HDTenEightyP/NetNews huggingface dataset:
From: pgf@srl01.cacs.usl.edu ("Phil G. Fraering")
Newsgroups: sci.space
Subject: Re: Asteroid Toutatis Closes in on Gaul
Date: 9 Oct 92 13:55:45 GMT
Article-I.D.: cs.BvuxG5.H7E.1
Distribution: sci
Organization: [via International Space University]
X-Added: Forwarded by Space Digest
Original-Sender: isu@VACATION.VENARI.CS.CMU.EDU


\baalke@kelvin.jpl.nasa.gov (Ron Baalke) writes:
/: [..]
\:      The approach of Toutatis this year and the one in 2004
/: represent the two closest Earth passages of any known asteroid
\: for the next 30 years, said Yeomans.
/: 
\:      Toutatis was discovered Jan. 4, 1989, by Astronomer
/: Christian Pollas at Caussols, France, and was named after a
\: Gallic deity called "protector of the tribe."

/And according to a popular comic strip, the only thing the worshipers
\of Toutatis ever feared was that the sky might fall on their heads.

/Wolfgang

So if Toutatis _is_ going to impact, can we count on Asterix the Gaul
to come save us?

Does he have one of those Arthurian "wake again in our hour of
need" clauses in his contract?

Phil

-- 
Phil Fraering pgf@srl0x.cacs.usl.edu where the x is a number from 1-5.
Phone: 318/365-5418 SnailMail: 2408 Blue Haven Dr., New Iberia, La. 70560
---------------------
Disclaimer: Some reasonably forseeable events may exceed this
message's capability to protect from severe injury, death, widespread
disaster, astronomically significant volumes of space approaching a
state of markedly increaced entropy, or taxes.
From: wats@scicom.AlphaCDC.COM (Bruce Watson)
Newsgroups: sci.space
Subject: Re: orbital lifetimes
Date: 14 Oct 92 23:36:40 GMT
Organization: Alpha Science Computer Network, Denver, Co.

In article <BvtKsG.HAD@zoo.toronto.edu| henry@zoo.toronto.edu (Henry Spencer) writes:
|In article <28396@scicom.AlphaCDC.COM| wats@scicom.AlphaCDC.COM (Bruce Watson) writes:
|||How many of these moons have stable orbits?  In this case, I define stable
|||to mean that they will stay in orbit for 100+ years...
||
||Anything above 1000 km will stay up for 100+ years...
|
|At lower altitudes there's a nice set of rules of thumb...
|
|At 100km your orbit lasts about an hour.
|At 150km your orbit lasts about a day.
|At 200km your orbit lasts about a week.
|At 250km your orbit lasts about a month.
|At 300km your orbit lasts about a quarter.
|At 350km your orbit lasts a bit under a year.
|
|Don't plan missions on this basis. :-)  Furthermore, don't try to extrapolate

|it further:  the more-or-less semilog relationship you would infer from it
|is visibly failing on both ends.  It's actually more like log-log, and the
|constants vary a lot with how dense your satellite is.

I put together some data from the graph on p. 153 of Bate, Meuller, and
White and some empirical data (all of it less than 35 years, of course)
and came up with results very much like these. My best fit is:

log_10 t_years = 7.4 log_10 a_km - 19.1

where t is time and a is altitude above the surface of the earth of the
circular orbit (except for Molniyas virtually all are these days).

Of course the atmospheric density varies daily, tidally with the sun
and the moon, annually and with the sun spot cycle, so the fit can
only be approximate.

As you say, the density of the satellite matters. Especially with the
balloon satellites of the 60's. Echo I lasted 8 years from its 1600 km
orbit. Had it been more iron than air it would still be up there with
10's of thousands of years to go.

