Purpose
This paper details the evolution of meteor tracking
networks from 1960 to the present. Meteor tracking depends on technology,
interest, and mission philosophy. This paper will analyze the evolution
of meteor tracking networks in terms of their era, mission, technology, and
overall support for the future.
Background
Since the L’Aigle fall, on April 26, 1803, it has been accepted that meteors are matter that can fall to the earth rather than venerable religious events. Therefore as time passed scientific interest in meteors and their associated meteorites has grown. Culminating in today's scientific philosophy that meteors/meteorites are the key to unlocking the configuration of the early Solar System and its evolution [Gaffey, 2002]. Consequently, scientists desire:
- to recover meteorites as soon as possible to minimize Earthly modification;
- to identify when and where meteors are entering the Earth’s atmosphere to potentially become meteorites;
- to understanding meteorite origins and meteor orbital characteristics [Poltkin, 1996].
In the Beginning
(1960 - 1980s)
A successful observation of a meteor consists of
two images (photographs) from stations separated by 20km or more [McCrosky,
1965]. This dual observation data set allows the scientist to determine
the true path the meteor will take through the atmosphere, its probable impact
location, as well as its previous heliocentric orbit. Two stations
could supply such data sets, as attempted by Harvard in 1936 and Ondrejov
in 1951, however success would be inhibited by the sky coverage limitations
of only two stations. Therefore networks of photographic observations
stations of greater than two stations were established (See Table 1) to formally
observe the night sky in hopes of acquiring the aforementioned data sets reliably.
The following are the original formal networks (> two stations) that began
from 1963 – 1969:
1. European Fireball Network (1963 – Germany/Czechoslovakia)
2. Prairie Network (1964 – United States of
America)
3. Meteorite Observation and Recovery Project
(MORP) Network (1971 - Canada).
| Parameter |
European Fireball Network |
Prairie Network |
MORP Network |
| Number of Stations |
46 |
16 |
12 |
| Station Spacing, km |
250 |
193 |
|
| Number of Cameras per Station |
1 |
4 |
5 |
| Focal Length, mm |
152 |
50 |
|
| Dash Length, mm |
0.034 |
0.236 |
0.330 |
| Meteor Timing |
Visual Observers |
Photometer/Shutter Code |
Photometer |
| Sky coverage, km2 |
10.8 x 105 |
11.4 x 105 |
8.3 x 105 |
| Effective Ground Search Area, km2 |
4.4 x 105 |
13.6 x 105 |
7.1 x 105 |
Table 1: Original Photographic Observation Network Characteristics [Halliday, 1971]
European Fireball Network. The first systematic
meteor tracking network, administered by the Ondrejov Observatory, was operational
in 1963 with 5 stations, prompted by the 1959 photographed fall of the Pribram
meteorite in Czechoslovakia. By 1968 it was expanded by the installation
of new stations (~15) in Germany and was named the European Fireball Network
[Oberst, 1998]. Its mission was to obtain meteor records from two or
more stations for scientific use. Each station in this network used
one all-sky camera (Figure 1), 36mm film, and a rotating shutter and performed
one manual exposure per night (See rendering of an all-night exposure results
in Figure 6B) [Ceplecha, 1965]. From 1963 to 1988 the European Fireball
Network (Figure 2) successfully observed fifteen (plus Pribram in 1959) meteors
[Oberst, 1998]. In 1988 this network began involving amateur astronomers
to operate stations and thereby expanded to northern Germany, Belgium, Switzerland,
and Austria. The success of this network continued and is therefore
operational at present.
Figure 1: All-sky Camera [Ceplecha, 1965]
Figure 2: European Fireball Network Stations Pre-1988 [Halliday, 1971]
Prairie Network. The second systematic
meteor tracking network, administered by the Smithsonian Institution, was
operational in March of 1964 with 10 stations in the Midwest United States.
This network evolved to its final configuration of 16 stations (Figure 3)
extending from South Dakota to Oklahoma and from Illinois to Nebraska by
May 1964 [McCrosky, 1965]. Its mission was to gather the most data
on the brightest meteors to find meteorites. Each station in this network
used four Super-Schmidt T-11 cameras (Figure 4), 390-ft of film, a switching
shutter, a sky photometer, and a cloud detector since each station was to
operate autonomously. During its operations from 1964 – 1975 this network
recorded approximately 320 fireball observations, with one resulting in a
meteorite find, the Lost City meteorite [Ceplecha, 1987]. However,
as the 1970s began the public and the US congress were more interested in
the war in Vietnam and civil riots than space/meteor science and this network
along with the Apollo program were victims of federal budget cutting.
Specifically, operations of the Prairie Network were terminated in 1975 due
to lack of funding and very limited fulfillment of its mission to assist
in finding meteorites.
Figure 3: Prairie Network Stations [McCrosky,
1965]
Figure 4: Super-Schmidt T-11 cameras [McCrosky, 1965]
MORP Network. The third of the original
systematic meteor tracking network, administered by the University of Saskatchewan,
was operational in 1971 with 12 stations in western Canada (Figure 5).
