Is there a cosmic ray jock out there who can
- tell me what the heaviest antinuclei recorded in the cosmic rays is?
-
- -Scott
- --------------------
- Scott I. Chase "The question seems to be of such a character
- SICHASE@CSA2.LBL.GOV that if I should come to life after my death
- and some mathematician were to tell me that it
- had been definitely settled, I think I would
- immediately drop dead again." - Vandiver
-
- ------------------------------
-
- Date: 17 Jul 92 20:11:48 GMT
- From: SCOTT I CHASE <sichase@csa2.lbl.gov>
- Subject: Antimatter (was propulsion questions)
- Newsgroups: sci.space
-
- In article <6y=mm0p@lynx.unm.edu>, cary@carina.unm.edu (Ed Gruberman) writes...
- >
- >It's fairly easy. E=mc^2. m=.001 kg, c=3x10^8 m/s, => E=9x13 J.
- >All in gamma rays unfortuately. The big problema are a) how to convert
- >all the gamma rays into kinetic energy for your ship or whatever and b)
- >how to keep your cargo from getting fried. Tough problems since gamma
- >rays are _very_ penetrating. Have fun. :-)
-
- All in gamma rays? Most of the energy comes not from electron-positron
- annihilation but from nuclear annihilation, which produces pions and a
- whole flurry of other stuff which you need to shower in some material
- in order to recoup the energy.
-
- -Scott
- --------------------
- Scott I. Chase "The question seems to be of such a character
- SICHASE@CSA2.LBL.GOV that if I should come to life after my death
- and some mathematician were to tell me that it
- had been definitely settled, I think I would
- immediately drop dead again." - Vandiver
-
- ------------------------------
-
- Date: 17 Jul 92 15:58:22 GMT
- From: "Harold G. Andrews II" <andrewsh@lonex.rl.af.mil>
- Subject: apollo 10
- Newsgroups: sci.space
-
- In article <1992Jul12.162633.7068@kakwa.ucs.ualberta.ca>
- martin@space.ualberta.ca (Martin Connors) writes:
- >In article <1992Jul10.210335.15289@organpipe.uug.arizona.edu>
- >jscotti@lpl.arizona.edu (Jim Scotti x2717) writes:
- >> The Apollo 16 ascent stage was accidentally left in lunar orbit when
- >> a switch was not set properly for remote control of the spacecraft
- >> after it's mission was completed. It's orbit, however, had a periluna
- >> of about 10 NM, and its orbit apparently decayed about 6 months after
- >> the mission.
- >
- >Can anyone comment on why such an orbit decay would occur so rapidly in
- >LUNAR orbit. There is no upper atmosphere at all to consider so I wonder
- >what is the relative role of radiation pressure on such a low density
- >reflective object as an LM ascent stage, or would it simply be Earth-Sun
- >perturbations causing the orbital parameters to change such that the
- >perilune became < lunar radius?
-
- I seem to recall two reasons why the orbit of an object in a lunar orbit
- will decay. Neither have to do friction or radiation pressure. Please note
- I have really not had much experience in this field, and I could be way off
- base here.
-
- Reason #1) The moon is not a very homogeneous body. It has regions
- which are very dense and others which are not so dense. In a lower orbit,
- these regions vary the gravitational interaction between the moon and the
- object in the lunar orbit. This in return causes instabilities to occur
- in the orbit until either the orbit intersects the surface of the moon, or
- the object leaves lunar orbit.
-
- Reason #2) In a higher lunar orbit, the periodic changes in the
- gravitational interaction between the Earth and the object in Lunar orbit
- will cause a instability in the orbit of the object. It would seem that
- this would eventually destabilize the orbit enough so that it intersected the
- lunar surface, or caused the object the leave a lunar orbit.
-
- These two things could be way off base. I don't recall where I read them,
- or even if it wasn't in a dream I had ;-). So no flames please if this turns
- out to be completely the wrong answer.
-
- -Andy
-
- *******************************************************************************
- * Harold G. "Andy" Andrews II * Support DAM... *
- * andrewsh@lonex.rl.af.mil * *
- * Rome Laboratory/OCPA * Mothers Against Dyslexia *
- * Air Force Photonics Center * *
- * Griffiss AFB, NY 13441-5700 * *
- * (315) 330-7669 (DSN Prfx 587) * (Not an official USAF viewpoint) *
- *******************************************************************************
-
- ------------------------------
-
- Date: Fri, 17 Jul 1992 18:19:36 GMT
- From: Larry Klaes <klaes@verga.enet.dec.com>
- Subject: FOR ALL MANKIND on TBS Sunday, July 19 (APOLLO lunar missions)
- Newsgroups: sci.astro,sci.space
-
- For those of you in the U.S. with cable television, National
- Geographic Explorer is presenting the film FOR ALL MANKIND on the
- Turner Broadcast Station (TBS) this Sunday, July 19 at 9 p.m. ET.
