PLEASE NOTE:


*

CCNet DIGEST, 14 June 1999
--------------------------


     POEM OF THE DAY

     THE ICE CORE  (after reading Nature, June 3 1999)

     Sweating in their polar gear at minus fifty
     the drillers extract and rack the cores of ice,
     four hundred thousand years of climate
     locked in frozen water rich with dissolved gas,
     dust, ash, samples of air, debris from space.
     Half a world from Vostok the careful probes
     reveal ice ages, climate changes, past snapshots
     of a world we never saw, but which may come again.
     At intervals of a hundred thousand years the ice
     returned, and after its reluctant long retreat
     the greenhouse gases surge to earlier levels -
     is this the clue we seek, cause and effect,
     or was it simply that a colder Earth resulted
     in less production of methane and the rest?
     Why is the present quantity of  greenhouse gas
     much higher than it ever was?  What have we done?
     Do slow changes in Earth's orbit bring the ice
     or could it be that other source we fear now,
     a fimbulwinter caused by dust and smoke
     and burning forests after some destructive impact?

     11.6.99

     Malcolm Miller
     stellar2@actonline.com.au



(1) THE SPACEGUARD PARADOX: OR WHY WE NEED TO SEARCH FOR THOSE
    ASTEROIDS MOST LIKELY TO HIT US HARD
    Benny J Peiser <b.j.peiser@livjm.ac.uk>

(2) WHY WAS THE EARTH-APPROACHING ASTEROID 1998 OX4 LOST, AND WAS IT A
    BIG DEAL TO LOSE IT?
    Robert McMillan <bob@LPL.Arizona.EDU>

(3) LOSING ASTEROID 1998 OX4 AND ITS IMPLICATIONS
    Brian Marsden <marsden@cfa0.harvard.edu>

(4) ASTEROID HEADING FOR EARTH GOES MISSING
    THE TIMES, 14 June 1999

(5) THE E.A.R.N. DATABASE OF PHYSICAL & DYNAMICAL PROPERTIES OF NEOs
     Gerhard Hahn <gerhard.hahn@dlr.de>

(6) SOME HIGHLIGHTS FROM THE TORINO INTERNATIONAL SPACEGUARD WORKSHIP:
    IMPACT (INTERNATIONAL MONITORING PROGRAMS FOR ASTEROID AND COMET
    THREAT)
    David Morrison <dmorrison@arc.nasa.gov>

(7) AIAA MEETING - SPECIAL SESSION ON METEOR PLASMA PHYSICS
    Peter Jenniskens <pjenniskens@mail.arc.nasa.gov>

(8) CORRECTIONS ON ERRORS IN TPS PRESS RELEASE
    Linda Wong <tps@planetary.org>


========================
(1) THE SPACEGUARD PARADOX: OR WHY WE NEED TO SEARCH FOR THOSE
    ASTEROIDS MOST LIKELY TO HIT US HARD

From Benny J Peiser <b.j.peiser@livjm.ac.uk>

Hardly a week has passed since Andrea Milani presented his calculations
for a potential earth-impact of asteroid 1998 OX4 in the year 2046.
Most of us who listened to his report pretty seemed convinced that this
latest PHA with a non-zero collision probability would not make
the news headlines. The reason seemed obvious enough: The chances of
OX4 impacting were one in ten million - simply too small to attract any
media attention. Yet in the debate that followed Andrea's exposition,
most participants failed to realise that the *real* story of OX4 was
not so much the rather minuscule value given for its impact chances.
Instead the fact that this potentially hazardous asteroid was lost
after just 9 days of observations featured prominently in last week's
discussions and some news reports in the UK.

I believe that these deliberations and reports about 1998 OX4 and how
it was lost will bring about a whole list of new questions, questions
which differ considerably from previous debates about XF11 or AN10
(i.e. PHAs with diameters larger than 1km).

Robert McMillan, the Principal Investigator of the Spacewatch Project which
discovered OX4 back in 1998 (the discovery was made by Jim Scotti of
XF11 fame), gives a thought-provoking explanation as to "why 1998 OX4
was lost" (see below). Bob's comment raises a number of interesting
questions about whether or not 'smaller' NEOs, such as OX4, are
worthwhile searching or following up - given that there may be as many
as 10,000 to 50,000 objects in this size-category (i.e. 300-600m).

