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

(meteorobs) Excerpts from "CCNet 12/2001 - 25 January 2001"




------- Forwarded Message

From: Peiser Benny <B.J.Peiser@livjm.acdot uk>
To: cambridge-conference <cambridge-conference@livjm.acdot uk>
Subject: CCNet, 25 January 2001
Date: Thu, 25 Jan 2001 09:25:59 -0000

CCNet 12/2001 - 25 January 2001
------------------------------

[...]

(7) VIDEO METEOR OBSERVATIONS 2000
    Sirko Molau <molau@informatik.rwth-aachendot de>

(8) METEOROIDS
    Duncan Steel <D.I.Steel@salford.acdot uk>

(9) SPIEGEL ARTICLE
    Hermann Burchard <burchar@mail.math.okstatedot edu>

(10) LISTENING TO SOUNDS FROM AN EXPLODING METEOR 
     GEOPHYSICAL RESEARCH LETTERS, VOL. 28, NO . 1, PAGES 41-44,
     JANUARY 1, 2001

(11) IS JUPITER A PLANET?
     Roy Tucker <tucker@noaodot edu>

[...]

=================================================================

(7) VIDEO METEOR OBSERVATIONS 2000
 
>From Sirko Molau <molau@informatik.rwth-aachendot de>

AKM Video Meteor Observations 2000 - Summary
============================================

The last year was a very successful one for the video observers in the
German Arbeitskreis Meteore. 8 (1999: 5) observers recorded in 239 (1999:
120) nights and 2301.3 hours (1999: 1002.4) effective observing time an
overall of 11,659 (1999: 6,476) meteors. In other words: The outcome of last
year could be doubled. 239 observing nights is a coverage of almost 2/3 of
the year!

There are three camera stations (Aachen, Dresden, Marquardt) which supplied
observations in all twelve months. The other stations were only part-time
operated. About 1/3 of the observing time was supplied by Juergen Rendtel
and Sirko Molau, the last third was contributed by the remaining observers.
Ulrich Sperberg had to give up already in January when his image intensifier
broke
down. As soon as the new AKM video cameras will be ready, his station
Salzwedel will become active again. Because of poor camera parameters, the
video system of Detlef Koschny recorded only very few meteors in the first
months. In August, however, it got a new fast wide-angle lens and yielded
similar detection rates as the other cameras from then on.

Table 1 gives the detailed statistics of operation times for all
participating video observers. RENJU and MOLSI operated their systems in
virtually every clear night, even if skies cleared only briefly. Hence, the
different number of observing nights reflects better weather conditions
especially in the cold months in east Germany. On the other hand, the image
intensifier of AVIS is more powerful than that of CARMEN, resulting in a
better limiting magnitude and more meteor records. Whereas CARMEN detected
an average of 3.8 meteors per hour, it was 6.3 meteors per hour for AVIS.

Table 1: Operation Times of the AKM Video Cameras 2000

Observer         Camera        Primary Site   Nights Time [h] Meteors
- ---------------------------------------------------------------------
Juergen Rendtel  CARMEN        Marquardt        158    811.7   3,085 
Sirko Molau      AVIS, ESCIMO  Aachen           146    709.9   4,507
Mirko Nitschke   VK1, VK2      Dresden           62    290.6   2,021
Ilkka Yrjola     NONAME        Kuusankosi        34    172.5     631
Joerg Strunk     FAMOS         Leopoldshoehe     26    149.0     858
Detlef Koschny   ICC           Noordwijkerhout   20    113.2     386
IAP team         IAP1          Kuehlungsborn      4     38.3     139
Ulrich Sperberg  ADAM          Salzwedel          2     16.1      32
- ---------------------------------------------------------------------
Overall                                         239   2301.3  11,659

Table 2 shows the monthly distribution of observations. Ignoring August, the
number of cameras operated each month was almost constant. The main weather
situation is best reflected by the observing time: March and July provided
extremely poor conditions, whereas in April and since August 20 and more
nights could be used for observations each month. On top of the list are
August and September.
 
The Perseids are well reflected in the number of meteor records. However,
there is some bias since during major meteor showers more cameras than usual
are operated. The last column gives the average number of meteors per hour
for the two cameras operated in every clear night (AVIS, CARMEN). Here we
can clearly see the annual variations in meteor activity.

