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 15 -- September 21, 2023 -- Hari Nair, JHU/APL Use rotation parameters from solution 542 pre-impact values. Revise asteroid sizes and GM values. Version 14 -- August 10, 2023 -- Hari Nair, JHU/APL Update Didymos radius. Version 13 -- August 9, 2023 -- Hari Nair, JHU/APL Update Didymos pole to be consistent with pre-impact Dimorphos pole. Version 12 -- June 12, 2023 -- Hari Nair, JHU/APL Use rotation parameters from solution 527 pre-impact values. Remove post-impact values in comments. NOTE: Rather than IAU_DIMORPHOS, most users should use the switch frame DIMORPHOS_FIXED, defined in didymos_system_005.tf. Version 11 -- May 26, 2023 -- Hari Nair, JHU/APL Use rotation parameters from solution 523 pre-impact values. Added ellipsoid dimensions of Dimorphos. Added post-impact rotation model in comments. NOTE: Rather than IAU_DIMORPHOS, most users should use the switch frame DIMORPHOS_FIXED, defined in didymos_system_004.tf. Version 10 -- April 20, 2023 -- Hari Nair, JHU/APL Set Didymos pole to be consistent with Dimorphos pole and update pole coordinates in ECLIPJ2000. Version 09 -- February 1, 2023 -- Hari Nair, JHU/APL Use rotation parameters from solution 516 pre-impact values. Added ellipsoid dimensions of Dimorphos. Added post-impact rotation model in comments. NOTE: Rather than IAU_DIMORPHOS, most users should use the switch frame DIMORPHOS_FIXED, defined in didymos_system_003.tf. 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. Naidu et al. 2023, "Orbital and physical characterization of Dimorphos following the DART impact", in preparation Contact Information ------------------------------------------------------------------------ Hari Nair, JHU/APL, Hari.Nair@jhuapl.edu. Olivier Barnouin, JHU/APL, Olivier.Barnouin@jhuapl.edu Alyssa Bailey, NAIF/JPL, alyssa.m.bailey@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 23:14:24.184 UTC. Most users should use the switch frame DIMORPHOS_FIXED, defined in didymos_system_007.tf and later versions of the frame kernel. DIMORPHOS_FIXED is valid for all times before and after the DART impact. Orientation Constants ------------------------------------------------------------------------ Didymos -------------------------------------- Didymos has a volume-equivalent diameter of 710.3 m, using the best-fit dimensions from [4]. The spin pole is taken to be longitude 310.0 degrees, latitude -80.6 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 = ( 0.39167, 0.39167, 0.29195 ) BODY920065803_POLE_RA = ( 69.326861266078069, 0, 0) BODY920065803_POLE_DEC = ( -72.724550395829496, 0, 0) BODY920065803_PM = ( 0.0, 3823.008849557522, 0.0 ) BODY920065803_PGR_POSITIVE_LON = 'EAST' \begintext Dimorphos -------------------------------------- Dimorphos has a volume-equivalent diameter of 145.6 m, using the best-fit dimensions from [4]. This PCK corresponds to the Dimorphos orbit solution 542. 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 23:14:24.184 UTC. The frame IAU_DIMORPHOS is constructed from these parameters. It will be the same frame before and after impact. Most users will probably want to use the switch frame DIMORPHOS_FIXED, defined in the frame kernel didymos_system_007.tf. DIMORPHOS_FIXED is equivalent to IAU_DIMORPHOS prior to impact and is a dynamic frame after impact, where the X axis points from Dimorphos to Didymos and the Z axis is parallel to the IAU_DIDYMOS Z axis. \begindata BODY120065803_RADII = ( 0.09078, 0.06932, 0.06131 ) BODY120065803_POLE_RA = ( 69.326861266078069, 0, 0) BODY120065803_POLE_DEC = ( -72.724550395829496, 0, 0) BODY120065803_PM = ( 73.070565080143595, 724.724388306834840, 1.0270736140e-06) BODY120065803_PGR_POSITIVE_LON = 'EAST' \begintext GM values ------------------------------------------------------------------------ The GM of the system is taken from [4]. The individual GM values are derived from the system GM, scaled by the relative volumes calculated from the dimensions given above and assuming the same density for both bodies. System GM = 3.48961209875640268354e-08 km^3/s^2 Didymos volume (va) = 0.1876 km^3 Dimorphos volume (vb) = 0.001616 km^3 GM for Didymos = [ va / (va + vb) ] * 3.48961209875640268354e-08 = 3.45980739686124e-08 GM for Dimorphos = [ vb / (va + vb) ] * 3.48961209875640268354e-08 = 2.9804701895163013e-10 Units below are km^3/s^2. \begindata BODY20065803_GM = 34.8961209875640268354E-9 BODY120065803_GM = 0.29804701895163013E-9 BODY920065803_GM = 34.5980739686124E-9 \begintext End of PCK file.