I noticed, however, that in his statement Bob McMillan does not refer
to the fact that OX4 is of particular interest mainly due to its
non-zero impact probability rather than its size or its nature as one
of many PHAs. In fact, it is this small impact risk which is the main
reason why *losing* it - and the prospect of losing similar objects in
the future - poses a real problem for the NEO search community. Brian
Marsden, whose most enlightening analysis of the impact threat posed by
asteroid 1997 XF11 has brought about the current understanding and
debate of resonant-return impact risks, not surprisingly underlines
that "we have reached the point were [follow-up programs are] the
single most important observational need" (see his comment below).

Another question raised is that of the 'background' hazard for NEOs in
this size-category. According to current impact rate estimates, objects
with a diameter of ~300m hit the earth on average every 4000-5000
years. Although the damage caused by 300m asteroids is 'only' regional
(according to David Morrision they can wipe out a small country - and
produce craters up to D = 6km), asteroids of this size are much more
dangerous to us because i) there are many more of them and ii) because
they will consequently impact more frequently. Obviously, the
'background' probability used for calculating the impact risk of 1998
OX4 was significantly lower than the values used for XF11 and AN10. It
is no surprise that losing such an object is perceived as an
"embarrassment" (see Nigek Hawkes' article in today's TIMES).

In short, it would appear that we are facing what I would call the
"Spaceguard Paradox": while the main Spaceguard goals (and its main
search programmes) are focusing on the detection of NEAs with diameters
> 1km, the most likely objects to actually threaten and hit us in the
*forseeable* future are those which diameter smaller than 1km. In fact,
asteroids in the OX4 class are the most dangerous of all given both
their devastating impact effects *and* their impact frequency. If this
interpretation of our current dilemma is fairly correct, could it be
that our current priorities are wrong? Of course, one could argue that
by searching the sky for >1km NEAs, we will inevitably come across many
objects smaller than 1km. Nevertheless, the whole issue of search and
follow-up strategies, access to larger and more telescopes, etc. could
be affected by these questions raised by the OX4 debate.

Tomorrow, an important Spaceguard debate will take place in the House
of Lords, Britain's Upper House in the heart of London. One can only
hope the British Government is wise and far-sighted enough to realise
that there is a growing need for a National Spaceguard Centre. After
all, neither the exploding list of newly discovered PHAs, nor the
overall impact risk will go away. Most likely, the public interest in
and the demands for adequate search strategies will become louder.
Surely, the logical and rational consequence of recent PHA discoveries
(and losses) is to significantly increase and widen our NEO search and
research efforts. A Spaceguard Centre in Britain would be an
appropriate first step to respond to the cosmic challenge we are
facing.

Benny J Peiser
14 June 1999

======================================
(2) WHY WAS THE EARTH-APPROACHING ASTEROID 1998 OX4 LOST, AND WAS IT A
    BIG DEAL TO LOSE IT?

From Robert McMillan <bob@LPL.Arizona.EDU>

Benny,

Your readers may be interested in why 1998 OX4 was lost. It was not
through lack of trying.  The object was discovered on 1998 July 26 (UT)
by Jim Scotti with the 0.9-m Spacewatch telescope on Kitt Peak.  Those
who are familiar with the climate of southern Arizona know that it can
be difficult to observe in the summer owing to frequent (although
localized) thunderstorms.

The object was V mag 20.7 at discovery, and although our discoveries
appear promptly on the Minor Planet Center's NEO Confirmation Page, we
are very conscious that many recovery observers cannot reach that
faint, especially on a fast- moving object with an uncertain ephemeris.
So a fast-mover such as this does get some priority at Spacewatch at
the expense of scanning for further discoveries.

Jim reobserved the object on two epochs the following night, but was
clouded out on the 28th.  By the 31st the Spacewatch observer was now
Dr. Jeff Larsen, who was ready to open and be on the object within 5
minutes, but was still clouded out on Kitt Peak.  However, thanks to
the localized weather pattern, it was clear at nearby Mt. Hopkins where
Carl Hergenrother recovered the object again with the 1.2-m telescope
there.

