Venus Climate Orbiter, AKATSUKI Data sets Users' Guide

You can find "vco-v-uvi-3-cdr-v1.0" directory that is lower case of DATA_SET_ID, "VCO-V-UVI-3-CDR-V1.0" ("DATA_SET_ID directory"). Under this directory, all of the calibrated UVI data are available.

You can find "vcouvi_1001" directory that is lower case of VOLUME_ID, "VCOUVI_1001" ("VOLUME_ID directory") under "vco-v-uvi-3-cdr-v1.0" directory. The "VOLUME_ID has naming convention as the following format: VCOINST_XTVV, where

For the SPICE kernels data set, XTVV is set to 1000 regardless of the convention described above.

For example, vcouvi_1001 is for the 1st release of the calibrated data, and vcouvi_1002 is for the 2nd release.

The directory structure under the "VOLUME_ID" directory is described in aareadme.txt, e.g., aareadme.txt in "VCO-V-UVI-3-CDR-V1.0" like the following:

   [top-level-directory]
   |
   |-- aareadme.txt           This file.
   |
   |-- errata.txt             Comments and errata on this volume.
   |
   |-- voldesc.cat            Description of the contents of this volume.
   |
   |--[browse]                Directory containing the JPEG files created from
   |  |                       files in the ``/data'' directory for browsing.
   |  |
   |  |-- browinfo.txt        Description of files in the browse directory.
   |  |
   |  +--[l2b]                Subdirectory for level 2b (l2b) data.
   |     |
   |     |-- list.html        HTML file including hyperlinks to the HTML
   |     |                    files in each orbit number string subdirectory.
   |     |
   |     |-- list.lbl         The corresponding detached PDS label file.
   |     |
   |     +--[PVVVV]           A series of subdirectories organized by the
   |        |                 orbit number string.
   |        |
   |        |-- list_*.html   HTML file that enumerates JPEG files in this
   |        |                 directory.
   |        |
   |        |-- *.jpg         A JPEG file created from corresponding
   |        |                 calibrated image in FITS format.
   |        |
   |        +-- *.lbl         The corresponding detached PDS label file.
   |
   |--[calib]                 Directory containing the calibration files.
   |  |
   |  |-- calinfo.txt         Description of files in the calib directory.
   |  |
   |  |-- *.fit               A flat-field image file used in the original
   |  |                       processing of the data, stored in FITS format.
   |  |                       A flat conversion factor file that can be used
   |  |                       to generate image suitable for photometry
   |  |                       analysis.
   |  |
   |  +-- *.lbl               The corresponding detached PDS label file.
   |
   |--[catalog]               Directory containing PDS catalog objects.
   |  |
   |  |-- catinfo.txt         Description of files in the catalog directory.
   |  |
   |  |-- dataset.cat         Description of the data set.
   |  |
   |  |-- uviinst.cat         Description of the instrument.
   |  |
   |  |-- uviref.cat          List of instrument-specific publications
   |  |                       mentioned in the uviinst.cat file.
   |  |
   |  |-- mission.cat         Description of the mission.
   |  |
   |  |-- person.cat          References for personnel who created this
   |  |                       volume.
   |  |
   |  |-- ref.cat             List of mission-wide publications mentioned in
   |  |                       *.cat files.
   |  |
   |  |-- target_dust.cat     Description of the target, dust.
   |  |
   |  |-- target_earth.cat    Description of the target, the earth.
   |  |
   |  |-- target_sun.cat      Description of the target, the sun.
   |  |
   |  |-- target_venus.cat    Description of the target, Venus.
   |  |
   |  +-- vcohost.cat         Description of the spacecraft.
   |
   |--[data]                  Directory containing the data files and PDS
   |  |                       labels describing the contents of those files.
   |  |
   |  +--[l2b]                Subdirectory for level 2b (l2b) data.
   |     |
   |     +--[PVVVV]           A series of subdirectories organized by the
   |        |                 orbit number string.
   |        |
   |        |-- *.fit         A VCO calibrated data product file in FITS
   |        |                 format.
   |        |
   |        +-- *.lbl         The corresponding detached PDS label file.
   |
   |--[document]              Directory containing volume related documents.
   |  |
   |  |-- docinfo.txt         Description of files in the document directory.
   |  |
   |  |-- uvical.txt          Description of calibration procedure.
   |  |
   |  |-- imagecoord.txt      Description of image coordinate used in this
   |  |                       dataset and corresponding indexes of the data
   |  |                       stored in FITS files.
   |  |
   |  |-- onlabels.txt        Description of PDS labels for this data set.
   |  |
   |  |-- vco_fits_dic_vVV.*  Header keyword dictionary file for Venus
   |  |                       Climate Orbiter FITS file in several formats
   |  |                       and corresponding detached PDS label file.
   |  |
   |  |-- vco_obsprg_vVV.*    Description of observation programs (sequence
   |  |                       of image acquisition) in several formats and
   |  |                       corresponding detached PDS label file.
   |  |
   |  +--[ft]                 Directory containing filter transmission data
   |     |                    files.
   |     |
   |     |-- ftinfo.txt       Description of filter transmission data files.
   |     |
   |     |-- ft_uvi_*.tab     Filter transmission data files.
   |     |
   |     +-- ft_uvi_*.lbl     PDS label for each filter transmission data
   |                          file.
   |
   +--[index]                 Directory containing index files.
      |
      |-- indxinfo.txt        Description of files in the index directory.
      |
      |-- checksum.tab        Table of MD5 checksums for files in this data
      |                       set.
      |
      |-- checksum.lbl        PDS label for checksum.tab file.
      |
      |-- index.tab           Index table of the data on this volume.
      |
      +-- index.lbl           PDS label for index.tab file.

The data are placed under data/ directory. There are subdirectories with "orbit number string" that is described in aareadme.txt.

For geometry information data sets, the main data are placed under geometry/ directory.

For quick-look purpose, see browse/ directory. Please find list.html file.

For calibrated data sets, there are files used to calibrated data in the data/ directory in calib/ directory. Note that data files are already calibrated, so you don't need to use files under calib/ directory in general.

The catalog files that are descriptive information about a data set, are placed under catalog/ directory. There are following files:

The documents except for catalog files are placed under document/ directory. There are following files:

The summary of the data files is placed under index/ directory. The table of MD5 checksum also placed under this directory.

The extra data files are placed under extras/ directory. Currently, the list of executed observation programs are stored as ASCII text table in this directory, e.g, vco_obsprg_executed_v02.tab in VCO-V-UVI-3-CDR-V1.0

Except for data/ directory, there are fooinfo.txt files. These files briefly describe files in the directory.

In PDS3 label file (e.g., uvi_20151207_051953_283_l2b_v10.lbl), you can find the following lines:

/* TARGET INFORMATION */

TARGET_NAME                  = VENUS
VCO:SPHERICAL_RADIUS         = 6051.8 <km>
VCO:ASSUMED_CLOUD_ALTITUDE   = 70.0 <km>

Meta data are described in "keyword = value" format. The "TARGET_NAME" describes name of target, VENUS.

You can also find the following keywords: INSTRUMENT_NAME, FILTER_NAME, EXPOSURE_DURATION, etc.

There is a way to describe meta data associated with not a whole part of the file but a part of the file. The OBJECT block defines a named group of the meta data and points to a part of the file by a pointer. An example of a pointer that points to a part of the file by the OBJECT block named "UVI_LEVEL2B_IMAGE". A pointer is expressed as a leading caret, "^", and name of the block, "UVI_LEVEL2B_IMAGE". An assignment of value of the pointer is expressed as follows:

^UVI_LEVEL2B_IMAGE           = ("uvi_20151207_051953_283_l2b_v10.fit", 8)

and an example of OBJECT block is as follows:

OBJECT                       = UVI_LEVEL2B_IMAGE
  LINE_SAMPLES               = 1024
  LINES                      = 1024
  SAMPLE_BITS                = 32
  SAMPLE_TYPE                = IEEE_REAL
  UNIT                       = "W m**-2 sr**-1 m**-1"
  MAXIMUM                    = 2.56932E+07
  MINIMUM                    = -759021    
  MEAN                       = 6.64511E+06
  STANDARD_DEVIATION         = 7.81745E+06
  UNKNOWN_CONSTANT           = NULL  /* dead pixel flag value */
  INVALID_CONSTANT           = UNK  /* saturated pixel flag value */
  MISSING_CONSTANT           = -3.4E+38
  LINE_DISPLAY_DIRECTION     = UP
  DESCRIPTION                = "Data of secondary HDU of UVI L2B FITS
                                file that contains the image data."
END_OBJECT                   = UVI_LEVEL2B_IMAGE

You can find descriptions of meta-data from the following:

Data dictionary for mission-specific entries is considered to be merged to the official PDS Data Dictionary. Until the they will be merged, the dictionary will put somewhere (TBD).

FITS file has an unit called as Header Data Unit ("HDU"). HDU has two parts: the header and the data. For usual FITS data file in the Akatsuki's data sets, the primary HDU has general information of the file in the header and no data in the data part, and the secondary HDU has main image data in the data part and its header in the header part.

In the header of FITS file, there are several records with each record of 80 characters. One record usually contains keyword and its value, separated by "=". You can see records by pager like less(1) in the terminal with 80 characters-width. There are various keywords, e.g., OBJECT (target of the image), INSTRUME (instrument used to acquire image), FILTER (filter used to acquire image), EXPOSURE (exposure time for acquiring image). See VCO FITS header keyword dictionary for the details.

You can extract a value of keyword by your script. For example, to extract value of P_ID that describes a combination of the instrument and the filter/channel used to acquire image in string from uvi_20151207_051953_283_l2b_v10.fit, use the following Python 3 script with the Astropy package:

from astropy.io import fits

hdulist = fits.open('uvi_20151207_051953_283_l2b_v10.fit')
p_id = hdulist[1].header['P_ID']
print(p_id)

and the output of this script will be:

VCO_UVI_283

This output means the image is acquired by "VCO_UVI_283" as NAIF name that represents UVI with the 283-nm filter onboard VCO (Akatsuki).

On special flag values, see catalog/dataset.cat for each data set.

You can find "vco_uvi_l3_v1.0" directory. Under this directory, all of the UVI Level 3 data are available.

The subdirectory under the top directory ("release" directory) is named as rel_VVVV, where

For example, rel_0001 is for the 1st release of the data, and rel_0002 is for the 2nd release.

00readme.txt, browse, data, doc