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Subject: SPACE Digest V13 #101

SPACE Digest                                     Volume 13 : Issue 101

Today's Topics:
             Re: Satalite/IS Probe manual
    Re: W. Larrison's Re:Fwd: NASA Plans To Redesign Space Station
         Comparing reliability [Part 1 of 2]
               ROSAT Update - 01/28/91
              Magellan Update - 01/28/91
  Re: Request for Feedback on Proposed Lunar Analog Robotics Contest
              Re: More on space cameras

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Date: 29 Jan 91 04:28:54 GMT
From: swrinde!cs.utexas.edu!news-server.csri.toronto.edu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Satalite/IS Probe manual

In article <[e-mail]> [e-mail] (Roland Stolfa) writes:
>1.    Is there a "manual" that describes what kinds of things a space
>    probe must be capable of in order to maintain trajectory?

Try "Spacecraft Attitude Determination and Control", ed by James R. Wertz,
Kluwer 1978.  This is pretty much the bible on the subject, and it is still
in print.  It is expensive and 850+ pages.  A non-trivial subject.

>2.    Are there actual "manufactures" of space probes?  By this I mean
>    is there any company that might just have a manual on how to "harden"
>    a space craft for flight, what kind of redundancy is needed, etc.
>    or is all of that kind of information classified beyond the reach
>    of the average mear-mortal?  :-)

Not classified, but not published much either.  There are only a handful
of satellite manufacturers, and except for a couple of books on comsats,
I'm not aware of any in-print technical books on the details.  Demand is
too limited to justify a lot of publishing on the topic.  I would also
suspect that some details are proprietary; it's a very competitive market.

>3.    I seem to remember that some of the earlier space probes had
>    core memory and 9-track tape players in them.  Are current probes
>    still using this kind of stuff for some "hardening" reason, or is
>    it out of vogue?

Magtape is still in use, although I don't think modern birds -- ones designed
today, that is, bearing in mind that some old designs are still in use -- are
still using core.  NASA has been persistently interested in solid-state
replacements for magtape, since tape recorders are historically a reliability
trouble area, but none has yet flown that I know of.  Space qualification
requires very high reliability and considerable radiation resistance.

>4.    I have never seen referenced what kind of (and or quanity for that
>    matter) processors are on space probes.  Do any of them use stock
>    CPU's or are they more likely to use custom units and why?

A little of both.  Space-qualification requirements rule out a lot of
routine commercial hardware.  Once the list has been thinned down, the
choice is made based on the requirements of the mission.  Stock CPUs
are used for undemanding things, with custom designs more common when
computing requirements get stiffer.
--
If the Space Shuttle was the answer,   | Henry Spencer at U of Toronto Zoology
what was the question?                 |  [e-mail]   utzoo!henry

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

Date: 29 Jan 91 04:35:22 GMT
From: swrinde!cs.utexas.edu!news-server.csri.toronto.edu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: W. Larrison's Re:Fwd: NASA Plans To Redesign Space Station

In article <[e-mail]> [e-mail] (Fraering Philip) writes:
>3. Maybe these disturbances don't really matter that much (?)(just
>guessing again). After all, a lot of noisy microgravity with people on
>hand might be better than a small amount of 'Perfect' microgravity.

Actually, both have their uses.  The space-station microgravity people were
originally very happy about finally having an *interactive* microgravity
lab, where they could modify experiments in real time instead of getting
one test every few years.  (Said happiness faded as the available power,
astronaut time, and facilities kept shrinking.)  But there is also an
important role for long periods of uninterrupted high-quality microgravity,
which pretty much requires an unmanned free-flier.
--
If the Space Shuttle was the answer,   | Henry Spencer at U of Toronto Zoology
what was the question?                 |  [e-mail]   utzoo!henry

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

Date: Tue, 29 Jan 91 00:19:03 EST
From: John Roberts <[e-mail]>
Disclaimer: Opinions expressed are those of the sender
    and do not reflect NIST policy or agreement.
Subject: Comparing reliability [Part 1 of 2]


