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Level 2: calibrated data

The calibration applied to LYRA data consists in:

Still present in the calibrated data:

  • the flat-field effects (i.e. some of the periodic features observed in the data might be linked to spacecraft maneuvers)
  • the slow stabilization from MSM-diamond detectors (only applicable to LYRA channels 1-1, 1-3, 2-1, 2-3, 2-4)
  • the varying Sun-Earth distance

ATTENTION: due to the strong degradation, data acquired by the nominal unit (unit2) in Lyman-alpha and Herzberg channels present a very low signal-to-noise ratio, and solar effects might not be easy to extract from them. These data must be used with caution.

Level2 data consist in daily fits files, updated after each contact with the spacecraft. They contain a primary header and a secondary header (described below), followed by the binary table of data.

fits keywords for lev2 Lyra product: primary header
KEYWORD EXAMPLE OF VALUE COMMENT
SIMPLE T Written by IDL: Tue Feb 15 09:27:46 2011
BITPIX 8  
NAXIS 0  
EXTEND T File contains extensions
ORIGIN ’ROB-SIDC’  
TELESCOP ’PROBA2 ’  
INSTRUME ’LYRA ’  
OBJECT ’EUV solar irrad’  
OBS_MODE ’standard’ science data
DATE ’2011-02-15’  
DATE_OBS ’2010-05-01T00:00:00.004000’ UTC start of observation
DATE_END ’2010-05-01T21:41:22.150995’ UTC end of observation
DATASRC ’Redu ’ receiving ground station
LEVEL ’2 ’ calibration level
ALGOR_V ’EDG=2.1 BSDG=0.5’ LYRA calibration S/W version
FILENAME ’lyra_20100501-000000_lev2_std.fits’ name of this FITS file
END    
fits keywords for lev2 Lyra product: secondary header
KEYWORD EXAMPLE OF VALUE COMMENT
XTENSION ’BINTABLE’ Written by IDL: Tue Feb 15 09:27:46 2011
BITPIX 8  
NAXIS 2 Binary table
NAXIS1 45 Number of bytes per row
NAXIS2 7789006 Number of rows
PCOUNT 0 Random parameter count
GCOUNT 1 Group count
TFIELDS 6 Number of columns
EXTNAME ’IRRAD LEVEL 2’ name of binary table extension
TFORM1 ’1D ’ Real*8 (double precision)
TTYPE1 ’TIME ’ Label for column 1
TUNIT1 ’s ’ Units of column 1
TFORM2 ’1D ’ Real*8 (double precision)
TTYPE2 ’CHANNEL1’ Label for column 2
TUNIT2 ’W/m**2 ’ Units of column 2
TFORM3 ’1D ’ Real*8 (double precision)
TTYPE3 ’CHANNEL2’ Label for column 3
TUNIT3 ’W/m**2 ’ Units of column 3
TFORM4 ’1D ’ Real*8 (double precision)
TTYPE4 ’CHANNEL3’ Label for column 4
TUNIT4 ’W/m**2 ’ Units of column 4
TFORM5 ’1D ’ Real*8 (double precision)
TTYPE5 ’CHANNEL4’ Label for column 5
TUNIT5 ’W/m**2 ’ Units of column 5
TFORM6 ’5A ’ Character string
TTYPE6 ’WARNING ’ Label for column 6
TUNIT6 ’ ’ Units of column 6
END    

Then follows the binary table containing the data, which consists in 6 columns: the time, the irradiance in the four channels, and an index describing the quality of the calibration and time interpolation on the data.