Objects In This Ephemeris -------------------------------------------------------- Name Id-code ------------- ------- Naiad.................803 Thalassa..............804 Despina...............805 Galatea...............806 Larissa...............807 Proteus...............808 Approximate Time Coverage From: 1998 JAN 01 00:00:00.000 To : 2010 JAN 01 00:00:00.000 Status -------------------------------------------------------- This is the current best estimate for the position of the minor satellites of Neptune as of 3-Dec-1998. Currently, no formal updates to this ephemeris 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 any of these objects, we recommend that you contact NAIF and to the extent that resources are available we will attempt to provide an update to this ephemeris. Production/History of this Ephemeris -------------------------------------------------------- This ephemeris was produced by Bill Taber of the Navigation Ancillary Information Facility (NAIF) at the Jet Propulsion Laboratory on 1-Dec-1998 for use by the Space Telescope Science Institute. It was transformed to SPK format from a equinoctial elements provided by Bob Jacobson of the Solar Systems Dynamics group of the Astrodynamics and Navigation section (section 312) of the Jet Propulsion Laboratory. The Release Form for the ephemeris description of these satellites is included as an appendix at the end of this note. Usage -------------------------------------------------------- To determine the state of these satellites with respect to any object other than the Neptune barycenter, you need at a minimum a planetary ephemeris. It is recommended that you use JPL developmental ephemers 403 (DE403) or later when computing states of these satellites with respect to anything other than the Neptune Barycenter. 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 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 ) In addition, if you need to plan observations of these satellites relative to Neptune, you will need a satellite ephemeris that includes Neptune relative to the Neptune Barycenter. Either of the following ephemerides are suitable for this purpose (both available in the same location as de403s.bsp) nep016.bsp ( binary format ) nep016.xsp ( transfer format ) nep022.bsp ( binary format ) nep022.xsp ( transfer format ) Accuracy -------------------------------------------------------- This ephemeris is based on observations made with the Voyager 2 spacecraft in 1989. At the time of creation of this ephemeris, no other observations of the satellites have been used in the analysis of the orbits of these satellites. The chief uncertaintly in the determination of the orbits of these satellites is in mean motion. Based upon this uncertainty we provide estimates of the positional uncertainty (as seen from earth) for the satellites in the tables below. Name Id-code Uncertainty Relative to Neptune. ------------------------------------------------------- Naiad........803....... 1.5 arc seconds Thalassa.....804....... 1.3 arc seconds Despina......805....... 0.3 arc seconds Galatea......806....... 0.4 arc seconds Larissa......807....... 0.3 arc seconds Proteus......808....... 0.3 arc seconds While these numbers appear to be quite small, the orbital longitude uncertainty is substantially larger. Name Id-code Position Angle Uncertainty. ------------------------------------------------------- Naiad........803....... 45 degrees Thalassa.....804....... 33 degrees Despina......805....... 9 degrees Galatea......806....... 8 degrees Larissa......807....... 5 degrees Proteus......808....... 