The total number of our basic products (Level_1, 2, and 3) are summarized here. The Level 1 and Level_2 data products are in instrument units (DN/sec/pixel). Conversion to physical units requires knowledge or assumption about the solar differential emission measure and the use of software (such as sxt_teem.pro in SolarSoft). The Level 3 images are scaled so that the solar structures are best viewed and the scaling varies with the Sun's activity level. Therefore, the Level 3 images best serve for browsing, and not suitable for quantitative analysis.
Except Level 0 (raw) products, the YLA products are available in both Yohkoh-specific (XDA) and FITS formats. For quick-look (or web-browsing) purposes, Level_3 images are also available in JPEG format.
Yohkoh/SXT has two observing modes with respect to the field of view; full-sun v.s. partial-sun.
Due to the failure of the SXT entrance filter, the Aspect Sensor (co-axially mounted visible-light telescope) images became unavailable after 14-Nov-1992. White-light images are available in Level_1 and Level_3 data. For the latter, they are included in the "wl" directory. There are no Level_2 products for the white-light images.
sxt_fits/ ----- level_1/ ------ full_sun/ --- YYYY/MM/DD/sxtf_YYYYMMDD_HHMMSS_XXX.fts | |--- part_sun/ --- YYYY/MM/DD/sxtp_YYYYMMDD_HHMMSS_XXX.fts |-- level_2/ -------------------- YYYY/MM/DD/sx2c_YYYYMMDD_HHMMSS_XXX.fts | or sx3c_YYYYMMDD_HHMMSS_XXX.fts |-- level_3/ ----- wl/ ---------- YYYY/MM/DD/sa08_YYYYMMDD_HHMMSS_XXX.fts | or sa12_YYYYMMDD_HHMMSS_XXX.fts |-- xray/ -------- YYYY/MM/DD/sx2m_YYYYMMDD_HHMMSS_XXX.fts or sx3m_YYYYMMDD_HHMMSS_XXX.fts sxt_jpeg/ ---- level_3/ ----- wl/ ---------- YYYY/MM/DD/YYYYMMDD_HHMMSS_sa08_XXX.jpg | or YYYYMMDD_HHMMSS_sa12_XXX.jpg |-- xray/ -------- YYYY/MM/DD/YYYYMMDD_HHMMSS_sx2m_XXX.jpg or YYYYMMDD_HHMMSS_sxem_XXX.jpg sxt_xda/ ----- level_0/ -------------------- YYYY_WW/sfrYYMMDD.HHMM (1 file per orbit) | or sprYYMMDD.HHMM (1 file per orbit) |-- level_1/ ------ full_sun/ --- YYYY/sfrYYMMDD_HHMM (1 file per day) | |--- part_sun/ --- YYYY/sprYYMMDD.HHMM (1 file per day) |-- level_2/ -------------------- YYYY/sscYYYYMMDD_HHMM_BBBBBBB.N (1 file per day) | or sstYYYYMMDD_HHMM_BBBBBBB.N (1 file per day) | or sscYYYYMMDD_HHMM_BBBBBBB.N_unc (1 file per day) | or sstYYYYMMDD_HHMM_BBBBBBB.N_unc (1 file per day) |-- level_3/ ----- wl/ ---------- YYYY/MM/DD/sa08_YYYYMMDD_HHMMSS_XXX.xda | or sx12_YYYYMMDD_HHMMSS_XXX.xda |-- xray/ -------- YYYY/MM/DD/sx2m_YYYYMMDD_HHMMSS_XXX.xda or sx3m_YYYYMMDD_HHMMSS_XXX.xda
Examples of the file name: sfr920720.0517, spr920720.0517. This file is included in the week directory, 1992_30/, because the date of observation belongs to the 30th week of 1992. sfr : prefix for SXT Full Frame (full-sun) Images. spr : prefix for SXT Partial Frame (partial-sun) Images other prefixes included in the same directory ; hda : HXT data bda : BCS data wda : WBS data ada, cba : for calibration purpose. 920720.0517 : date and approximate time (yymmdd.hhmm) at which the satellite started observation in the orbit.
Files are organized by date, and each contain all level 1 images obtained
during the orbits started in the day. Note, therefore, that the data for
the first 1 hour of a day might be found in the file of the day before.
Large PFI images (larger than 512 pixel in x- or y-direction), which are
occasionally obtained by special operation or for a campaign observation,
are collected in separate files to reduce the total file size of the day.
Those files are marked with '_large' at the end of the file name.
(e.g. spr930428_large).
