Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V16_5/V16NO545.TXT

Internet Message Format | 1993-07-13 | 19KB

Date: Sat,  8 May 93 05:14:28
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V16 #545
To: Space Digest Readers
Precedence: bulk


Space Digest                Sat,  8 May 93       Volume 16 : Issue 545

Today's Topics:
              ASTRONAUTS---WHAT DOES WEIGHTLESSNESS FEEL
                             DC-X Status?
                 Gamma Ray Bursters. WHere are they.
                       Heard MIR on my scanner
                 Magellan's Radio Science Experiments
          Space Manuevering Tug (was HST servicing mission_)
                         Vandalizing the sky.

    Welcome to the Space Digest!!  Please send your messages to
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----------------------------------------------------------------------

Date: 7 May 1993 15:12 CDT
From: "PATE, DENNIS WAYNE" <[e-mail]>
Subject: ASTRONAUTS---WHAT DOES WEIGHTLESSNESS FEEL
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Henry Spencer) writes...
> 738 764 776
>Organization: U of Toronto Zoology
>
>In article <Bob_Hearn-050593084014@192.35.50.165> [e-mail]
>(Robert Hearn) writes:
>>> : Some people are more prone to it than others, like some people are more
>>> : prone to get sick on a roller coaster ride than others.
>>
>>But are they the same set of people?  If I get queasy on a roller coaster,
>>would I necessarily have a problem with zero G? ...
>
>Nobody has yet found *any* test that can be done on the ground which predicts
>spacesickness especially well.  There is a great deal of interest in being
>able to predict who will get sick, since it hurts productivity on extremely
>expensive missions, but so far no way to do it.  In particular, there is no
>particularly strong correlation between susceptibility to more ordinary
>forms of motion sickness and susceptibility to spacesickness.  At least,
>not that the research people have been able to find -- I don't know if
>they've tried roller coasters :-).

Two years ago a took a tour of the Johnson Space Center with a group of fellow
Human Factors Engineering graduate students.  Our guide was a manager in the
Man Systems Dept. and a friend of our prof.  While showing us the mockup of
space station Freedom (the pre-Clinton design), he pointed out a new project
one of the groups was working on.  They had observed that some of the
astronauts prone to developing motion sickness were not as succeptable to
it once they had returned from a mission.  The positive side-effect apparently
last for a couple of weeks, depending on the individual.  They hoped a reversal
of the situation might also work (i.e. Get them motion sick on the ground,
let them recover, and then boost them into space).  To accomplish this, they
were constructing some type of miniature roller-coaster (that's how our guide
describe the device).

I don't know if the device worked, or if it was ever actually completed and
used.  If anyone knows anything about it, please post.

-----------------------------------------------------------------------------
Dennis Pate, unemployed        | Will build spacestation for food.
[e-mail]         |

------------------------------

Date: 7 May 1993 19:52:01 GMT
From: Andy Cohen <[e-mail]>
Subject: DC-X Status?
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Bill
Innanen) wrote:
>
> What is the current status of the DC-X program?  Wasn't there supposed to be
> a static test firing recently/real soon now?
>
> Bill
> --
> Bill Innanen             (Internet) [e-mail]
> #include <stdDisclaimers.h>   /* Unless otherwise noted */

It was supposed to be a week ago....no word back from the dessert yet......

------------------------------

Date: 7 May 93 20:41:22 GMT
From: "Richard M. Mathews" <[e-mail]>
Subject: Gamma Ray Bursters. WHere are they.
Newsgroups: sci.space,sci.astro

[e-mail] (john baez) writes:
>How can you tell the difference between an intensity distribution which
>is due to an "edge" in the spatial distribution and an intensity
>distribution which is due an a sharp dropoff of intrinsic luminosities
>below a certain threshold?

The distribution in apparent luminosities is independent of the distribution
in intrinsic luminosities if the sources are uniformly distributed from r=0
to r=infinity and if space-time is flat.  That luminosity distribution is
    dN = constant * L^(-5/2) * dL
(see below).  If we observe that L^(-5/2) dependence down to the limit
of our instruments, we know that the sources are uniformly distributed
in space all the way out to where they are too dim for us to find; but
we have no idea just how far we are looking.  Similarly, if we find
something other than the L^(-5/2) dependence, we know that the spatial
distribution can't be uniform (or space-time is not flat over the distance
we are looking); but again we have no idea what the distance scale is to
that "edge".