3 degrees References -------------------------------------------------------- W.M. Owen, Jr., R.M. Vaughan, and S.P. Synnott, "Orbits of the Six New Satellites of Neptune" The Astonmical Journal, April 1991, Volume 101, Number 4 pp. 1511-1515 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 Appendix --- Rock Element File Release =========================================================================== Rock Element File: NEP022 File location: murphy:/home6/raj/Satellite/Neptune/Rocks/Data/rckin.nep022.txt Elements from Owen (1991) AJ 101, 1511 Equinox Reference Julian Date: 2433282.50 Bodies on the File: Name Number GM AX BX CX Proteu 808 0.000000000000000E+00 210.000 0.000 0.000 Lariss 807 0.000000000000000E+00 100.000 0.000 0.000 Despin 805 0.000000000000000E+00 70.000 0.000 0.000 Galate 806 0.000000000000000E+00 80.000 0.000 0.000 Thalas 804 0.000000000000000E+00 45.000 0.000 0.000 Naiad 803 0.000000000000000E+00 40.000 0.000 0.000 Elements for Proteu at Julian Date: 2447757.0 Semi-major axis 117647.1083951678 km h = esin(omega+node) 4.316469704955329E-04 k = ecos(omega+node) -7.210801844660832E-05 mean longitude 213.6694288751446 deg p = tan(i/2)sin(node) 1.711883968958595E-04 q = tan(i/2)cos(node) -2.965561624132692E-04 apsidal rate 9.133585598101285E-07 deg/sec mean longitude rate 3.712562763632274E-03 deg/sec nodal rate -8.950702955262804E-07 deg/sec Reference plane pole RTA 298.7578382787378 deg Reference plane pole DEC 42.26923434586892 deg Elements for Lariss at Julian Date: 2447757.0 Semi-major axis 73548.33124009847 km h = esin(omega+node) 6.945237904710838E-04 k = ecos(omega+node) -1.198878746228356E-03 mean longitude 184.8281238454398 deg p = tan(i/2)sin(node) 3.042139870660792E-04 q = tan(i/2)cos(node) 1.726074245672686E-03 apsidal rate 4.550153261802315E-06 deg/sec mean longitude rate 7.512192673335218E-03 deg/sec nodal rate -4.539452511249425E-06 deg/sec Reference plane pole RTA 298.8486977376166 deg Reference plane pole DEC 42.76431656177704 deg Elements for Despin at Julian Date: 2447757.0 Semi-major axis 52525.94522658495 km h = esin(omega+node) 1.128043758916851E-04 k = ecos(omega+node) -8.098417055716583E-05 mean longitude 85.27195918648782 deg p = tan(i/2)sin(node) 2.452222625008457E-04 q = tan(i/2)cos(node) -5.160964833839523E-04 apsidal rate 1.477732764822587E-05 deg/sec mean longitude rate 1.245062680798036E-02 deg/sec nodal rate -1.475538975056945E-05 deg/sec Reference plane pole RTA 298.8559427260777 deg Reference plane pole DEC 42.80345379429418 deg Elements for Galate at Julian Date: 2447757.0 Semi-major axis 61952.67233239824 km h = esin(omega+node) -7.643954764882611E-05 k = ecos(omega+node) -9.261893592328374E-05 mean longitude 46.64428546874267 deg p = tan(i/2)sin(node) 4.399399135144454E-04 q = tan(i/2)cos(node) -1.791773877212785E-04 apsidal rate 8.286590313969883E-06 deg/sec mean longitude rate 9.718284359168671E-03 deg/sec nodal rate -8.273570255118341E-06 deg/sec Reference plane pole RTA 298.8538628232021 deg Reference plane pole DEC 42.79222332505918 deg Elements for Thalas at Julian Date: 2447757.0 Semi-major axis 50074.55197063884 km h = esin(omega+node) 1.123719252646464E-04 k = ecos(omega+node) 1.079729369013819E-04 mean longitude 239.7371428952268 deg p = tan(i/2)sin(node) 1.792404076448216E-03 q = tan(i/2)cos(node) 4.684855446979837E-06 apsidal rate 1.747529721870989E-05 deg/sec mean longitude rate 1.337680047670611E-02 deg/sec nodal rate -1.744878934774183E-05 deg/sec Reference plane pole RTA 298.8562812366566 deg Reference plane pole DEC 42.80528119838995 deg Elements for Naiad at Julian Date: 2447757.0 Semi-major axis 48227.30488030718 km h = esin(omega+node) 3.264408052171053E-04 k = ecos(omega+node) 2.676346632678553E-05 mean longitude 60.26044459305379 deg p = tan(i/2)sin(node) 3.106248110850256E-02 q = tan(i/2)cos(node) 2.732694604457570E-02 apsidal rate 1.966548948527533E-05 deg/sec mean longitude rate 1.415328843692009E-02 deg/sec nodal rate -1.983882754543970E-05 deg/sec Reference plane pole RTA 298.8564946497789 deg Reference plane pole DEC 42.80643322459633 deg Release to: Horizons/NAIF Date: 19-MAY-1998 Time: 09:45:45 Preparer: R.A. Jacobson Comments: Elements for inner Neptunian satellites from fit to Voyager data.