[Prev][Next][Index][Thread]

(meteorobs) AMS Electronic Circular, Winter 1998



                     The American Meteor Society, Ltd.
                           ELECTRONIC CIRCULAR
                       Issue #3...Late Winter, 1998
                            --------=======*

Contents of this issue:

     1. Editor's Notes  
     2. Danes Plan Meteorite Recovery Expedition to Greenland
     3. AMS Announces C. P. Olivier Award Winners for 1997 and 1998
     4. Lunar Prospector Finds Evidence of Ice at Moon's Poles
     5. Call for Observations: 1998 Lyrids and Eta Aquarids
     6. Observing Meteors in Jordan
     7. Astronomers Track Down Asteroids in Hubble Archive
     
-------======*

1.  Editor's Notes

Jim Bedient
AMS Electronic Information Coordinator
wh6ef@pixi.com

Winter in the northern hemisphere marks a traditional lull in meteor work,
punctuated only by the Quadrantids for a lucky few living in the proper
longitude.  The end of winter is almost here, though, and many of us are
preparing for the warmer weather to come.  Observers are anticipating the
Lyrids in April, and amateurs and professionals alike are continuing to
prepare for two potential meteor outbursts this year, the Draconids in
October and the Leonids in November.  An expedition from Denmark will
search the Greenland icecap this July, seeking meteorites that may have
been deposited after the bright bolide of December 9, 1997.  It promises to
be an exciting year, and won't it be grand if in another thirty years or
so, the next generation hangs on our words as we say:

"Yes, I was there in 1998!"
 
-------======*

2.  Danes Plan Meteorite Recovery Expedition to Greenland

Bjørn Franck Jørgensen
Tycho Brahe Planetarium & Omnimax Theater
Copenhagen, Denmark
bjorn@inet.uni-c.dk

The Tycho Brahe Planetarium & Omnimax Theater is now organizing a search
for meteorites from the fall of December 9, 1997.  Several institutions are
involved in the preparing for an expedition that, considering the surface
conditions, must take place in late July.  Currently the area is covered by
2-3 meters (7-8 feet) of snow, which will normally melt in May and June.
During this time the site will be a very dangerous area to visit.  Floods
and ice sumps cover the melting zone and there will be hidden ice canyons
and holes in the surface, where the water suddenly disappears and falls
hundreds of meters into deep tunnels.  We have to wait until the surface
dries out in late July.

Holger Pedersen and Torben Risbo (Niels Bohr Institute, Copenhagen) have
put a lot of work into predicting possible locations of the strewn field,
or dispersion ellipse, on the icecap.  The suspected area is in the area of
what we call the melting zone, about 10-15 km (8-10 miles) from the edge of
the icecap on the southwest coast of Greenland.

The size of the original object was probably from meter-size to a small
house.  After the object had penetrated nearly 200 km (125 miles) of
atmosphere it came to an explosive fragmentation at an altitude of 14 km (9
miles).  Nearby eyewitnesses noticed that more than twenty larger fragments
continued in the original direction, still moving fast enough to ionize the
air around them, until they disappeared behind the local horizon (zenith
distance 87ø), equal to an altitude of 3.5 km (2.2 miles). The calculated
fall area has an altitude of 1400-1500 meters (4200-4500 feet) and is
located on the icecap.

The fact that the fragments continued to travel fast enough to cause
ionization of the air around them tells us that they must be rather massive
and of a size that should make it resonable to search for them, when icecap
conditions permit.

We are now preparing a four man expedition.  The logistics of such an
expedition are difficult, but we are receiving great help from more
experienced groups that have worked in similar regions.

We are convinced that this work is scientifically important, and it would
be of a great help if anyone with satellite data (military or otherwise)
that traced the visible or infrared signal from the meteor of December 9,
1997 (8.11 UT) over the southwestern coast of Greenland would contact us.
We need this assistance to narrow our search area.  We have two predicted
areas, about 19 km (12 miles) apart.  One is the direct result of geometric
measurements from the eye-witness reports and the other is based on
mathematical calculations of the track. The distance between the areas is
not large, but considering the very difficult conditions we will be working
under, concentrating the search in one 50-70 square kilometer (20-30 square
mile) area rather than two will greatly aid our effort. We hope to solve
this problem in one way or another before leaving for Greenland.

Involved in the search:
* Niels Bohr Institute, Copenhagen University
* Tycho Brahe Planetarium & Omnimax Theater (TBP)
* Greenland Geological Investigations
* Danish Meteorological Institute
* Danish Polar Center

TBP web site: http://www.astro.ku.dk/tycho.html (mostly Danish, but links
in English).

