MEX CK SPICE Kernels ==================== This "aareadme.txt" file describes the contents of the kernels/ck directory of the MEX SPICE data server. It also provides the file naming conventions used for the MEX CK files. The CK in this subdirectory provide information on: - predicted, measured and reconstructed spacecraft orientation CKs, - "planning" spacecraft CKs, - orientation CKs for instruments with moving parts. - orientation for the Solar Arrays. Each kernel file provides information of only one of the types above. * Predicted spacecraft orientation CK files generated with the commanded attitude. These files also contain a long Earth pointing block (of around 24 hours) that reflects the attitude the S/C would fly without a command update. Theses files are produced by a system located at ESAC, operated by the ESA SPICE Team. * "Planning" CK files are also produced using ADCS. These files contain the spacecraft orientation requested by the MEX Project Science Team through the Pointing Timeline Request (PTR) files. Each of these files is produced at the end of a medium term planning cycle. These files also contain a long Earth pointing block (of around 24 hours) that reflects the attitude the S/C would fly without a command update. They should only be used in support of the planning activity and NEVER for data analysis since the pointing may change before being implemented on the spacecraft during the short term planning activities. * The third kind of spacecraft orientation CK files contain MEASURED data. These files contain the attitude obtained from the quaterions extracted from the housekeeping telemetry data. In some occasions the measured quaternions may be of reduced quality. For example if the number of stars tracked by the star tracker is not sufficient and the attitude is controlled only based on gyro-information for a period of time, the on-board estimated quaternions can drift. In such cases the available information would have to be analysed specifically. * The fourth kind of spacecraft orientation CK files contain RECONSTRUCTED data. There should be only one kernel of this type, with the orientation of the spacecraft for all the time periods for which the predicted attitude was not accurate enough; for these periods, a recostruction of the attitude was requested to ESOC, and stored in this kernel. * The instrument CKs are generated by the instrument teams, and contain orientation of the moving parts for each instrument. * The CKs for the Solar Arrays contain information about their orientation, with respect to the spacecraft reference frame. The contents and time span covered by any CK file may be easily determined using the "ckbrief" utility program available in all copies of the SPICE Toolkit. Examples of usage: %ckbrief This utility requires a SPICE sclk file and an lsk file in addition to the CK file; use the latest versions of these files. Descriptive information about how/why/when an CK 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 CK files (*.BC) 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). For information on the content of this folder or information in general on SPICE for MEX, contact ESA SPICE Team spice@sciops.esa.int , or Alfredo Escalante Lopez aescalante@sciops.esa.int References ========== 1. Data Delivery Interface Document (DDID), Appendix H - FD products Issue 3.0 (MEX-ESC-IF-5003) 2. CK Required Reading (NAIF Document). 3. NAIF IDs Required Reading (NAIF Document). 4. Mars Express Frames Definition Kernel (FK), latest version. All the NAIF Documents are available at the NAIF web: http://naif.jpl.nasa.gov Mars Express CK Directory Structure =================================== aareadme.txt This file. former_versions Subdirectory that contains obsolete versions of the CK files that have been updated in the Current CK Kernels Set. ATNM_PYYMMDDhhmmss_xxxxx.BC SPICE Kernel (CK) that contains Mars Express predicted attitude as commanded information and an extension of Earth pointing covering the time span starting at the date YY-MM-DD hh:mm:ss. This attitude information corresponds to the ESOC attitude file named: ATNM_FDLMMA_DAPYYMMDDhhmmss_xxxxx.MEX where xxxxx designates the version number. ATNM_T6_PYYMMDDhhmmss_xxxxx.BC SPICE Kernel (CK) that contains Mars Express predicted attitude as commanded information starting at the date YYMMDDhhmmss. This product is a Type 6 CK kernel and requires at least the SPICE Toolkit N0065 to be used. This attitude information corresponds to the ESOC attitude file named: ATNM_FDLMMA_DAPYYMMDDhhmmss_xxxxx.MEX where xxxxx designates the version number. ATNM_SGS_PYYMMDDhhmmss_xxxxx.BC SPICE Kernel (CK) that contains Mars Express spacecraft predicted attitude information and an extension of Earth pointing covering the time span starting at the date YY-MM-DD. This product is a Type 6 CK kernel and requires at least the SPICE Toolkit N0065 to be used. This attitude information corresponds to the ESOC attitude file named: ATNM_FDLMMA_DAPYYMMDDhhmmss_xxxxx.MEX where xxxxx designates the version number. ATNM_PTRvvvvv_YYMMDD_xxx.BC SPICE Kernel (CK) that contains Mars Express predicted attitude information and an extension of Earth pointing covering the covering the time span starting at the date YY-MM-DD. This attitude information corresponds to the PTR file version vvvvv delivered from POS to ESOC and it is intended for the Teams to check the pointings. The final attitude file is fixed after iterating the PTR and it may differ from this planning C-Kernel. ATNM_MEASURED_YYYY_Vvv.BC SPICE Kernel (CK) that contains Mars Express measured attitude, provided by the onboard AOCS system. The coverage is for the year indicated by YYYY. ATNM_RECONSTITUTED_xxxxx.BC SPICE kernel (CK) that contains Mars Express reconstituted attitude information. This attitude information corresponds to all reconstituted attitude files delivered from ESOC to PST. This file is updated every time new reconstituted data are available. The file contains gaps between data segments. Extensive documentation specifying valid interpolation intervals (periods with no data gaps) is provided in the comment area. Please refer to text above for information about using the COMMNT utility. MEX_ASPERA_SAF_YYMMDD_xx.BC SPICE kernel (CK) that contains the Mars Express ASPERA-3 Sensor Assembly Frame (SAF) orientation data relative to the ASPERA-3 Unit Reference Frame. These data describe the rotation of the ASPERA-3 scanner. The file covers the time span starting at the date YY-MM-DD. MEX_PFS_ZERO_Vvv.BC SPICE kernel (CK) that contains the Mars Express PFS Scanner position. These data provide a zero rotation of the PFS scanner for the entire mission duration. MEX_SA_YYYY_Vvvvv.BC SPICE kernel (CK) that contains orientation for the Mars Express Solar Arrays, for the year YYYY. Vvvvv is the version number. ------------------- This file was last modified on March 22th, 2021. (R. Valles) End of aareadme file.