PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM OBJECT = TEXT INTERCHANGE_FORMAT = ASCII PUBLICATION_DATE = 2019-12-16 NOTE = "JUNO C-Kernel Information" END_OBJECT = TEXT END General Information About SPICE C-Kernels ========================================= In the SPICE system, pointing data for an instrument platform, or for a specific instrument, are stored C-kernels. The pointing of a platform or an instrument is often expressed in terms of a transformation matrix from some standard inertial reference frame to a instrument-fixed frame. In the past, the instrument was often a camera, and the transformation was thus dubbed the ``C-matrix''; hence the choice of C as the name for the pointing kernel. The data contained in C-kernel files can be accessed and manipulated using the SPICE Toolkit APIs, calls to which can be integrated into user application programs. The information regarding how to obtain the SPICE system toolkit for a number of languages and computer platforms is located in the ``/software'' subdirectory of the main directory of this data set. To use C-kernels, a Spacecraft Clock Kernel (SCLK) is required. Also, for C-Kernels containing orientation of a project-defined frames, a Frame Definitions File is required. Refer to the ``ck.req'' document provided with the toolkit to get more information on how to access C-kernel data. JUNO C-kernels Contained in This Data Set ========================================= The following JUNO C-kernels are provided in this data set (only name portion of the file name is shown; the extension of all file names is ``.bc''): JUNO Spacecraft Orientation CK Files: juno_sc_rec_BEG_END_vVV CK files providing reconstructed orientation of the JUNO spacecraft bus for the BEG to END time period, version VV, produced by NAIF from reconstructed attitude data products (ATT_RECON DRFs) produced by the Spacecraft Team, LMCO. The dates are specified in the YYMMDD format. juno_sc_raw_BEG_END CK files providing low-accuracy reconstructed orientation of the JUNO spacecraft for the BEG to END time period, created by NAIF using data from low-frequency channelized telemetry. These files are provided only for time periods, for which there is no coverage in the reconstructed CKs. The dates are specified in the YYMMDD format. MAG ASC CHU and MOB Orientation CK Files: juno_chuX_rec_BEG_END_vVV CK files providing actual telemetry- juno_mobXb_rec_BEG_END_vVV based orientation of the MAG Advanced Stellar Compass (ASC) Camera Head Units (CHU) or Magnetometer Optical Benches (MOB) relative to inertial space for the BEG to END time period, version VV, produced by NAIF from CHU channelized telemetry. The dates are specified in the YYMMDD format. The X for CHU CKs is a, b, c, or d (for corresponding CHU ID) and for MOB CKs is i (for in-board) or o (for out-board). juno_chuX_ali_BEG_END_avg_vVV juno_mobXb_ali_BEG_END_avg_vVV CK files providing averaged alignments of MAG ASC CHUs and MOBs for the BEG to END time period, version VV, relative to the spacecraft frame, produced by NAIF by comparing inertially referenced spacecraft and CHU/MOB orientations provided in their reconstructed CKs. The dates are specified in the YYMMDD format. The X for CHU CKs is a, b, c, or d (for corresponding CHU ID) and for MOB CKs is i (for in-board) or o (for out-board). juno_mobXb_ali_BEG_END_thm_vVV CK files providing temperature-based alignments of MAG MOBs for the BEG to END time period, version VV, relative to the spacecraft frame, produced by the MAG Team, GSFC using the DTU solar array and SRU bracket thermal distortion model. The dates are specified in the YYMMDD format. The X is i (for in-board) or o (for out-board). juno_sc2fgmXb_zero_BEG_END_vVV CK files providing fixed alignments of MAG MOBs for the BEG to END time period, version VV, relative to the spacecraft frame, produced by NAIF. The dates are specified in the YYMMDD format. The X is i (for in-board) or o (for out-board). UVS Orientation CK Files: juno_uvs_rec_BEG_END_v01 CK files providing actual telemetry-based orientation of the JUNO UVS instrument observation frame for the BEG to END time period, version VV, created by NAIF by merging individual UVS CKs produced by the UVS Team, SWRI. The dates are specified in the YYMMDD format. Kernel File Details =================== The most detailed description of the data in a binary CK file is provided in metadata included inside the comment area of the file. This information can be viewed using utility programs COMMNT and SPACIT included into the NAIF Toolkit. Note on MAG CKs =============== Of the MAG alignment CKs provided in the data set, the MOB temperature-based alignment CKs are the most accurate but they cover only perijoves. The averaged alignment CHU/MOB CKs are slightly less accurate but provide a nearly complete coverage. The fixed alignment MOB CKs are the least accurate of the three. Because all of these three kinds of CKs rely on data from spacecraft CKs to built the complete inertial to MAG sensor frame chains, and because the accuracy of spacecraft CKs during attitude maneuvers is greatly reduced, neither of them can produce accurate MAG orientation during precessions. The actual telemetry-based orientation CHU/MOB CKs on the other hand, while ``suffering'' from a significant noise in the data, provide actual measured CHU/MOB attitude and thus more are accurate during attitude maneuvers. Gaps in Spacecraft Reconstructed CK Coverage ============================================ The following gaps exist in the combined coverage of the reconstructed spacecraft CKs due to safe modes and other anomalies: 2011-08-05T17:18 to 2011-09-15T10:16 no source TLM data (*) 2014-03-13T20:36 to 2014-03-25T19:38 safe mode 2016-07-05T00:24 to 2016-07-05T21:20 no source TLM data (*) (*) spacecraft telemetry did not contains sufficient data to perform accurate spacecraft attitude reconstruction The spacecraft attitude provided for these periods by the low-accuracy, "raw" spacecraft CKs, is good to 0.1-0.25 degrees for "quiet" periods with relatively dense data points but has errors of many tens of degrees during spacecraft attitude maneuvers (spin-ups, precession re-pointings, etc) and during periods with very sparse data points (points spaced hours or even days apart). Contact Information =================== Regarding JUNO project specific information provided in this data set and for general information about SPICE system: Boris Semenov (818)-354-8136 Boris.Semenov@jpl.nasa.gov address: Navigation and Ancillary Information Facility (NAIF) Jet Propulsion Laboratory MS 301-125L 4800 Oak Grove Drive Pasadena CA 91109 USA