Space & Astronomy/Space and Astronomy (October 1993).iso/pc/text/spacedig/v11_0/v11_028.txt

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Subject: SPACE Digest V11 #28

SPACE Digest                                      Volume 11 : Issue 28

Today's Topics:
             Re: Galileo Mission Schedule
       USSR to put spysat pictures in public domain ?!
             RE: Radio Astronomy
             Re: More Info on SSX
             Re: More Info on SSX
            Re: metric vs. imperial units
              Galileo Update - 02/09/90
              Kepler fudged the Numbers?
----------------------------------------------------------------------

Date: 8 Feb 90 18:15:27 GMT
From: mnetor!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Galileo Mission Schedule

In article <[e-mail]> [e-mail] (Dan Tilque) writes:
>As I understand it, one or both of the asteroid flybys may not happen.
>They will require extra fuel...
>Does anyone have more specifics?  That is, when will the decision be made
>as to whether to make them and how much extra fuel they need for the
>flybys?

The amount of extra fuel needed for the flybys is quite well known.  The
question is how much Galileo uses en route, which could be predicted before
launch only in statistical terms.  Last I heard, a tentative decision
was to be made after Venus encounter, as this would provide enough in-flight
experience to give a better prediction of cruise fuel needs.
--
SVR4:  every feature you ever |     Henry Spencer at U of Toronto Zoology
wanted, and plenty you didn't.| uunet!attcan!utzoo!henry [e-mail]

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

Date: 8 Feb 90 11:59:32 GMT
From: mcsun!ukc!strath-cs!cs.glasgow.ac.uk!icdoc!syma![e-mail]  (Nick Watkins)
Subject: USSR to put spysat pictures in public domain ?!

Two weeks ago Flight International carried a report to the effect that
the Russians were to put their high resolution reconnaissance satellite
pictures into a database managed by the UN. They would thus become
generally available, unless the country in question objected to having
photographs of itself distributed.

 This is not to be confused with the existing lower resolution imagery
being marketed by Soyuzkarta. I have not seen anything else published on
this at all though, does anybody have the full scoop?

Nick

--
Nick Watkins, Space & Plasma Physics Group, School of Mathematical
& Physical Sciences, Univ. of Sussex, Brighton, E.Sussex, BN1 9QH, ENGLAND
JANET: [e-mail]   BITNET: [e-mail]

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

Date: Thu, 8 Feb 90 21:40:49 est
From: Thomas Lapp <[e-mail]>
Subject: RE: Radio Astronomy

In SPACE Digest V11 #17 the journal of the Astro. Soc. of the atlantic
has its latest issue.  I wish to expand on one of the articles:
>                 RADIO ASTRONOMY: A HISTORICAL PERSPECTIVE
>
>                           by David J. Babulski
>
>         Reprinted with author's permission from HANDBOOK OF RADIO
>     ELECTRONICS.
> [...]
>     One of these large communications companies, Bell Telephone
>     Laboratories, assigned a radio engineer named Karl Jansky to
>     investigate the source of this periodic radio interference.  Jansky
>     put together a large steerable radio antenna tuned to a wavelength
>     of 14.6 meters (48 feet).
> [...]
>     Way Galaxy at a wavelength of 187 centimeters (75 inches).  This
>     translates to a frequency of about 150 MegaHertz (MHz).  In addition,
>     Reber was also the first scientist to detect radio emission from the
>     Sun.
> [...]
>         In the United States and Puerto Rico, many professional radio
>     telescopes are operated by a number of organizations, which include
>     Cornell University, the National Astronomy and Ionospheric Center, the
>     National Radio Astronomy Observatory, and the Department of the Navy.
>     The largest radio telescope in the continental United States is the
>     VLA (Very Large Array) interferometer, located in Socorro, New Mexico.

The article also goes on to talk about other radio observatories in the
world.  The only problem I have is the glaring omission of the Green
Bank Radio Observatory located in Green Bank, West Virginia.  Green Bank
is operated by the NRAO (who also built the VLA in New Mexico.  Green
Bank had (until it collapsed last year) a 300 ft. diameter dish which
was steerable in one axis.  It also has three 85-foot dishes, one which
is permanent and two which can move along a one mile-long track.  The
three 85-foot dishes are used for interferometry, which as the article
describes, is a method of making several small telescopes "look" like
one large one.

These dishes are sometimes linked with the VLA in New Mexico to make
a VLBI (very long baseline interferometer) telescope which gives an
effective 'scope the size of a large portion of the United States.

The Green Bank site was one of the major radio observatory sites until the
VLA was built, at which time it became rather a "second billing" site.
One of the reasons the site was chosen (and continues to be useful in
this world of broadcast emissions) is that this valley in West Virginia
is surrounded by hills, and provides a rather radio-quiet area.  All
requests for transmission facilities in the area must be cleared by the
radio observatory before being allowed to go on the air.  As far as I know,
the only radio emissions in the area are from a low power FM public
radio station (WVPR-FM).  Driving through the area in one's car is
interesting because you can get NOTHING much on the radio....

Oh, the other interesting thing about the site is that they have the
Jansky and Reber telescopes at the enterance to the grounds.  I'm
pretty sure that the Jansky telescope is the original, but I do
know that the Reber telescope is a replica.  It is a working replica,
though, and is used to locate local interferance when they find that
the dishes are being interferred with by man-made noise.

Disclaimer: Yeah, I *did* grow up in West Virginia, so I *do* know
            what I'm talking about.  I've even been there three
            times to visit, so there.
                         - tom
--
internet     : mvac23![e-mail]  or  [e-mail]
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Quote   : Virtual Address eXtension.  Is that like a 9-digit zip code?



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

Date: 9 Feb 90 17:10:16 GMT
From: hplabsb![e-mail]  (David Smith)
Subject: Re: More Info on SSX

In article <[e-mail]> [e-mail] (Larry Smith) writes:
>[Max Hunter] prefers to NOT use LH2...  He said that during his whole
>career as a rocket engineer, high Isp was always promoted over
>everything else. He said that it took him years to learn that
>today there is another possibility. And that is structure. If the design
>were left up to him, he would prefer to use a Methane+Oxygen or
>Propane+Oxygen 2000 psi chamber pressure rocket engine.

One reason which has not been mentioned for wanting a non-hydrogen engine
is the difficulty of working with LH2.  The original development of the
Centaur/RL-10 was hampered by the low temperature causing brittleness of
structure and greater thermal contraction; and small molecular size allowing
leaks where no previous fuel or oxidizer would have leaked.  Have these
problems been totally overcome, or can we expect to reduce cost of this
nature in a new generation vehicle by avoiding LH2?
--

            David R. Smith, HP Labs
            [e-mail]
            [phone]

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

Date: 8 Feb 90 20:25:08 GMT
From: orc!mipos3!iwarp.intel.com!omepd!omews10.intel.com![e-mail]  (Larry Smith)
Subject: Re: More Info on SSX


Subject: Re: More Info On SSX

[e-mail] (Paul Dietz) writes:
>Two questions... (1) how much liquid hydrogen evaporates during
>this trip, and (2) how many tanker flights would be required with
>lunar LOX production?

I don't know the answers Paul. But, your questions are good.

I had a chance to talk with Max Hunter about SSX, and he really
prefers to NOT use LH2 (allot of the companies that are evaluating
bidding on SSX are calling him daily, and they all are assuming
high Isp Hydrogen engines. Of coarse the RL-10 is Hydrogen as well,
but Max's philosophy is different). He said that during his whole
career as a rocket engineer, high Isp was always promoted over
everything else. He said that it took him years to learn that
today there is another possibility. And that is structure. If the design
were left up to him, he would prefer to use a Methane+Oxygen or
Propane+Oxygen 2000 psi chamber pressure rocket engine. He also said
that he realizes that rocket engine design has been frozen for 15
years, and one just cannot buy a Methane or Propane engine off
the shelf. He said that allot of the engineers that are starting to
seriously look at SSX are assuming high Isp, high chamber pressures,
aerospikes, etc ... . He doesn't think such things are needed if the
structure of the vehicle is done properly. As to the RL-10, he said
an uprated version is being evaluated (sorry, no details). In his
opinion, he thinks that P&W's RL-10 was one of the best rocket
engine design jobs done so far. He believes that Rocketdyne has
gone in the wrong direction with the SSME. It remains to be seen
what kind of role he will have during the bid, bid selection process,
and then development.

He said there are 3-4 technical things about SSX that need a good
"thrashing out", and he is very excited about that now starting
to happen with the companies thinking of bidding on SSX.
He hopes though, that they will do so in the same spirit as he.
In other words the Keep It Simple and Inexpensive (KISI ?)
principle.

About the Lunar Society, Max said that it was started by Jerry
Pournelle. Jerry might be a source of more information about the
Lunar based SSX logistics. Max also said that Jerry can usually be
reached on BIX. He said that Jerry is a good source of information
on SSX because they talk from time to time. I don't know to what
extent the Lunar Society impacts the design of SSX (at least
Max Hunter's vision of SSX).

If I get any more technical information on SSX, I will post it, as
I hope everyone else that gets new SSX information will.

Larry

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

Date: 8 Feb 90 16:57:44 GMT
From: mcsun!unido!mpirbn![e-mail]  (S.Petra Zeidler)
Subject: Re: metric vs. imperial units

I can't help myself, regarding interplanetary probes I find km almost as
unhelpfull as miles (as I'm a German, miles don't mean anything to me;
and most times I am too lazy to transfer them to km).
I'd rather have those distances in lightsec' ,like the distance from
earth; NASA is using hours/minutes/seconds like the rest of the world (I hope),
and the vacuum velocity of light is a natural constant.
(By the way, what about speed in units of c ? ;-) )

About using imperial for the space station ,satellites etc pp:

NASA isn't the only space agency in business, and as the rest is using
metric (as far as I'm informed (what are the Britons using ?)), and it
is quite a inconvenience for a manufactorer to work with such odd numbers,
they shouldn't be surprised if someone took their business elsewhere.
(May Saenger proceed !!)