>From: [e-mail] ("Allen W. Sherzer")
>Newsgroups: sci.space
>Subject: Why man rate? (was: space news from Dec 17 AW&ST)
>Date: 25 Jan 91 00:25:59 GMT
[Part 1 of 2]
In the months that this has been debated, I have come to the tentative
conclusion that the comparison of launch success rates of various systems
is not really deserving of the heat that has sometimes been generated.
Aside from questions of accuracy of the calculations, it's really not
practical to come up with a single number that adequately describes the
performance that can be expected. With the more valid approach of a complex
statistical analysis, there will often be situations in which one system
or the other will be considered better, depending on the exact task to
be performed. Nevertheless, overall ratings do give some information, so
discussion is worthwhile as long as people take it with a grain of salt
(like the college football team ratings :-).

>>I just got out some Martin Marietta literature on the Delta.  In it they
>>advertise a launch success rate of 93.9%.
>You need to look deeper since Martin makes the Titan not the Delta. They
>will fudge the figures to make Titan look better.
>In the entire 30 year history of the Delta this is an accurate figure.
>However, their success rate over the last 13 years is 98.33%.

And of course the pro-Delta folks will want to use the figures that
make Delta look good, though I believe they will still make an effort to
be fairly accurate. A few months ago I saw a 1989 Delta promotional film
that used the figure of 96%, which I believe was their prediction for the
success rate of upcoming launches. That *is* a good rate by current
standards, better than Ariane (I think).

Both Delta and the Shuttle are sufficiently reliable and have flown a
sufficiently small number of missions that operational records are not
really an extremely accurate predictor of future performance, and the
continual improvement of both systems makes the job even harder. For
instance, before the last Challenger flight, the Shuttle had a 100%
success rate, which was clearly not a good predictor. Immediately after
Challenger, the overall success rate was something around 96%. Analysis
of the accident revealed that it was the result of a failure mode that had
previously received inadequate attention, namely the stiffness of the solid
booster O-rings at low temperatures. That failure mode was pretty much
eliminated, as well as many others that turned up during the investigation.
The net effect was to make the Shuttle even more expensive to operate, but
hopefully safer. After the changes, there are three approaches for using
launch success rate as an indicator of future performance: (1) regard the
Shuttle as a completely new craft, with only a small number of launches, and
thus not much direct evidence for good future performance, (2) continue
to keep a tally from the start of the Shuttle program, thus equating the
old and new systems, or (3) start with the same number as in method (2),
but consider that since known failure modes have been eliminated or reduced in
likelihood, the indicated success rate is actually higher than the number
produced by (2). Methods (1) and (2) basically reflect a concern that the
modifications may introduce significant new failure modes. My own opinion
is that extensive analysis and the launches since Challenger do not *appear*
to have turned up introduced failure modes, so the indicated future performane
probably *is* higher than the overall success ratio to date.

>Independant
>estimates of Shuttle success rates put it at about 95% and it's operational
>record so far is about 96.66%.

It's hard to keep count with the mission numbers all out of sequence, but
I *think* that there have now been either 39 or 40 launch attempts, one
of which failed. This puts the operational record at around 97.4%, with,
as I said, some hope that the known repairs make the performance-based
prediction of future reliability somewhat better than that.

The 95% figure is about the most pessimistic available, thus often used
by companies who want to promote alternates to the Shuttle (fair enough,
I suppose). NASA's best attempt at an accurate estimate, which they claim
to be based on a fairly conservative analysis, is that reliability (in terms
of loss of orbiter, I think) is somewhere in the range of 98.5-99%. (They
have a single number as a best guess, but I forgot what it was.) This
translates roughly to one or a couple of orbiter losses expected over the
lifetime of the Shuttle program, an estimate which NASA does not now
attempt to hide.

I think it is clear that before Challenger, NASA Shuttle reliability
estimates were rather poor, based on excessive optimism, and without
much effort to make sure that they were accurate. After Challenger and the
blast of criticism, NASA has a tremendous incentive to present risk
estimates that are as realistic as possible, lest they be accused of
dishonesty in the event of a future accident, and they are known to
have expended vastly more effort on risk analysis than had previously
been the case. I think it is also interesting that they tend to avoid
public use of their estimate except when forced to by congressional
hearings, etc., which may indicate that their number is lower than they
would like. One might speculate that if they did not feel constrained
to produce an accurate "best guess" or conservative number, then they
would have come up with an estimate that they would be happy to brag
about. Added to the fact that NASA knows much more about the Shuttle than
anyone else and has a tremendous base of knowledge in launch systems,
this tends to make me believe that the NASA estimate of Shuttle reliability
is *probably* the most accurate estimate that we can currently hope for,
and even then it *may* turn out to be a little on the conservative side.