Kitt Peak remained completely clouded out through the rest of the dark
run in early August, except for Jeff's attempt at recovery on Aug. 3 UT

which was aborted by clouds after he opened.  Dave Balam recovered the
object on 1998 Aug 3 and 4 UT with the 1.8-m telescope of the Dominion
Astrophysical Observatory in Victoria, BC, Canada.

Spacewatch's next opportunity to observe was Aug. 20, but by then the
object (at 20.5 magnitude) was immersed in the Milky Way. By the
September run, 1998 OX4 was too far west to observe. So Balam's
observations were the last to be reported to the MPC.

With the help of Bruce Koehn of LONEOS's fine website at Lowell
Observatory (http://asteroid.lowell.edu/cgi-bin/koehn/obsstrat) we see
that the 1 sigma uncertainty in 1998 OX4's position in 1999 March
when its magnitude peaked at about V=21.6 was a few thousand
arcseconds. That means too much sky area to search for such a faint
object. At the next opposition passage the uncertainty will be in the
10's to 100 thousand arcseconds (1 sigma again), though it peaks at
about V=20. It'll again be in the Milky Way then. It's fainter than
V=25 at the present time.

Is it worthwhile to discover objects during a season of persistently
bad weather?  I think so, because even if the objects cannot be
recovered, the discoveries contribute to the accumulation of statistics
on the distributions of asteroids with absolute magnitude and orbital
parameters, and to an extrapolation to their total number. Jedicke
and Metcalfe (1998 Icarus 131, 245-260) showed how much can be done
with very short arcs on a number of main belt asteroids. Spacewatch
will be doing similar analyses on its discoveries of Earth-approachers.

Is it worthwhile to discover objects that faint when the recovery
network is so leaky at those magnitudes? This is a "chicken-or-the-egg"
problem:  if no asteroids were discovered fainter than 20th mag then
there would be no motivation for recoverers to reach fainter. In any
case, reaching fainter tends to explore the distribution of smaller
sizes, which leads to the next question:

Are objects as "small" as 1998 OX4 important enough to follow,
considering that there could be 10,000 objects of this size and
that Spacewatch is not finding such small objects fast enough to
significantly mitigate the hazard of their impacts? I think they
are worth discovering and following for scientific reasons. The
distribution of sizes of small asteroids holds clues to the cohesive
strength of asteroid material (Durda, Greenberg, and Jedicke 1998
Icarus 135, 431-440).  Small asteroids may also rotate rapidly, and such
rotation also provides information on the binding strength of asteroid
material (Pravec 1999 ACM abstract).

How can losses such as 1998 OX4 be prevented?  For the moment I'll put
aside the question of whether it is worth following up every faint Earth
approacher; there will always be some objects at the limit of detection
that will get lost, so one can question whether precious observing
resources should be overly concentrated on that one aspect of the
campaign. Such objects might be more easily rediscovered at another
epoch when they might be brighter.

Additionally, improving the followup network is too large an issue for
this email message, so I will restrict my remarks to the specifics of
the case of 1998 OX4.  For much of the time that 1998 OX4 was at southerly
declinations it was also in the Milky Way.  This is inevitable for
low-inclination asteroids.  Although Grant Stokes' LINEAR asteroid
survey group at MIT apparently has advanced software to discover and
recover asteroids in those crowded star fields, their all-sky survey
mode does not currently reach faint enough to have recovered 1998 OX4,
nor do I know whether it would be technically feasible or politically
appropriate for their methodology or software to be distributed to the
world-wide recovery network.

Certainly an expanded image scale helps in crowded fields, such as one
obtains with a "large" telescope.  The last observation of 1998 OX4 was
by Dave Balam, not by virtue of a southerly observatory location (his
latitude is +48.5 degrees!) but thanks to the 1.8-m telescope he uses.
A "large" (2-m class) telescope in the southern hemisphere with an
image scale of less than one arcsecond per pixel and good software for
crowded fields would be effective for recoveries of faint, fast-movers
in the Milky Way, but again, that would have to be traded against other
(probably more efficient) ways to accelerate discovery and follow-up of
Earth-approachers in general.