-- 
Bruce Watson (wats@scicom)  Tumbra, Zorkovick; Sparkula zoom krackadomando.
From: roberts@CMR.NCSL.NIST.GOV (John Roberts)
Newsgroups: sci.space
Subject: Re: Dyson sphere (followup)
Date: 16 Oct 92 11:59:53 GMT
Article-I.D.: cmr.9210161159.AA19033
Organization: National Institute of Standards and Technology
	formerly National Bureau of Standards


-Date: Fri, 16 Oct 92 01:05:49 EDT
-From: John Roberts <roberts>
-Subject: Re: Dyson sphere

-A black sphere surrounding the sun at 1AU would have an outer surface 
-temperature of about 140 degrees Celsius (pretty hot - for a temperature
-of 25 C you'd want the radius to be about 1.9AU), and would heat the surface
-of the sun only a fraction a degree. A reflecting sphere would be *hotter*
-and would heat the sun more. To make the calculations more interesting, try
-a sphere that's reflective on the inside and black on the outside.

-I'll try a few more calculations, based on the simplifying assumption that
-a given substance is equally reflective at all wavelengths (generally not
-true). Then if you assign each substance a reflectance rating of N (where
-0 = black and 1 = perfectly reflective), and if you only consider diffuse
-reflection, then for a sphere of a uniform substance, the incident radiation
-on the inner surface is 2/(1-N) times the normal flux at that distance
-from the star, the net photon pressure is 0.5 + 1/(1-N) times the normal
-amount, and the temperature of the outer surface will be (1-N)^0.25 times
-the temperature of a black sphere of the same dimensions, with the 
-temperature measured in kelvins. For instance, with N of 0.9 (90% reflectance,
-pretty good for a silver reflector, and probably not too far off for an
-aluminum reflector), the incident flux on the inner surface would be 20
-times the normal amount, the net photon pressure would be 10.5 times the
-normal amount, and the temperature of the outer surface (1AU) would be about
-470 degrees Celsius. To get back down to 25 C, you'd have to set the radius
-to about 6AU.

Attempting to extend the calculations for a sphere that has different 
reflectivity on the inner and outer surfaces:

Let Ni be the reflectivity of the inner surface of the sphere, and No be
the reflectivity of the outer surface of the sphere. Then the multiplying
factor for the incident radiation on the inner surface is 
((1 - Ni) + (1 - No)) / ((1 - Ni)(1 - No)). If we want to minimize the
outer temperature of the sphere, then No should be set to zero (outer
surface black). If that is done, then the incident radiation multiplier
is 1 + 1/(1 - Ni) and the net photon pressure multiplier is 1 + 0.5/(1-Ni).
So a sphere with 90% reflectance on the inner surface and 0% reflectance
on the outer surface would have a radiation multiplier of 11, and a photon
pressure multiplier of 6. The outer temperature would be no greater than
that of an all-black sphere of the same size.

John Roberts
roberts@cmr.ncsl.nist.gov
From: eatlv@cbnewsg.cb.att.com (thomas.vandoren)
Newsgroups: sci.space
Subject: Re: Drop nuc waste into sun
Date: 9 Oct 92 19:09:19 GMT
Article-I.D.: cbfsb.1992Oct9.190919.11386
Organization: AT&T

In article <Bvv558.JpG@zoo.toronto.edu> henry@zoo.toronto.edu (Henry Spencer) writes:
>Actually, as Larry Niven pointed out, if you can get the stuff as far as
>Venus, you might as well just fly it *into* Venus.  It's not as if Venus
>is good for anything else.  (Although one would want to do rather more
>thorough studies of Venus before starting to use it as a dump...)


  I was thinking the same thing myself.  "Use it as a dump.." haha, that's
funny.  But, hey, maybe that IS the best use for Venus!  With all that
pressure, heat, and sulfuric acid, it would burn up in a relatively short
period of time.  
  Every planet/moon should have its purpose, and that just seems to fit
Venus well.

Lee
From: amon@elegabalus.cs.qub.ac.uk
Newsgroups: sci.space
Subject: Re: Alleged Benefits of Military $
Date: 7 Oct 92 15:59:12 GMT
Article-I.D.: cs.BvrELo.7KA.1
Distribution: sci
Organization: [via International Space University]
X-Added: Forwarded by Space Digest
Original-Sender: isu@VACATION.VENARI.CS.CMU.EDU

> I believe it is also true that higher income people spend less of their
> money than low income people, so their money is likely to go into the
> economy fewer times.  I have heard this as an explanation for the fact
> that the increase in income during the Reagan years did not produce
> sustained increases in consumer demand; the increases went to people
> who spend less of their money.  Not being an economist, I cannot vouch
> for the validity of this argument, but it tends to contradict what Gary
> said.
> 


The funny thing is... the most common complaint about the US economy is  
not that people are spending too little, but that they are not SAVING  
enough. Savings is what is used for capital investment according to  
standard economics. I think that is even true with old fashioned Keynesian  
economics as well as the more modern Austrian and Chicago schools.