Proof:

First consider the distribution in apparent luminosity in the simplest
case: all objects have the same absolute luminosity and are uniformly
distributed in flat space-time.  All we need to know is the density which
applies everywhere and the intrinsic luminosity:
    dN = 4 * pi * density * r^2 * dr
and
    L = L0 / r^2

Now differentiate the latter equation and manipulate to eliminate all
r's and dr's:
    dN = constant * L^(-5/2) * dL
The constant depends on the intrinsic luminosity and the density.

Now make it a little more complicated.  We have two populations with
different intrinsic luminosities.  If we can distinguish the two
populations we get
    dN1 = constant1 * L^(-5/2) * dL
and
    dN2 = constant2 * L^(-5/2) * dL
The only difference is the two constants which depend only on each
population's density and intrinsic luminosity.  If we can't distinguish
them, all we get is the sum of the two luminosity distributions:
    dN = dN1 + dN2 = (constant1 + constant2) * L^(-5/2) * dL
This follows the same form as when there was only one intrinsic luminosity.

Now take an arbitrary distribution of intrinsic luminosities.  Consider
this to be an infinite number of individual populations each with its
own specific intrinsic luminosity.  Add up the contributions from all
of those, and we still get
    dN = constant * L^(-5/2) * dL

The key here is that the spatial distribution must be uniform all the
way out to where the intrinsically brightest objects are too dim to see.
If that is the case, all effects due to the distribution of intrinsic
luminosities is blurred out.  If the effects due to the distribution of
intrinsic luminosities is not blurred out, it follows that the spatial
distribution cannot be uniform (or space-time is not flat).

     Richard M. Mathews            F oster
                     E stonian-Latvian-Lithuanian
[e-mail]          I ndependence and
                       F reedom!

------------------------------

Date: Fri, 7 May 1993 20:15:19 GMT
From: "William K. McFadden" <[e-mail]>
Subject: Heard MIR on my scanner
Newsgroups: rec.radio.amateur.misc,rec.radio.shortwave,sci.space,alt.radio.scanner

I heard the Russian space station MIR on my scanner (PRO-2006 using built-in
whip, 145.55 MHz) last week and would like to know where to send my reception
report for a QSL card.  Thanks!

--
Bill McFadden    Tektronix, Inc.  P.O. Box 500  MS 58-639  Beaverton, OR  97077
[e-mail], ...!tektronix!tv.tv.tek.com!bill      Phone: [phone]
How can I prove I am not crazy to people who are?

------------------------------

Date: 7 May 1993 20:41 UT
From: Ron Baalke <[e-mail]>
Subject: Magellan's Radio Science Experiments
Newsgroups: sci.space,sci.astro,alt.sci.planetary