- It is a film about the APOLLO manned lunar missions, taken from
- thousands of hours of NASA film footage.
-
- Larry Klaes klaes@verga.enet.dec.com
- or - ...!decwrl!verga.enet.dec.com!klaes
- or - klaes%verga.dec@decwrl.enet.dec.com
- or - klaes%verga.enet.dec.com@uunet.uu.net
-
- "All the Universe, or nothing!" - H. G. Wells
-
- EJASA Editor, Astronomical Society of the Atlantic
-
- ------------------------------
-
- Date: 18 Jul 92 01:06:14 GMT
- From: Ron Baalke <baalke@kelvin.jpl.nasa.gov>
- Subject: Galileo Update - 07/17/92
- Newsgroups: sci.space,sci.astro
-
- Forwarded from Neal Ausman, Galileo Mission Director
-
- GALILEO
- MISSION DIRECTOR STATUS REPORT
- POST-LAUNCH
- July 10 - 16, 1992
-
- SPACECRAFT
-
- 1. On July 10, realtime commands were sent to change the System Fault
- Protection (SFP) AACS-INIT (Attitude and Articulation Control Subsystem)
- pointing slot from the sun to the Earth. These commands reconfigured the
- value to the background state assumed by the EE-6 (Earth-Earth 6) sequence
- memory load.
-
- 2. On July 13, a NO-OP command was sent to reset the command loss timer
- to 264 hours, its planned value for this mission phase.
-
- 3. On July 14, a Command Detector Unit Signal-to-Noise Ratio (CDUSNR) test
- along with a Radio Frequency Subsystem Automatic Gain Control (RFSAGC) test
- were performed using LGA-1 (Low Gain Antenna #1) over DSS-43 (Canberra 70
- meter antenna). Quick look analysis indicates the test went well. Detailed
- analysis is in progress.
-
- 4. On July 15, the periodic RPM (Retro-Propulsion Module) 10-Newton thruster
- flushing maintenance activity was performed. All 12 thrusters were flushed
- and their performance was as expected.
-
- 5. On July 15, the Energetic Particle Detector (EPD) motor maintenance
- exercise was performed which stepped the motor through its eight operating
- positions and then returned it to the normal position (No. 4). The motor
- maintenance exercise was successfully verified by Memory Readout (MRO)
- commands.
-
- 6. On July 15, realtime commands were sent to change the System Fault
- Protection (SFP) to turn off the LGA-2 motor if the sequence memory load is
- terminated. This change prevents a continuous undervoltage situation in
- the low probability scenario of a relay failure causing a DC bus short
- circuit while retracting the LGA-2 antenna. The commands were transmitted
- but not successfully received due to a ground station problem. Specifically,
- the wrong standards and limit tables were being used in the command system at
- Station 43 (Canberra). Command retransmission is being planned.
-
- 7. On July 16, routine Extreme Ultraviolet Spectrometer (EUV) Memory
- Readouts (MROs) were performed. The MROs were received without incident.
-
- 8. On July 16, cruise science Memory Readouts (MROs) were performed for the
- Dust Detector (DDS) and Magnetometer (MAG) instruments. Preliminary analysis
- indicates the data was received properly.
-
- 9. On July 16, an Ultra-Stable Oscillator (USO) test was performed to verify
- the health status of the USO and collect gravitational red shift experiment
- data; long term trend analysis is continuing.
-
- 10. On July 16, a command threshold test was performed. Initial results,
- similar to the test run on May 14, indicates the command threshold to be
- approximately -140 to -141 dbm which is its nominal value.
-
- 11. On July 16, a Radio Frequency Subsystem Tracking Loop Capacitor (RFSTLC)
- test was performed over DSS-43. Preliminary analysis indicates the capacitors
- continue to operate normally.
-
- 12. On July 16, telemetry map changes were performed to replace the Command
- Detector Unit Signal-to-Noise (CDUSNR) telemetry readings to the AC/DC bus
- imbalance telemetry readings at the completion of the scheduled
- telecommunication tests.
-
- 13. During the week, the DC bus imbalance reading has continued to change
- significantly. The DC measurement has ranged from 97DN (11.2 volts) to 151DN
- (17.8 volts) and now reads 150DN (17.7 volts). This measurement variation is
- consistent with the model developed by the AC/DC special anomaly team. The
- AC measurement has decreased 1DN and reads 3.1 volts.
