KPL/PCK Asteroid Ceres P_constants (PcK) SPICE kernel file =========================================================================== Organization -------------------------------------------------------- The sections of this file are as follows. Introductory Information: -- Version description -- Disclaimer -- Sources Pck Data: -- Orientation constants for asteroid Ceres -- Radii for asteroid Ceres -- GM for asteroid Ceres Version Description -------------------------------------------------------- Version 0.2 -- March 2, 2015 -- Don Han, DAWN NAV; Boris Semenov, NAIF Ceres rotation constants were updated based on [4]; Keyword for Ceres GM was added to the file and set to the value from [4]. Version 0.1 -- February 25, 2011 -- Boris Semenov, NAIF Ceres pole orientation constants and radii were set to the values from [3]. Version 0.0 -- October 12, 2004 -- Boris Semenov, NAIF Initial PCK containing draft values for the pole direction, rotation period and shape (from [1] and [2]) and placeholder value for prime meridian. Disclaimer -------------------------------------------------------- This constants file may not contain the parameter values that you prefer. Note that this file may be readily modified by you or anyone else. NAIF suggests that you inspect this file visually before proceeding with any critical or extended data processing. NAIF requests that you update the ``Version Description'' section if you modify the file. Sources -------------------------------------------------------- The sources for the constants listed in this and the earlier versions of this file are: 1) Saint-Pe, O., M. Combes, F. Rigaut (1993). Ceres surface properties by high-resolution imaging from Earth. Icarus 105, 271-281. 2) JPL Solar System Dynamic Group Horizon's System. 3) "Dawn Planetary Constants and Models Document", Revision 2.0, Feb 16, 2011 4) "DAWN Planetary Constants and Models Document", Revision 4.0, Mar 2, 2015 Orientation constants for asteroid Ceres -------------------------------------------------------- The inertial reference frame for Ceres constants is J2000; this is the default reference frame for PCK orientation data. The epoch of the constants is J2000; this is Julian ephemeris date (JED) 2451545.0. The NAIF integer code for Ceres is 2000001. See the NAIF_IDs required reading for further information on NAIF integer codes. Values in the Version 0.0 The PCK version 0.0 provided the pole direction RA = 300.4 deg and DEC = 53.1 deg (derived from the ecliptic equinox B1950.0 latitude = 70 deg and longitude = 332 deg values given in [1]), the W1 term = 952.06611570 deg/day (derived from the rotation period of 9.075 hours provided in [2]), and the W0 term arbitrarily set to 0. The corresponding keywords were set follows: body2000001_pole_ra = ( 300.4 0.0 0.0 ) body2000001_pole_dec = ( 53.1 0.0 0.0 ) body2000001_pm = ( 0.0 952.0661157 0.0 ) Values in the Version 0.1 In the PCK version 0.1 the pole direction, prime meridian location, and rotation period were set to the following values from [3]: 6.3 Ceres Pole and Prime Meridian The Ceres pole and prime meridian values are shown below. RA Ceres 291 deg Right Ascension in EME2000 [17] DEC Ceres 59 deg Declination in EME2000 W Ceres 0 + w * D deg Prime Meridian w Ceres 951.5418502 deg/day Rotation rate ... 9 References ... 17. "Ceres: High-resolution imaging with HGA and the determination of physical properties," J. W. Parker et al., Advances in Space Research 38 (2006) 2039-2042. 18. "Differentiation of the asteroid Ceres as revealed by its shape", P. C. Thomas, et al, Nature, 437, 224, 2005. ..." The corresponding keywords were set follows: body2000001_pole_ra = ( 291.0 0.0 0.0 ) body2000001_pole_dec = ( 59.0 0.0 0.0 ) body2000001_pm = ( 0.0 951.5418502 0.0 ) Values in the Current Version 0.2 In the current PCK version 0.2 the pole direction, prime meridian location, and rotation period are set to the following values from [4]: 6.3 Ceres Pole and Prime Meridian The Ceres pole and prime meridian values are shown below. RA Ceres 291.82 deg Right Ascension in EME2000 [29] DEC Ceres 66.88 deg Declination in EME2000 [29] W Ceres 353.7987 + w * D deg Prime Meridian [*] w Ceres 952.055 deg/day Rotation rate [29] [*] This document overlooked the Ceres prime meridian and rotation rate recommended by Archinal et. al. [28] in IAU working group report and listed the prime meridian with zero offset until revision 4 date. While updating the prime meridian definition, Dawn project decided to update other physical parameters of Ceres by navigation team~s latest estimation result. The rotation rate is from navigation team report [29] and the prime meridian offset was calculated to match the value from IAU recommendation [28] at the time of RC2 (2015/02/20 12:00:00 UTC). ... 9 References 29. "Ceres Parameters from OD", Brian Kennedy, JPL internal E-mail, Feb. 26, 2015 \begindata BODY2000001_POLE_RA = ( 291.82 0.0 0.0 ) BODY2000001_POLE_DEC = ( 66.88 0.0 0.0 ) BODY2000001_PM = ( 353.7987 952.055 0.0 ) \begintext Radii for asteroid Ceres -------------------------------------------------------- Values in the Version 0.0 In the PCK version 0.0 the radii were set to the following values from [2]: body2000001_radii = ( 475.0 475.0 475.0 ) Values in the Versions 0.1 and 0.2 (current) In the version 0.1 and 0.2 the radii are set to the following values from [3]/[4]: 6.4 Ceres Shape Parameters The Ceres shape is described by an oblate spheroid with values 487.3 km and 454.7 km [18] or as a sphere with a radius of 480 km. ... 9 References ... 18. "Differentiation of the asteroid Ceres as revealed by its shape", P. C. Thomas, et al, Nature, 437, 224, 2005. ..." \begindata BODY2000001_RADII = ( 487.3 487.3 454.7 ) \begintext GM for asteroid Ceres -------------------------------------------------------- Value in the Versions 0.0 and 0.1 No Ceres GM was provided in the PCK version 0.0 and 0.1. Value in the Current Version 0.2 In the current PCK version 0.2 the Ceres GM is set to the following value from [4]: 6.2 Ceres Gravity Model GM Ceres = 62.68 km3/s2 Gravitational Parameter [29] ... 9 References 29. "Ceres Parameters from OD", Brian Kennedy, JPL internal E-mail, Feb. 26, 2015 \begindata BODY2000001_GM = ( 62.68 ) \begintext End of PCK file.