-------======*

3.  AMS Announces Dr. Charles P. Olivier Award Award Winners for 1997 and 1998

Jim Bedient
AMS Electronic Information Coordinator
wh6ef@pixi.com

The American Meteor Society has established an award for meritorious
service in amateur meteor science.  The award consists of a cash prize of
$200, and is named for Dr. Charles P. Olivier, the founder of the AMS and
leader until shortly before his passing in 1976.

The Dr. Charles P. Olivier Award for 1997 is awarded to:

                            Lisa R. Richardson

Lisa is the wife of Poplar Springs Radiometeor Station developer James
Richardson, and lives in Graceville, Florida.  Only two months after the
commencement of full-time station operation in March of 1993, James was
permanently blinded in a work related injury.  This injury came as a severe
blow to James, his family, and his work for the American Meteor Society.
Over the following two years of extensive medical visits, rehabilitation,
and career reestablishment, it was Lisa's undaunted efforts which carried
James and his family through this difficult transition period.

Throughout this time, the Poplar Springs Radiometeor Station remained in
nearly continuous operation, and even underwent equipment and software
upgrades.  While James was away in either hospitals or training schools,
Lisa maintained the system in proper operation.  While James was home, the
couple worked together to perform tasks such as system calibrations,
periodic maintenace, and data copying and archive.  Even now that James has
completed rehabilitation and is back in college full-time, he still relies
upon the able assistance of Lisa in the performance of his new American
Meteor Society duties as Operations Manager.

In addition, Mrs. Richardson has acted as editor for the AMS Annual Reports
for the last three years, as well as for two monographs for the Radiometeor
Project.

It is with great pleasure that we make Lisa Richardson the first recipient
of the Charles P. Olivier Award.

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

The Dr. Charles P. Olivier Award for 1998 is awarded to:

                            James W. Riggs, Jr.

James Riggs is a retired Physics teacher who lives in the western foothills
of the Sierra Nevada mountain range, near West Point, California.  In early
1994, James commenced the establishment of a forward-scatter receiving
station for inclusion in the AMS Radiometeor Project.  For more than two
years, James worked diligently to reach this goal, having to overcome
several difficulties and setbacks along the way.  On September 20, 1996,
his efforts were rewarded by having West Point Station declared fully
operational and calibrated for data collection within the project.  The
station has been functioning continuously ever since that time.

In addition to his radiometeor work, James is also an avid visual meteor
observer, and does meteor photography as well.  In 1994, his visual
observations totaled over 2000 events.

It is with great pleasure that we make James Riggs the recipient of the
1998 Charles P. Olivier Award. 

-------======*

4.  Lunar Prospector Finds Evidence of Ice at Moon's Poles

NASA Public Relations Staff

There is a high probability that water ice exists at both the north and
south poles of the Moon, according to initial scientific data returned by
NASA's Lunar Prospector. 

The Discovery Program mission also has produced the first operational
gravity map of the entire lunar surface, which should serve as a
fundamental reference for all future lunar exploration missions, project
scientists announced today at NASA's Ames Research Center, Moffett Field, CA. 

Just two months after the launch of the cylindrical spacecraft, mission
scientists have solid evidence of the existence of lunar water ice,
including estimates of its volume, location and distribution.  "We are
elated at the performance of the spacecraft and its scientific payload, as
well as the resulting quality and magnitude of information about the Moon
that we already have been able to extract," said Dr. Alan Binder, Lunar
Prospector Principal Investigator from the Lunar Research Institute,
Gilroy, CA.

The presence of water ice at both lunar poles is strongly indicated by data
from the spacecraft's neutron spectrometer instrument, according to mission
scientists. Graphs of data ratios from the neutron spectrometer "reveal
distinctive 3.4 percent and 2.2 percent dips in the relevant curves over
the northern and southern polar regions, respectively," Binder said. "This
is the kind of data 'signature' one would expect to find if water ice is
present."

However, the Moon's water ice is not concentrated in polar ice sheets,
mission scientists cautioned. "While the evidence of water ice is quite
strong, the water 'signal' itself is relatively weak," said Dr. William
Feldman, co-investigator and spectrometer specialist at the Department of
Energy's Los Alamos National Laboratory, NM. "Our data are consistent with
the presence of water ice in very low concentrations across a significant
number of craters." Using models based on other Lunar Prospector data,
Binder and Feldman predict that water ice is confined to the polar regions
and exists at only a 0.3 percent to 1 percent mixing ratio in combination
with the Moon's rocky soil, or regolith.