Japan is said to have a very high savings rate. One of the things you see  
very often in US discussions of opening up the Japanese markets is the  
desire for them to have a more consumer oriented economy. Right now rich  
and poor alike save at a very high rate and the investment is poured back  
into the economy.

Savings and consumption BOTH drives economic well being. But to say that  
there is a higher multiplier by simply increasing the velocity of money is  
fool hardy. Without a high savings rate a high money velocity will just  
buy more Japanese consumer goods per unit time.
From: amon@elegabalus.cs.qub.ac.uk
Newsgroups: sci.space
Subject: Re: Drop nuc waste into sun
Date: 8 Oct 92 12:48:03 GMT
Article-I.D.: cs.BvszLx.79E.1
Distribution: sci
Organization: [via International Space University]
X-Added: Forwarded by Space Digest
Original-Sender: isu@VACATION.VENARI.CS.CMU.EDU

> P.S. I think sending the waste outside the solar system is like  
dumping it
> in the ocean..it just sends the problem somewhere else.
> 


Well, I'd hang onto it for other reasons. It will one day be  
considered a valuable resource. Probably after the nucleophobic  
generation dies off.

But nonetheless, perform the following reality check on what you just  
said. Try this thought experiment.

Assume the Earth is entirely made out of Plutonium.
Now atomize it and spread it over the volume of a sphere of solar  
space representing half the average distance between stars in our  
regions of space. (r = 2ly or 12e12 miles is a good "Fermi number"  
for this.)

Now...  how good do your instruments have to be to detect it's  
presence over the background cosmic radiation? (Other than by the  
velocity distribution. That's cheating :-)

A slightly more difficult one is to break the Earth into n chunks of  
radius r, spread them equidistant within the volume, and figure out  
how often a random walk will approach one to within distance d.

My point is, there is simply not enough matter in the universe to  
pollute the universe, and besides which, all the matter started off  
in free space anyway. There were more radioactives in the pre-solar  
nebula than exist now... it was all spread out nice and evenly. Well,  
mostly evenly anyway.

The only reason for not firing it out of the solar system is that it  
would be pretty much lost to everyone forever (or if someone finds it  
in a billion years or so, they'll probably find not much more than  
lead and a few long lived fissionables... which they'll thank us for,  
for all the good it does us...)
Newsgroups: sci.space
From: wjg@bluemoon.rn.com (william grimm)
Subject: Re: UFO EVIDENCE VS. Carl Sagan
Organization: Blue Moon BBS ((614) 868-998[024])
Date: Thu, 08 Oct 92 20:06:22 EDT

> >          Roswell Incident in which UFO WRECKAGE and ALIEN BODIES were 
> >          found on a ranch (in New Mexico, I think), gathered up by the 
> >          U.S. military, and hidden away in an Air Force hanger 
> >          somewhere.  The wreckage included materials NOT KNOWN on 
> >          Earth, and some of it even had ALIEN SYMBOLS written on it.  
> ...
> >                                   Robert E. McElwaine
> >                                   B.S., Physics and Astronomy, UW-EC
> 
> 

Well, Mr. McElwaine, what happened was- and watch who you repeat this to- 
Carl Sagan was brainwashed at Wright Patterson's infamous hangar 13, and 
convinced by certain govt. agencies to keep quiet regarding the inhuman 
alien monsters that frequently visit our planet <G>.  The aliens, you see, 
are working hand-in-hand with the feds- they supply the technology, we 
supply the bovine and human body parts for their genetic research :}.