All of which, of course, is not much comfort if there *is* an accident
resulting in loss of shuttle or human life, except perhaps as some
reassurance that such loss was the result mostly of chance rather than
of gross negligence (as seen in the commendable decision by the Soviets
to resume immediate use of the Zenit boosters after one had exploded). No
current launcher has anywhere near the safety record of commercial airlines.

Another word on the use of "percent reliability" in general - if you are
launching a hundred payloads of some bulk material and need to estimate
how many extra loads to launch to make up for losses, this is indeed the
best figure to use. If, however, you're launching a single device or
a number of noninterchangeable components, and need to know the chance that
there might be a failure (which could seriously hamper your project), then
chance of failure (i.e. 1 in n) is the measure you need, and it's much
better to deal with it that way. That's because for this use, and with
highly reliable launchers, percent reliability is highly sensitive to even
small errors. For instance, if you have a satellite you want to launch,
and you know the launcher is considered either 98% or 99% reliable, that's
only a ~1% uncertainty in the number you have, but 2 to 1 ratio in the
odds of failure. Note that this caution mainly applies to use of the numbers
in rough calculations - if sufficient care is taken, the two approaches
are equivalent.
[Continued in Part 2]
      John Roberts
      [e-mail]

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

Date: 28 Jan 91 16:12:18 GMT
From: pacific.mps.ohio-state.edu!zaphod.mps.ohio-state.edu!usc!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: ROSAT Update - 01/28/91


                           ROSAT STATUS REPORT
                            January 28, 1991

     The German Space Operations Center (GSOC) declared a spacecraft
emergency for the Rosat spacecraft on January 26, 6:19 AM UTC.  A 26 meter
antennas was scheduled in real time to support the emergency.  The spacecraft
disconnected is on-board systems due to a loss of power.  On January 26,
15:00 UTC,  GSOC cancelled the emergency and the spacecraft was in standby
mode.

     GSOC requested that 26 meter antenna in Madrid be used to support a
boost manuever on the Eutlesat II-F2 satellite, since the Weilheim was
pulled off for the Rosat emergency.  The Madrid antenna was used to support
the maneuver on January 26 from 8:30 AM through 9:28 AM (UTC), and the burn
was successful.

     GSOC also reports that downlink was reestablished with the ROSAT
spacecraft on January 27, 4:51 AM, using the Weilheim station.  All
spacecraft systems are operating nominally.
      ___    _____     ___
     /_ /|  /____/ \  /_ /|      Ron Baalke         | [e-mail]
     | | | |  __ \ /| | | |      Jet Propulsion Lab |
  ___| | | | |__) |/  | | |___   M/S 301-355        | It's 10PM, do you know
 /___| | | |  ___/    | |/__ /|  Pasadena, CA 91109 | where your spacecraft is?
 |_____|/  |_|/       |_____|/                      | We do!

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

Date: 28 Jan 91 23:09:50 GMT
From: swrinde!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Magellan Update - 01/28/91


                         MAGELLAN STATUS REPORT
                           January 28, 1991

     The Magellan spacecraft and its radar system continue to perform
nominally.  All STARCALS (star calibrations) and DESATS (desaturations) of
the weekend were successful.

     On January 25, the mapping command sequence M1026 was sent to the
spacecraft, along with the associated parameter files.  The 4-day sequence
returned Magellan to its non-occulted mapping mode.  Return to the normal
Tuesday uploads will start with tomorrow's M1030 upload.

     Commands were sent up earlier today to perform the first of several
in-flight tests of tape recorder "A".  The tests will start at 11:20 AM PST
and will include playback of data from two of the suspect tape tracks at 268
kbps and 115 kbps.