How much lunar water ice has been detected? Assuming a water ice depth of
about a foot and a half (.5 meters) -- the depth to which the neutron
spectrometer's signal can penetrate -- Binder and Feldman estimate that the
data are equivalent to an overall range of 11 million to 330 million tons
(10-300 million metric tons) of lunar water ice, depending upon the
assumptions of the model used.  This quantity is dispersed over 3,600 to
18,000 square miles (10,000-50,000 square kilometers) of water ice-bearing
deposits across the northern pole, and an additional 1,800 to 7,200 square
miles (5,000-20,000 square kilometers) across the southern polar region.
Furthermore, twice as much of the water ice mixture was detected by Lunar
Prospector at the Moon's north pole as at the south.

Dr. Jim Arnold of the University of California at San Diego previously has
estimated that the most water ice that could conceivably be present on the
Moon as a result of meteoritic and cometary impacts and other processes is
11 billion to 110 billion tons. The amount of lunar regolith that could
have been "gardened" by all impacts in the past 2 billion years extends to
a depth of about 6.5 feet (2 meters), he found.  On that basis, Lunar
Prospector's estimate of water ice would have to be increased by a factor
of up to four, to the range of 44 million to 1.3 billion tons (40 million
to 1.2 billion metric tons).  In actuality, Binder and Feldman caution
that, due to the inadequacy of existing lunar models, their current
estimates "could be off by a factor of ten in either direction."

The earlier joint Defense Department-NASA Clementine mission to the Moon
used a radar-based technique that detected ice deposits in permanently
shadowed regions of the lunar south pole.  It is not possible to directly
compare the results from Lunar Prospector to Clementine because of their
fundamentally different sensors, measurement "footprints," and analysis
techniques.  However, members of the Clementine science team concluded that
its radar signal detected from 110 million to 1.1 billion tons (100 million
to 1 billion metric tons) of water ice, over an upper area limit of 5,500
square miles (15,500 square kilometers) of south pole terrain.

There are various ways to estimate the economic potential of the detected
lunar water ice as a supporting resource for future human exploration of
the Moon.  One way is to estimate the cost of transporting that same volume
of water ice from Earth to orbit.  Currently, it costs about $10,000 to put
one pound of material into orbit. NASA is conducting technology research
with the goal of reducing that figure by a factor of 10, to only $1,000 per
pound. Using an estimate of 33 million tons from the lower range detected
by Lunar Prospector, it would cost $60 trillion to transport this volume of
water to space at that rate, with unknown additional cost of transport to
the Moon's surface.

From another perspective, a typical person consumes an estimated 100
gallons of water per day for drinking, food preparation, bathing and
washing. At that rate, the same estimate of 33 million tons of water (7.2
billion gallons) could support a community of 1,000 two-person households
for well over a century on the lunar surface, without recycling.  

"This finding by Lunar Prospector is primarily of scientific interest at
this time, with implications for the rate and importance of cometary
impacts in the history and evolution of the Solar System," said Dr. Wesley
Huntress, NASA Associate Administrator for Space Science.  "A
cost-effective method to mine the water crystals from within this large
volume of soil would have to be developed if it were to become a real
resource for drinking water or as the basic components of rocket fuel to
support any future human explorers."

Before the Lunar Prospector mission, historical tracking data from various
NASA Lunar Orbiter and Apollo missions had provided evidence that the lunar
gravity field is not uniform.  Mass concentrations caused by lava which
filled the Moon's huge craters are known to be the cause of the anomalies.
However, precise maps of lunar mass concentrations covering the moon's
equatorial nearside region were the only ones available.

Lunar Prospector has dramatically improved this situation, according to
co-investigator Dr. Alex Konopliv of NASA's Jet Propulsion Laboratory,
Pasadena, CA.  Telemetry data from Lunar Prospector has been analyzed to
produce a full gravity map of both the near and far side of the moon.
Konopliv also has identified two new mass concentrations on the Moon's
nearside that will be used to enhance geophysical modeling of the lunar
interior. This work has produced the first-ever complete
engineering-quality gravity map of the moon, a key to the operational
safety and fuel-efficiency of future lunar missions.

"This spacecraft has performed beyond all reasonable expectations," said
NASA's Lunar Prospector mission manager Scott Hubbard of Ames.  "The
findings announced today are just the tip of the iceberg compared to the
wealth of information forthcoming in the months and years ahead."

Lunar Prospector is scheduled to continue its current primary data
gathering mission at an altitude of 62 miles (100 kilometers) for a period
of ten more months.  At that time, the spacecraft will be put into an orbit
as low as six miles (10 kilometers) so that its suite of science
instruments can collect data at much finer resolution in support of more
detailed scientific studies.  In addition, surface composition and
structure information developed from data returned by the spacecraft's
Gamma Ray Spectrometer instrument will be a crucial aspect of additional
analysis of the polar water ice finding over the coming months.

