KPL/PCK Planetary constants kernel for the Didymos system. =========================================================================== This file makes available for use in SPICE-based application software orientation and size/shape data for the Didymos system. Version and Date ------------------------------------------------------------------------ Version 08 -- December 4, 2022 -- Hari Nair, JHU/APL Use rotation parameters from solution 501 pre-impact values. Added ellipsoid dimensions of Dimorphos. Added post-impact rotation model in comments. Version 07 -- October 28, 2022 -- Hari Nair, JHU/APL Revise Dimorphos rotation; previous PM longitude was shifted by 180 degrees. Add post-impact rotation model in comments. Version 06 -- July 25, 2022 -- Hari Nair, JHU/APL Formatting changes: wrap lines longer than 80 characters and replace tab characters Version 05 -- January 31, 2022 -- Hari Nair, JHU/APL Update GM values for Didymos and Dimorphos. Version 04 -- December 6, 2021 -- Hari Nair, JHU/APL fix typo: BODY120065803_POLE was used rather than BODY920065803_POLE Version 03 -- October 11, 2021 -- Hari Nair, JHU/APL Update to DRA 3.10, rename to didymos_system_03.tpc Version 02 -- September 3, 2021 -- Marc Costa Sitja, NAIF/JPL Removed reference frame definitions and done cosmetic updates. Version 01 -- March 2, 2021 -- Hari Nair, JHU/APL Based on Design Reference Asteroid (DRA) version 3.00 and JPL IOM 392R-21-004. References ------------------------------------------------------------------------ 1. ``Frames Required Reading'' 2. ``Kernel Pool Required Reading'' 3. ``C-Kernel Required Reading'' 4. https://physics.nist.gov/cgi-bin/cuu/Value?bg Contact Information ------------------------------------------------------------------------ Hari Nair, JHU/APL, Hari.Nair@jhuapl.edu. Olivier Barnouin, JHU/APL, Olivier.Barnouin@jhuapl.edu Boris Semanov, NAIF/JPL, Boris.Semenov@jpl.nasa.gov Disclaimer ------------------------------------------------------------------------ The Reference Frame is defined to be EME2000 [1]. The Epoch is defined to be Jan 1 2000 12:00 (2451545.0D0). NOTE: These keywords break the 32 character limit for SPICE kernel pool variable names. EME2000 and epoch J2000 are the defaults so it's not necessary to explicitly put them in. BODY920065803_CONSTANTS_REF_FRAME = ( 1 ) BODY920065803_CONSTANTS_JED_EPOCH = ( 2451545.0D0 ) BODY120065803_CONSTANTS_REF_FRAME = ( 1 ) BODY120065803_CONSTANTS_JED_EPOCH = ( 2451545.0D0 ) Applicability of Data -------------------------------------- The rotation parameters for Dimorphos are only valid prior to the DART impact time of 2022 SEP 26 23:14:24.183 UTC. Rotation values for the post-impact period are in the commented section below. Orientation Constants ------------------------------------------------------------------------ Didymos -------------------------------------- Didymos has a volume-equivalent diameter of 761 m +/- 26 m. It is here modeled as a triaxial ellipsoid with semi-axes equal to half of the shape model's extents along principal axis. The spin pole is taken to be longitude 320.6 degrees, latitude -78.6 degrees in the ECLIPJ2000 frame. The spin period is taken to be 2.2600 +/- 0.0001 hours. The Prime Meridian for Didymos is arbitrarily set to 0 at the epoch. \begindata BODY920065803_RADII = ( 0.4250, 0.4250, 0.310 ) BODY920065803_POLE_RA = ( 60.936309840897856, 0, 0) BODY920065803_POLE_DEC = ( -71.674565992873852, 0, 0) BODY920065803_PM = ( 0.0, 3823.008849557522, 0.0 ) BODY920065803_PGR_POSITIVE_LON = 'EAST' \begintext Dimorphos -------------------------------------- Dimorphos is modeled as triaxial ellipsoid with semi-axes derived from DRACO imaging (Daly et al, in review). This PCK corresponds to the Dimorphos orbit solution 501. It is designed to keep the body-fixed X-axis of Dimorphos oriented towards the Didymos primary center of mass. It is only valid prior to the DART impact time of 2022 SEP 26 23:14:24.183 UTC. The rotation state of Dimorphos is given by {RA, DEC, W_0+W_1*delta_t +W_2*delta_t^2}, where RA represents the spin pole right ascension, DEC represents the spin pole declination, W_0 represents the prime meridian angle, W_1 represents the rotation rate, and delta_t represents the time elapsed since J2000 = JD 2451545.0, i.e. 2000 January 1 12 hours TDB (Barycentric Dynamical Time). An acceleration in the orbit period of Dimorphos and thus in spin rate (assuming Dimorphos was tidally locked before the DART impact) has been measured. RA = 60.936309840897856 +/- 7.0 [deg] DEC = -71.674565992873852 +/- 2.2 [deg] W_0 = 64.914870949788195 +/- 0.2 [deg] W_1 = 724.723943017441570 +/- 0.2 [deg/day] W_2 = 1.0840372309e-06 +/- 2.3e-07 [deg/day^2] \begindata BODY120065803_RADII = ( 0.0885 0.0870 0.0580 ) BODY120065803_POLE_RA = ( 60.936309840897856, 0, 0) BODY120065803_POLE_DEC = ( -71.674565992873852, 0, 0) BODY120065803_PM = ( 64.914870949788195, 724.723943017441570, 1.0840372309e-06 ) BODY120065803_PGR_POSITIVE_LON = 'EAST' \begintext These values are valid after the DART impact time of 2022 SEP 26 23:14:24.183 UTC. BODY120065803_POLE_RA = ( 60.438964751082167, 0, 0) BODY120065803_POLE_DEC = ( -71.722479348711090, 0, 0) BODY120065803_PM = ( 191.001229243909535, 759.961387826767236, 0.0000000000e+00 ) GM values ------------------------------------------------------------------------ The value for G is taken to be 6.67430e-11 m^3/kg/s^2 from [4] The GM of the system is taken from Table 2 of JPL IOM 392R-21-008. The individual GM values are derived from the system GM and DRA parameters 20 and 21 and assuming both bodies have equal density. System GM = 37.0362727488241445575 m^3/s^2 Didymos volume equivalent radius = 390 m Dimorphos volume equivalent radius = 82 m GM for Didymos = [ 390^3 / (390^3 + 82^3) ] * 37.0362727488241445575 = 36.69519223913071 GM for Dimorphos = [ 82^3 / (390^3 + 82^3) ] * 37.0362727488241445575 = 0.3410805096934375 Units below are km^3/s^2. \begindata BODY20065803_GM = 37.0362727488241445575E-9 BODY120065803_GM = 0.3410805096934375E-9 BODY920065803_GM = 36.69519223913071E-9 \begintext End of PCK file.