General description:
Note: fpC files are no longer produced as of DR8. Instead, equivalent data is stored in frame files.
The corrected frame, having
been bias subtracted, flat-fielded, and purged of bright stars. A fit
to the sky is not subtracted, but stored in the header
keyword SKY - this is a change between the EDR data and the
DR1 data.
An offset of SOFTBIAS is added to each pixel to avoid
negative pixel values. Thus, in the image the "sky" will everywhere
equal approximately SOFTBIAS + SKY.
There is one more new keyword in DR1 data which helps with quick
photometric calibration: FLUX20, the flux for a 20th
magnitude object. (A FLUX0 field is also written but not
calculated.)
Note that FLUX20 is calculated from a preliminary
photometric calibration. The full photometric calibration is
calculated only after fpC frames have been written. To
use the full calibration, you will need the zeropoint aa
and extinction coefficient kk from the tsField file.
The corrected frame, having been bias subtracted, flat-fielded, purged of bright stars, and sky subtracted. After subtracting a fit to the sky, an offset of SOFTBIAS is added to each pixel to avoid negative pixel values. Thus, in the image the "sky" will everywhere equal approximately SOFTBIAS.
Naming convention: fpC-rrrrrr-bc-ffff.fit, where rrrrrr is the imaging run number, b is the filter used (u, g, r, i, or z), c is the column location in the Imaging Array of the CCD which acquired the data (1-6), and ffff is the field number within the run.
Approximate size: 5,581.44 Kb per file. 5 files per field. Total of 27,907.2 Mb for a single frames pipeline run with 1000 fields.
File type: FITS image
Read by products:
Written by products: frames
All of the header parameters from the raw image are inherited as well.
The following is just the copy of an fpC fits file header as produced by the current version of the frames pipeline (v5_3_53 or so). See below for an old version (probably not even adequate for EDR).
SIMPLE = T BITPIX = 16 NAXIS = 2 NAXIS1 = 2048 NAXIS2 = 1489 BZERO = 3.27680000000000E+04 BSCALE = 1.00000000000000E+00 TAI = 4461556376.78 / 1st row - Number of seconds since Nov 17 1858 RA = 252.64468 / 1st row - Right ascension of telescope boresigh DEC = 65.127927 / 1st row - Declination of telescope boresight (d SPA = 155.615 / 1st row - Camera col position angle wrt north ( IPA = 294.868 / 1st row - Instrument rotator position angle (de IPARATE = 0.0004 / 1st row - Instrument rotator angular velocity ( AZ = 160.80974 / 1st row - Azimuth (encoder) of tele (0=N?) (de ALT = 53.523581 / 1st row - Altitude (encoder) of tele (de FOCUS = -999999999999.999999 / 1st row - Focus piston (microns?) DATE-OBS= '2000-04-04' / 1st row - TAI date TAIHMS = '09:12:56.77' / 1st row - TAI time (HH:MM:SS.SS) (TAI-UT = appr COMMENT TAI,RA,DEC,SPA,IPA,IPARATE,AZ,ALT,FOCUS at reading of col 0, row 0 BUNITS = 'ADUs ' ORIGIN = 'SDSS ' TELESCOP= '2.5m ' TIMESYS = 'TAI ' RUN = 1336 / Run number FRAME = 11 / Frame sequence number within the run CCDLOC = 11 / Survey location of CCD (e.g., rowCol) STRIPE = 42 / Stripe index number (23 <--> eta=0) STRIP = 'N ' / Strip in the stripe being tracked. FLAVOR = 'science ' / Flavor of this run SYS_SCN = 'mean ' / System of the scan great circle (e.g., mean) EQNX_SCN= 2000.00 / Equinox of the scan great circle. (years) NODE = 95.00000 / RA of the great circle's ascending node (deg) INCL = 80.00000 / Great circle's inclination wrt cel. eq. (deg) XBORE = -22.74 / Boresight x offset from the array center (mm) YBORE = 0.00 / Boresight x offset from the array center (mm) OBJECT = '42 N ' / e.g., 'stripe 50.6 degrees, north strip' EXPTIME = '53.907456' / Exposure time (seconds) EQUINOX = '2000.0 ' / Equinox of the TCC coordinates (years) SYSTEM = 'FK5 ' / System of the TCC coordinates (e.g., mean) CCDMODE = 'DRIFT ' / 'STARING' or 'DRIFT' C_OBS = 26322 / CCD row clock rate (usec/row) COLBIN = 1 / Binning factor perpendicular to the