The third launch in NASA's Discovery Program of lower cost, highly focused
planetary science missions, Lunar Prospector is being implemented for NASA
by Lockheed Martin, Sunnyvale, CA, with mission management by NASA Ames.
The total cost to NASA of the mission is $63 million.

Additional information about the Lunar Prospector mission can be found on
the Internet at URL:

http://lunar.arc.nasadot gov

-------======*

5.  Call for Observations: 1998 Lyrids and Eta Aquarids

Mark Davis
AMS Visual Program Coordinator
MeteorObs@charlestondot net

The first quarter of the year is somewhat barren of good meteor rates once
the Quadrantids end. This is a characteristic of the mostly minor meteor
streams active during this period. One possible exception, with a zenithal
hourly rate of 10 or more meteors, is the Lyrids.

This shower peaks on April 22 from a radiant that is located a little
southwest of the star Vega. Maximum rates are produced for only about an
hour or two, but has been known to be erratic. In 1996 for example, peak
rates of 15-20 persisted for 8 hours or more.

The Lyrids are associated with Comet Thatcher 1861 I and have produced
several bursts of activity in the past. The most recent occurred over North
America in 1982. Rates at that time reached nearly 100 meteors per hour!
Useful watches can be carried out after 2230 hours local time when the
radiant has reached sufficient height above the horizon.

This year, we will be facing a waning crescent moon that rises a little
before dawn. But conditions will still be favorable for us and
opportunities to observe should not be missed since the predicted maximum
favors North American observers.  Specific information about the shower is
listed below:

Lyrids (LYR)
Active: Apr 16-Apr 25
Maximum: Apr 22
Radiant: 271 +34 (18h 04m)
Velocity: 49 km/s
ZHR: 15

About two weeks later, another shower is visible that does produce good
rates for observers.  The Eta Aquarids are the outbound particles of the
famous Halley's Comet. It has a long activity period and broad maximum
which can occur May 2 through May 10. Unfortunately for Northern Hemisphere
observers, its radiant favors the southern half of the globe.  According to
the IMO, an observer may see nearly 40 meteors per hour at shower maximum
from tropical latitudes, decreasing to invisibility as you approach 50
degrees north latitude. Still, the shower is observable from some North
American locations. The Eta Aquarids are known to produce a high rate of
trains, normally exceeding all of the other major showers. One study has
train production as high as fifty percent!

Although the published ZHR for this shower is 60, that is the rate
associated with Southern Hemisphere locations.  Here in North America there
has been various ZHR's published, but the true number is probably at most
20 per hour and is highly dependent on latitude.  Keep in mind though, that
the Eta Aquarids exhibit a broad maximum, and rates are usually one-half
the maximum rate for almost a week centered on the main maximum.

Unfortunately, in 1998 this shower suffers from some moonlight as the moon
is about three days before full when they reach maximum. Below is the
specifics on this shower:

Eta Aquarids (ETA)
Active: Apr 19-May 28
Maximum: May 05
Radiant: 338 -01 (22h 32m)
Velocity: 66 km/s
ZHR: 60

Both paper and electronic reports of observations for these showers are
accepted. Send all reports to:

Mark Davis
AMS Visual Program Coordinator
1054 Anna Knapp Blvd.
Apt. 32-H
Mt. Pleasant, SC  29464

E-mail: MeteorObs@charlestondot net

Reporting forms and/or instructions on how to hold a meteor watch may also
be obtained from the above address.

-------======*

6.  Observing Meteors in Jordan  

Mohammad Shawkat Odeh
Head of Occultation Observation Committee
Jordanian Astronomical Society
odehjas@geocities.com

The Jordanian Astronomical Society (JAS) was founded in 1987 to assemble
the amateur astronomers in Jordan, and recently meteor observation became
one of the most important activities of JAS.  We are members in the
International Meteor Organization (IMO), and there is a special committee
in JAS for meteor observation.  Recently a delegation of IMO visited us,
consisting of the president of IMO, Mr. Juergen Rendtel, and two other
experts in meteor observation.  Together we held together an observational
camp in May 1997.

So far the JAS has held 19 astronomical camps, 10 of which were for meteor
observation.  The first astronomical camp was held in 1990 to observe Comet
Austin. 