Bob

Robert S. McMillan
Principal Investigator
Spacewatch Project
Lunar and Planetary Laboratory
University of Arizona

===================
(3) LOSING ASTEROID 1998 OX4 AND ITS IMPLICATIONS

From Brian Marsden <marsden@cfa0.harvard.edu>

Dear Benny,

     It was good to see Bob McMillan's attempt to place the 1998 OX4
situation in perspective. As I have stressed many times, most recently
at the Turin workshop, extended follow-up at the first apparition and
recovery at subsequent oppositions require access to large-aperture
telescopes, in both the northern and southern hemispheres, and
well-enough separated in longitude that vagaries of the weather, such
as the summer "monsoons" in the southwestern U.S., can be overcome.
Indeed, many of us involved with the Turin subgroup 1, which was
concerned with search and follow-up programs, felt that we have reached
the point where this is the single most important observational
need--yet it has traditionally been the area in which the least amount
of progress is made. Of course, the problem is most severe for the
intrinsically fainter objects, but it is also applicable for brighter
objects (e.g., those believed to be relevant to the goal of discovering
most of the km-sized objects) at distant oppositions.

     At absolute magnitude H = 21.3, 1998 OX4 is presumably much
smaller than 1997 XF11 and 1999 AN10, the first two cases where
possible earth impacts were identified during the next half century.
Indeed, much of the interest in these objects has been because they are
in the range where an impact would have global consequences.  If we
direct our attention to intrinsically fainter objects, more and more
cases of noticeable impact probabilities will surely be found. At one
level, I am delighted that my drawing attention, originally in the
CCNet on June 8 last year, to the post-2028 danger of 1997 XF11 has
given rise to a "cottage industry" of making such calculations. At
another, I understand Bob's rather guarded questioning of whether it is
worth following up objects as small as 1998 OX4. Since it had  H = 22.0
or brighter, 1998 OX4 could qualify as a PHA, and it was indicated as
one in the discovery announcement on MPEC 1998-O27 on July 31. The H =
22.0 limit, corresponding roughly to a diameter of 200 meters, was
selected to include objects that might yield tsunami damage on a rather
global scale. Even so, the limit is arbitrary in the sense that there
could always be a fainter, sub-Tunguska-sized object, not classified as
a PHA, that on discovery yields a 99-percent chance of earth impact
just a few days later.

     When it comes to the impact-probability calculations, where, if
anywhere, should one draw the line?  That is indeed the question. But
since there are now so many PHAs, with 75 of the 179 having been
discovered during the past 18 months, and with some people perhaps
wishing to extend the limit to fainter than H = 22.0, it is really
mainly a question of when the specific possibilities of impact are
identified. For 1997 XF11 the 2040 possibility was identified from the
first 88-day arc of observations. For 1999 AN10 the 2039 possibility
was from a 38-day arc, the 2044 and 2046 possibilities from a
123-day arc. The 1998 OX4 case involved only a 9-day arc. Of course, it
is always in principle possible to recognize the possibility of an
impact when the observations cover a smaller arc, but the orbital
uncertainty then means that the actual probability of an impact decades
later will also be smaller. However, if it had in fact been possible to
extend the Spacewatch observations of 1998 OX4 until mid-September,
thus yielding an arc of some 50 days, chances are that the possibility
of a 2046 impact, estimated as 1 in 10 million from the initial 9-day
arc, would completely vanish--just as the 2040 impact possibility for
1997 XF11 disappears with the consideration of the 1990 data.

     But that's not what happened with 1999 AN10, when -surprisingly-
Frank Zoltowski's recovery observations confirmed a close approach in
2027 and substantially enhanced the likelihood of impact during the
following two decades. Furthermore, if the 2046 impact possibility for
1998 OX4 had already been identified during the week or so following
the publication of the observations from Day 9 on Aug. 7, a special
campaign for further August-September observations could have been
launched, using appropriately large telescopes.

     It's a tricky problem. While there is clearly merit to following
up PHAs, as well as other NEOs, both astrometrically and physically,
with too many computations of non-zero impact probabilities from
short-arc orbits, there is the danger of going on too many wild-goose
chases, with unnecessarily large efforts (including "peer review"
recomputations of the impact probabilities by others) expended on
objects that turn out, not only not to be any threat to the earth
during the foreseeable future, but not even to be particularly
interesting. Meanwhile, more significant objects could be ignored.
Against this one weighs the reassurance that the additional
observations in most instances will render an object harmless. As with
the other dangers we face daily, some reasonable balance is in order.
Since 1998 OX4 is one of very few (i.e., two) objects for which
non-zero impact probabilities are still extant for upcoming decades, I
suggest we simply tag it as of some interest to the astronomical
community, but about which nothing can be done unless it is
accidentally rediscovered.