columns ROWBIN = 1 / Binning factor perpendicular to the rows DAVERS = 'v14_20 ' / Version of DA software COMMENT CCD-specific parameters CAMROW = 1 / Row in the imaging camera BADLINES= 0 / Number of bad lines in frame SOFTBIAS= 1000 / software "bias" added to all DN FLUX20 = 2.05987000000000E+03 / Number of DN in 20th mag object FLUX0 = -9.9990000000000E+03 / Number of DN in 0th mag object FCALI_ID= 'None ' SKY = 1.30960000000000E+02 / Approx. sky level (DN) BUNIT = 'DNs ' FILTER = 'r ' / filter used CAMCOL = 1 / column in the imaging camera VERSION = 'XXX ' / Version of photo used. DERV_VER= 'v8_15 ' / Version of dervish used ASTR_VER= 'v5_13 ' / Version of astrotools used ASTRO_ID= 'XXX ' / Astrometric pipeline run identifier. BIAS_ID = 'XXX ' / Bias pipeline run identifier. FRAME_ID= 'XXX ' / Frames pipeline run identifier. KO_VER = 'XXX ' / Version of known object catalog used. PS_ID = '2002-09-04T17:49:34 19844 camCol 1' ATVSN = 'v5_13 ' / ASTROTOOLS version tag RADECSYS= 'ICRS ' / International Celestial Reference Sys CTYPE1 = 'DEC--TAN' / X (Column) Axis Projection CTYPE2 = 'RA---TAN' / Y (Row) Axis Projection CUNIT1 = 'deg ' / Column Axis Units CUNIT2 = 'deg ' / Row Axis Units CRPIX1 = 1.02450000000000E+03 / Column Pixel Coordinate of Reference CRPIX2 = 7.44500000000000E+02 / Row Pixel Coordinate of Reference Pix CRVAL1 = 6.42142612400000E+01 / DEC at Reference Pixel CRVAL2 = 2.51207342810000E+02 / RA at Reference Pixel CD1_1 = 4.75626416015645E-05 / DEC degrees per column pixel CD1_2 = -9.9116868279565E-05 / DEC degrees per row pixel CD2_1 = 9.91802898939385E-05 / RA degrees per column pixel CD2_2 = 4.76632658513898E-05 / RA degrees per row pixel END
The following is out of date at least for DR1. I am leaving it in in case it applies to EDR data, but looking at an EDR fpc file, I doubt even that. See above for a DR1 version copied from a DR1 fpC file.
SIMPLE = T BITPIX = 16 NAXIS = 2 NAXIS1 = 2048 NAXIS2 = 1489 BSCALE = 1 BZERO = 32768 VERSION = 'XXX ' / Version of software used. PS_ID = 'XXX ' / Postage stamp pipeline run identifier. BIAS_ID = 'XXX ' / Bias pipeline run identifier. ASTRO_ID= 'XXX ' / Astrometric pipeline run identifier. FRAME_ID= 'XXX ' / Frames pipeline run identifier. KO_VER = 'XXX ' / Version of known object catalog used. RUN = XXX / Imaging run number. CAMCOL = XXX / Column in the imaging camera. FIELD = XXX / Field sequence number within the run. FILTER = 'XXX ' / Filter (u, g, r, i, or z). TAI = XXXXXXXXXX.XX / Number of seconds since Nov 17 1858 0 TAI RA = XXX.XXXXXX / Right ascension of telescope boresight (deg) DEC = XXX.XXXXXX / Declination of telescope boresight (degrees) SPA = XXX.XXX / Camera col position angle wrt north (degrees) IPA = XXX.XXX / Instrument rotator position angle (degrees) IPARATE = XXX.XXXX / Instrument rotator angular velocity (deg/sec) AZ = XXX.XXXXXX / Azimuth (encoder) of tele (0=N?) (degrees) ALT = XXX.XXXXXX / Altitude(encoder) of tele (degrees) FOCUS = XXXXX.X / Focus piston (microns?) DATE-OBS= 'DD/MM/YY' / TAI date (DD/MM/YY) TAIHMS = 'HH:MM:SS.SS' / TAI time (HH:MM:SS.SS) (TAI-UT =approx 30 s) CCDLOC = XXX / Survey location of CCD (e.g., rowCol) FRAME = XXX / Frame sequence number within the run DAVERS = 'XXX ' / Version of DA software RADECSYS= 'ICRS ' / International Celestial Reference Sys CTYPE1 = 'DEC--TAN' / X (Column) Axis Projection CTYPE2 = 'RA---TAN' / Y (Row) Axis Projection CUNIT1 = 'deg ' / Column Axis Units CUNIT2 = 'deg ' / Row Axis Units CRPIX1 = 1.02400000000000E+03 / Column Pixel Coordinate of Reference CRPIX2 = 6.80000000000000E+02 / Row Pixel Coordinate of Reference Pix CRVAL1 = -3.1788873000000E-01 / DEC at Reference Pixel CRVAL2 = 1.88473355950000E+02 / RA at Reference Pixel CD1_1 = 1.10005818270640E-04 / DEC degrees per column pixel CD1_2 = 1.31691176470661E-08 / DEC degrees per row pixel CD2_1 = -4.1308597225549E-08 / RA degrees per column pixel CD2_2 = 1.09963954550070E-04 / RA degrees per row pixel END