Objects In This Ephemeris -------------------------------------------------------- Name Id-code ------------- ------- Asteroid Agamemnon........2000911 Asteroid Aneas............2001172 Asteroid Chiron...........2002060 Asteroid Davida...........2000511 Asteroid Diomedes.........2001437 Asteroid Frigga...........2000077 Asteroid Hektor...........2000624 Asteroid Hygeia...........2000010 Asteroid Palisana.........2000914 Asteroid Phaethon.........2003200 Asteroid Pholus...........2005145 Comet Comas-Sola..........1000015 Comet Encke...............1000025 Comet Hale-Bopp...........1000132 Comet Hyakutake...........1000131 Comet Shoemaker-Holt 1....1000117 Comet Wirtanen............1000109 Approximate Time Coverage All objects have data for the interval From: 1996 JUL 08 00:00:00.000 (ET) To : 1999 FEB 09 00:00:00.000 (ET) The actual coverage for the various bodies is given below Asteroid Phaethon.........2003200 From: 1996 JUL 06 12:00:00.000 (ET) To : 1999 FEB 10 12:00:00.000 (ET) Comet Encke...............1000025 Comet Hale-Bopp...........1000132 Comet Hyakutake...........1000131 Comet Shoemaker-Holt 1....1000117 Comet Wirtanen............1000109 From: 1996 JUL 07 00:00:00.000 (ET) To : 1999 FEB 10 00:00:00.000 (ET) Asteroid Agamemnon........2000911 Asteroid Aneas............2001172 Asteroid Chiron...........2002060 Asteroid Davida...........2000511 Asteroid Diomedes.........2001437 Asteroid Frigga...........2000077 Asteroid Hektor...........2000624 Asteroid Hygeia...........2000010 Asteroid Palisana.........2000914 Asteroid Pholus...........2005145 Comet Comas-Sola..........1000015 From: 1996 JUL 08 00:00:00.000 (ET) To : 1999 FEB 09 00:00:00.000 (ET) Status -------------------------------------------------------- This ephemeris provides JPL's current best estimate for the position of the objects listed above as of July 26, 1996. It is anticipated that the ephemeris for Comet Encke will be updated in July 1997. No formal updates for the ephemerides of other objects are planned. However, if you need a more recent ephemeris and have reason to believe that observations following the creation date of this ephemeris may significantly improve the positional knowledge for that object, we recommend that you contact NAIF. If resources are available, we will attempt to provide an update to this ephemeris. Production/History of this Ephemeris -------------------------------------------------------- This SPICE format ephemeris was produced by Bill Taber of the Navigation Ancillary Information Facility (NAIF) at the Jet Propulsion Laboratory on July 31, 1996 for use by ESA's Infrared Space Observatory mission. This file was merged from a set of ephemerides (one for each body listed). Each individual ephemeris was transformed to SPK format from a numerical integration performed by Don Yeomans of the Solar Systems Dynamics group of the Navigation and Flight Mechanics Section of the Jet Propulsion Laboratory. The particulars of each of the individual ephemerides is given below. Each object is listed with the number of observations used to construct an orbit for the object, the range of dates of those observations and the source of the Initial conditions used in the integration of the ephemeris supplied in this file. MPC refers to the "Minor Planet Circular." Yeomans' solution number "n" refers to the n'th solution (performed by Don Yeomans at JPL) for the initial conditions of a body . These solutions make direct use of the observations of the particular object. The ephemeris for each object was integrated using the JPL developmental ephemeris DE403 to provide the gravitational force model. Asteroid Agamemnon Number of Observations : 129 Observation dates : 1919 to 1995. Source of Initial Conditions: MPC 22666 Asteroid Aneas Number of Observations : 133 Observation dates : 1930 to 1990. Source of Initial Conditions: MPC 22666 Asteroid Chiron Number of Observations : 209 Observation dates : 1895 to 1993. Source of Initial Conditions: MPC 