From the "JPL Universe"
May 7, 1993

Magellan, DSN join forces on radio science experiments

     JPL's Deep Space Network (DSN) has joined forces with the
Magellan spacecraft in performing three types of radio science
experiments.
     Magellan, which has been orbiting Venus since August 1990
and has mapped more than 98 percent of the planet, has utilized
its downlink capabilities to probe Venus' upper atmosphere and
the sun's plasma. Using open-loop receivers at the DSN stations,
signals were received from the spacecraft, digitized and recorded
on tape.
     "The radio science instrument, which is comprised of a
transmitter aboard the spacecraft and a ground-based receiver, is
unique because it is distributed between the spacecraft and DSN
stations; it is at the latter where the data observables are
actually generated," explained Dr. Nick Renzetti, manager of the
Telecommunications and Data Acquisition Science Office.
     "Six Magellan radio science experiments have been conducted
over the last two years," said Magellan Project Manager Doug
Griffith. "Three of them studied the atmosphere of Venus, one is
an ongoing gravity-field data-collection campaign, and the other
two have studied the scintillations in the solar wind and the
Faraday rotation effect in the solar corona," he said.
(Scientists can discern the nature of the corona's magnetic field
by understanding how much a signal polarization rotates.)
     "Magellan's large High Gain Antenna and powerful X- and
S-band downlink, as well as its ability to accurately maneuver to
track the Earth through the refracting atmosphere, allowed radio
occultation measurements deeper than ever before into Venus'
atmosphere," explained Dr. Steve Saunders, Magellan project
scientist.
     When the radio signal transmitted by the spacecraft traveled
through Venus' atmosphere on its way to Earth -- a geometrical
configuration called occultation -- it was changed in phase and
attenuated in amplitude by the gases forming Venus' atmosphere.
These perturbations were recorded by specialized equipment at the
DSN stations. The data produced highly accurate profiles of
atmospheric refractivity and absorptivity that, in turn, produced
temperature and pressure profiles of the Venusian atmosphere. Of
special interest to investigators Paul Steffes of Georgia Tech
University and Jon Jenkins of NASA's Ames Research Center is a
study of the abundance of sulfur dioxide, carbon dioxide and
sulfuric acid vapor in the Venusian atmosphere.
     In order for the DSN to remain in communication with the
spacecraft, even as it went behind the planet, Griffith said "a
complicated limb-track maneuver was performed to maintain the
radio link as long as possible while the signal was refracted in
the atmosphere." The maneuver, he said, which was designed and
implemented jointly by JPL's Magellan team and the spacecraft
team at Martin Marietta -- in combination with the strength of
the transmitted signal and accurate predictions of the DSN
receiving equipment -- enabled Venus' atmosphere to be probed to
depths of 35 kilometers at the 3.6 centimeter wavelength radio
signal (X-band) and 33 kilometers at the 13 centimeter signal
(S-band).
     During superior conjunction in late spring 1992, a
four-month solar-wind radio-scintillation experiment was
conducted to investigate the near-sun solar-wind region not yet
explored by direct spacecraft, according to Principal
Investigator Richard Woo of the Radio Frequency and Microwave
Subsystems Section. For part of the experiment, data were also
generated to study the Faraday rotation effect in the solar
corona. Michael Bird of Germany's University of Bonn will obtain
information about the electron density and magnetic field in the
corona.
     In its current cycle around Venus, Magellan and the DSN --
in a third investigation -- are measuring the planet's
gravitational field. Accelerations of the spacecraft are tracked,
according to gravity field investigator William Sjogren of the
Navigation Systems Section. Using the DSN to communicate with the
spacecraft and record the returned signals, small changes in the
X- and S-band Doppler signatures can be seen. (The Doppler effect
is the change in frequency due to relative motion of either the
transmitter or receiver.) These changes are caused by
perturbations in the spacecraft's orbit that result from
irregularities in the mass distribution of the planet.
     "The gravity data will allow geophysical models to examine
the internal structure and dynamics of Venus, as well as look
below the surface for the forces that have created the geologic
features that Magellan has mapped," Saunders said.
                            ###
     ___    _____     ___
    /_ /|  /____/ \  /_ /|     Ron Baalke         | [e-mail]
    | | | |  __ \ /| | | |     Jet Propulsion Lab |
 ___| | | | |__) |/  | | |__   M/S 525-3684 Telos | Once a year, go someplace
/___| | | |  ___/    | |/__ /| Pasadena, CA 91109 | you've never been before.
|_____|/  |_|/       |_____|/                     |

------------------------------

Date: Fri, 7 May 1993 19:05:09 GMT
From: fred j mccall 575-3539 <[e-mail]>
Subject: Space Manuevering Tug (was HST servicing mission_)
Newsgroups: sci.space

In <1s8c85$[e-mail]> [e-mail] (Pat) writes:

>In article <[e-mail]> [e-mail] (fred j mccall 575-3539) writes:
>|In <1s15p6$[e-mail]> [e-mail] (Pat) writes:
>|
>|There is a difference between 'on orbit servicing' and taping a motor
>|to its butt and firing it, Pat.  Keep in mind that this motor is going
>|to have to thrust exactly through the center of mass of the HST or
>|you're going to tumble.  It is then going to have to cease firing
>|cleanly, unbolt itself from HST, and move away (all without leaving
>|any contamination).  Note that most of this is not a problem when
>|using the Shuttle for reboost, because it can basically wrap itself
>|around the HST and all that stuff with center of mass is already
>|computed.  Plus, there are people on scene if anything goes wrong.
>|

>I guess fred, you never heard of guidance navigation and control
>thrusters.  as long as the tug,  can balance the expected forces,
>it will cope.