Examples of the file name: sfr920720, spr920720, spr930428_large. The first file is found in the yearly directory, sxt_xda/level_1/full_sun/1992/, while the second found in sxt_xda/level_1/part_sun/1992/. These files contains the images obtained from 20-Jul-1992 00:31:59 through 21-Jul-1992 00:15:27 (the end of the last orbit in 20-Jul-1992). The third file found in the directory, sxt_xda/level_1/part_sun/1993/, contains 5 images with irregular size (512x64). sfr: prefix for SXT Full Frame (whole sun) Images. spr: prefix for SXT Partial Frame (partial sun) Images. 920720 : date (yymmdd) of the observation. 930428 : date (yymmdd) of the observation (of the third file). _large : surfix used for files containing PFIs larger than 512 pix.
Each file contains one solar image, and is organized in the daily directories located under the tree structure of the type, year/month/day/. (e.g. to reach the images obtained on 20-Jul-1992, go stepping down the directory to 1992/07/20/.)
Examples : sxtf_19920720_141055_131.fts, sxtp_19920720_141047_021.fts These file are included in the daily directory, sxt_fits/level_1/full_sun/1992/07/20/, and sxt_fits/level_1/part_sun/1992/07/20/, respectively. sxtf : prefix for SXT Full Frame (whole sun) Images. sxtp : prefix for SXT Partial Frame (partial sun) Images. _19920720_141055 : date (_yyyymmdd) and approximate time (_hhmmss) of observation. _19920720_141047 : date (_yyyymmdd) and approximate time (_hhmmss) of observation. _131 : stands for spatial resolution (0:full, 1:half, 2:quarter) and the filter pair (in the order of the filter wheel B and A). Filter B (1:open, 2:thin-Al, 3:AlMgMn, 4:Be, 5:thick-Al, 6:Mg), Filter A (1:open, 2:WL-narrow 3:UV-flood, 4:diffuser 5:WL-wide, 6:ND). This example shows that the image was taken with the half resolution (4.9"/pix) with the filter pair, B/A=3/1=AlMgMn/Open. _021 : this expression indicates the image was taken with the full resolution (2.45"/pix) and with the filter pair, B/A=2/1=thin-Al/Open. .fts : suffix for the FITS format.
SXT composite images combine 2(long/short) or 3(long/medium/short) exposures taken very close in time to increase the overall dynamic range of the image. The pixels with detector saturation are replaced with those of shorter exposure image(s). Level_2 images are thus most suitable for quantitative analysis. Each composite image has a related uncertainty image which provides the statistical error for each pixel. The Level 2 data only use complete or nearly-complete images. The Level 2 images are not co-aligned, but may be readily co-aligned with existing SSW mapping tools.
Files are organized by date. Like Level_1 XDA files, each file contains Level_2 images obtained during the orbits started in the day. Note, therefore, that the data for the first 1 hour of a day might be found in the file of the day before. The file name of the 2-image composites starts with 'ssc', and that of the 3-image composites starts with 'sst'. The uncertainty arrays have the same file name as the corresponding composites except having '_unc' in the last part.
Examples: ssc19930720_0014_1110110.4 <-- 2-image composites for 20-july-1993. ssc19930720_0014_1110110.4_unc <-- the uncertain array of the above. sst19930720_0014_1110110.4 <-- 3-image composites for 20-july-1993. sst19930720_0014_1110110.4_unc <-- the uncertain array of the above. All these files are included in the yearly directory, sxt_xda/level_2/1993/. ssc: prefix for 2-image composites. sst: prefix for 3-image composites, or triple composites. 19930720 : date (yyyymmdd) of the observation. _0014 : start time of the first orbit of the day. _1110110 : flags showing levels of calibration. .4 : identifier of product version. _unc : surfix used for uncertainty arrays.
Each file contains one solar image, is organized in the daily directories locating under the tree structure of the type, year/month/day/. (e.g. to reach the images obtained on 20-Jul-1993, go stepping down the directory to 1993/07/20/.) Their file name is defined similarly to the Level 1 products except the prefix (see examples in below).
Examples: sx2c_19930720_214131_231.fts <-- a composite image made of 2 exposures. sx2cu_19930720_214131_231.fts <-- the uncertainty array of the above. sx3c_19930720_035753_121.fts <-- a composite image made of 3 exposures. sx3cu_19930720_035753_121.fts <-- the uncertainty array of the above. These files are included in the daily directory, sxt_fits/level2/1993/07/20/. sx2c: prefix for 2-image composites. sx2cu: prefix for the uncertainty array of 2-image composites. sx3c: prefix for 3-image composites, or triple composites. sx3cu: prefix for the uncertainty array of 3-image composites. _19930720_214131 : date (_yyyymmdd) and time (_hhmmss) of observation. _231 : stands for spatial resolution (0:full, 1:half, 2:quarter) and the filter pair (in the order of the filter wheel B and A). Filter B (2:thin-Al, 3:AlMgMn, 4:Be, 5:thick-Al, 6:Mg), Filter A (1:open, or 6:NuDen). This example shows that the image was taken with the quarter resolution (9.8"/pix) and with the filter pair, B/A=3/1=AlMgMn/Open. _121 : this expression indicates the image was taken with the half resolution (4.9"/pix) and with the filter pair, B/A=2/1=thin-Al/Open. .fts : suffix for the FITS format.