 This is from
     wjg@bluemoon.rn.com
who doesn't have his (or her) own obnoxious signature yet
Newsgroups: sci.optics
From: siegman@EE.Stanford.EDU (Anthony E. Siegman)
Subject: Re: Optical Simulator Software
Organization: Stanford University
Date: Thu, 8 Oct 92 19:18:55 GMT


>Does anybody out there know about any software packages for simulation of 
>geometric (ray) optics and wave optics ? I am in particular interested in 
>software that is in the public domain and available with the sources, but
>any pointers to both academic and commercial packages will be appreciated.

* PARAXIA (for the Mac), written by my research group, now available
from Genesee Optics Software, Rochester NY, 716-272-9944, 716-272-8108
(fax).  Complex ABCD matrix calculations, Huygens integral
calculations, unstable resonator modes, VRM resonator modes.  Superb,
of course.  (A lowered academic price supposed to be available.)

* OPTICS LAB, Intellimation Library for the Macintosh, P. O. Box 1530,
Santa Barbara CA 93116-1530, 800-346-8355, 805-968-8899 (fax).  Cheap
and simple ray tracing, mostly for teaching or demo purposes rather
than research.  ($25 or so).
From: rwc124@rsphy1.anu.edu.au (Roderick Vance)
Newsgroups: sci.optics
Subject: Helmholtz Equation
Date: 12 Oct 1992 07:02:07 GMT
Organization: Optical Sciences Centre, Australian National University
Distribution: world
Reply-To: rwc124@rsphy1.anu.edu.au (Roderick Vance)
NNTP-Posting-Host: 150.203.15.51



My question concerns the eigenvalue equation:

 (del^2 + k^2 n(x,y)^2) psi = beta^2 psi

where psi is a function of the rectangular co-ordinates (x,y)
      del^2 is the two dimensional Laplacian d2/dx2 + d2/dy2
and   beta is the real eigenvalue.

This equation is gotten from the three dimensional Helmholtz 
equation when we assume a three dimensional solution of the form

   psi(x,y) exp(-i beta z)

My question is: when can there be two or more linearly independent
solutions psi1(x,y), psi2(x,y), ...  corresponding to the SAME 
eigenvalue. 

I'd be most greatful for hints/thoughts about the above.

Many thanks in advance


Roderick Vance
Optical Sciences Centre
Australian National  University
Newsgroups: sci.optics
From: siegman@EE.Stanford.EDU (Anthony E. Siegman)
Subject: Re: Ref on Thermal IR Properties?
Keywords: Thermal infrared, properties of materials
Organization: Stanford University
Date: Thu, 8 Oct 92 19:12:45 GMT

Somewhat elderly, but was the standard in its time:

   HANDBOOK OF MILITARY INFRARED TECHNOLOGY
   William L. Wolfe, Editor
   U.S. Government Printing Office (1965).
   Library of COngress Catalog 65-62266.
   906 pages, $3.75 (!!!)

Lots of good solid data.  Maybe there's an updated version?

There also used to be a government organization called IRIS that
maintained databases and meetings about IR applications.  Can't say if
it still exists.



Newsgroups: sci.optics,alt.sci.planets
From: knapp@spot.Colorado.EDU (David Knapp)
Subject: Re: Color of the moon
Organization: University of Colorado, Boulder
Date: Tue, 13 Oct 1992 21:32:06 GMT

In article <1bf3jrINNias@tangelo.usc.edu> skoehler@tangelo.usc.edu (steffen koehler) writes:
>Why is the moon white (or silver)colored?  Anyone know?

Because you're looking against a black sky. It is actually *very* dark. 
Bond albedo of ~.06. If you were *on* it and let your eyes get adjusted, you'd
be asking "Why is the moon so gray?" Then we'd answer that it was because of 
the minerals in the lava which comprise most of what you see (or something to 
that effect.)