Its mission was to obtain meteor records from two or more stations for scientific
use. Each station in this network used five Super-Komura cameras, 70-mm
film, masking and chopping shutter, meteor detector (photomultiplier tube)
and exposure control circuitry since as with the Prairie Network each station
was to operate relatively autonomously. During its operations from 1971 –
1985 this network recorded many fireball observations, with only one resulting
in a meteorite find, the Innesfree meteorite [Halliday, 1978]. Therefore
the MORP Network was dismantled in 1985 due to a lack of funding support
given that Canadian meteorite finds/discoveries were continuing during this
period mostly without the use of MORP data.
Figure 5: MORP Stations [MIAC, 2002]
(Note: Innesfree is meteorite fall location not
station)
At Present
(1980s - 2002)
The success of
the original three meteor tracking networks shows that photographic data on
meteors can be acquired and used for orbital characteristics, its origins,
and/or its character but meteorite impact predictions have been problematic.
The problem in predicting an impact location for a meteorite from photographic
data is primarily due to a meteor’s luminosity variations as it traverses
the atmosphere. A meteor’s luminosity terminates as it slows down (~
3km/s) in the atmosphere and heating is too low create a visible fireball.
Although with an observed terminal velocity and deceleration an impact location
can be predicted to within 1 km [Ceplecha, 1987]. However the meteorite
ground search itself can be the restricting factor as seen by the 50 searches
done for all three of the original networks only yielding 3 meteorite finds.
Therefore the original network that remains, the European Fireball Network,
and those that have recently been established have the ultimate goal of identifying
orbital and atmospheric characteristics, its origins, and its potential to
become a meteorite rather than predicting its exact impact location.
European Fireball Network. This network was
successful in its mission to record meteor events in the beginning of meteor
tracking chronology, given that its success was not intimately tied to the
recovery of meteorites, and therefore remains operational today. In
1990 the European Fireball Network expanded again due to the reunification
of Germany and today the network has 34 stations across Germany, Czech and
Slovak Republics, Belgium, Switzerland, and Austria (Figure 6A). Each
station now uses either Leitz cameras or all-sky cameras with a Zeiss-Distagon
fish-eye lenses, 9x12cm film, and 12.5Hz shutters [Oberst, 1998]. The
operations of this network are no longer just coordinated by the Ondrejov
Observatory. At present the German Aerospace Center’s Institute of
Planetary Exploration and the Ondrejov Observatory are co-coordinators of
the network’s efforts. Currently, the network detects over 50 fireballs
per year with 50% of those being successful observation of a meteor consisting
of two images [Oberst, 1998]. However this network’s post-creation-data
and spectacular images (Figure 6B) has produced no more meteorite finds to
date.
Figure 6A: European Fireball Network Stations
[Oberst, 1998]
Figure 6B: European Fireball Network Station All-Night Exposure Fireball Image
“This exceptionally bright fireball meteor trail was photographed with a fish-eye camera at a Czech Republic station of the European Fireball Network on January 21, 1999. Of the star trails visible in this night-long exposure, the bright short arc in the upper left is due to Polaris, the north star. The breaks seen near the beginning of the fireball trail itself were produced by a shutter rotating 15 times a second. In all, three stations recorded the dazzling streak and their combined tracking information has revealed details of the meteor's brief atmospheric flight and previous interplanetary voyage. For example, the luminous trail is measured to begin at an altitude of 81.9 kilometers and covered 71.1 kilometers in 6.7 seconds.” [GSFC, 1999]
Dutch Meteor Society. Hans Betlem founded
the Dutch Meteor Society (DMS) in 1979 as an informal society of observers.
Since then the DMS’s members have been involved in meteor astronomy and meteorite
searches/analyses. The DMS began informal visual/photographic meteor
observations circa 1980. Since then the DMS has added video observation
(1987) and radio meteor scatter observations (1993) to its capabilities via
its member’s research initiatives. The majority of DMS members currently
use Cannon T-70 cameras equipped with high quality FD f/1.8-50 mm for photographic
observations. Between 1980 and 1995, 998 successful photographic meteor
observations (multi-station) have been made while video and radio data has
been recorded for many periodic storms [Betlem, 2001]. In addition,
the DMS currently runs 7 permanent automatic all-sky stations (Dutch All-Sky
Network w/Cannon fish-eye lenses), as part of the European Fireball Network.
However, like many other meteor networks the DMS’s observations have not
led to a meteorite find as of yet.
Dutch All-Sky Stations |
||||
| Code |
Station |
Longitude |
Latitude |
|
| EN91 |
Leiden |
52-11-02 |
04-30-01 |
|
| EN92 |
Elsloo |
50-56-45 |
05-46-02 |
|
| EN95 |
Benningbroek |
52-42-08.1 |
05-01-30.9 |
|
| EN96 |
Loenen |
52-07-17.6 |
06-01-27.4 |
|
| EN97 |
Oostkapelle |
51-34-21.7 |
03-32-15.9 |
|
| EN98 |
Harderwijk |
52-20-01.1 |
05-39-30.1 |
|
|
Bosschenhoofd |
51-34-14.2 |
04-32-32.6 |
|
Spanish Photographic Meteor Network.
