Description of the giro ON THE DETAILS OF THE IMPLEMENTATION Bartolomeo Viticchiè Acknowledgments: Sebastien Wagner & Masaya Takahashi

The GIRO application

The GIRO application The GIRO is SRF-content driven! This means that it cycles on the channels that can be calibrated using the ROLO model, i.e., the ones in the spectral range [ 0.3 , 2.5 ] µm. It looks into the lunar observation files for the information related to each channel that is calibrated. The GIRO_fourthrelease expects to find all the channels in each lunar observation file. In the latest version of the executable this approach has been modified, i.e., the user can also omit some of the channels.

The GIRO application: handling of the inputs NetCDF reader: the input is organized in three groups (structures) stGIRO_OBS is the structure carrying the information about the observables: irradiance integrated DC signal number of Moon pixels (related to 1. and 2.) DC offset (i.e., deep space level) pixel solid angle oversampling factor radiance imagette DC imagette columns of the imagette rows of the imagette DC threshold (related to 1., 2., and 3.)

The GIRO application: handling of the inputs NetCDF reader: the input is organized in three groups (structures) stGIRO_OBS is the structure carrying the information about the observables stROLO_INPUTS is the structure carrying the input to the Computation of the ROLO irradiance: epoch time of the observation time of the observation in calendar format (YYYYMMDDThh:mm:ss) satellite x satellite y satellite z reference frame of x, y, and z

The GIRO application: handling of the inputs NetCDF reader: the input is organized in three groups (structures) stGIRO_OBS is the structure carrying the information about the observables stROLO_INPUTS is the structure carrying the input to the Computation of the ROLO irradiance stList_Chans is the structure carrying the information about the channels TO CALIBRATE, i.e., the channels completely included in the spectral range [ 0.3 , 2.5 ] µm

The GIRO application: handling of the inputs NetCDF reader: the input is organized in three groups (structures) stGIRO_OBS is the structure carrying the information about the observables stROLO_INPUTS is the structure carrying the input to the Computation of the ROLO irradiance stList_Chans is the structure carrying the information about the channels TO CALIBRATE: satellite name instrument name WMO code number of channels to calibrate array of structures stChannel channel Name SRF SRF wavelengths number of wavelengths

The reading is performed by using the The GIRO application: handling of the inputs NetCDF reader: the input is organized in three groups (structures) stGIRO_OBS is the structure carrying the information about the observables stROLO_INPUTS is the structure carrying the input to the Computation of the ROLO irradiance stList_Chans is the structure carrying the information about the channels TO CALIBRATE The reading is performed by using the NetCDF C interface

The GIRO application

The GIRO application: imagette processing rows Fill Value = -999 DC imagette cols

The “real” dimensions of the imagette The GIRO application: imagette processing 1/3 rows Fill Value = -999 “real” rows DC imagette The “real” dimensions of the imagette are found by looking for the first occurrence of Fill Value along the first column and the first row, respectively “real” cols cols

The GIRO application: imagette processing 2/3 rows Fill Value = -999 “real” rows DC imagette 5 pixels The “real” dimensions are crucial to evaluate the DC offset as the average of the DC imagette in a border region with width equal to 5 pixels “real” cols cols

The GIRO application: imagette processing 3/3 Fill Value = -999 DC imagette >= DC threshold By comparing the value of each DC imagette pixel against the DC threshold the Moon pixels are identified and (at the same time) the integrated DC signal, the number of Moon pixels and the irradiance are derived

The GIRO application: sanity check stGIRO_OBS is the structure carrying the information about the observables: irradiance integrated DC signal number of Moon pixels (related to 1. and 2.) DC offset (i.e., deep space level) pixel solid angle oversampling factor radiance imagette DC imagette columns of the imagette rows of the imagette DC threshold (related to 1., 2., and 3.)