Gee, now *that* sounds like a prime example of 'good engineering
analysis'.  "It will cope."  This tug is starting to sound a lot
bigger than something you're going to 'cobble together'.

>Nesides,  with the service points on the HST, i am sure there are
>places where a tug could be securely bolted on for a low impulse
>thrust,  and a few explosive bolts,  and it can cut itself free.

>You have heard of explosive bolts?

Oh yes.  Not exactly the sort of thing I'd want to use for detaching a
tug from service points on a $1G instrument.  They are, after all,
*explosive* bolts.  They're not named that for the fun of it.

>as for using the STS,  from what i understand,  it is going to be
>on the long end of the arm,  so if a forward RCS thruster fires,
>the HST gets to fly through the vapor cloud.  i'm sure
>they have programmed to mostly use the  aft RCS system,
>but that chance is always possible,  escpecially if you get a
>thruster leak.  rare,  but possible.

Well, as opposed to the Pat Plan of certain contamination from all

sorts of firings trying to correct off-center thrust and explosive
bolt disconnects that leave crap all over the vicinity, I think a
remote possibility is to be favored.  I also think you may be mistaken
as to where it will be, judging by the manifest for the current
mission, which includes a repair stand, of sorts.

>|>I suspect, the BUS-1, may not have enough basic thrust for the HST
>|>re-boost.  it mayu need bigger tanks,  or bigger thrusters.
>|
>|I see.  So we change a bunch of stuff on it, then take it up and duct
>|tape it to a $1G instrument and hope everything comes out ok?  I think
>|not.
>|

>gee fred,  i better let you do all the thinking for the world.

Sounds like you need to get someone to do yours for you, at the very
least.

>|>Also,  please tell me how some sort of sublimated  material  like
>|>CO2, or H2O  would manage to contaminate the mirror,  anything
>|>that goes to vapor state, shouldn't adhere to the mirror.
>|
>|Sounds like you're thinking of things in atmosphere, Pat.  Any stray
>|molecule in space may adhere to any solid surface it hits, whether
>|it's 'vapor' or not.  That's why there's a worry about contamination
>|of the instruments by thruster exhaust, which is something of a vapor,
>|last time I checked.
>|

>i chatted with a guy from lockheed missiles and space.  he said that
>actually most short chain  molecules have a low condensed volatile
>material quotient (CVM).  even hydrazine is  not really a big
>problem for optical systems,  and even though he couldn't
>name birds (classified)  he said, the use of hydrazine around
>optical arrays was not considered a problem,  at least for the
>systems they worked on.

Different birds, and those are designed to be moving about.  I would
bet some care was taken with their design -- which you aren't going to
be able to duplicate with your 'cobbled together system'.

>so somehow, i dount that stray CO2, or H2O  would really wreck
>up the HST.

I don't consider "well, Pat doubts it will be a problem" to be
particularly convincing.

--
"Insisting on perfect safety is for people who don't have the balls to live
 in the real world."   -- Mary Shafer, NASA Ames Dryden
------------------------------------------------------------------------------
[e-mail] - I don't speak for others and they don't speak for me.

------------------------------

Date: Fri, 7 May 1993 19:29:38 GMT
From: fred j mccall 575-3539 <[e-mail]>
Subject: Vandalizing the sky.
Newsgroups: sci.astro,sci.space

In <[e-mail]> [e-mail] writes:

>I said persuade - "Paint it" "Take it off" "Junk it" are demands.
>Methinks you are arguing for pleasure.

Methinks you should take a course in thinking.  I'm sure you'll
understand if I refuse to conform to what youthinks.

>Reminds me of a belligerent drunk
>I know who delights in goading people for entertainment.

Well, at least we know who you hang around with now.

>You'll make
>more friends with a little love, sweet'ums.

Sorry, you're not my type.

[Since you decided to get snide, I thought I would return the favor.]

>Wm. Hathaway
>Baltmore MD

--
"Insisting on perfect safety is for people who don't have the balls to live
 in the real world."   -- Mary Shafer, NASA Ames Dryden
------------------------------------------------------------------------------
[e-mail] - I don't speak for others and they don't speak for me.

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End of Space Digest Volume 16 : Issue 545
------------------------------