ADC/CDS Standard Document for Catalog:/external/astrom/E1006/
ADC/CDS Standard Document for Catalog:
E/1/6 Orbits of Minor Planets (Bowell 2001)
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The Asteroid Orbital Elements Database, version 2001-May-31
Bowell E.
<Lowell Observatory (2001)>
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ADC_Keywords: Minor planets; External catalog
Location: ftp://ftp.lowell.edu/pub/elgb/astorb.html
Description:
astorb.dat is an ASCII file of high-precision osculating orbital elements,
ephemeris uncertainties, and some additional data for all the numbered
asteroids and the vast majority of unnumbered asteroids (multi-apparition
and single-apparition) for which it is possible to make reasonably
determinate computations. It is currently about 9.1 Mb in size in its
compressed form (astorb.dat.gz), 33.1 Mb in size when decompressed
(astorb.dat), and contains 123952 orbits computed by Edward Bowell. Each
orbit, based on astrometric observations downloaded from the Minor Planet
Center, occupies one 266-column record.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
astorb.dat 266 94540 The catalog of Orbits - version 2000-Oct-15
astorb.html 80 829 Introductory text (HTML version)
astorb.txt 78 446 Introductory text (plain ascii)
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See also:
II/190 : IRAS Minor Planet Survey (Tedesco 1992)
Byte-by-byte Description of file: astorb.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- Planet [1/]?+ Asteroid number (blank if unnumbered)
7- 24 A18 --- Name Name or preliminary designation.
26- 40 A15 --- CompName Orbit Computer.
42- 46 F5.2 mag H Absolute magnitude H parameter (1)
48- 52 F5.2 --- G Slope magnitude parameter (1)
54- 57 F4.2 mag B-V ? Color index (see E.F.Tedesco, pp.1090-1138)
59- 63 F5.1 km Diam ? IRAS diameter (see E.F.Tedesco,
pp.1151-1161; catalog <II/190>)
65- 68 A4 --- IRASclass IRAS Taxonomic classification
71- 73 I3 --- CrossCode [0/31] Planet-crossing code (4)
75- 77 I3 --- OrbitCode [0/255] Orbit computation code (5)
79- 81 I3 --- SurveyCode [0/31] Survey observation code (6)
83- 85 I3 --- MPCCode [0/7] MPC critical-list code (7)
87- 89 I3 --- LowellCode [0/3] Lowell Observatory discovery code (8)
91- 93 I3 --- FlagCode [0/10] Flagstaff Station Code (9)
95- 99 I5 --- Narc Orbital arc, days, spanned by observations
used in orbit computation.
101-104 I4 --- Nobs Number of observations used in orbit
computation.
106-113 A8 "YYYYMMDD" Epoch Epoch of osculation, yyyymmdd (TDT) (2)
115-124 F10.6 deg M Mean anomaly (3)
126-135 F10.6 deg omega Argument of perihelion (3)
137-146 F10.6 deg Omega Longitude of ascending node (3)
147-156 F10.6 deg i Inclination (3)
158-167 F10.8 --- e Eccentricity (3)
169-180 F12.8 AU a Semimajor axis (3)
182-189 A8 "YYYYMMDD" DateOrb Date of orbit computation
191-197 E7.1 arcsec CEU ?Current 1-{sigma} ephemeris uncertainty (10)
199-206 E8.1 arcsec/d dCEU ?Rate of change of CEU (10)
208-215 A8 "YYYYMMDD" DateCEU ?Date of CEU
217-223 E7.1 arcsec PEU0 ?Next peak ephemeris uncertainty (PEU) (11)
225-232 A8 "YYYYMMDD" DatePEU0 ?Date of PEU0
234-240 E7.1 arcsec PEU1 Greatest PEU, in 10 years from DatePEU0 (11)
242-249 A8 "YYYYMMDD" DatePEU1 Date of PEU1
251-257 E7.1 arcsec PEU2 As PEU1, assuming that two observations
were made at DatePEU0 (11)
259-266 A8 "YYYYMMDD" DatePEU2 Date of PEU2
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Note (1):
Absolute magnitude H, mag [see E. Bowell et al., pp. 549-554, in
"Asteroids II", R. P. Binzel et al. (eds.), The University of Arizona
Press, Tucson, 1989 and more recent Minor Planet Circulars].
