ison.bsp was produced on 2/26/2013 by C. Acton, using JPL's Horizons system. Horizons production notes are shown below, and are included in the "comment area" of the file. This spk must be assumed to degrade in fidelity as time passes since non-gravitational forces will begin having an increasing effect on the trajectory. To get the most accurate possible ISON trajectory from Horizons, use Horizons to generate a new spk as indicated below. ------------ Horizons Production Notes --------------- IMPORTANT NOTICE: This informal file release should not be used for purposes affecting the safety and success of spacecraft hardware or missions without first contacting Donald.K.Yeomans@jpl.nasa.gov (Supervisor, Solar System Dynamics Group, 818-354-2127) or Jon.D.Giorgini@jpl.nasa.gov (SSDG analyst). This is because an object's orbit solution may be insufficiently determined over the chosen time-span to be suitable for some high-precision purposes, due to the quantity of measurements available for an object, the time-span they cover, and the object's dynamical path. Although not stored in this file, statistical uncertainty of the trajectory as a function of time may be available from the JPL Horizons system. This can help interpret the accuracy of the trajectory. Orbit solutions are updated in Horizons as new measurements are made, so this trajectory may be superceded by more recent solutions. Check the orbit solution number for an object (given below as "source") against the latest Horizons entry to determine if an updated orbit solution is available. This parameterized post-Netwonian numerically integrated perturbed trajectory was produced by: Horizons On-Line Ephemeris System Solar System Dynamics Group Jet Propulsion Laboratory 4800 Oak Grove Drive Pasadena, CA 91109 USA Horizons information & documentation: http://ssd.jpl.nasa.gov/?horizons Connection for small-body SPK generation (automation scripts available): telnet ssd.jpl.nasa.gov 6775 (interactive UNIX/Linux command-line) telnet://ssd.jpl.nasa.gov:6775 (interactive browser URL window) http://ssd.jpl.nasa.gov/x/spk.html (passive browser form) Inquiries: Jon.D.Giorgini@jpl.nasa.gov (program author; 818-393-3107) SPK file contents: OBJECT #01 ========== Requested by : charles.acton@jpl.nasa.gov Execution date : Tue Feb 26 17:13:19 2013 (Pasadena time) Target body : ISON (C/2012 S1) {source: Horizons_SPK:JPL#15} Target SPK ID : 1003203 Coord center : Sun ( 10) {source: DE-0405LE-04} GM of center : 2.9591220828559109E-04 AU^3/D^2 Small perturbers: Ceres, Pallas, Vesta {source: SB405-CPV-2} Small body GMs : 6.32E+01, 1.43E+01, 1.78E+01 km^3/s^2 Start time : 2012-Jan-01 00:00:00.0000 CT Stop time : 2014-Jan-02 00:00:00.0000 CT ******************************************************************************* Initial FK5/J2000.0 heliocentric ecliptic osculating elements (AU, DAYS, DEG): EPOCH= 2456282.5 != 2012-Dec-21.0000000 (CT) Residual RMS= .50627 EC= 1.000003840002629 QR= .01250718992752768 TP= 2456625.2866813405 OM= 295.7428450059515 W= 345.5057438683777 IN= 61.82939000266723 Comet physical & dynamic parameters (KM, SEC; A1,A2,A3=AU/d^2; DT=days): GM= n.a. RAD= n.a. A1= n.a. A2= n.a. A3= n.a. DT= n.a. M1= 6.7 M2= 9.8 k1= 9. k2= 5. PHCOF= .030