The GIRO application: sanity check stGIRO_OBS is the structure carrying the information about the observables: irradiance integrated DC signal number of Moon pixels (related to 1. and 2.) DC offset (i.e., deep space level) pixel solid angle oversampling factor radiance imagette DC imagette columns of the imagette rows of the imagette DC threshold (related to 1., 2., and 3.) The quantities provided by the user are derived (again) via the imagette processing for checking purposes. WHY? These are the quantities from which the calibration results are derived!

The GIRO application: sanity check

The GIRO application: sanity check W_XX-EUMETSAT-Darmstadt,VISNIR+SUBSET+MOON,MSG1+SEVIRI_C_EUMG_20031107105604_01.nc Quantity User Imgt Processing Observed Irradiance 0.002066243279734236 0.002066243279734259 Observed DC 884123.00000000000000 884123.00000000000000 DC Offset 51.01373239436619 51.01373239436619 Total number of pixels 7108 7108 Complete agreement between the observables provided by the user and the outcome of the imagette processing. EXACTLY THE SAME PROCEDURE WAS USED TO DERIVE THE TWO GROUPS OF QUANTITIES.

The GIRO application: sanity check W_US-MCST-GSFC,VISNIR+SUBSET+MOON,TERRA+MODIS_C_KCGS_20141012174519_01.nc Quantity User Imgt Processing Observed Irradiance 0.001124984002672136 0.001109618885481683 Observed DC 45625.55016709724441 44649.88412075559609 DC Offset 0.00000000000000 0.51703453744555 Total number of pixels 447 447

The GIRO application: sanity check W_US-MCST-GSFC,VISNIR+SUBSET+MOON,TERRA+MODIS_C_KCGS_20141012174519_01.nc Quantity User Imgt Processing Observed Irradiance 0.001124984002672136 0.001109618885481683 Observed DC 45625.55016709724441 44649.88412075559609 DC Offset 0.00000000000000 0.51703453744555 Total number of pixels 447 447 Private communication with Zhipeng Wang (NASA GSFC): DIFFERENT METHODS ADOPTED.

The GIRO application: sanity check W_US-MCST-GSFC,VISNIR+SUBSET+MOON,TERRA+MODIS_C_KCGS_20141012174519_01.nc Quantity User Imgt Processing Observed Irradiance 0.001124984002672136 0.001109618885481683 Observed DC 45625.55016709724441 44649.88412075559609 DC Offset 0.00000000000000 0.51703453744555 Total number of pixels 447 447 Private communication with Zhipeng Wang (NASA GSFC): DIFFERENT METHODS ADOPTED.

The GIRO application: sanity check W_US-MCST-GSFC,VISNIR+SUBSET+MOON,TERRA+MODIS_C_KCGS_20141012174519_01.nc Quantity User Imgt Processing Observed Irradiance 0.001124984002672136 0.001109618885481683 Observed DC 45625.55016709724441 44649.88412075559609 DC Offset 0.00000000000000 0.51703453744555 Total number of pixels 447 447 Private communication with Zhipeng Wang (NASA GSFC): DIFFERENT METHODS ADOPTED.

The GIRO application: sanity check W_US-MCST-GSFC,VISNIR+SUBSET+MOON,TERRA+MODIS_C_KCGS_20141012174519_01.nc Quantity User Imgt Processing Observed Irradiance 0.001124984002672136 0.001109618885481683 Observed DC 45625.55016709724441 44649.88412075559609 DC Offset 0.00000000000000 0.51703453744555 Total number of pixels 447 447 Private communication with Zhipeng Wang (NASA GSFC): DIFFERENT METHODS ADOPTED. WHEN THE IMAGETTES ARE PROVIDED: the sanity check files are very important to check that everything is in order with the preparation of the imagette and/or with the computation of the observables provided by the user (even when an approach different from the imagette processing has been adopted)

The GIRO application: selenographic coordinates The SPICE (JPL) tool is used to derive the selenographic coordinates for the description of the observation geometry. The following SPICE kernels have been adopted: de421.bsp (planetary & lunar ephemeris) naif0010.tls (leap seconds) pck00010.tpc (constants) Earth rotation description earth_000101_130520_130227.bpc earth_070425_370426_predict.bpc earth_assoc_itrf93.tf Moon orientation description moon_080317.tf moon_pa_de421_1900-2050.bpc moon_assoc_me.tf

The GIRO application: selenographic coordinates Computation steps: Position provided in ITRF93 (example MSGs) Sun position in MOON_ME Satellite position: ITRF93  MOON_ME (translation + rotation) Computation of the selenographic coordinates Tested the alternative approach of “passing for” the J2000 (native reference of SPICE), but the differences are practically null.

The GIRO application: computation of the ROLO irradiance Computation of the ROLO irradiance, the “ingredients”: Smoothed ROLO reflectance interpolated on the band wavelengths (ROLO_SRF) Smoothed solar irradiance interpolared on the band wavelengths (SUN_SRF) SRF of the band (SRF)

The GIRO application: computation of the ROLO irradiance Computation of the ROLO irradiance, the “ingredients”: Smoothed ROLO reflectance interpolated on the band wavelengths (ROLO_SRF) APOLLO reference spectrum (APO_ref) interpolated on the 32 ROLO wavelengths (APO_32). Linear fit between APO_32 and ROLO spectra (using “robust” least absolute deviation method, i.e., ladfit) to derive two correction/shift coefficients A and B. Smoothed ROLO (ROLO_smooth) derived as ROLO_smooth = A + B · APO_ref. This is a spectrum at the APOLLO reference wavelengths. (Spline) Interpolation of the ROLO_smooth on the band wavelengths.

The GIRO application: computation of the ROLO irradiance Computation of the ROLO irradiance, the “ingredients”: Smoothed ROLO reflectance interpolated on the band wavelengths (ROLO_SRF) Smoothed solar irradiance interpolared on the band wavelengths (SUN_SRF) Weighted (with a Gaussian function, σ = 0.002 µm) sum of the Solar Irradiance Spectrum within a reach of 0.006 µm from each wavelength of the band. The Gaussian weight is derived by using the wavelength distance between the band wavelength and the solar spectrum wavelength. In the case in which less than 3 solar irradiance points are available within the reach a linear interpolation is performed.

The GIRO application: computation of the ROLO irradiance Computation of the ROLO irradiance, the “ingredients”: Smoothed ROLO reflectance interpolated on the band wavelengths (ROLO_SRF) Smoothed solar irradiance interpolared on the band wavelengths (SUN_SRF) SRF of the band (SRF)

The writing is performed by using the The GIRO application: handling of the output The outcome of the different processing steps is organized in structures. Such a content is used to fill the output file. The writing is performed by using the NetCDF C interface

The GIRO application: handling of the output WARNING! In the output file the user finds: rolo_spectr rolo_smooth_spectr These have been provided for checking purpose. In fact, THESE SPECTRA SHOULD NOT USED AS REFLECTANCE REFERENCES FOR OTHER APPLICATION! WHY? Bias due to the solar irradiance modelling.

LOOKING FORWARD TO SEE YOUR RESULTS! The GIRO application: conclusions Thanks to the collaboration between organizers and users we have been able to define a functioning version of the GIRO executable. This has been successfully validated against the USGS lunar calibration tool. A perturbation analysis tool is available, and can be used in combination with the GIRO executable to run examples of perturbation analyses. LOOKING FORWARD TO SEE YOUR RESULTS!

The GIRO application: points to be discussed The handling of the observation time Leap seconds (see Masaya’s presentation) Observation time format in the file The GIRO implementation concept SRF-content driven vs. lunar observation-content driven Content of the lunar observation files The role of the imagette processing PRO: important to have a standard approach for deriving the observables CON: case-by-case differences The use of the observables from the DC imagette See presentations from Bartolomeo and Masaya about the calibration results Update of the SPICE kernels e.g. soon the leap second kernel must be updated! GIRO version number Different lunar observation data for different channel (format of the name)

Back-up slides

Comparison GIRO vs. USGS/ROLO (Tom’s results)

Comparison GIRO vs. USGS/ROLO (Tom’s results)

Comparison GIRO vs. USGS/ROLO (Tom’s results)