The SXT Level_3 data, or "movie" images are prepared from Level_2 composite full-frame-images for convenience in viewing in movie mode to facilitate the study of coronal evolution and dynamic phenomena. This processing included co-alignment, rebinning 256x256 images to 512x512, logarithmic and byte scaling, adjustment of effective exposure to minimize movie flicker and enhance coronal intensity around solar minimum, and deletion of images unduly contaminated by radiation-belt particles or stray light. As a result, Level_3 SXT images sacrifice photometric accuracy for improved time-lapse viewing. Therefore, they are not intended for quantitative analysis.
The co-aligned full-sun white-light(WL) images are also categorized as Level_3 images. They are obtained with the SXT Aspect Sensor, the optical telescope coaxial with the SXT. It was in operation until 13-Nov-1992 when SXT had the entrance filter failure. The data have 12-bit or 8-bit intensity depth and archived in floating point. The images are co-aligned and have been cleaned to eliminate obvious hot pixels. The WL images are not photometrically useful, because the Aspect Sensor exponentially lost sensitivity after launch and because radiation damage to the CCD from excessive x-ray exposure left dark artifacts on the WL images.
Examples: sx2m_19970720_201339_231.xda <-- a Level_3(movie) composite image made from 2 exposures. sx3m_19970720_215723_121.xda <-- a Level_3(movie) composite image made from 3 exposures. These files are included in the daily directory, sxt_xda/level_3/xray/1993/07/20/. sx2m: prefix for 2-image movie composites. sx3m: prefix for 3-image movie composites. _19970720_201339 : date (_yyyymmdd) and time (_hhmmss) of observation. _19970720_215723 : date (_yyyymmdd) and time (_hhmmss) of observation. _231 : stands for spatial resolution (0:full, 1:half, 2:quarter) and the filter pair (in the order of the filter wheel B and A). Filter B (2:thin-Al, 3:AlMgMn, 4:Be, 5:thick-Al, 6:Mg), Filter A (1:open, or 6:NuDen). This example shows that the image was taken with the quarter resolution (9.8"/pix) and with the filter pair, B/A=3/1=AlMgMn/Open. _121 : this expression indicates the image was taken with the half resolution (4.9"/pix) and with the filter pair, B/A=2/1=thin-Al/Open. .xda : suffix for the XDA format data. sa08_19920120_025432_112.xda <-- a Level_3 white light image ( 8-bit depth) sa12_19920120_025224_112.xda <-- a Level_3 white light image (12-bit depth) These files are included in the daily directory, sxt_xda/level_3/wl/1992/10/10/. sa08 : prefix for WL images with 8-bit intensity depth. sa12 : prefix for WL images with 12-bit intensity depth. _19920120_025432 : date (_yyyymmdd) and time (_hhmmss) of observation. _19920120_025224 : date (_yyyymmdd) and time (_hhmmss) of observation. _112 : stands for spatial resolution (0:full, 1:half, 2:quarter) and the filter pair (in the order of the filter wheel B and A). Filter B (1:open), Filter A (2:WL-narrow 5:WL-wide). This example shows that the image was taken with the half resolution (4.9"/pix) and with the filter pair, B/A=1/2=Open/Narrow-band WL. .xda : suffix for the XDA format data.
Examples: sx2m_19970720_201339_231.fts <-- a Level_3(movie) composite image made from 2 exposures. sx3m_19970720_215723_121.fts <-- a Level_3(movie) composite image made from 3 exposures. These files are included in the daily directory, sxt_fits/level_3/xray/1993/07/20/. sx2m: prefix for 2-image movie composites. sx3m: prefix for 3-image movie composites. _19970720_201339 : date (_yyyymmdd) and time (_hhmmss) of observation. _19970720_215723 : date (_yyyymmdd) and time (_hhmmss) of observation. _231 : stands for spatial resolution (0:full, 1:half, 2:quarter) and the filter pair (in the order of the filter wheel B and A). Filter B (2:thin-Al, 3:AlMgMn, 4:Be, 5:thick-Al, 6:Mg), Filter A (1:open, or 6:NuDen). This example shows that the image was taken with the quarter resolution (9.8"/pix) and with the filter pair, B/A=3/1=AlMgMn/Open. _121 : this expression indicates the image was taken with the half resolution (4.9"/pix) and with the filter pair, B/A=2/1=thin-Al/Open. .fts : suffix for the FITS format data. sa08_19920120_025432_112.fts <-- a Level_3 white light image ( 8-bit depth) sa12_19920120_025224_112.fts <-- a Level_3 white light image (12-bit depth) These files are included in the daily directory, sxt_fits/level_3/wl/1992/01/20/. sa08 : prefix for WL images with 8-bit intensity depth. sa12 : prefix for WL images with 12-bit intensity depth. _19920120_025432 : date (_yyyymmdd) and time (_hhmmss) of observation. _19920120_025224 : date (_yyyymmdd) and time (_hhmmss) of observation. _112 : stands for spatial resolution (0:full, 1:half, 2:quarter) and the filter pair (in the order of the filter wheel B and A). Filter B (1:open), Filter A (2:WL-narrow, or 5:WL-wide). This example shows that the image was taken with the half resolution (4.9"/pix) and with the filter pair, B/A=1/2=Open/Narrow-band WL. .fts : suffix for the FITS format data.
Examples: 19970720_201339_sx2m_231.jpg <-- a Level_3(movie) composite image made from 2 exposures. 19970720_215723_sx3m_121.jpg <-- a Level_3(movie) composite image made from 3 exposures. These files are included in the daily directory, sxt_jpeg/level_3/xray/1992/10/10/. 19970720_201339 : date (yyyymmdd) and time (_hhmmss) of observation. 19970720_215723 : date (yyyymmdd) and time (_hhmmss) of observation. _sx2m: identifier of 2-image movie composites. _sx3m: identifier of 3-image movie composites. _231 : stands for spatial resolution (0:full, 1:half, 2:quarter) and the filter pair (in the order of the filter wheel B and A). Filter B (2:thin-Al, 3:AlMgMn, 4:Be, 5:thick-Al, 6:Mg), Filter A (1:open, or 6:NuDen). This example shows that the image was taken with the quarter resolution (9.8"/pix) and with the filter pair, B/A=3/1=AlMgMn/Open. _121 : This expression to shows that the image was taken with the half resolution (4.9"/pix) and with the filter pair, B/A=2/1=thin-Al/Open. .jpg : suffix for the JPEG format. 19920120_025432_sa08_112.jpg <-- a Level_3 white light image ( 8-bit depth) 19920120_025224_sa12_112.jpg <-- a Level_3 white light image (12-bit depth) These files are included in the daily directory, sxt_jpeg/level_3/wl/1992/10/10/. 19920120_025432 : date (_yyyymmdd) and time (_hhmmss) of observation. 19920120_025224 : date (_yyyymmdd) and time (_hhmmss) of observation. sa08 : identifier of WL images with 8-bit intensity depth. sa12 : identifier of WL images with 12-bit intensity depth. _112 : stands for spatial resolution (0:full, 1:half, 2:quarter) and the filter pair (in the order of the filter wheel B and A). Filter B (1:open), Filter A (2:WL-narrow, or 5:WL-wide). This example shows that the image was taken with the half resolution (4.9"/pix) and with the filter pair, B/A=1/2=Open/Narrow-band WL. .jpg : suffix for the JPEG format data.
(a) | tags for the mandatory keywords of the FITS standard file : e.g., SIMPLE, BITPIX,,, c.f., Section 5.4.1 of http://archive.stsci.edu/fits/fits_standard/fits_standard.html . |
(b) | flattened version of the nested IDL index structre
designed for the Yohkoh original (XDA) data format : e.g., DP_MODE, DP_RATE, CCD_TEMP,,,. c.f., the ".inc" files in a SolarSoft directory ($SSW/yohkoh/gen/idl/ref_access) or here. |
(c) | additional tags required to be handled with SolarSoft
on a common platform with the other data sorces : e.g., CRPIXn, XCEN, YCEN,,, c.f., http://www.lmsal.com/solarsoft/ssw_standards.html. |
(d) | a comment tag describing the calibration history process by YLA : i.e., HISTORY, c.f., sample description of the HISTORY tag . |
The tags in group (b) are often incomplete, because the original XDA index structures generally have vector values while the FITS tags only allow scalar values. To avoid information from lost by truncation, the vector components of some important tags are specifically labeled (e.g., SHAPE_Cn, CORNE_Cn) in the FITS header as the needs arises. Most of the group-(b) tags are expressed in binary in accordance with the original XDA index. Their decimal values are derived through a series of IDL/SolarSoft functions (e.g., gt_date.pro, gt_temp_ccd.pro), in the same way as they worked with XDA indexes.
Here is an example of the typical FITS headers of the YLA products (Level_2 data).