Note that H may be given to 2 decimal places (e.g., 13.41), 1 decimal
place (13.4) or zero decimal (13.), depending on its estimated
accuracy. H is given to two decimal places for all unnumbered
asteroids, even though it may be very poorly known.
Note (2):
The epoch is the Julian date (TDT) ending in 00.5 nearest the date the
file was created. Thus, as the file is updated, epochs will succeed
each other at 100-day intervals on or after Julian dates ending in
50.5 (19960308, 19960616, 19960924, 19970102,...)
Note (3): the osculating elements are heliocentric, on J2000
Note (4): Planet-crossing asteroids
(Note: Because some orbits are very poor (or erroneously linked),
there may be errors in assignment of these parameter values)
The values are:
1 Earth-crossing asteroid (ECA), according to Shoemaker et al.'s
definition (In "Asteroids", pp. 253-282, T. Gehrels, ed., The
University of Arizona Press, Tucson, 1979 ). Some ECAs are
currently Amors (q.v.). ECAs have been identified prior to May
1991. After that date, asteroids having q < 1.0167 AU have been
assumed to be ECAs. Thus, in the latter group, some may not be
ECAs, and some asteroids assumed to be Amors may be ECAs.
2 Asteroids having perihelia less than the aphelion distance of the
Earth (1.0167 AU), but which are not ECAs.
4 Amors (1.0167 < q < 1.3 AU) (but see also type 1).
8 Mars crossers (1.3 < q < 1.6660 AU).
16 Outer-planet crossers (excluding Jupiter Trojans).
n Asteroids (excluding Mars and Jupiter Trojans) that cross both
inner- and outer-planet orbits. For example, n = 24 crosses the
orbits of Mars (q < 1.6660 AU) and Jupiter (Q > 4.950 AU).
Note (5): Orbit computation.
1 Orbits derived from uncertainly, perhaps erroneously linked
observations.
2 Eccentricity assumed.
4 Eccentricity and semimajor axis assumed.
8 For numbered asteroids, omitted observations have resulted in
degradation of a so-called orbit-quality parameter (OQP, see K.
Muinonen and E. Bowell, Icarus 104, 255-279, 1993), generally by
more than 0.1. The corresponding ephemeris uncertainty has
increased by about 25% or more.
16 OQP degrades by more than 0.1 if unsubstantiated observations
(e.g., one-night apparitions) are omitted.
32 Orbit derived from data containing observations not in
Minor Planet Center files
64 H is unknown; H = 14 mag assumed.
128 Asteroid sought, but not found.
n Sum of preceding entries. For example, n = 3 pertains to an
uncertainly linked orbit for which the eccentricity was assumed.
Note (6): Asteroids observed during the course of major surveys.
Our definition includes asteroids that were observed but not
discovered during the course of a survey.
1 Palomar-Leiden survey (PLS) asteroids.
2 Palomar-Leiden T-2 survey asteroids.
4 Palomar-Leiden T-3 survey asteroids.
8 U.K. Schmidt Telescope-Caltech asteroid survey (UCAS) asteroids.
16 Palomar-Leiden T-1 survey asteroids.
n Asteroids observed in more than one survey. For example, n = 3
denotes an asteroid observed in both the PLS and T-2 surveys.
Note (7): Minor Planet Center (MPC) critical-list numbered asteroids.
1 Lost asteroid.
2 Asteroids observed at only two apparitions.
3 Asteroids observed at only three apparitions.
4 Asteroids observed at four or more apparitions, last more than
ten years ago.
5 Asteroids observed at four or more apparitions, only one night in
last ten years.