Regards
Brian

=================
(4) ASTEROID HEADING FOR EARTH GOES MISSING

From THE TIMES, 14 June 1999
http://www.the-times.co.uk/news/pages/Times/frontpage.html?1032133

By Nigel Hawkes, Science Editor

THE good news (sic) is that astronomers have identified an asteroid
that could be on a collision course with Earth. The bad news is that
they have lost it.

The object, called 1998 OX4, was found last year by a team at the
University of Arizona, who tracked it for two weeks.

The information the scientists gathered gave an approximate orbit for
the object, which is believed to be several hundred yards in diameter
and capable of continent-wide destruction if it were to collide with
Earth.

A team at the University of Pisa, led by Dr Andrea Milani, used the
orbital information to calculate the chances of a collision. He told a
conference in Turin last week that there was a one-in-ten-million
chance that it would hit the Earth in 2046 - slightly better odds than
the 14 million to one on winning the National Lottery.

The asteroid is only the second such object found with a non-zero
chance of a collision. And while a one in ten million chance is not
enough to lose sleep over, it is embarrassing that 1998 OX4 has now
been lost. The problem is that the orbit was not known with sufficient
accuracy to track it. If it could be found, the chances are that more
precise observations would dispel the fear of a collision.

Duncan Steel, a British astronomer who specialises in watching out for
potential asteroid collisions, says that the dilemma posed by 1998 OX4
will become increasingly common. "The searches being done in the US are
finding more and more objects that could potentially collide with
Earth - so many that there aren't enough people to keep track of them,"
he says.

"The rate at which these objects are found has increased by three or
four times in the past few years. False alarms are getting more
frequent. Where we fall down is in following up on the original finds."

He is not too concerned about 1998 OX4. "But sooner or later we are
going to find one with a one-in-a-thousand chance of colliding, and
that could set off a panic," he says.

If it happened tomorrow, the Government would have to rely on experts
overseas to give a proper assessment of the danger. "We need much
better machinery in Britain to take responsibility for giving advice,"
he says.

Next week the Liberal peer Lord Tanlaw will ask a question in the House
of Lords, seeking to discover whether the Government has any plans to
establish a national "Spaceguard" programme of observation for
near-Earth asteroids.

Dr Mark Baily of Armagh Observatory says that he believes such a
programme is necessary and inevitable. "There are going to be more and
more of these objects found. If we don't have a national agency, advice
on the real level of risk will have to come from astronomers who do
this sort of work in their spare time, or from those with no allegiance
to the United Kingdom."

The lesson of 1998 OX4 is that, having found near-Earth objects, they
should not be lost again, he says. "I won't lose any sleep over it," he
says. "The risk it will hit us is much less than the risk of a totally
unknown object doing so. All these calculations show is that we should
go on tracking it - if we knew where it was."

Dr Steel does not rate highly the chances of finding 1998 OX4 again.
"It's like finding a needle in a haystack, and then throwing it back in
again," he says.

Copyright 1999, The Times Newspapers Ltd.

==================
(5) THE E.A.R.N. DATABASE OF PHYSICAL & DYNAMICAL PROPERTIES OF NEOs

From Gerhard Hahn <gerhard.hahn@dlr.de>

Dear Benny,

We would appreciate if you could announce the existence of our
database on the CC-Net for wider spread within the interested NEO
community.

With kind regards

Gerhard Hahn

P.S.: It was great to meet you in Turin and talk about NEOs.

-----------

To all friends of NEOs...

We have recently installed an updated, and hopefully improved, version
of the

Data Base of Physical and Dynamical
Properties of Near Earth Asteroids (NEAs)

which is hosted at the European Asteroid Research Node (E.A.R.N.) and
can be reached at the following web address

http://earn.dlr.de/nea

It contains published data on all known NEAs and the corresponding
bibliographic references.