The year starts relatively slow (the Quadrantids 2000 were clouded out).
Shortly thereafter meteor actitivy reaches it's absolute minimum without any
major shower in February and March. Despite the Lyrids not much happens in
April. The May data are biased by our eta-Aquarid expedition to Jordan, but
at least in June increasing meteor activity becomes evident. Due to the
short nights, this is not reflected in the absolute meteor counts, however.
By July activity has reached the all-year average thanks to a number of
minor showers, and briefly thereafter we have the annual maximum in August
caused by the Perseids and their long activity period. Meteor counts drop
briefly in September, but recover in October again thanks to the Orionids,
Taurids, and increased sporadic rates. The remainder of the year stays
active, even though we missed both the maxima of the Leonids and Geminids in
2000.

The net effect of all factors (duration of night, global weather situation,
meteor activity) is that more than 80% of all meteors were recorded in the
second half of the year. Our video data show also clearly the daily
variations in meteor activity. On long winter evenings it may happen, that
there is not one meteor detected in one hour, whereas in the morning hours
there are typically more than ten meteors per hour.

Table 2: Monthly Distribution of Video Meteor Observations 2000

Month      Cam Nights Time   Meteors Met/Hour
- ---------------------------------------------
January     5    17   190.8     679    3.2
February    3    16   137.1     391    2.8
March       4     9    52.4     101    2.0
April       5    21   182.4     429    2.4
May         4    19   107.4     342    3.4
June        3    19    93.5     286    3.2
July        5    14    60.5     339    5.1
August      8    27   342.2   2,997    8.6
September   5    28   339.2   1,601    4.9
October     5    20   217.3   1,321    6.5
November    6    25   259.9   1,354    5.3
December    5    24   318.6   1,819    6.4
- ----------------------------------------------
Overall    10   239  2301.3  11,659    5.0

************************************************************************** 
*  Dipl.-Inform. Sirko Molau                  *                          *
*  RWTH Aachen, Lehrstuhl fuer Informatik VI  *              __          *
*  Ahornstr. 55, D-52056 Aachen, Germany      *       " 2B v 2B "        *
*                                             *                          * 
*  phone: +49-241-8021615                     *             Shakespeare  *
*  fax  : +49-241-8888219                     *                          *
*  email: molau@informatik.rwth-aachendot de     *                          *
**************************************************************************
*  www  : http://www-i6.informatik.rwth-aachendot de/Colleagues/molau       *
**************************************************************************

============================
* LETTERS TO THE MODERATOR *
============================

(8) METEOROIDS

>From Duncan Steel <D.I.Steel@salford.acdot uk>

Japanese meteorite finds in Antarctica story:

>A meteorite is a meteor that survives the destructive effects of a flight
>through the atmosphere and falls to the ground whole or in pieces. 

No: A meteorite is a meteorOID that survives the destructive effects of a
flight through the atmosphere and falls to the ground whole or in pieces. 

The term 'meteor' (synonym 'shooting star') refers to the phenomenon seen in
the atmosphere when a meteoroid arrives. The term, then, covers the flash of
light seen, or the train of ionisation produced, and so on. It does NOT
refer to any solid object, either in space or on the ground.

This is according to the IAU definitions of terminology (common dictionaries
may say something different, but specialist subjects require specialist
jargon). In 1995 Martin Beech and I proposed that the definitions should be
modified slightly:

M. Beech & D. Steel, "On the definition of the term 'meteoroid'," Quarterly
Journal of the Royal Astronomical Society, 36, 281-284 (1995).

The major point we were making, however, was not related to the meteor
versus meteoroid confusion. We were concerned with the fact that advancing
technology (i.e., NEO detection with CCDs pioneered by Spacewatch) had led
to the point where the IAU definition of 'meteoroid'
was (and still is) inadequate, the point being that it had become possible
to detect solid objects smaller than 100 metres in space, and so it becomes
necessary to decide where asteroids start, and meteoroids begin. Our
suggestion was an arbitrary dividing line at 10 metres (larger is an
asteroid - or a minor planet in IAU parlance - while smaller is a
meteoroid). 

Similarly one needs to define a lower size limit for meteoroids, our
suggestion being 100 microns, as it is about there that solid particles
survive entry without melting/ablating, and so do not produce meteors.  Such
tiny particles may be called 'interplanetary dust', and 'micrometeorites'
when they reach the ground.