We face many of the same difficulties in meteor observation that others do.
Firstly, we are like other amateurs, suffering from the light pollution as
well as cloudy weather.  After studying many sites we found that Hamza
field in Al-Azraq City, near Al-Azraq Oasis, (about 150 km east of the
capital, Amman) is one of the best places for observation, since it is far
away of light polluted areas and mostly has clear nights.  And since we are
a voluntary society, such camps are at the expense of our jobs and other
responsibilities.  Furthermore, one of the most serious problems we face is
that JAS dose not have any observational instruments, such as telescopes,
binoculars, cameras, etc. and we just rely on personal instruments, and
those provided by the Haya Cultural Center, where JAS is temporarily located.

For information on our latest activities, please visit our Internet web
site at:
http://www.geocities.com/CapeCanaveral/1092/jas.html

-------======*

7.  Astronomers Track Down Asteroids in Hubble Archive

NASA Public Relations Staff

Astronomers have stumbled on an unusual asteroid hunting ground:  the
thousands of images stored in the Hubble Space Telescope archive.

The hunt, by Robin Evans and Karl Stapelfeldt of NASA's Jet Propulsion
Laboratory, Pasadena, CA, has yielded a sizable catch of small asteroids --
about 100.  Their preliminary analysis suggests that a total population of
300,000 small asteroids -- essentially rocks just over half a mile to two
miles wide (1-3 kilometers) -- are orbiting between Mars and Jupiter in a
band of space debris known as the main belt.  Currently, there are 8,319
confirmed main-belt asteroids whose orbits have been measured, and about
the same number have been sighted but not confirmed.

Most astronomers stalk the Hubble archive for bigger game, such as quasars,
distant galaxies, and supernovae, but Evans and Stapelfeldt have discovered
that the pursuit of smaller prey such as asteroids can be equally successful. 

Over a three-year period, the two astronomers and their collaborators have
searched through more than 28,000 Wide Field and Planetary Camera 2 (WFPC2)
images, looking for wide, looping streaks of light, the telescope's
tell-tale signatures of asteroids.  Most of the ones they found are too
faint to be observed by current ground-based search programs.  Hubble
captures their images purely by accident:  Nearby asteroids inevitably
wander across the telescope's field of view while other, higher priority
targets are being observed.

"The archive images are distributed fairly evenly across the sky, so we
find asteroids according to both their position in the sky and their
number," Evans said.  "As expected, we see the asteroids concentrated
towards the ecliptic plane and we see small asteroids because they are the
most numerous.  Small main-belt asteroids such as these are the ones most
likely to evolve into Earth-crossing asteroids due to encounters with their
larger neighbors.  Some of the asteroids in our survey could eventually
migrate toward Earth."  

The Hubble archives represent a newly tapped information resource which
could help scientists more precisely estimate the risks the asteroids pose
to Earth.  

According to Evans and Stapelfeldt, the Hubble archival data also strongly
limit the number of small comets that could be passing very near Earth.
Last year, Dr. Louis A. Frank of the University of Iowa in Iowa City, using
data from NASA's Polar spacecraft, reported he found evidence that about a
dozen small comets strike Earth's upper atmosphere each minute.  Evans and
Stapelfeldt estimate the such small comets should be bright enough to
produce thousands of detectable trails in the Hubble archival images, but
these were not seen. 

The Hubble images capture an asteroid as a long trail produced by its
motion across the camera's field of view.  The trails appear like the
streaks of light found on photos taken at night of speeding cars with their
headlights on.

Finding asteroids isn't what the two astronomers originally had in mind.
As members of the WFPC2 science team, Evans and Stapelfeldt were examining
test images of distant stars and galaxies to ensure that the new camera was
functioning properly.  These were among the first images taken with WFPC2,
which had restored sharp focus to Hubble's images when it was installed in
late 1993. Stapelfeldt's wife, Deborah Padgett (also an astronomer),
pinpointed the first asteroid in 1994 while looking at images on the
couple's home computer.  Intrigued, Evans and Stapelfeldt began combing
through more than 1,600 of the science team's survey photos, finding 12
more asteroids.  This discovery prompted their large-scale search, by eye,
of two years worth of Hubble archival images.

Evans' and Stapelfeldt's initial results are reported in the February 1998
issue of the research journal Icarus.

The Space Telescope Science Institute is operated by the Association of
Universities for Research in Astronomy, Inc. (AURA) for NASA, under
contract with the Goddard Space Flight Center, Greenbelt, MD.  The Hubble
Space Telescope is a project of international cooperation between NASA and
the European Space Agency (ESA).

-------======*
Original Material Copyright 1998, American Meteor Society, Ltd., Geneseo,
New York

Follow-Ups: