You are here

Level 2: calibrated data

The calibration applied to LYRA data consists in:

  • rescaling the data to a Sun-satellite distance of 1 AU
  • removing the dark current
  • correcting the data for the degradation trend
  • converting the data in physical units

For more information about any of these steps, please refer to the LYRA instrument paper.

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)

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 after mid-2010.

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.