BepiColombo ORBNUM files =========================================================================== This "aareadme.txt" file describes the contents of the misc/orbnum directory of the BepiColombo SPICE data server. It also provides the file naming conventions used for the MEX Orbit Number files, and it provides identification of the most current version of each kind of ORBNUM file. It was last modified on February 20, 2017 by Marc Costa Sitja, ESAC/ESA. Contact Information -------------------------------------------------------- If you have any questions regarding this file contact the ESA SPICE Service at ESAC: Alfredo Escalante Lopez (+34) 91-8131-429 spice@sciops.esa.int or NAIF at JPL: Boris Semenov (818) 354-8136 Boris.Semenov@jpl.nasa.gov References and required readings -------------------------------------------------------- 1. ``ORBNUM User Guide'', NAIF Document 2. ``BepicColombo Space to Ground Interface Control Document - Volume: Flight Dynamics Events File'', BC-ESC-IF-50002 Brief Summary -------------------------------------------------------- This directory contains the SPICE ORBNUM files for the BepiColombo mission. Please note that ORBNUM files are not considered SPICE kernels. The orbnum These are created from the SPK files converted from the Flight Dyamics Orbit Epehemeris Messages (OEM) files and the trajectory files provided by Mission Analysis. The Orbit Number files (*.ORB) contained in this directory are unix text files. These may be used in a non-compatible text environment by using the ASCII mode of FTP to port the files. Important Note Regarding Orbit Number Files -------------------------------------------------------- In the BepiColombo orbit number files produced by NAIF's ORBNUM utility program each of the records contains the time of THAT orbit's apocenter and the time of the NEXT orbit's pericenter. For example, the line for orbit '3' provide UTC and SCLK of orbit '3' apocenter and UTC of orbit '4' pericenter. Orbit number 1 corresponds to the first science phase orbit. This is derived from [2]: ``Orbit numbers are incremented by one with each apocentre passage starting from the first apocentre after orbit insertion.'' All derived quantities provided on each record -- sub-solar lon/lat, sub-spacecraft lon/lat/alt, and orbital elements -- are computed for the time of apocenter. Example ~~~~~~~ This is an example of a BepiColombo orbit number file (spacing is altered to fit the page): No Event UTC APO Event SCLK APO OP-Event UTC PERI ... == ==================== ================== ==================== ... 1 2026 MAR 14 16:47:12 1/0305225233.04972 2026 MAR 14 17:58:03 ... 2 2026 MAR 14 19:08:55 1/0305233735.61936 2026 MAR 14 20:19:47 ... 3 2026 MAR 14 21:30:38 1/0305242239.00886 2026 MAR 14 22:41:30 ... 4 2026 MAR 14 23:52:21 1/0305250742.10490 2026 MAR 15 01:03:13 ... Given this example one can determine that: -- orbit 3 pericenter time is ``2026 MAR 14 22:41:30'' -- orbit 3 time boundaries are from ``2026 MAR 14 21:30:38'' to ``2026 MAR 14 23:52:21'' File naming conventions -------------------------------------------------------- Naming Scheme for BepiColombo ORBNUM files: The naming scheme for the BepiColombo spacecraft ORBNUM files is: bc_SC_TYPE[_ID][_DESC]_YYYYMMDD_YYYYMMDD_vNN.orb where SC accronym of the spacecraft: mcs: for the Mercury Composite Spacecraft (MCS); mpo: for the Mercury Planetary Orbiter (MPO) spacecraft; mmo: for the Mercury Magnetospheric Orbiter (MPO) spacecraft; TYPE Data type, where a reference to the originator of the data, the type of data and the and the reference period is provided. This is a three letter acronym. The first letter defines the file originator: s: Science Operations Center; m: Mission Analysis; f: Flight Dynamics; the second letter defines the reference period of the data: c: Cruise phase; l: Science phase Long term; m: Science phase Medium term; s: Science phase Short term; o: Undefined; the third letter indicates the type of data p: Predicted data; r: Reconstructed data; t: Test data; ID mapping to the original file product IDs as defined per an ICD document (optional); DESC description of the original reference file of of any particular of the original fule (optional); YYYYMMDD coverage start and stop times in TDB (required); NN version number, starting from 01 (required; e.g. 01); Orbit Number Directory Structure -------------------------------------------------------- aareadme.txt This file. former_versions Subdirectory that contains obsolete versions of the ORBNUM files that have been updated in the Current ORBNUM File Set. bc_mpo_mlt_XXXXX_YYYYMMDD_YYYYMMDD_vNN.orb Contains BepiColombo orbit apocenter and pericenter times, orbital elements, and additional geometry parameters computed from the SPK long term file named: bc_mpo_mlt_XXXXX_YYYYMMDD_YYYYMMDD_vNN.bsp where XXXXX designates the reference to the Mission Analysis version number. YYYYMMDD_YYYYMMDD specifies the coverage of the original file and NN specifies the version of the file. This is a mission analysis test file that corresponds to the latest CReMa release. Particulars -------------------------------------------------------- Nothing to report. Kernel File Details -------------------------------------------------------- The most detailed description of the data in a text ORBNUM file is provided in metadata included inside the descriptive text areas of the file. End of aareadme file.