Duncan Steel

=================================================================

(9) SPIEGEL ARTICLE

>From Hermann Burchard <burchar@mail.math.okstatedot edu>

Benny:

The SPIEGEL Article about a powerful meteor explosion on 8 Nov 1999 over
Northern Germany was recorded by microbarometers, meant for nuclear test
verification.

SPIEGEL refers to GEOPHYSICAL RESEARCH LETTERS. By clicking on the LINK in
the SPIEGEL article, you can get the full text from there for posting on
CCNet. It's in English. Below are publication date, volume #, and abstract,
and here is the URL.

    http://www.agu.org/GRL/articles/2000GL011859/GL11077W01.html

Best regards,

   Hermann G.W. Burchard
   Dept. of Mathematics
   Oklahoma State University
   Stillwater, OK 74078-0613
   (405) 744-5690/5688 (office)
   (405) 377-8919
   burchar@math.okstatedot edu

=================================================================

(10) LISTENING TO SOUNDS FROM AN EXPLODING METEOR 

GEOPHYSICAL RESEARCH LETTERS, VOL. 28, NO . 1, PAGES 41-44, JANUARY 1, 2001
Listening to sounds from an exploding meteor and oceanic waves.
L.G. Evers and H.W. Haak, Royal Netherlands Meteorological Institute,
Seismology Division, de Bilt, the Netherlands

Received June 12, 2000, revised September 29, 2000, accepted October 5, 2000

Abstract:
Low frequency sound (infrasound) measurements have been selected within the
Comprehensive Nuclear-Test-Ban Treaty (CTBT) as a technique to detect and
identify possible nuclear explosions. The Seismology Division of the Royal
Netherlands Meteorological Institute (KNMI) operates since 1999 an
experimental infrasound array of 16 micro-barometers. Here we show the rare
detection and
identification of an exploding meteor above Northern Germany on November
8th, 1999 with data from the Deelen Infrasound Array (DIA). At the same
time, sound was radiated from the Atlantic Ocean, South of Iceland, due to
the atmospheric coupling of standing ocean waves, called microbaroms.
Occurring with only 0.04 Hz difference in dominant frequency, DIA proved to
be able to discriminate between the physically different sources of
infrasound through its unique lay-out and instruments. The explosive power
of the meteor being 1.5 kT TNT is in the range of nuclear explosions and
therefore relevant to the CTBT.

=================================================================

(11) IS JUPITER A PLANET?

>From Roy Tucker <tucker@noaodot edu>

	"In a nutshell, Pluto likely would not be considered a planet if it
were discovered 	today," said Bernie Walp, an assistant for the
Extrasolar Planetary Search team at 	Berkeley. 

Dear Dr. Peiser,

	I've heard planets defined as dark bodies that shine by reflected
light. Jupiter radiates more energy than it receives from the sun, although
it shines in the infrared where our eyes are not sensitive. So, if Pluto is
not a planet because of its size, then neither is Jupiter. If Jupiter had
been discovered today by some infrared telescope out in the distant Oort
cloud, would we be arguing about what it was, planet or failed star? Has
poor old Pluto become politically incorrect?

				Best regards,
				  - Roy Tucker, asteroid observer

--------------------------------------------------------------------
THE CAMBRIDGE-CONFERENCE NETWORK (CCNet) 
--------------------------------------------------------------------
The CCNet is a scholarly electronic network. To subscribe/unsubscribe,
please contact the moderator Benny J Peiser <b.j.peiser@livjm.acdot uk>.
Information circulated on this network is for scholarly and educational use
only. The attached information may not be copied or reproduced for
any other purposes without prior permission of the copyright holders. The
fully indexed archive of the CCNet, from February 1997 on, can be found at:
    http://abob.libs.ugadot edu/bobk/cccmenu.html

DISCLAIMER: The opinions, beliefs and viewpoints expressed in the articles
and texts and in other CCNet contributions do not  necessarily reflect the
opinions, beliefs and viewpoints of the moderator of this network.

------- End of Forwarded Message

To UNSUBSCRIBE from the 'meteorobs' email list, use the Web form at:
http://www.tiacdot net/users/lewkaren/meteorobs/subscribe.html