-
- 14. The Spacecraft status as of July 16, 1992, is as follows:
-
- a) System Power Margin - 42 watts
- b) Spin Configuration - Dual-Spin
- c) Spin Rate/Sensor - 3.15 rpm/Star Scanner
- d) Spacecraft Attitude is approximately 31 degrees off
- Earth (lagging) and 2 degrees off-sun (leading)
- e) Downlink telemetry rate/antenna-40 bps (coded)/LGA-1
- f) General Thermal Control - all temperatures within
- acceptable range
- g) RPM Tank Pressures - all within acceptable range
- h) Orbiter Science- UVS, EUV, DDS, MAG, EPD, and HIC are
- powered on
- i) Probe/RRH - powered off, temperatures within
- acceptable range
- j) CMD Loss Timer Setting - 264 hours
- Time To Initiation - 185 hours
-
- GDS (Ground Data Systems):
-
- 1. The July System Engineers Monthly Report (SEMR) review was conducted
- Thursday, July 16. A review of current Project and Institutional (MOSO & DSN)
- system status was conducted. Pre-Earth 2 delivery schedules, past months
- accomplishments and potential problem areas were discussed. No significant
- problems or errors were reported.
-
- 2. An end-to-end GDS data flow test was successfully conducted this past week
- to demonstrate the ground capability to process and display 40 bps AACS Flood
- Mode telemetry data. First use of this telemetry format in flight is
- scheduled for 24 July.
-
-
- TRAJECTORY
-
- As of noon Thursday, July 16, 1992, the Galileo Spacecraft trajectory
- status was as follows:
-
- Distance from Earth 135,214,000 miles (1.46 AU)
- Distance from Sun 170,085,000 miles (1.83 AU)
- Heliocentric Speed 45,300 miles per hour
- Distance from Jupiter 673,747,000 miles
- Round Trip Light Time 24 minutes, 22 seconds
-
-
- SPECIAL TOPIC
-
- 1. As of July 16, 1992, a total of 8028 real-time commands have been
- transmitted to Galileo since Launch. Of these, 3159 were pre-planned in
- the sequence design and 4869 were not. In the past week, 2 real time commands
- were transmitted and all were pre-planned in the sequence design. In addition,
- 4534 mini-sequence commands have been transmitted since March 1991; 2283 were
- pre-planned and 2251 were not. In the past week, no mini-sequence commands
- were transmitted. Major command activities this week included commands to
- update the System Fault Protection (SFP) and to reset the command loss timer.
- ___ _____ ___
- /_ /| /____/ \ /_ /| Ron Baalke | baalke@kelvin.jpl.nasa.gov
- | | | | __ \ /| | | | Jet Propulsion Lab |
- ___| | | | |__) |/ | | |__ M/S 525-3684 Telos | Most of the things you
- /___| | | | ___/ | |/__ /| Pasadena, CA 91109 | worry about will never
- |_____|/ |_|/ |_____|/ | happen.
-
- ------------------------------
-
- Date: 17 Jul 92 18:36:08 GMT
- From: Bill Higgins-- Beam Jockey <higgins@fnalc.fnal.gov>
- Subject: How to find limiting magnitude? (was Re: Solar Power Satellites)
- Newsgroups: sci.space,sci.astro
-
- In sci.space there has been a recent discussion about building a
- constellation of multi-kilometer satellites to harness solar energy
- and beam it to users on Earth. One drawback is that having some
- new bright objects in the sky would make it harder-- in some sense--
- to do professional and amateur astronomical observations on the
- ground.
-
- In article <pgf.711337196@srl03.cacs.usl.edu>, pgf@srl03.cacs.usl.edu (Phil G. Fraering) writes:
- > tjn32113@uxa.cso.uiuc.edu (Thomas J. Nugent) writes:
- >>ralph.buttigieg@f635.n713.z3.fido.zeta.org.au (Ralph Buttigieg) writes:
- rb>>> Most people will live on Earth for some time to come,
- rb>>> to have humanity denied the sight of the stars would be tragic.
-
- tjn>>Well, if you live anywhere near any half pint city, you are mostly denied
- tjn>>the sight of the stars. I live in Urbana, with the local population on
- tjn>>the order of 100,000. You have to go really far out of town to see more
- tjn>>than a dozen stars or so.
- >
- pgf> That's what bothers me about all the people griping about light pollution
- pgf> from the SPS's. They probably won't be much brighter than Jupiter, and
- pgf> in most major cities, the light pollution will be so bad you'll be lucky
- pgf> to see the powersats to begin with.
-
- How do you do this calculation? (It's related to "why is the sky
- blue?")
-
- The Sun provides direct sunlight in the daytime. But some direct
- light also scatters off the molecules of air above us. Blue light
- scatters through larger angles than red. So when the Sun is up, air
- all over the sky gives off blue light which is brighter than most
- stars. The Moon is bright enough to be seen in the daytime despite
- this background glow, and so is Venus, sometimes, and so are a few
- other bodies, maybe.
-
- At night, the Moon is bright enough to create the same sort of sky
- glow. The brightness of the sky when the Moon is up is enough to rule
- out observing many of the dimmer objects in the sky. Most people
- don't notice this, but astronomers (professionals and amateurs) are
- painfully aware of the fact. Being rather slow, I learned about this
- only at an advanced age, searching for Comet Halley during a full
- Moon. This phenomenon divides professional observers into two social
- classes-- "dark sky" people, who can use telescope time only during
- the two weeks a month when the Moon is absent from the night sky, and
- "bright sky" people, who are lucky enough to be studying fairly bright
- objects and can still do useful things with the Moon up.
-
- When the Moon is down, our sky is still not perfectly black. There
- is still a sky glow due to other, much dimmer sources. It would be
- fun to investigate the more obscure ones, but the obvious ones include
- starlight, planet light, and the glow scattered from sources on the
- ground (as Tom Nugent mentions above).
-
- So. Suppose we add another object to the sky, say, as bright as
- Jupiter. How much will this increase the background glow? How will
- it change the limiting magnitude of the dimmest object one can observe
- with a telescope? (I'll bet this is a homework problem in some class
- on observational astronomy somewhere.) How does it vary with angular
- distance from the bright object?
-
- If we can learn how to do this calculation, we can compare the alleged
- damage that any proposed configuration of powersats will do to
- ground-based astronomy. As Phil Fraering suggests, the effect is
- probably meaningless for people close to any illuminated town. But it
- may be significant for deep-sky professional observers.
-
- I've checked at least one handbook but it's a tougher problem than
- applying one simple formula. Perhaps someone else will *ahem* shed a
- little light on the problem.
-
- O~~* /_) ' / / /_/ ' , , ' ,_ _ \|/
- - ~ -~~~~~~~~~~~/_) / / / / / / (_) (_) / / / _\~~~~~~~~~~~zap!
- / \ (_) (_) / | \
- | | Bill Higgins Fermi National Accelerator Laboratory
- \ / Bitnet: HIGGINS@FNAL.BITNET
- - - Internet: HIGGINS@FNAL.FNAL.GOV
- ~ SPAN/Hepnet: 43011::HIGGINS
-
- ------------------------------
-
- Date: Fri, 17 Jul 1992 17:27:05 GMT
- From: Edmund Hack <arabia!hack>
- Subject: Looking gif horse in mouth
- Newsgroups: sci.space
-
- In article <1992Jul16.231235.1@indyvax.iupui.edu> tffreeba@indyvax.iupui.edu writes:
- >Does anybody know if you can get gifs on discs (or send them
- >a disc with a wish list) from Ames? I am ftp-ing them through
- >school but it takes _forever_ to get them onto my machine via
- >Kermit. I am losing valuable sack time, what with the time
- >differences and all.
-
- All of the CD-ROMs that have been mounted at ames are available from the
- National Space Science Data Center at cheap prices. The disks are $20
- for the first in an order, $6 each after that. For more info, send
- email to: request@nssdca.gsfc.nasa.gov and they will send you a catalog
- by email in a week or so.
-
- Included are Viking, Viking Orbiter, Voyager and Pioneer data. Note
- that most of what is send is RAW DATA, not the pretty pictures you see
- on TV and in magazines. Some software tools for PCs and Macs for
- looking at the images and limited processing is available too.
-
-
-
- --
- | Edmund Hack - Lockheed Engineering & Sciences Co. - Houston, TX
- | hack@aio.jsc.nasa.gov SpokesPersonp(Me,or(NASA,LESC)) = NIL
- | **** Papoon for President! You Know He's Not Insane!! ****
-
- ------------------------------
-
- Date: 17 Jul 92 16:44:55 GMT
- From: Jim Scotti x2717 <jscotti@lpl.arizona.edu>
- Subject: Now, where at last ? (Re: apollo 10)
- Newsgroups: sci.space
-
- In article <24597@scicom.AlphaCDC.COM> wats@scicom.AlphaCDC.COM (Bruce Watson) writes:
- >Satellite Situation Report, NASA, Project Operations Branch, Code 513,
- >Goddard Space Flight Center, Greenbelt, MD, USA 20771 is published
- >quarterly and is available to interested persons.
