Description of the imageinfo-structure February 6, 2003, Harald U. Frey ====================================== The imageinfo structures for all FUV-instruments contain the same fields but with different sizes for WIC and for the two SI-channels. They are written with IDL 5.3. This is an example for WIC. IDL> restore,'IMFHWIC_2001_0915_011009i.sav' IDL> help,imageinfo,/str ** Structure IMAGEDATA, 47 tags, length=2359600: INST_ID STRING ' WIC ' Instrument ID EPOCH DOUBLE 6.3167735e+13 Epoch of middle of exposure TIME LONG Array[2] Time of middle of exposure in YYYYDDD Milliseconds of day ROWS INT 256 rows in raw image COLS INT 256 columns in raw image IMAGE FLOAT Array[256, 256] original image either in raw counts, calibrated counts, Rayleigh SPIN LONG 64998 spin number RADIUS FLOAT 8.09488 geocentric distance in R_e HV_PHOS FLOAT 3978.80 HV of phosphor HV_MCP FLOAT 1147.07 HV of MCP FOVSCALE INT 1 scaling factor of FoV SPIN_PHASE DOUBLE 55.878356 spin phase angle in middle of exposure A_GCI3 DOUBLE Array[3] GCI unit vector of spin axis direction O_GCI DOUBLE Array[3] GCI vector of spacecraft position HFOV DOUBLE 17.270000 horizontal field of view in degrees VFOV DOUBLE 17.200001 vertical field of view in degrees INST_AZIMUTH DOUBLE 43.160000 instrument azimuth angle from spacecraft x-axis INST_CO_ELEV DOUBLE 0.41000000 instrument elevation angle from spacecraft spin plane INST_ROLL DOUBLE -2.4500000 instrument roll angle from spacecraft spin axis SC_SV DOUBLE Array[3] spin axis unit vector in spacecraft frame ANGL_RES_R DOUBLE 0.067187503 angular resolution vertically ANGL_RES_C DOUBLE 0.067460939 angular resolution horizontally IP FLOAT 0.00000 unused HGT FLOAT 8.09488 geocentric distance in R_e SRC STRING 'HWIC' instrument identifier LAT_CTR DOUBLE 75.119938 geographic latitude of spacecraft footprint LON_CTR DOUBLE 220.71419 geographic longitude of spaceraft footprint MIN FLOAT 3.00000 minimum in image MAX FLOAT 13569.0 maximum in image MINVAL FLOAT 0.00000 unused MAXVAL FLOAT 0.00000 unused MEAN FLOAT 0.00000 unused STD FLOAT 0.00000 unused L0 DOUBLE Array[3] GCI unit vector of look direction RA DOUBLE 11.494235 RA of look direction DEC DOUBLE -81.011016 DEC of look direction EMIS_HGT FLOAT 130.000 assumed emission height in km MLAT FLOAT Array[256, 256] magnetic latitude of every pixel in image MLON FLOAT Array[256, 256] magnetic longitude of every pixel in image MLT FLOAT Array[256, 256] MLT of every pixel in image MLT_IMG FLOAT Array[256, 256] magnetically mapped image GLAT FLOAT Array[256, 256] geographic latitude of every pixel in image GLON FLOAT Array[256, 256] geographic longitude of every pixel in image SZA FLOAT Array[256, 256] solar zenith angle of every pixel in image DZA FLOAT Array[256, 256] spacecraft zenith angle of every pixel in image AIRGLOW_SCALE FLOAT Array[3] parameters for airglow correction CALIBRATION_FLAG c=0 means raw counts in image and mlt_img INT = 0 c=1 means corrected (flatfield, sensitivity) counts in image and mlt_img c=2 means Rayleigh (flatfield, sensitivity) in image and mlt_img In the SI-structures all [256,256] fields are [128,128] except the mlt_img which is always mapped to 256x256 pixels. The lat/long positions are always valid for the bottom left corner of the respective pixel. NOTE: The geomagnetic latitude/longitude/MLT information is only valid for the original image, not for the mapped MLT_IMG. If you want to determine, which magnetic coordinates are related to a certain pixel in the mlt_img, the following IDL-lines will calculate this information. nxpix=256 nypix=256 latmin=50. xr=(x-(nxpix-1)/2)*((90.-latmin)/((nxpix-1)/2)) yr=(y-(nypix-1)/2)*((90.-latmin)/((nypix-1)/2)) maglat=90.0-SQRT(xr*xr+yr*yr) maglt=(ATAN(-xr,yr)/!DTOR + 180.)/15. ======= modification May 2003 ==================== imageinfo.mlt_img[0,0]*1.e6 minimum latitude of mapped image, default is 50. imageinfo.mlt_img[0,1]*1.e6 1 for northern, -1 for southern hemisphere