The idea is to update these pages continuously, i.e. add data for new
discoveries as soon as available, the entries for newly published data
will be made on a monthly or so basis. In order to keep the entries up
to date, cooperation with the researcher working in the field is
essential and therefore it would be greatly appreciated if new data
are brought to our attention as soon as possible.

Looking forward to comments and/or suggestions for further improvement
or extension of this service and its possible integration into other
databases.

Gerhard Hahn
Alan Harris
Stefano Mottola
   Institute of Space Sensor Technology  and Planetary Exploration
   German Aerospace Center (DLR )
   Berlin, Germany

==================
(6) SOME HIGHLIGHTS FROM THE TORINO INTERNATIONAL SPACEGUARD WORKSHIP:
    IMPACT (INTERNATIONAL MONITORING PROGRAMS FOR ASTEROID AND COMET
    THREAT)

From David Morrison <dmorrison@arc.nasa.gov>

Turin
June 1-4, 1999

* Nature of the Impact Hazard: For any given size (energy) of potential
impactor, there is a "background probability" of impact from unknown
objects. As more NEOs are discovered, this background probability
decreases. However, occasionally a newly discovered NEO is found to be
on an orbit that repeatedly brings it close to the Earth, and that has
a non-zero chance of impact at one or more discrete times in the
future. As the orbit is refined, these discrete moments of risk will
generally disappear. There are no more than a handful of truly
threatening NEOs (D >1 km) in any century, and perhaps none.  The
progress of Spaceguard can then be thought of as a replacement of a
general background risk with discretely identified risks from a very
small number of NEOs, which will of course be carefully tracked to
determine their future orbits with high precision.

* Appreciation of the Risk:  Although the public is broadly aware of
the impact hazard, and there has recently been evidence of increased
interest in the U.S. Congress and the UK Parliament, it appears that
the reality of the impact hazard has still not been accepted by many
decision-makers, including most professionals in the risk assessment
profession. Geof Sommer of RAND provided the workshop a provocative
discussion of how we might formulate some of our issues in terms that
can communicate better with policy makers and perhaps enhance the
credibility of NEO impacts as a risk issue.

* Search and Discovery: The rate of discovery of NEAs has greatly
accelerated, with the bulk of the recent discoveries coming from the
MIT LINEAR program using a single 1-m telescope.  Grant Stokes reported
that a second identical LINEAR telescope is about to begin regular
operations, and other systems are also working, as described in
previous NEO News notes. However, to meet the Spaceguard objective of
discovering 90% of NEAs >1 km in diameter by 2009, it will be necessary
to extend the search down to approximately visual magnitude 20.5, which
has not been demonstrated for LINEAR or other systems that use 1-m
telescopes. Thus it is not yet clear whether an expanded network of 1-m
telescopes can do the full job.

* Follow-up Observations: NEA discoveries must be rapidly followed up
to determine orbits. Many groups, including amateur astronomers, now
contribute to follow-up observing programs. This work is quite
effective, but most of the present observers do not have large enough
telescopes to observe discoveries that reach to magnitude 20.5.  Thus
as the discovery rate of faint NEAs increases, there may be a crises in
follow-up. We also lack follow-up capability in the Southern
Hemisphere, which could lead to the loss of many NEAs that are moving
south at the time of discovery.

* Availability of data: As the number of NEA observers increases, and
as more people have the capability to calculate orbits and impact
probabilities, it is essential to move toward more rapid dissemination of
data on NEA positions. Probably a system can be developed soon to
provide automatic, essentially instantaneous posting of observational
data on the Internet.

* Cooperation and Coordination: A successful Spaceguard program
requires detailed coordination of observations to avoid redundancy and
make full use of the available resources.  Some observers are already
posting their observing plans on the Internet.  Better coordination
will be required, however, as the rate of discovery continues to
increase.

* Physical Characterization: There is a continuing need for physical
characterization of NEOs, primarily using ground-based telescopes and
radar.  In addition, a number of spacecraft missions to comets and
asteroids are planned or underway, which should greatly increase our
knowledge of the nature of these objects.

* Impact Hazard Scale: A new Torino Impact Hazard Scale, developed by
Rick Binzel, was endorsed by attendees at the workshop.  This scale,
ranging from 0 (risk well below background level) to 10 (certain
catastrophic impact), will be described in detail in a future message.