- >
- >It lists 1969 043C LM/descent in orbit around the moon and 1969 043D
- >LM/ascent in orbit about the sun, but there are errors in this
- >publication.
-
- This publication gives the LAST KNOWN ORBIT for an untracked satellite
- such as the Apollo 10 LM ascent and descent stages, so this is consistent
- with what has been said in this thread. If tracked, it also lists the time
- of decay. You might look up Apollo 9, and check the data on the LM.
-
- ---------------------------------------------
- Jim Scotti
- {jscotti@lpl.arizona.edu}
- Lunar & Planetary Laboratory
- University of Arizona
- Tucson, AZ 85721 USA
- ---------------------------------------------
-
- ------------------------------
-
- Date: Fri, 17 Jul 1992 20:14:54 GMT
- From: Brent Kellmer <kellmer@milton.u.washington.edu>
- Subject: Pathogens and the Orbiting Quarantine Facility
- Newsgroups: sci.space,rec.art.sf.science
-
- I've got a problem that I wonder if someone could help me with:
-
- I'm writing an SF story in the course of which some sort of pathogen gets through quarantine and to Earth. I'm using NASA's 1981 Antaeus Report as
- a model for the orbiting quarantine facility in the story. What I need is
- and idea or two on how such quarantine could be bypassed or broken. I've
- already thought of the possibility of an accident on board the OQF, as well
- as the possibility of Industrial Espionage, but in this case, these might
- be somewhat of a cliche.
-
- If there's anyone out there that could help me, I'd greatly appreciate it.
-
- Brent Kellmer
- kellmer@u.washington.edu
-
- ------------------------------
-
- Date: 18 Jul 92 00:03:03 GMT
- From: Ron Baalke <baalke@kelvin.jpl.nasa.gov>
- Subject: Space Transportation Infrastructure Costs
- Newsgroups: sci.space
-
- In article <BrGDD1.3rv@zoo.toronto.edu>, henry@zoo.toronto.edu (Henry Spencer) writes...
- >I think the demand is going to have to come from the manned programs.
- >Most of the unmanned people are very thoroughly locked into the mindset
- >of never depending on new technology if they can avoid it. (As witness
- >Cassini being shrunk to fit on a Titan IV without the new SRBs... which
- >have now been successfully tested.)
-
- You left out a few pertinent details about the SRMs. To date, the SRMs
- has had only one successful test firing which occurred just a month ago,
- and they still have to undergo several more test firings before they can
- be declared flight ready. The first test firing resulted in a spectacular
- explosion that totally destroyed the launch complex and caused 120 million
- dollars in damage. The SRM program has been plagued by a number of setbacks,
- and the contractor who built the SRM's, Hercules, have already exceeded
- their contract cap of $700 million. Hercules now has to foot the remaining
- costs of the development of the SRM themselves. Hercules has sued Martin
- Marietta claiming that they did not assist them properly in the SRM
- program, and Martin Marietta is countersuing. The SRMs was originally planned
- to be used with the Cassini launch, but considering the track record of
- the SRM development, NASA decided that using the SRMs was too risky.
- ___ _____ ___
- /_ /| /____/ \ /_ /| Ron Baalke | baalke@kelvin.jpl.nasa.gov
- | | | | __ \ /| | | | Jet Propulsion Lab |
- ___| | | | |__) |/ | | |__ M/S 525-3684 Telos | Most of the things you
- /___| | | | ___/ | |/__ /| Pasadena, CA 91109 | worry about will never
- |_____|/ |_|/ |_____|/ | happen.
-
- ------------------------------
-
- Date: Fri, 17 Jul 92 15:43:48 EST
- From: "Kevin R. Cain" <KEVIN@VM.CC.FAMU.EDU>
- Subject: THE DIGEST IS BACK!!!!
-
- Just a quick congratulations to all those who brought the Digest back.
- I was beginning to wonder what had happened.
-
- THANY YOU THANK YOU THANK YOU. (Just my $.02 worth)
- *************************************************************************
- * KEVIN R. CAIN PHONE: (904) 599-3685 *
- * USER SUPPORT EMAIL: KEVIN@VM.CC.FAMU.EDU *
- * FLORIDA A&M COMPUTER CENTER SNAIL: KEVIN R. CAIN, 106 PERP, FAMU *
- * TALLAHASSEE, FL 32307 *
- *************************************************************************
-
- ------------------------------
-
- End of Space Digest Volume 15 : Issue 012
- ------------------------------
-