VEX SPK Files ============= This "aareadme.txt" file describes the contents of the kernels/spk directory of the VEX SPICE data server. It also provides the file naming conventions used for the VEX SPK kernels, and it provides identification of the most current version of each kind of SPK file. Some of these SPK files are produced by an automated system located at ESAC, operated by the ESA SPICE Service. The contents and time span covered by any SPK file may be easily determined using the "brief" utility program available in all copies of the SPICE Toolkit. Example of usage: $ brief Descriptive information about how/why/when an SPK file was created is usually available in the "comment area" of the file. This may be viewed using the "commnt" utility program available in all copies of the SPICE Toolkit. Use the "-r" option to read the comments. Example: $ commnt -r All binary SPK files (*.BSP) contained in this directory are Unix binary files. These may be used as is (without format conversion) in a non-unix environment when using any recent version of the SPICE Toolkit (Version N0052 or later). Contact ESA SPICE Service esa_spice@sciops.esa.int , or Marc Costa Sitja marc.costa@esa.int if you have any questions. References ========== 1. Data Delivery Interface Document (DDID) Appendix H - FD products Issue 3.0 (VEX-ESC-IF-5003) 2. SPK Required Reading (NAIF Document). All the NAIF Documents are available at the NAIF web: http://naif.jpl.nasa.gov Venus Express SPK Directory Structure ==================================== aareadme.txt This file. former_versions Subdirectory that contains obsolete versions of the SPK files that have been updated in the Current SPK Kernels Set. DE405.BSP SPICE kernel containing ephemeris data for planet barycenters, and for the sun, earth and moon mass centers. Spans the entire VEX mission. EARTHSTNS_FX_YYMMDD.BSP SPICE kernel containing ephemeris data for NASA DSN stations relative to the terrestrial reference frame ITR93. In the interest of flexibility, in this file the reference frame is labeled with the alias 'EARTH_FIXED'. Any application using this file must map the alias 'EARTH_FIXED' to either 'ITR93' or 'IAU_EARTH'. This file was released on YY-MM-DD. EARTHSTNS_ITRF93_YYMMDD.BSP SPICE kernel containing ephemeris data for NASA DSN stations relative to the terrestrial reference frame label 'ITR93'. This file was released on YY-MM-DD. ESTRACK_Vvv.BSP This kernel defines the position for each of the ESA ESTRACK ground stations relative to the center of the Earth. In the interest of flexibility, in this file the reference frame is labeled with the alias 'EARTH_FIXED'. Any application using this file must map the alias 'EARTH_FIXED' to either 'ITR93' or 'IAU_EARTH'. OUTERPLANETS_Vvvvv.BSP Ephemeris information for the outer planets of the solar system: Jupiter, Saturn, Uranus and Neptune. It is meant to complement DE405.BSP, which contains information for their barycenters, but not the bodies themselves. VEX_STRUCT_Vvv.BSP SPICE kernel containing the location of various Venus Express instruments and structures. ORHV_T19___________xxxxx.BSP SPICE kernel containing VEX spacecraft reconstructed cruise ephemeris. This ephemeris corresponds to the ESOC orbit file named: ORHV_FDLMMA_DA______________xxxxx.VEX where xxxxx designates the version number. ORVF_______________xxxxx.BSP SPICE kernel containing VEX spacecraft long term planning operational Venus centric ephemeris. This ephemeris corresponds to the ESOC orbit file named: ORVF_FDLMMA_DA______________xxxxx.VEX where xxxxx designates the version number. This is the file that should be used for planning. For data analysis you have to use the ORVV files below. ORVV_T19_YYMMDD000000_xxxxx.BSP SPICE kernel containing VEX reconstructed ephemeris after orbit insertion, starting from 20YY-MM-DD. This ephemeris corresponds to the ESOC orbit file named: ORVV_FDLMMA_DA_YYMMDD000000_xxxxx.VEX where xxxxx designates the version number. These are the files that should be used for data analysis. ORVM_______________xxxxx.BSP SPICE kernel containing the latest VEX reconstructed ephemeris for both cruise and after orbit insertion and until End of Mission. This ephemeris corresponds to the final ESOC orbit file named: VOEM_150721OAS_PREDICT__0001.CR.gz.txt This is the file that should be used for data analysis after the End of Mission. ORVM_T19___________xxxxx.BSP SPICE kernel containing the latest VEX reconstructed ephemeris for both cruise and after orbit insertion and until End of Mission. This ephemeris corresponds to the final ESOC orbit file named: VOEM_150721OAS_PREDICT__0001.CR.gz.txt This is the file that should be used for data analysis after the End of Mission. Note: Files EARTHSTNS_FX_yymmdd.BSP and EARTHSTNS_ITRF93_yymmdd.BSP contain the same data. These files only differ in that the second one use the reference frame label 'ITR93' instead of 'EARTH_FIXED'. 'EARTH_FIXED' alias must be map to either 'ITR93' or 'IAU_EARTH' before using the file. For high accuracy work, the EARTHSTNS_ITRF93_yymmdd.BSP is recommended (on the basis of ease of use). ------------------- This file was last modified on January 21st, 2020. (A. Escalante)