Venus Climate Orbiter Akatsuki LIR Level 3 data set =================================================== Releases -------- release of vcolir_7009 Release Date: 2023-12-01 Data Coverage: 2022-06-09 -- 2022-12-02 Data Citation ------------- The citation for this data set is as follows: Murakami, S., K. Ogohara, M. Takagi, H. Kashimura, M. Yamada, T. Kouyama, T. Horinouchi, T. Imamura, Venus Climate Orbiter Akatsuki LIR Longitude-Latitude Map Data v1.1, JAXA Data Archives and Transmission System, https://doi.org/10.17597/isas.darts/vco-00019, 2018. Overview -------- This data set contains longitude-latitude map data created from images acquired by the LIR instrument of the Venus Climate Orbiter (VCO, also known as PLANET-C and AKATSUKI) spacecraft. This data set consists of NetCDF and FITS files. The longitude-latitude map data are included as Level 3 product in NetCDF. During process of creating longitude-latitude map data, pointing of spacecraft was corrected using limb-fitting technique. Detected limb points and information on fitted ellipse are provided as auxiliary data, the level 3x product in NetCDF. The level 3x product in FITS was also provided in the release before vcolir_7007, and it was not provided as part of this data set from the vcolir_7007 release. It's privided as part of Venus Climate Orbiter Akatsuki Longwave Infrared Camera Bundle, which can be used as geometry information file with poiting correction instead of "geo" file. This data set is procuded from calibrated image, geometry information, and SPICE kernel data sets. Please refer Venus Climate Orbiter Akatsuki Longwave Infrared Camera Bundle urn:jaxa:darts:vco_lir and Venus Climate Orbiter Akatsuki SPICE Kernel Archive Bundle urn:jaxa:darts:vco_spice for detailed information on the instrument and acquired data. The level 3b and the level 3bx products were not provided in the vcolir_7007 release or later, because Level 2b was provided as a starting point for development of the calibration procedure, and the level 3b and the level 3bx products generated from the Level 2b product might not be appropriate to the usual end users. Please use the level 3c and the level 3cx products instead of the level 3b and the level 3bx products. From the vcolir_7008 release, the level 3c and level 3cx products are not provided. Please use the level 3d and level 3dx products instead of level 3c and level 3cx products. Relation to the other data set ------------------------------ Data sets used to create this data set: - Venus Climate Orbiter Akatsuki Longwave Infrared Camera Bundle urn:jaxa:darts:vco_lir https://doi.org/10.17597/isas.darts/vco-00600 - Venus Climate Orbiter Akatsuki SPICE Kernel Archive Bundle urn:jaxa:darts:vco_spice https://doi.org/10.17597/isas.darts/vco-00200 Level 3 data was created from the Calibrated Data collection of the VCO Akatsuki LIR Bundle, urn:jaxa:darts:vco_lir:data_calibrated, and the VCO Akatsuki SPICE Kernel Archive Bundle. The L3d NetCDF data was converted into the FITS file with the BINTABLE extension, and is stored to the Map Data collection of the VCO Akatsuki LIR Bundle. The L3dx FITS file is stored to the Geometry collection of the VCO Akatsuki LIR Bundle. Processing ---------- Overview -------- The data processings are done on DANS (Data Analysis Network System) managed by C-SODA (Center for Science-satellite Operation and Data Archive), ISAS/JAXA at Sagamihara, Kanagawa, Japan. Note that DANS consists of SIRIUS (Scientific Information Retrieval and Integrated Utilization System), EDISON (Engineering Database for ISAS Spacecraft Operation Needs), "Reformatter", DARTS (Data ARchives and Transmission System) and data analysis servers. The summary of the data processing is as follows. The data downlinked as telemetry are transferred to the data accumulation system at ISAS, and are registered to SIRIUS and are sorted in time. From SIRIUS, level 0 data are retrieved to the Reformatter for the PLANET-C Project Team that is provided by C-SODA to each mission. All processings (data pipeline) after level 0 until level 3 are done on the Reformatter. These procedures are executed automatically. To implement these procedures, various program codes are used, written in C, C++, Fortran 90/95, Ruby, Python, Perl, and POSIX shell. Definition of Products ---------------------- Definition of products is as follows: abbr name description ----- ------------ ------------------------------------------------- l3b Level 3b calibrated, physical values projected onto equally spaced longitude-latitude grid derived from l2b data with pointing correction using limb-fitting technique. l3bx Level 3b aux data for evaluation of automated limb-fitting and pointing corrected data product, l3b. l3c Level 3c same as l3b, but data are derived from l2c. l3cx Level 3c aux same as l3bx, but data are associated with l3c. l3d Level 3d same as l3b, but data are derived from l2d. l3dx Level 3d aux same as l3bx, but data are associated with l3d. Detailed description of the processings --------------------------------------- From L2d FITS file, L3d NetCDF file, and L3dx NetCDF file are created using SPICE kernels and SPICE toolkits. The fully-automated algorithms of limb-detection, limb-fitting and interpolation onto equally spaced longitude-latitude grids has been implemented for the processing. For verification of the result of limb-detection and limb-fitting, L3dx NetCDF file is also created. This file also contains correction of pointing of the camera. See Ogohara et al. (2017), Ogohara et al. (2012), and doc/vco_l3_algorithm_v${VV}.pdf for detailed description of algorithms and processings, where ${VV} is zero-padded two-digit version number. Data ---- Overview -------- There are two kinds of data, L3d NetCDF file and L3dx NetCDF file. Each L3d NetCDF file corresponds to L3dx NetCDF file that has same filename except for the abbreviation of "product" part, e.g., "l3dx" instead of "l3d". File format and structure ------------------------- The files with the extension ".nc" under "data" directory are NetCDF-4 file. These NetCDF files are considered to be compliant with the CF convention (CF Version CF-1.7). Compliance to CF-1.7 is verified as no "Errors" using following conditions: - CF Checker Version 4.1.0 (https://github.com/cedadev/cf-checker), - Using Standard Name Table Version 81 (2023-04-25T10:43:33Z), - Using Area Type Table Version 10 (23 June 2020), - Using Standardized Region Name Table Version 4 (18 December 2018). In L3d NetCDF file, there is "btemp" variable which is a function of "longitude", "latitude", and "time" variables. In L3dx NetCDF file, there are "btemp" and "radiance" variables which is a function of "axis1", "axis2", and "time" variables. For these two kinds of NetCDF files, the "time" variable has only one value of the representative observation time in hours since 2000-01-01T00:00:00 UTC. Other variables are described doc/vco_l3_variable_v${VV}.pdf where ${VV} is zero-padded two-digit version number. The "axis1" and "axis2" are position of the full-size image coordinate that is defined in Software Interface Specification for the Venus Climate Orbiter Akatsuki Longwave Infrared Camera Data Products, urn:jaxa:darts:vco_lir:document:vco_lir_dpsis . Filename -------- File under browse and data directories has the following filename format: ${cam}_${YYYYMMDD}_${hhmmss}_${filter}_${product}_v${ver}.${ext} where ${cam}: abbreviation of the instrument, lir. ${YYYYMMDD}: observation date, YYYY is year, MM is month, and DD is day. ${hhmmss}: observation time, hh is hour, mm is minute, and ss is second. ${filter}: abbreviation of the filter, pic. ${product}: abbreviation of the product, l3d and l3dx. ${ver}: version of the product, 10. ${ext}: extension of the file, nc, png, and jpg. Text dump of header of NetCDF file has similar filename format: ${cam}_${YYYYMMDD}_${hhmmss}_${filter}_${product}_v${ver}_header.txt Directory Structure ------------------- Directory structure is as follows: 00readme.txt this file browse/ browsing directory browse/${prd}/ product directory browse/${prd}/${t}/ file type directory browse/${prd}/${t}/list.html HTML file for browsing browse/${prd}/${t}/${PVVVV}/ orbit number string directory browse/${prd}/${t}/${PVVVV}/list_*.html HTML file for browsing browse/${prd}/${t}/${PVVVV}/*.png PNG image of data file browse/${prd}/${t}/${PVVVV}/*.jpg JPEG image of data file data/ directory for data data/${prd}/${t}/ directory for each file type data/${prd}/${t}/${PVVVV}/ orbit number string directory data/${prd}/${t}/${PVVVV}/*.nc NetCDF file doc/vco_l3_algorithm_v${VV}.pdf description of algorithm used to create products in this data set doc/vco_l3_variable_v${VV}.pdf description of variable stored in L3 and L3x NetCDF file where ${prd}: abbreviation of the product, l3d and l3dx. ${t}: file type of data, netcdf. ${PVVVV}: orbit number string directory (see below). ${VV}: version of the file. In 'data/' and 'browse/' directories, there are subdirectories with orbit number string as its name. The orbit number string is defined as PVVVV format, where 'P' indicates period before the successful orbit insertion ('c', the first character of 'cruise') or after the successful orbit insertion, i.e., orbiting phase ('r', the first character of 'revolution'). 'VVVV' indicates orbit number that is represented by zero-padded 4 digits. For the period before the successful orbit insertion, we assign the orbit number '0000', therefore, the orbit number string is 'c0000'. For orbiting phase, the orbit number begins from '0001', and it is incremented when the spacecraft passes the periapsis. So we'll have the orbit number strings, 'c0000', 'r0001', 'r0002', and so on. The orbit numbers for the VCO spacecraft are defined in 'vco_spice/miscellaneous/orbnum/vco_vVV.orb' in the Venus Climate Orbiter Akatsuki SPICE Kernel Archive Bundle, where VV is the version number of the orbit number file. License ------- This data set is distributed under "ISAS Data Policy" (*1). Rules described in the policy follow "Government of Japan Standard Terms of Use (Version 2.0)" (*2) and are compatible with Creative Commons Attribution 4.0 International License (CC BY 4.0) (*3). (*1) https://www.isas.jaxa.jp/en/researchers/data-policy/ (*2) https://www.digital.go.jp/assets/contents/node/basic_page/field_ref_resources/f7fde41d-ffca-4b2a-9b25-94b8a701a037/b33c8db5/20220706_resources_data_betten_03.pdf (*3) https://creativecommons.org/licenses/by/4.0/deed.en References ---------- Ogohara, K., M. Takagi, S. Murakami, T. Horinouchi, M. Yamada, T. Kouyama, G. L. Hashimoto, T. Imamura, Y. Yamamoto, H. Kashimura, N. Hirata, N. Sato, A. Yamazaki, T. Satoh, N. Iwagami, M. Taguchi, S. Watanabe, T. M. Sato, S. Ohtsuki, T. Fukuhara, M. Futaguchi, T. Sakanoi, S. Kameda, K. Sugiyama, H. Ando, Y. J. Lee, M. Nakamura, M. Suzuki, C. Hirose, N. Ishii, T. Abe, Overview of Akatsuki data products: definition of data levels, method and accuracy of geometric correction, Earth, Planets and Space, 69, 167, https://doi.org/10.1186/s40623-017-0749-5, 2017. Ogohara, K., T. Kouyama, H. Yamamoto, N. Sato, M. Takagi, T. Imamura, Automated cloud tracking system for the Akatsuki Venus climate orbiter data, Icarus, 217, 661-668, https://doi.org/10.1016/j.icarus.2011.05.017, 2012.