SOHO LASCO header
本文记录 SOHO 卫星 LASCO 仪器 fits 头文件详细内容说明
前言
本文是在学习分析 SOHO 卫星 LASCO 仪器数据时记录，因需要一些头文件的数据，但是限于个人水平，大多数头的含义没有看懂，个人在网络上搜寻许久，终于在这里找到详细记录，由于以上方式查阅比较困难，特在此记录方便查阅。
内容
S 代表字符串 (string)，I 代表整数 (Integer)，R 代表实数 (Real)
| 关键词 | 格式 | 值 | 详细说明 |
|---|---|---|---|
| SIMPLE | S*1 | T | 表明符合 fits 格式标准 |
| BITPIX | I*2 | 8,16,32 | 每个像素点代表的位数 |
| NAXIS | I*2 | 2 | 图像中的轴数 |
| NAXIS1 | I*2 | 正整数 | 第一个轴的长度（列）编号 |
| NAXIS2 | I*2 | 正整数 | 第二个轴的长度（列）编号 |
| TELESCOP | S*8 | SOHO | 卫星名字 |
| INSTRUME | S*8 | LASCO | 仪器名字 |
| DETECTOR | S*8 | C1/C2/C3 | 望远镜名字 |
| FILENAME | S*30 | fits 文件的文件名 | |
| FILEORIG | S*17 | 原始测量文件 (形式为 YYMMDD_HHMMSS.img) | |
| DATE | S*23 | 文件编写时间，如 1996/05/21 17:28:48.208 | |
| DATE-OBS | S*10 | 开始曝光的日期，如 1996/05/20 | |
| TIME-OBS | S*12 | 开始曝光的时间，如 00:40:05.407 | |
| MID_DATE | I*2 | 曝光中点日期（简化儒略日） Modified Julian Date at the mid-point of the exposure |
|
| MID_TIME | R*4 | 曝光中点时间（在当天的秒数） Number of seconds of the day at the mid-point of the exposure |
|
| OBT_TIME | R*4 | Value of the On-Board Time | |
| EXPTIME | R*4 | Number of seconds of the exposure time | |
| EXP0 | R*4 | Measured exposure delay time | |
| EXPCMD | R*4 | Commanded exposure delay time | |
| EXP1 | R*4 | Length of time since CCD clear | |
| EXP2 | R*4 | Length of time to open shutter | |
| EXP3 | R*4 | Length of time to close shutter | |
| READPORT | S*1 | A/B/C/D | CCD readout port |
| SUMROW | I*2 | 0/2/4 | Number of rows being summed on the CCD |
| SUMCOL | I*2 | 0/2/4 | Number of columns being summed on the CCD |
| LEBXSUM | I*2 | 0/2/4 | Number of columns being summed in the LEB |
| LEBYSUM | I*2 | 0/2/4 | Number of rows being summed in the LEB |
| SHUTTR | I*2 | 0 1 |
Shutter was commanded open during the exposure Shutter was not commanded during the exposure |
| LAMP | I*2 | 0 1 |
Calibration lamp was not commanded on Calibration lamp was commanded on |
| FILTER | S*8 | Clear Orange FeXIV FeX CaXV Blue Red IR Lens |
Position of the filter wheel |
| POLAR | S*8 | Clear 0 deg +60 deg -60 deg H alpha ND |
Position of the polarizer wheel |
| LP_NUM | S*8 | Normal Cal Lamp Dark Line Scan Pol Seq |
Description of the LEB Program (LP) used to generate the image |
| OS_NUM | I*2 | Observing Sequence Number | |
| IMGCTR | I*2 | Sequential counter since the last LEB reboot | |
| IMGSEQ | I*2 | Number of the image in the current sequence, starting at 0 | |
| COMPRSSN | S*8 | Code indicating the steps used in compressing the data | |
| PLATESCL | R*4 | Number of arc seconds per pixel | |
| OFFSET | I*2 | Electronic offset in DN | |
| P1COL | I*2 | CCD column number of start of image, 0-19 are underscan pixels, 20-1043 are imaging pixels, 1044 - 32000 are overscan pixels | |
| P1ROW | I*2 | CCD row number of start of image, 1-1044 are imaging rows, 1025-32000 are overscan rows | |
| P2COL | I*2 | CCD column number of start of image, 0-19 are underscan pixels, 20-1043 are imaging pixels, 1044 - 32000 are overscan pixels | |
| P2ROW | I*2 | CCD row number of start of image, 1-1044 are imaging rows, 1025-32000 are overscan rows | |
| RECTIFY | I*2 | TRUE FALSE | Status of rectification to put solar north to the top of the image |
| R1COL | I*2 | The rectified coordinate, equivalent to P1COL, as though the image had been read out with this coordinate | |
| R1ROW | I*2 | Rectified P1ROW | |
| R2COL | I*2 | Rectified P2COL | |
| R2ROW | I*2 | Rectified P2ROW | |
| EFFPORT | S*8 | A/B/C/D | Rectified read out port |
| VERSION | I*2 | Version number of LEB header | |
| DATAMIN | R*4 | Minimum value of the image, including the bias | |
| DATAMAX | R*4 | Maximum value of the image | |
| DATAZER | I*4 | Number of zero pixels in the image | |
| DATASAT | I*4 | Number of saturated values in the image | |
| DATAAVG | R*4 | Average value of the image | |
| DATASIG | R*4 | Standard deviation in computing the average | |
| DATAP01 | I*4 | Intensity of 1st percentile of image | |
| DATAP10 | I*4 | Intensity of 10th percentile of image | |
| DATAP25 | I*4 | Intensity of 25th percentile of image | |
| DATAP75 | I*4 | Intensity of 75th percentile of image | |
| DATAP90 | I*4 | Intensity of 90th percentile of image | |
| DATAP95 | I*4 | Intensity of 95th percentile of image | |
| DATAP98 | I*4 | Intensity of 98th percentile of image | |
| DATAP99 | I*4 | Intensity of 99th percentile of image | |
| CRPIX1 | R*4 | Column number of the reference pixel.（太阳中心） | |
| CRPIX2 | R*4 | Row number of the reference pixel.（太阳中心） | |
| CRVAL1 | R*4 | Number of arc seconds of the center of the sun from the reference position in the azimuthal direction (E-W). Positive is to the solar west | |
| CRVAL2 | R*4 | Number of arc seconds of the center of the sun from the reference position in the azimuthal direction (N-s). Positive is to the solar north | |
| CROTA1 | R*4 | Rotation of axis 1 with respect to solar north. Positive is westward (clockwise) | |
| CROTA2 | R*4 | Rotation of axis 2 with respect to solar north. Positive is westward (clockwise) | |
| CTYPE1 | S*8 | SOLAR-X | Type of units of axis #1 |
| CTYPE2 | S*8 | SOLAR-Y | Type of units of axis #2 |
| CUNIT1 | S*8 | ARCSEC | Units along axis #1 |
| CUNIT2 | S*8 | ARCSEC | Units along axis #2 |
| CDELT1 | R*8 | Increment along axis #1 (Same as PLATESCL) | |
| CDELT2 | R*8 | Increment along axis #2 (Same as PLATESCL) | |
| HISTORY | S*80 | History of processing. | |
| COMMENT | S*80 | Comments. | |
| END | Last keyword in the FITS header |