In 1997 the Spanish Photographic Meteor Network (SPMN) was established.
This network uses both professional and amateur astronomers under the auspices
of University Juam I, University of Barcelona, and Catalonian Institute Studies.
The main mission of the SPMN is to study meteors, fireballs and meteorites
in terms of there orbits from conventional photography, video and Charge-Coupled
Device (CCD) techniques as well as each meteor streams’ spatial densities,
parent bodies, and spectroscopy. SPMN has 17 stations, with semi-automatic
all-sky cameras with rotating shutters and CCD, as shown in Figure 7 [Pique,
2002]. All SPMN observation campaigns are open to amateur participation
and the SPMN has been successfully meeting its objectives thus far.
Figure 7: Spanish Photographic Meteor Network Stations [Pique, 2002]
NAMN Network. The North American Meteor Network
was founded in June 1995. Its mission objectives are:
1. “Promote astronomy and related sciences
2. Recruit and train new observers in the methods of meteor observation
3. Coordinate North American observations”
[Davis, 2001]
NAMN is an informal group of over
200 observers who collect large numbers of meteor and fireball observations.
Observations consist of visual accounts, 35mm camera images, telescopic accounts,
and radio detections. Routinely meteor images are collected via this amateur
network and therefore the network is continuing to thrive.
Japan Fireball Network. The Japan Fireball
Network is an observation network to collect meteor photographic footage.
Footage is acquired via automatic camera every night in various parts of
Japan [Shimoda, 1998]. This network’s efforts consist of amateur astronomers
capturing meteor images on 35mm cameras with rotating shutters, and/or on
video tape using curved mirrors, and/or on Charge-Coupled Device (CCD) cameras
at the stations shown in Figure 8. This network routinely acquires
consistent and usable images and is therefore operational at present.
Figure 8: Japan Fireball Network Stations [Shimoda,
1998]
In the Future
(2002 - ****)
As shown by the demise of the Prairie and MORP networks
and the success of the current networks involvement of amateurs is a must
[Oberst, 1998]. Not only does it provide ease of network expansion as shown
in the European Fireball Network history but also provides free efforts and
increased public support. There are currently a few organizations like The
American Meteor Society, The International Meteor Organization, and NAMN
as well as select Universities that promote meteor interest but the birth
of the Internet, and its associated technology may mean the re-birth of more
global interest. In addition, space-based observation platforms (i.e.; DOD/NOAA/GOES/ARGOS
Satellites), airborne observatories, infrasound listening devices (i.e.; LANL
– Figure 9), and global positioning systems may also increase the frequency
of observations and increase the possibility of meteorite recovery. To date
many meteor observation reports are available from these types of sources,
which include sufficient data to assist researchers in meteor calculations
and possible meteorite recovery. To illustrate the value of information from
these types of sources a sample DOD report follows:
“On 9 December 1997, sensors aboard DOD satellites
detected the impact of a meteoroid at 08:15:55 UTC roughly midway between
Nuuk and Qaqortoq, Greenland. The object broke into at least 4 pieces. One
piece detonated at an altitude of about 46km at 62.9 degrees North Latitude,
50.9 degrees West Longitude. The remaining 3 pieces detonated in close proximity
to one another at altitudes between 28 km, at 62.9 degrees North Latitude,
50.1 degrees West Longitude and 25 km at 62.9 degrees North Latitude, 50.0
degrees West Longitude." [GSFC, 1998]
However these
types of assets are orbital and/or operational for other purposes and their
operation and/or data releases can be discontinued at anytime.
Figure 9: LANL Infrasound Listening Station [NNSA,
2001]
Note: “Using Los Alamos listening stations that can help alert international authorities to weapons tests by rogue groups or nations, researchers Rod Whitaker, Doug ReVelle and Peter Brown of Atmospheric and Climate Science (EES-8) detected two meteors entering the atmosphere on April 23 of this year [2001] and on Aug. 25 2000. Data from orbiting platforms confirmed the objects. … The meteors were very large, measuring about six and 10 feet in diameter. ”Entrances were equivalent to 2000 – 8000 tons of TNT. [Rickman, 2001]
Conclusion
Today’s scientific philosophy that meteors/meteorites
are the key to unlocking the configuration of the early Solar System and
its evolution depends on meteorite recovery. Thus since meteor tracking/observation,
both advanced and amateur, can aid researchers in finding meteorites, although
with only limited success to-date, then efforts need to continue in this area.
However, amateur involvement will most likely only keep the current level
of capability thriving, therefore professional involvement will be needed
to advance this field technologically (i.e., dedicated space-based efforts
or advanced ground systems) and increase its meteorite locating success potential.
References
[Gaffey 2002] Gaffey, Michael
(2002), Asteroids, Meteoroids, and Comets, Department of Space Studies, University
of North Dakota, Class Lectures.
[GSFC 1999] Goddard Space Flight Center, “Astronomy
Picture of the Day - February 19, 1999”, http://antwrp.gsfc.nasa.gov/apod/ap990219.html,
Retrieved April 2002.