>
>Using someone else's account to post, so please respond by e-mail only
>to Mahgeref@alnitak.usc.edu
>
>-- 
>---------------------------------------------------------------------------
>Steffen Koehler    |                      University of Southern California
>skoehler@usc.edu   |                               Center for Laser Studies
>(213) 740-4249     |    National Center for Integrated Photonics Technology


-- 
David Knapp                                      University of Colorado, Boulder
Perpetual Student                                   knapp@spot.colorado.edu
Newsgroups: sci.optics
From: gawne@stsci.edu
Subject: Re: Ref on Thermal IR Properties?
Organization: Space Telescope Science Institute
Distribution: na
Date: Thu, 8 Oct 1992 21:04:03 GMT

In article <1992Oct8.191245.5800@EE.Stanford.EDU>, 
siegman@EE.Stanford.EDU (Anthony E. Siegman) writes:
> Somewhat elderly, but was the standard in its time:
> 
>    HANDBOOK OF MILITARY INFRARED TECHNOLOGY
>    William L. Wolfe, Editor
>    U.S. Government Printing Office (1965).
>    Library of COngress Catalog 65-62266.
>    906 pages, $3.75 (!!!)
> 
> Lots of good solid data.  Maybe there's an updated version?

Just happen to have the updated version on my desk.  It is:

	THE INFRARED HANDBOOK
	Wm. L. Wolfe and Geo. J. Zissis, Editors
	Prepared by the Infrared Information and Analysis Center
	Environmental Research Institute of Michigan
	for the Office of Naval Research, Dept of the Navy
	U.S. GPO (1985) Lib of Congress Cat 77-90786

25 Chapters, well over 1000 pages.  No price given.

I understand there's a newer edition, but I don't have it.

-Bill Gawne,  Space Telescope Science Institute
From: sdr57@cas.org
Newsgroups: sci.optics
Subject: Re: Refractive index of windscreens
Date: 13 Oct 92 14:42:50 GMT
Organization: Chemical Abstracts Service, Columbus, Ohio

In article <1992Oct13.134054.12027@vms.eurokom.ie> dleger@vms.eurokom.ie writes:
>I am looking for the index of refraction of glasses used for car windscreens;
>does anybody have an idea of the value or know a reference.
>Thanks.
>
You might get a start by looking at the article "Design of
selective transmissive/reflective coatings for windows" in
J. Vac. Sci. Technol., A, 10(4, Pt. 2), pages 1892 et seq.

It's not exactly what you want, but some of the references might be.

******************************************************************************
Renegade academician. They're a dangerous breed when they go feral,
academics are...a chemist, too.
		    -(James P. Blaylock in "Lord Kelvin's Machine")

My organization hasn't agreed with any of my opinions so far, and
I doubt they'll start now.

Stanley "Ya nee speon" Roberts
Newsgroups: sci.optics
From: sprent@sol.surv.utas.edu.au (Tony Sprent)
Subject: Help on distance measuring system
Organization: University of Tasmania
Date: Thu, 8 Oct 1992 01:11:57 GMT

I am looking for an electro-optical or acoustic distance measuring system which
is capable of measuring the distance (approx 10 metres) from the deck of a ship
down to the water surface as the ship moves at up to 30 knots in order to analyse
the motion of the vessel under differing sea conditions.  An update rate of 
10 - 20 Hz with a precision of +/- 0.1 metre would be ideal. The surface of the
water will not be flat and in general not level and the optical reflectivity of 
the water surface will vary considerably.

Any assistance in obtaining information on suitable measuring systems and the 
names and addresses of suppliers would be appreciated. 
______________________________________________________________________________
Tony Sprent
Department of Surveying and Spatial Information Science
University of Tasmania
GPO Box 252C Hobart
Tasmania

Phone 61-02-202110 Fax 61-02-202110  International         
        002-202110       002-240282  Australia
email sprent@surv.utas.edu.au
______________________________________________________________________________
Newsgroups: sci.optics
From: ellis@msl475a.erim.org (Ken Ellis)
Subject: IR refractive index of air
Organization: Environmental Research Institute of Michigan, Ann Arbor, Michigan
Date: 12 Oct 92 07:46:30


	I am trying to determine the refractive index of air in the IR
(3-15 microns) as a function of temperature and pressure. Many
references that I have found have a relationship for the visible:

	n-1=Ap/T(1+Be/Tp)x10E-6

where T is temperature, p is pressure, e is the water vapor pressure
and A and B are other parameters. Many authors imply that this
relation does not hold in the IR. People I have talked to say that the
gas molecule absorption in the IR makes this relationship invalid. 

	Is there a relationship valid in the IR? Is this one valid in
the atmospheric windows where the absorption is small? What does
LOWTRAN use for the atmospheric refraction calculations when computing
the apparent solar zenith angle in the IR?

	Thanks in advance for your help.

		-Ken


--
_____
\                                      |  Opinions expressed here are solely
 \   ERIM   Ken Ellis                  |  those of the author and do not
 /          ellis@erim.org             |  necessarily represent those of 
/____|                                 |  his employer. 



Newsgroups: sci.optics
From: "glen mead" <glen.mead@canrem.com>
Subject: help - tech project
Reply-To: "glen mead" <glen.mead@canrem.com>
Organization: Canada Remote Systems
Distribution: sci
Date: 10 Oct 92 19:01:52 EST

Hi All,

With regards to my original questions regarding the control of a stepper
motor, I have recently discovered that this is not actually a stepper
motor but a 3-phase motor.  The actual part is a Tohoku Ricoh type
7M100200 with ratings of DC24V, 0.2A, 48W.  This 3-phase motor is part
of an optical housing assembly from a laser assembly which also includes
a laser drive assembly and scanning mechanicals.  What I need to know
is, how to operate and control this stepper motor, how to operate and
control the laser, and how to replace the laser diode with which
produces a visible beam.  For further project description and 3-phase
motor pin numbers and names, see below.

 Any help would be greatly appreciated.  Thanks for any help in advance.
 Comments and suggestions are welcome.

 Glen Mead

 ---

 Project Summary:

By utilizing the optical housing from a laser printer and replacing the
laser diode with one of a visible wavelength, a display type laser
device can be constructed providingproper control circuitry is utilized.
Scanning functions would be provided by mirrors mounted on a 3-phase
motor assembly and a series of focusing lenses and mirrors.  Graphics
would be generated by turning the laser on and off at specific places
(determined by the frequency and duty cycle of the control waveform)
during each scan. Timing of the 3-phase motor and laser would be based
on a sync pulse generated in the optical housing assembly at the end of
each scan line.


 3-Phase motor pins:

 1 - W-Phase
 2 - V-Phase
 3 - U-Phase
 4 - H-W2
 5 - H-W1
 6 - H-V2
 7 - H-V1
 8 - H-U2
 9 - H-U1
 10 - H-GND
 11 - H-VCC
 12 - FG1
 13 - FG2

 NOTE: The H-??? pins are power and output pins for Hall elements,
 something else I could use a hand with. :-)
--
Canada Remote Systems  - Toronto, Ontario
World's Largest PCBOARD System - 416-629-7000/629-7044
From: tomrice@netcom.com (Tom R. Rice)
Newsgroups: sci.optics
Subject: Photo resist for glass reticles?
Date: 9 Oct 92 01:06:08 GMT
Article-I.D.: netcom.1992Oct9.010608.18089
Organization: Netcom - Online Communication Services  (408 241-9760 guest)

I want to make etched-glass reticles, using a photographic
process for versatility, and would appreciate recommendations
for commercially-available resists, liquid or solid, which
will stand up to the usual glass-etchants (fluorine-based).

Thank you, trr

-- 
"Start off every day with a smile and get it over with."  --W.C.Fields
Tom R. Rice   WB6BYH                   Holler Observatory - 
tomrice@netcom.com                     Longitude:  121 d  30 m  20 s W 
CIS: 71160,1122                        Latitude:    37 d  25 m  10 s N 
Newsgroups: sci.optics
From: aye@raman.ECE.CMU.EDU (Anqi Ye)
Subject: Where to buy a hologram?
Organization: Electrical and Computer Engineering, Carnegie Mellon
Distribution: usa
Date: Wed, 7 Oct 1992 20:24:46 GMT

Does anyone know where I can order a transmission hologram that I can
run a laser beam through and see 3-D figures? This is for a class demo.
Any information will be appreciated.

Anqi Ye
aye@raman.ece.cmu.edu