22797 Asteroid Davida Number of Observations : 930 Observation dates : 1903 to 1995. Source of Initial Conditions: MPC 2257 Asteroid Diomedes Number of Observations : 134 Observation dates : 1919 to 1989. Source of Initial Conditions: MPC 22667 Asteroid Frigga Number of Observations : 106 Observation dates : 1914 to 1991. Source of Initial Conditions: MPC 21760 Asteroid Hektor Number of Observations : 268 Observation dates : 1907 to 1990. Source of Initial Conditions: MPC 22797 Asteroid Hygeia Number of Observations : 1247 Observation dates : 1849 to 1993. Source of Initial Conditions: MPC 24219 Asteroid Palisana Number of Observations : 138 Observation dates : 1919 to 1995. Source of Initial Conditions: MPC 25715 Asteroid Phaethon Number of Observations : 227 Observation dates : 1983 to 1996. Source of Initial Conditions: Yeomans' Solution number 4 Asteroid Pholus Number of Observations : 58 Observation dates : 1977 to 1992. Source of Initial Conditions: MPC 19850 Comet Comas-Sola Number of Observations : 188 Observation dates : 1977 to 1996. Source of Initial Conditions: Yeomans' solution 6. Comet Encke Number of Observations : 187 Observation dates : 1984 to 1996. Source of Initial Conditions: Yeomans' solution 24 Comet Hale-Bopp Number of Observations : 1008 Observation dates : July 14, 1995 to June 23, 1996. Source of Initial Conditions: Yeomans' solution 35 Comet Hyakutake Number of Observations : 943 Observation dates : January 1, 1996 to June 10, 1996. Source of Initial Conditions: Yeomans solution 53 Comet Shoemaker-Holt 1 Number of Observations : 65 Observation dates : 1987 to 1989. Source of Initial Conditions: MPC 23484 Comet Wirtanen Number of Observations : 16 Observation dates : 1985 to 1996. Source of Initial Conditions: Yeomans' solution 12 Usage -------------------------------------------------------- To determine the state of an object with respect to any object other than the sun, you need at a minimum a planetary ephemeris. Since the planetary ephemeris used for the dynamical force model in the integration of the objects in this ephemeris was DE403, it is recommended that you use DE403 when computing states of the object with respect to anything other than the sun. DE403 is available via anonymous ftp on NAIF's ftp server: naif-sun (ip address 128.149.126.11) in the directory pub/naif/generic_kernels/spk. Both IEEE binary and transfer format ephemerides are available. They are in the files. de403s.bsp ( binary format ) de403s.xsp ( transfer format ) de403s.cmt ( comments about de403s ) Accuracy -------------------------------------------------------- The error in the plane of the sky positions of the objects stored in this ephemeris vary from body to body. Estimates for the upper bound of uncertainty in the positions of the object (on the plane of the sky as viewed from earth) are given in the table below. 1-sigma Plane of Sky Object Name Uncertainty (arc seconds) ------------- ------- Asteroid Agamemnon........ 10 Asteroid Aneas............ 10 Asteroid Chiron........... 10 Asteroid Davida........... 10 Asteroid Diomedes......... 10 Asteroid Frigga........... 10 Asteroid Hektor........... 10 Asteroid Hygeia........... 10 Asteroid Palisana......... 10 Asteroid Phaethon......... 10 Asteroid Pholus........... 10 Comet Comas-Sola.......... 20 Comet Encke............... 20* Comet Hale-Bopp........... 20 Comet Hyakutake........... 10 Comet Shoemaker-Holt 1.... 30 Comet Wirtanen............ 10 * The accuracy of the position of Comet Encke will degrade as it nears its closest approach to Earth in 1997. An upgrade to the ephemeris is anticipated in July 1997. References -------------------------------------------------------- The table of accuracies above was provided via private communication from Don Yeomans. Inquiries If you have any questions regarding this ephemeris contact Bill Taber btaber@spice.jpl.nasa.gov Phone (818) 354-4279 FAX (818) 393-6388 JPL MS 301/125L 4800 Oak Grove Drive Pasadena, CA 91109