     The SAR (Synthetic Aperture Radar) Data Processing Team has processed
standard image strips for orbits up to orbit #1111.  Since Magellan is now on
orbit #1370, it means that the team is processing radar image data from 35
days ago, that is, from Christmas Eve.  This is because the processing of
standard images must wait for data tapes to be shipped from the DSN (Deep
Space Network) stations in Australia and Spain.  During the first 40 days of
mapping these tapes were "expedited" - delivered to JPL by courier - so that
early images could be processed and evaluated quickly.
      ___    _____     ___
     /_ /|  /____/ \  /_ /|      Ron Baalke         | [e-mail]
     | | | |  __ \ /| | | |      Jet Propulsion Lab |
  ___| | | | |__) |/  | | |___   M/S 301-355        | It's 10PM, do you know
 /___| | | |  ___/    | |/__ /|  Pasadena, CA 91109 | where your spacecraft is?
 |_____|/  |_|/       |_____|/                      | We do!

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

Date: 29 Jan 91 01:34:25 GMT
From: deccrl!news.crl.dec.com!shlump.nac.dec.com!sousa.enet.dec.com!sndpit.enet.dec.com![e-mail]  (Willie Smith)
Subject: Re: Request for Feedback on Proposed Lunar Analog Robotics Contest


In article <[e-mail]>, [e-mail] (Douglas E Helbling) writes...
>
>    I am working toward putting together a robotic competition for small
>    rover-like vehicles.  The contest would take place on the Oregon
>    desert at the Oregon Moonbase, an earth analog of a lunar lavatube.
>    The Oregon Moonbase is a project of The Oregon L-5 Society, Inc., a
>    chapter of the National Space Society.  The robotics competition,
>    if it comes to reality, will probably take place in late 1992 or
>    early 1993.

The Sunswick Engineering team will be there with the Tycho and Waldo
vehicles if this happens.  Just what we've been looking for!

>       b) Size - the current limit on physical size for the "unextended unit"
>          is two feet square.  (Must fit in a box two by two by two feet.)
>          The notion that a robot could "expand" out of its shipping crate
>          after delivery (particularly for units basing their design on
>          insect models from the natural world) is acceptable.

Aw, c'mon, make it a three-foot cube, so we can bring Waldo (the real thing)
, instead of just Tycho (the toy).


A few more things I'd like to see thrown in for good measure:

1)    All teleoperated vehicles should properly emulate the 3-second
    speed-of-light communications delay.

2)    Make the contest a little more useful, and ask that some useful
    work be performed.  F'rinstance, clearing a landing field, digging
    habitat foundations, covering habitat modules, etc.

Sounds like a blast, we'll be there!

Willie Smith
[e-mail]
[e-mail]
{Usenet!Backbone}!decwrl!sndpit.enet.dec.com!smith

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

Date: 28 Jan 91 15:27:27 GMT
From: usc!sdd.hp.com!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!watserv1!watcgl!imax![e-mail]  (Hugh Murray)
Subject: Re: More on space cameras

In article <[e-mail]> [e-mail] (Garrett Wollman) writes:
>Maybe the guy from IMAX Systems (is that still their name?) can talk a
>bit about the "Large Format Camera" (which *is* one of theirs,
>right?)... I remember seeing a feature on them on "Venture" about
>three or four years ago, when they were just starting to make waves...
>
>
>Does NASA pay to have the LFC up there (as a supply), or does IMAX--or
>a file producer--pay to put it there, so that they can make a movie of
>it later?
>
>-GAWollman
>
>Garrett A. Wollman - [e-mail]
>

Imax Systems Corp. is the name of the company and IMAX(r) is the name of
our motion picture system which encompasses a large film format (each frame
is 2.74" wide by 1.91" high, oriented horizontally on standard 70mm film stock),
special cameras and projectors, all patented.

The space films have been co-sponsored by the Smithsonian and Lockheed. We
have two cameras specially constructed for Shuttle use, an in-cabin camera
and a cargo bay camera which sits in a can at the very rear of the cargo bay.


Hugh Murray     [e-mail]
Imax Systems Corp.

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

End of SPACE Digest V13 #101
*******************