Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V08/V8_288.TXT

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Date: Fri, 22 Jul 88 01:05:59 PDT
From: Ted Anderson <[e-mail]>
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Subject: SPACE Digest V8 #288

SPACE Digest                                      Volume 8 : Issue 288

Today's Topics:
            Re: NASA news - Seasat
        Re: A New Holiday? (awkward question)
             Re: Ramscoop engine
               LPS info request
               Re: OZONE cont.
         Comment about science was Re: Rocket engine
----------------------------------------------------------------------

Date: Thu,  7 Jul 88 14:04:19 -0400 (EDT)
From: Ted Anderson <[e-mail]>
X-Andrew-Message-Size: 8462+0
Subject: Re: NASA news - Seasat
Date: 6 Jul 88 19:08:03 GMT

A U-2 just took off, must be 1100.  BTW I saw the Nova on Spy Machines.
Thanks for the previous offers.  I go on vacation again and some fool at
NASA HQ has to send a press release out on a skeleton in a closet [well
not that bad].  Let me see if I can address all these notes in
a single article [the last time was grossly misinterpreted].  What's
this doing in space.shuttle?

In article <[e-mail]> [e-mail] (Jim Meritt) writes:
>In article <[e-mail]> [e-mail] (Mike Wooding) writes:
>} How does the radar altimeter decouple its "height" above ocean
>} surface from the "height" of the ocean's surface? What scales
>} are involved (+-10 meters)? A reference point?
>
>There is an altimeter on the geosat that is a follow-up to the seasat
>one.  I do the real-time processing of the data - you not only get
>"height above ocean", but significant wave height, winds, and a measure
>of roughness off the altimeter.  (probably more, but that is all I lift).
>This can be used to get current "edges", fronts, eddy locations, and all
>kinds of neat stuff.  I asked about satellite oceanography earlier, but
>didn't hear about anyone else using altimeter data for oceanography.

This is basically correct.  Let me sort out some things.  We have
questions of scale and decoupling.  Now, I didn't work on the Altimeter,
(I worked on the SAR) but I had it as a grad school project and talked
to most of the people since they were across the street.

The Altimeter sent out a 1 ns chirp [square wave].  This gave an inherent
resolution of 30 cm (one of GMH's nanoseconds).  This made lots of
assumptions:
1) the spacecraft was oriented perfectly vertically, the reality was at
800 KM a slight difference in angle is critical.  The pulse (chirp) hits
the earth in a spherical manner and it radiates it's point of contact.
Now the footprint was designed to be 1 KM (if this seems gross,
please make an other altimeter suggestion [exer. for reader: why can't
use you a laser: answer: won't penetrate clouds].  Anyway, you send out
this perfectly spherical chirp (pulse of 1 ns thinkness against a
topography of unknown surface roughness, and you get a signal back which
is distorted by troughs and peaks of various wave types or land forms.
(Like plane cross-sections).  Yes, you can get undersea features like
canyons and seamounts, but all the instrument does is solve D=cT.

The decoupling isn't done using ground stations in realtime, much too
expensive and the real-time compute and relativistic effect is murder.
Basically I have would have to summarize this book on Accuracy
Assessment of Orbit and Height Measurement for Seasat.  There are models
for satellite orbit which take gravitational anomalies in account, these
are plugged into the T data and the sea height and state are "solved."
Remember this is all done in nano seconds precision.


Also written:
>The position of the satellite can be determined in three-space (X, Y
>and Z co-ordinates, with no reference to the radius of the Earth), by
>the use of radar data from several observers.  Studies of the motion

This was done infrequently as verification.  I have the list of tracking
station, but it was not radar, only radio.

>derived mathematically from the parameters of the reference geoid,
>which was derived from studies of satellite motion in three-space, not
>satellite altitude.  The expected mean sea level can then be compared
>with the actual sea level observed by the radar altimeter, to
>determine the variations caused by tides, waves, and meteorologic
>phenomena.
>
>An aside on SeaSat 1 -- The satellite failed some time before the end
>of its expected service life.  A persistent rumor states that it was
>intentionally disabled, possibly by aiming sensors at the Sun; the
>purported explanation was that it was able to detect the wakes of
>ballistic-missile submarines.
>
>Kevin Kenny                       UUCP: {ihnp4,pur-ee,convex}!uiucdcs!kenny

Also:
>status. I've met one of the engineers in charge of building and
>testing Seasat, and he is still bitter about what happened. It was
>paul cooper

I will be curious, who?

Lee @ JPL wrote:
>The investigation into the failure of Seasat assigned the probable
>cause to a short across the slip rings that transfer the power
>generated by the solar cells to the power buss where the solar panels
>rotate.  They attributed this to the poor design of the slip rings
>that had the various voltages (48 rings) alternating plus and minus,
>creating the maximun potential to catastrophic electical short.  It
>was shown  that there was a galling problem (in the ring bearings I
>believe) that created metal slivers.  These slivers more than likely
>shorted the main power buss at the rings. The telemetery showed large
>voltage and current excursions in the milliseconds prior to loss of
>signal from the spacecraft.
>
>I too have heard unconfirmed rumors of the possibility that SSBM wakes
>could be seen in the radar imaging data.  I was clear on the images
>that I saw that surface wakes were very visible.
>
>The spacecraft lasted only 90 days in a planned life of one year.  I
>have had people tell me that they were not unhappy that the spacecraft
>had shut down because of the enourmous quantity of data that was
>pouring in.

We called Seasat-A then -1 after launch (B's and C's were planned as
exercises).  The "slip ring" on the Agena bus was the cited case of
failure by the Congressional Investigative Service.  LMSC [Lockheed
Sunnyvale] had the burden slapped on them.  They had "gotten too lax in
the quality control on Agena boosters.  You have to understand this
satellite was slapped together with parts of an existing booster, not
designed from scratch.  JPL's scientists were too lax in overseeing
LMSC Corp.  So said Congress.  So how would you lose $90M of the
People's money?

Regarding FMB subs: shortly before I came on board the project, the
Navy Department came by and the SAR group had discussions about
resolution, visibility, etc.  They didn't want this thing flying at all.
Fortunately, other parts of the Navy like the Numerical Weather Central
people did want it.  Compromises were made.  This is the SAR now, not
the altimeter.  [Oh, SAR== Synthetic Aperature Radar, aka Side-looking
Radar, SLAR].  These fears were partially unfounded because the digital
processing time for one image was 2 weeks.  Partially because it could
show where they had been rather than where they were.

Optically processed images came out in about a week.

Anyway, the project is over, reports are made, a few images were made,
SIR [Shuttle Imaging Radar] is off the ground [having a few problems].
Most of the data sits unused.  Time for other projects (in this case
Magellan).

Some reflections, the other day someone stopped me at PARC and noticed
an old and faded Project sticker and expressed the conspiracy theory
yet again [tired of this].  Launching money into orbit is a sticky
thing.  One senior engineer (who will go unnamed) was hoping the Atlas
was blow up on the pad at VAFB because there were no indication his
antenna would unfold in 0-G.  I know others who felt the same way about
the kludges they had installed and got flight certified.  It's like
saying, "Your next school project will make or break your future."
No second chances.

Anyway, we launched at 6:01 PDT. Into the fog, gone in 3 seconds.
We went to Solvang for dinner (about 30 miles from where I went to
college).  Quite a birthday present, three of us (Vickie, myself, and
Dave Drake [now at DEC]) -1,0,+2 days).

BTW: Dave and I tried getting an early v6 Unix system running on a
PDP-11/34 [without MMU].  We learned of Joe Ossanna's satellite tracker
[azel] which was not distributed, too bad, we were the space program.
Years later, I got "track" from Phil Karn [thanks Phil].  And I
occasionally run track with seasat-1 and watch the numbers tick by.
It reminds me a bit of the old film Robinson Crusoe on Mars knowing
something up there is orbiting because of thing you did.

Another gross generalization from

--eugene miya, NASA Ames Research Center, [e-mail]
  resident cynic at the Rock of Ages Home for Retired Hackers:
  "Mailers?! HA!", "If my mail does not reach you, please accept my apology."
  {uunet,hplabs,ncar,decwrl,allegra,tektronix}!ames!aurora!eugene
  "Send mail, avoid follow-ups.  If enough, I'll summarize."

Lee, if you want track, I don't think Phil would object.

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

Date:         Thu, 07 Jul 88 13:05:16 CDT
From: Jonathan C. Sadow <[e-mail]>
Subject:      Re: A New Holiday? (awkward question)

cfa!cfa250![e-mail]  (Jonathan McDowell) writes:

>From article <[e-mail]>, by [e-mail] (Richard Brown):
>> Is my memory playing tricks on me?  I had always thought the actual
>> _landing_ took place on 19 July (Oklahoma time).  The EVA was
>> postponed until the crew had rested, &c.  The "...giant leap for
>> mankind" occurred after midnight.
>
>Yes, your memory is a day out - the landing was on 20 July at 2017:45 UT
>which is 20 July at 1517:45 Oklahoma time (I think?); the EVA was something
>like 0200-0300 UT on 21 July, or late evening 20 July US time.

For the sake of future reference, the official time at which Neil Armstrong
first stepped on the lunar surface is 02:56:20 UT on 21 July 1969, and the
EVA lasted 2 hours and 31 minutes.

Jonathan Sadow
[e-mail]

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

Date: 7 Jul 88 16:40:25 GMT
From: ecsvax![e-mail]  (D Gary Grady)
Subject: Re: Ramscoop engine

In article <[e-mail]> [e-mail] writes:
>
>The ramscoop engine idea is used in larry Niven's books.  I don't know if
>he "invented" it.

I believe the "interstellar ramjet" was first proposed in the 60s by
Bussard.  Someone has walked off with my reference, however.  The first
place I read about it was in an article by Ben Bova about 1965.

>The advantage (especially plot-device-wise), is that with constant
>acceleration, no need for fuel-storage, fusion-propulsion of some kind,
>you could eventually build up speeds close to the speed of light,
>and thus travel long distances in a short period of time (by the reference
>of the ship) because of the relativistic effects of near-light speed.

Assuming constant one-G acceleration to the halfway point and one-G
deceleration to the destination, it turns out that one could reach the
Andromeda Galaxy in something like 25 years of ship time.  Of course,
the trip would be one-way, since things back home would have changed a
mite by the time you returned...

Criticisms of the concept based on current technology are a little silly
-- rather like a 17th-Century physicist pointing out the problems of
sending a probe to Neptune.  We can hypothesize that hundreds of years
hence we'll be able to fuse protium, to create magnetic scoop fields
as big as North America, and to blast any asteroids in our way.  On the
other hand, I have to admit that I wonder how the passengers would
survive the incident radiation, all blue-shifted into very nasty X-rays.
Maybe shielding made of degenerate matter?  Who knows!

There's a Poul Anderson novel published both as _Tau Zero_ and _To
Outlive Eternity_ (I think) about passengers on a runaway Bussard ramjet
that just keeps accelerating.  Presumably they wind up at the restaurant
at the end of the universe.
--
D Gary Grady
[phone]
USENET:  {seismo,decvax,ihnp4,akgua,etc.}!mcnc!ecsvax!dgary
BITNET:  [e-mail]

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

Date: 4 Jul 88 22:14:00 GMT
From: silver![e-mail]
Subject: LPS info request


Hello everyone. I was wondering if anyone out in netland knows anything about,
or can direct to me to information regarding the Shuttle Launch Process
System, GOAL (I believe it stands for Ground Operations Aerospace Language) or
the current state of contract affairs regarding the Launch Process System.

Please send email - if there is enough feedback I will summarize the responses
and post, since this information might be of interest to other
sci.space and .shuttle followers.

Thanks in advance,

-John Copella

[e-mail]
ihnp4!inuxc!iuvax!silver!sl144003

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

Date: 7 Jul 88 17:38:32 GMT
From: ubvax!unisv![e-mail]  (Mike Van Pelt)
Subject: Re: OZONE cont.

In article <[e-mail]> [e-mail] (Keith Lofstrom) writes:
>I'm sure to get flamed for this:

 No doubt.  By your flagrant doubting of Conventional Wisdom, you are
 obviously guilty of ThoughtCrime.

>Biologically Effective Ultraviolet Radiation:
>Surface Measurements in the United States, 1974 to 1985
>J. Scotto et. al.

 [fascinating paper, the very first words I've yet seen on what ought
  to be the real issue -- how much UV is actually reaching the ground?]

>The data in the paper actually show a 0.7% DECREASE [in UV-B] per year.
>Perhaps, before we panic and replace clorinated fluorocarbons with something
>that could be MORE dangerous, we should calm down and look at ALL the data.

