Precision meteor orbits obtained by the Dutch Meteor Society - Photographic Meteor Survey (1981-1993)
Astron. Astrophys. Suppl. Ser.
Precision meteor orbits obtained by the Dutch Meteor Society - Photographic Meteor Survey (1981-1993)
H. Betlem 1
C.R. ter Kuile 1
M. de Lignie 1
J. van't Leven 1
K. Jobse 1
K. Miskotte 1
P. Jenniskens 0
0 NASA/Ames Research Center , Mail Stop 239-4, Mo ett Field, CA 94035-1000 , U.S.A
1 Dutch Meteor Society , Lederkarper 4, 2318 NB Leiden , The Netherlands
359 precisely reduced meteor orbits are pre- Multi-station photography provides the very accurate sented that are the result of the Dutch Meteor Society's orbital elements of meteoroids needed in theoretical studPhotographic Meteor Survey in the period 1981 until 1993. ies. The accuracy of photographic orbits is typically an orOrbits include those of major and minor showers, dou- der of magnitude better than those of radar orbits. Unlike bling the number of known precise orbits of some meteor radar orbits, photographic data potentially allow resolving streams. From the spread in solutions of all possible sets of the intrinsic scatter in the distribution of orbital elements. two photographic stations, we derive the measurement un- The photographed meteors are typically in the size range certainties from which we are able to calculate the intrinsic of millimeter or centimeter size and larger, depending on scatter in the Perseid meteor stream. The new Geminid entry velocity. These large grains contain most of the mass orbits are compared to those obtained in similar surveys in comet ejecta and are least a ected by radiation presin the 1950's. This rst measurement of the rate of change sure. of Geminid orbits over time agrees well with model predictions.
meteoroids
1. Introduction
The recent establishment of the IAU Meteor Data Center
in Lund (Sweden) (Lindblad & Steel 1994), and an
ongoing list of publications that make use of it, testify to
the continued interest in meteor orbits. The advances in
computer modeling has generated a new interest in meteor
streams and their relationship to the parent comets
(e.g.
Fox et al. 1983; Jones 1985; Gustafson 1989; Williams &
Wu 1993; Wu & Williams 1995)
. Key observations have
been made in other elds, such as the discovery of IRAS
dust trails in the orbit of short period comets (Sykes et al.
1986; Sykes & Walker 1992). Hence, new observations of
meteor streams promise exciting discoveries and an
increased understanding of meteor stream formation and
evolution (Steel 1993; Jenniskens 1994).
The rst meteor was photographed during the
Andromedid storm of 1885 (Weinek 1886). An attempt
at multi-station photography did not succeed at that
time. Optical surveys of meteor orbits were started at
Harvard where a small camera network was operated
from 1936 to 1959 in a project led by F.L. Whipple
(Whipple 1938). In total, some 1245 orbits were obtained
(Lindblad & Steel 1994). Later, specially designed Baker
Super-Schmidt cameras were used
(Whipple 1947; Jacchia
& Whipple 1956)
, from which almost 2529 orbits were
measured (McCrosky & Posen 1961). Only 413 of these
were calculated from a precise reductions of the data
(Jacchia & Whipple 1961; Jacchia et al. 1967). At the
same time, small camera surveys were performed in the
former Soviet Union, in Dushanbe, Odessa and Kiev in
the period 1940-1983, which resulted in 1111 precise orbits
(e.g. Babadzanov & Kramer 1967)
. Small camera surveys
have since been abandoned and are only used by
amateur observers, with notable results by the Nippon Meteor
Society (NMS) in Japan in the period 1974-1982 (325
orbits) (e.g. Koseki et al. 1990). These data, too, have not
always been reduced precisely.
The Photographic Meteor Survey program of the
Dutch Meteor Society started in 1982, when software
developed at the University of Poznan (TURNER - Tadeusz
1983) and Ondrejov Observatory
(REDCON, FIRBAL
Ceplecha et al. 1979)
became available for astrometry and
trajectory calculations. The programs were adapted for
use on MS-DOS computers. Since that time, some of the
older data in
Betlem & de Kort (1976
) have been
reduced with the new techniques and the database now also
contains some orbits from meteors dating back to 1972
(Betlem 1990)
. Preliminary results of 70 orbits were
published in Betlem & de Lignie (1990).
In this publication we present all 359 meteor orbits of
annual meteor streams and sporadic meteors obtained in
the survey prior to August of 1993. Special attention is
given to measurement uncertainty, which will allow
addressing the intrinsic dispersion in meteor streams. An
example will be given. In addition, the new data span a
large gap in time between previous surveys in the mid
1950's and the present, which allows the rst
measurement of the rate of change of the orbital elements of the
Geminid stream.
2. Experimental techniques
The meteors are photographed with batteries of 35 mm
cameras equipped with F/2, f = 50 mm standard optics
(e.g. Bone 1993)
. In front of the camera lens is a rotating
shutter which interrupts the im (...truncated)