6 Other poorly observed asteroids observed at four or more
apparitions.
7 Absolute magnitude poorly known (not on MPC critical-list).
Note (8): Lowell Observatory and related discoveries
1 Asteroids discovered by E. Bowell.
2 Non-Bowell discoveries from Lowell search programs.
3 Discovered jointly by E. Bowell and another person connected
with Lowell search programs.
Note (9): Rank, in decreasing importance, for our collaborative
program of astrometry using the transit circle of the
U.S. Naval Observatory Flagstaff Station.
10 Exceptionally important, to be observed frequently. Principally
space mission targets and occultation candidates.
9 Asteroids useful for mass determination.
8 Asteroids for which one or two additional nights' observation
are required to satisfy orbit-update requirements. Asteroids
of type 6:7 whose ephemeris uncertainties are between 2 and 5
arcsec within the next ten years or so.
7 Bowell unnumbered discoveries whose ephemeris uncertainties
are less than 2 arcsec within the next ten years or so. MPC
critical-list asteroids.
6 Planet-crossers of type 6:5.
5 Numbered asteroids whose ephemeris uncertainties are between
2 and 5 arcsec within the next ten years or so. Unnumbered
asteroids that should be numberable after one or two more
nights' observation.
Note (10): The current ephemeris uncertainty CEU and its rate of
change dCEI indicate whether an asteroid ought to be located in an
observer's field of view. A CEU greater than all three of the peak
ephemeris uncertainties (PEU) implies that the asteroid's ephemeris
uncertainty is currently greater than at any time in the next ten
years. Such asteroids are prime targets for observation because their
orbits are subject to the greatest improvement for years to come. Note
that, because ephemeris uncertainties have been computed using 2-body
rather than n-body error propagation (see K. Muinonen and E. Bowell,
Icarus 104, 255-279, 1993), uncertainties for Earth-approaching
asteroids may have been misestimated by a factor of several.
Note (11): Peak ephemeris uncertainties generally occur
near opposition or conjunction (the latter are more prevalent for
Earth-crossing asteroids). The next PEU [parameter PEU0] usually
indicates the best time to make astrometric observations for orbit
improvement, as will the PEU over the next 10 years [parameter PEU1].
Special effort should be made to observe asteroids whose next PEUs are
the greatest during the next 10 years [i.e., parameter PEU0 exceeds
both parameters PEU1 and PEU2]. Parameter PEU2 may be used to quantify
the amount of orbital improvement that would result from observing at
or near the date of next PEU. For example, if the next PEU is 1.2D+02
arcsec, and parameter PEU2 has value 6.0D+00 arcsec, a 20-fold
ephemeris improvement (and approximately equal improvement in the
uncertainties of the orbital elements) could be made. Note that
numbered asteroids whose orbits are satisfactory have all three PEUs
less than about 2 arcsec (absolute). Consequently, numbered asteroids
whose ephemeris uncertainties, as indicated by the CEU and PEUs, at
any time exceed about 2 arcsec should be targeted for observation.
Unnumbered asteroids whose ephemeris uncertainties [as per parameter
PEU2] could be brought below about 2 arcsec, would probably then be
candidates for numbering. A parameter PEU2 PEU greater than a
parameter PEU1 PEU implies that observing at or near the date of the
next PEU [parameter PEU0] may actually cause ephemeris and orbit
degradation. Thus, there is no point in making such observations
unless they are numerous and/or of high accuracy.
Author's address:
Ted Bowell <elgb@lowell.edu>
Lowell Observatory,
1400 West Mars Hill Road
Flagstaff, AZ 86001, USA
Acknowledgments:
The research and computing needed to generate astorb.dat were funded
principally by NASA grant NAG5-4741, and in part by the Lowell
Observatory endowment. astorb.dat may be freely used, copied, and
transmitted provided attribution to Dr. Edward Bowell and the
aforementioned funding sources is made. Hypertext links to this WWW
site are welcome.
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(End) CDS Catalogues Service 1996-Oct-14