Now that's a fascinating statistic.  It's always seemed to me that if
somehow you were to get rid of the ozone in the upper atmosphere, you'd
just get ozone production at a lower altitude.  After all, short-wave UV
does a pretty good job creating ozone from ordinary oxygen.

I'm glad that someone has FINALLY measured the actual ground-level UV,
instead of just assuming that upper atmospheric ozone is the only
thing attenuating UV.
--
"Dreams of flight are universal among space-faring  | Mike Van Pelt
 races, and may form much of the motivation for     | Unisys, Silicon Valley
 becoming space-faring."   --  T'chaih Hrinach      | [e-mail]

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

Date: 7 Jul 88 22:07:10 GMT
From: pioneer.arc.nasa.gov![e-mail]  (Eugene N. Miya)
Subject: Comment about science was Re: Rocket engine

In article <[e-mail]> [e-mail] (Phil R. Karn) writes:
I wrote:
>> Designing and constructing rocket engines is largely an art.
>
>I'm not a rocket designer, but I think I can agree with this.
>
> . . .
>Before castigating the "rocket scientists" for their computational
>backwardness, however, consider what it would take to model a large
>rocket engine like Ariane's Viking on a computer. Pressures in the order
>of 50-60 atmospheres. Hypersonic hot gas flows, with extreme variations
>in temperature and pressure over very short distances and times. Mass
>flows on the order of tons/second.  I don't know how much computational
>modeling of rocket engines is going on now, but it has got to be one of
>the most demanding CAD jobs around.

There is a somewhat alarming thing about some computer people (I think
Phil knows this, he's not one, but I want the net to understand this):
There is a whole lot of this universe which we don't understand.  Some
people view the world as a place where we knows lots, in fact, some go
so far to say, that all that needs inventing has been invented.  That's
none of you right?

One of my favorite quotes (it's in the Unix fortunes someplace goes
"there's a disturbing trend that there is a lot  more unknown stuff
out there than previosuly thought" or something like that, I buchered
this.  Anyway, that's why I'm into science.  That's what distinguished
science from engineering: engineering seeks to find answrs, but science
seeks to understand the questions, and there are a lot of questions.

The problem is you only here various people's ANSWERs here.  Some one
types a note (me included) and some people go off and take things as teh
word of God.  It's like the early laser printing systems (or Xeroxes),
wow! if they went to the trouble of typesetting the stuff it must be
correct!

The truth is, we only have opinions.  We don't understand very much
about our world, and we haven't been on it very long.

From: [e-mail] (Jordan Brown)
>Los Alamos simulates nuclear explosions using their Crays; I suspect that
>the pressures and speeds are somewhat larger than in rocket engines.
>(they like to make color 16mm films of the explosion in various axes -
>temperature, pressure, etc.)

Well, that's very interesting!  I will have to tell my officemate
George!  Maybe the guys at Livermore (Livenomore) can use that method,
too.  Well, I'm being facietous.

Well, see, we are in the business of building models (I keep telling
myself this).  Models get replaced with better models and the cycle
should have some transference.  The key is to model the right thing,
maybe something isn't right about a model, maybe we don't understand ho
ozone is formed (we don't).

Some years ago, I was escorting a VIP around JPL.  We stopped by the
computer graphics lab, and Blinn gave one of his early flyby demos.
As we were walking away, this VIP said, "Great!  We can simulate this
all on a computer!  We don't have to fly to these outer planets! So
expensive, this is much cheaper!"

No: most airplanes don't have electronic computers in them.  I had to
tell this to a noted computer scientist.

Our problem is differentiating reality from what we think we know and
what we would like to exist.  Science has this great way of
pontificating (like networks), but we forgot what distinguishes science
from philosophy and mathematics is testing, verification, rebuilding,
etc.

Anyways, I have pontificated myself too much as late, I should get back
to my ETA-10.

Another gross generalization from

--eugene miya, NASA Ames Research Center, [e-mail]
  resident cynic at the Rock of Ages Home for Retired Hackers:
  "Mailers?! HA!", "If my mail does not reach you, please accept my apology."
  {uunet,hplabs,ncar,decwrl,allegra,tektronix}!ames!aurora!eugene
  "Send mail, avoid follow-ups.  If enough, I'll summarize."

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

End of SPACE Digest V8 #288
*******************