* Verification of Threatening NEOs:  The workshop attendees recommended
that the International Astronomical Union take responsibility for
establishing a system for voluntary rapid peer review of predictions or
announcements of any NEO with significant impact risk (level 1 or
higher on the Torino risk scale).  This review will also be described
on NEO News when the IAU works out the details.

David Morrison
NASA Ames Research Center
Tel 650 604 5094; Fax 650 604 1165
david.morrison@arc.nasa.gov or dmorrison@mail.arc.nasa.gov
website: http://space.arc.nasa.gov
website: http://astrobiology.arc.nasa.gov
website: http://impact.arc.nasa.gov

====================
(7) AIAA MEETING - SPECIAL SESSION ON METEOR PLASMA PHYSICS

From Peter Jenniskens <pjenniskens@mail.arc.nasa.gov>

FIRST ANNOUNCEMENT (JUNE 10, 1999)

Dr. Christophe Laux of Stanford University has proposed to create a
special session on meteors at the next 38th Aerospace Sciences
Meeting&Exhibit of the AIAA (American Institute of Aeronautics and
Astronautics).  The meeting will be held at Reno, NV, from January
10-13, 2000.

The special session will be entitled "Aerothermochemistry effects in
meteoric plasmas" and will be chaired by meteor astronomer Dr. Peter
Jenniskens of The SETI Institute at NASA/Ames Research Center and
co-hosted by plasma physicists Dr. Olga Popova of the Moscow Institute
for Dynamics of Geospheres RAS and Dr. Iain Boyd of the Department of
Aerospace Engineering of the University of Michigan. It will be a half
day session and will feature a maximum of eight half-hour oral
presentations.

The AIAA meeting is usually very well attended (1600 participants last
year).   This would be a tremendous opportunity for the plasmadynamics,
thermophysics, and fluid dynamics communities to learn more about the
physics, aerochemistry, and optical diagnostics of meteorids. Many
participants at the AIAA meeting work in the area of hypersonic flows,
plasma chemistry and plasma diagnostics. I trust this would be a great
venue to present the exciting findings that were described at the last
Leonid conference as well as some first results from the 1999 Leonid
campaign.

The deadline for abstracts for this conference for this particular
session is June 22. Because of the short notice, all abstract
requirements are waived. At this time, we will collect proposed titles
for presentations only. No

abstract needs to be submitted. Note that all presenters must submit a
written paper by the first day of the conference.

We will need the following information for each paper (by June 22,
1999):

- Paper title
- List of all authors with their affiliations (e.g.: NASA-Ames, Moffett
  Field, CA, USA)
- Name, address, phone, fax and email of the one author who will receive
  all correspondance
- Indicate any special needs for video equipment (VCR, 35 mm projector)
  [the default is an overhead projector in each room].

Please respond to: pjenniskens@mail.arc.nasa.gov

This information will go into a printed program mailed to all
registrants.  It will also be posted on the Web.

Additional information on the conference and venue can be found on the
Web at: http://www.aiaa.org/calendar/asm00cfp.html

I look forward to this exciting session.  I hope it will be possible to
put it together despite the very short notice.  Thank you in advance.

Best regards,

Peter Jenniskens

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

Dr. Peter Jenniskens
The SETI Institute
NASA Ames Research Center
Mail Stop 239-4
Moffett Field
CA 94035-1000

pjenniskens@mail.arc.nasa.gov
tel.: 1-650-6043086
fax.: 1-650-6041088

===============
(8) CORRECTIONS ON ERRORS IN TPS PRESS RELEASE

From Linda Wong tps@planetary.org

THE FOLLOWING CORRECTIONS APPLIES TO THE PRESS RELEASE ORIGINALLY SENT
OUT ON JUNE 10, 999

1. THE QUOTE ORIGINALLY ATTRIBUTED TO PAUL CHODAS ON THE JPL WEB SHOULD
HAVE BEEN ATTRIBUTED TO ANDREA MILANI

2. THE EXPECTED MISS DISTANCE OF 1999 AN10 WAS INCORRECTLY STATED OF
39,000 KM; THE CORRECT MOST LIKELY MISS DISTANCE IS 200,000 KILOMETERS.

WE APOLOGIZE FOR ANY CONFUSION THESE ERRORS MAY HAVE CAUSED.

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