Greetings to all folks out there, including NASA

           spz

uunet!unido!mpirbn!spz  or  [e-mail]  or  [e-mail]
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------------------------------

Date: 9 Feb 90 23:57:58 GMT
From: elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Galileo Update - 02/09/90


                             GALILEO
                      MISSION STATUS REPORT
                        FEBRUARY 9, 1990

     As of noon Friday, February 9, 1990, the Galileo Spacecraft is 30,906,100
miles from the Earth, 206,700 miles from Venus and is travelling at a
Heliocentric velocity of 83,721 miles per hour. Round trip light time is 5
minutes, 26 seconds.

     Several crucial spacecraft recovery events were planned to occur during
the past week including celestial reference acquisition (SEQID), updating gyro
parameters based on December minical data and a SITURN to lead the sun.  All
these events were successfully accomplished on February 2, 3 and 4,
respectively.

     Commands were sent on February 5 to reconfigure several spacecraft
electrical loads to create sufficient power margin to allow safe power-on of
the SSI instrument and still maintain a safe overall system power margin.

     The first part and second part of the EV-6 sequence memory load were both
successfully transmitted and received by the spacecraft without incident on
February 6 and February 8, respectively.  The EV-6 sequence covers spacecraft
activities from February 7 through February 18.

     Commands were sent on February 6 to power off the NIMS replacement heater
and power on the NIMS instrument.  This action was taken, after interaction
with the Principal Investigator (PI), in response to a perceived low
temperature condition (zero DN reading) in the Focal Plane Assembly (FPA).
The perceived temperature may have dropped to near 60 degree K before action
was taken. This temperature is lower than those experienced in ground based
testing.  However, the PI's preliminary assessment was that this low
temperature condition did not pose a threat to the instrument.  About 18 hours
after instrument power on, the FPA temperature reached 65 degree K, closer to
its flight of allowable lower limit of 70 degree K.

     A set of commands were sent on February 8 to update the Venus flyby star
set, enable bright body fault protection, and for a limited period (about 2.5
hours) close the star scanner shutter to protect the scanner from possible
Venus bright body induced damage.  During the Venus flyby phase, if attitude
reference is lost, it is possible that Venus, a bright body, could be observed
by the star scanner; therefore, to protect the scanner vector bright body
avoidance fault protection  was enabled for a period of about 21.5 hours during
the flyby period.  In addition, planned closure of the star scanner shutter for
about 2.5 hours near closest approach was performed to protect the scanner from
possible damage caused by expected "Venus light" entering the scanner
stray-light field-of-View (>52degree). Subsequent to the 2.5 hour period, the
shutter was reopened and stars reacquired.  Prior to implementing this
strategy,  detailed analysis and testing was performed to evaluate the attitude
control performance under both nominal and simulated fault conditions; no
surprises, anomalies or problems were observed.

     A set of commands were sent on February 7 and 8 to perform EUV and DDS
memory readouts to return stored science data. Other commands were sent on
February 8 to put the EUV instrument into a science data taking mode consistent
with Venus data collection.

     During the closest approach phase, science data will be collected from
instruments and stored on board in the tape recorder for subsequent playback.
Due to telecommunications performance (1200 bps maximum rate), no science data
will be returned in real time.  Early next week, however, some limited amount
of Imaging, NIMS and other science data will be returned to Earth via a
special technique (called DMS MRO) which plays back the tape recorder into the
CDS and then data is telemetered to Earth at 1200 bps.

     The AC/DC bus voltage imbalance measurements have remained relatively
stable and have fluctuated only slightly between 45 and 48 volts (AC) and 18.5
and 21 volts (DC). Review of data covering the transition from all-spin back
to dual-spin (cruise and inertial) operation did not reveal any significant
measurement differences.

 Ron Baalke                       |    [e-mail]
 Jet Propulsion Lab  M/S 301-355  |    [e-mail]
 4800 Oak Grove Dr.               |
 Pasadena, CA 91109               |

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

Date: 9 Feb 90 22:27:51 GMT
From: ucsdhub!hp-sdd!ncr-sd!ncrcae!hubcap![e-mail]  (Robert M. Panoff)
Subject: Kepler fudged the Numbers?

I have heard (or read) recently that Kepler fudged his numbers.
He claimed to have an independent check on his theory, but the charge
is used the theory to calculate the numbers he said verified his theory.

Could someone point me to a specific published article that gives
the particulars of this subterfuge? Thanks. (You all did a fine job
in tracking down the E. Wolf article on anomalous red shifts for me,
by the way.  I even ended up with copies of the original papers from
Wolf himself.)
--
rmp, for the Bob's of the World

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

End of SPACE Digest V11 #28
*******************