KPL/PCK Asteroid Vesta 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 Vesta -- Radii for asteroid Vesta Version description -------------------------------------------------------- Version 0.4 -- November 2, 2011 -- Carol Raymond, DAWN Deputy PI, Boris Semenov, NAIF Corrected W0 (76.06 -> 75.39). Version 0.3 -- September 29, 2011 -- Carol Raymond, DAWN Deputy PI, Boris Semenov, NAIF Per MCR-112436 Vesta pole orientation and prime meridian (Ra, Dec, W0) were changed to (309.031, 42.235, 76.06) degrees Version 0.2 -- February 25, 2011 -- Boris Semenov, NAIF Vesta pole orientation (Ra, Dec) was changed to (305.8, 41.4) degrees per MCR-111475 and "Dawn Planetary Constants and Models Document" Revision 2.0, Feb 16, 2011 Version 0.1 -- October 12, 2004 -- Boris Semenov, NAIF VESTA_FIXED frame definition was removed. It is now in the DAWN Frames Kernel file. Version 0.0 -- October 6, 2003 -- Boris Semenov, NAIF This is a preliminary PCK containing draft values for the pole direction, prime meridian location, rotation period and shape (from [1].) 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 ``by line'' and date if you modify the file. Sources -------------------------------------------------------- The sources for the constants listed in this and the earlier versions of this file are: 1) Thomas, Peter C. et al. ``Vesta: Spin Pole, Size, and Shape from HST Images.'' ICARUS 128, 1997. Article NO. IS975736. pp. 93-94. 2) "Dawn Planetary Constants and Models Document" Revision 2.0, Feb 16, 2011 3) Analysis of Data from Dawn's Survey Orbit, Sep 23, 2011. (IOM attached to MCR-112436). Orientation constants for asteroid Vesta -------------------------------------------------------- The inertial reference frame for these 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 Vesta is 2000004. See the NAIF_IDs required reading for further information on NAIF integer codes. Values in the Versions 0.0 and 0.1 The pole direction, prime meridian location, and rotation period in the versions 0.0 and 0.1 were set to the following values from [1]: "New data from the 1996 Hubble HST observations of Vesta allow a refinement of the pole solution to: RA = 301 deg, Dec = 41 deg, +/- 5 deg. The prime meridian is now given by W = 292 deg + 1617.332776 deg * d; see Section 3a and Eq. 1. The new data, and a scaling correction, change the fit radii to 289, 280, 229, +/- 5 km." Values in the Version 0.2 The pole direction, prime meridian location, and rotation period in the version 0.2 were set to the following values from [2]: "5.3 Vesta Pole and Prime Meridian The Vesta pole and prime meridian values are shown below. RA Vesta = 305.8 +/- 3.1 deg Right Ascension in EME2000 [25] DEC Vesta = 41.4 +/- 1.5 deg Declination in EME2000 [25] W Vesta = 292 + w * D deg Prime Meridian w Vesta = 1617.332776 deg/day Rotation rate 5.4 Vesta Shape Parameters The Vesta shape is described as a triaxial ellipsoid with values 289, 280, 229 km [15] or as a sphere with a radius of 265 km [16]. ... 9 References ... 15. "Vesta: Spin Pole, Size, and Shape from HST Images", P. Thomas, et al., Icarus, v128, p88~94 (1997)." 16. "Impact Excavation on Asteroid 4 Vesta: Hubble Space Telescope Result", P. C. Thomas, et al, Science, 227, 1492-1494, 1997. ... 25. "Improved Measurement of Asteroid (4) Vesta's Rotational Axis Orientation", Jian-Yang Li, et al., Icarus, 211, 528-534, 2010.." Values in the Version 0.3 The pole direction, prime meridian location, rotation period and radii in this version are set to the following values from [3]: "... The recommended new pole is: - RA: 309.031 Dec: 42.235 - Error is estimated as +/-0.03deg 3-sigma Data considered: - Konopoliv (Gravity) 309.029 42.225 - Preusker (DLR) Survey 309.031 42.235 - OpNav 309.025 42.245 - NAV OD radio 309.025 42.247 The rotation rate of Vesta was determined to be .222588677 +/- .000000009 days/rev, which agrees very well with the weighted average of all previous determinations. ... A new prime meridian was chosen as defined by a small crater that is assigned a longitude of 356 deg East. This new system was chosen because the old system was not well-defined and the team wanted to make a clear distinction between the old and new to avoid confusion. The offset between the old W0 (292) from Thomas et al. (1997) and the new W0 (76.06) is about 144.06 deg." These values are provided in the keywords below. The W1 was derived from .222588677 days/rev as follows: W1 = 1 / 0.222588677 * 360 = 1617.3329428 Values in the Current Version 0.4 The pole direction, rotation period, and radii in the version 0.4 are the same as in the version 0.3. The W0 value is 75.39 deg (changed from 76.06 deg to match the correct rotation rate.) \begindata BODY2000004_POLE_RA = ( 309.031 0.0 0.0 ) BODY2000004_POLE_DEC = ( 42.235 0.0 0.0 ) BODY2000004_PM = ( 75.39 1617.3329428 0.0 ) \begintext Radii for asteroid Vesta -------------------------------------------------------- The Vesta radii from [2] are provided in the keyword below. \begindata BODY2000004_RADII = ( 289.0 280.0 229.0 ) \begintext End of PCK file.