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

2. The GIRO application

3. 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.

4. 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.)

5. 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

6. 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

7. 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

8. 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

9. The GIRO application

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

11. 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

12. 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

13. 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

14. 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.)

15. 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!

16. The GIRO application: sanity check

17. The GIRO application: sanity check
W_XX-EUMETSAT-Darmstadt,VISNIR+SUBSET+MOON,MSG1+SEVIRI_C_EUMG_ _01.nc
Quantity User Imgt Processing
Observed Irradiance
Observed DC
DC Offset
Total number of pixels
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.

18. The GIRO application: sanity check
W_US-MCST-GSFC,VISNIR+SUBSET+MOON,TERRA+MODIS_C_KCGS_ _01.nc
Quantity User Imgt Processing
Observed Irradiance
Observed DC
DC Offset
Total number of pixels

19. The GIRO application: sanity check
W_US-MCST-GSFC,VISNIR+SUBSET+MOON,TERRA+MODIS_C_KCGS_ _01.nc
Quantity User Imgt Processing
Observed Irradiance
Observed DC
DC Offset
Total number of pixels
Private communication with Zhipeng Wang (NASA GSFC): DIFFERENT METHODS ADOPTED.

20. The GIRO application: sanity check
W_US-MCST-GSFC,VISNIR+SUBSET+MOON,TERRA+MODIS_C_KCGS_ _01.nc
Quantity User Imgt Processing
Observed Irradiance
Observed DC
DC Offset
Total number of pixels
Private communication with Zhipeng Wang (NASA GSFC): DIFFERENT METHODS ADOPTED.

21. The GIRO application: sanity check
W_US-MCST-GSFC,VISNIR+SUBSET+MOON,TERRA+MODIS_C_KCGS_ _01.nc
Quantity User Imgt Processing
Observed Irradiance
Observed DC
DC Offset
Total number of pixels
Private communication with Zhipeng Wang (NASA GSFC): DIFFERENT METHODS ADOPTED.

22. The GIRO application: sanity check
W_US-MCST-GSFC,VISNIR+SUBSET+MOON,TERRA+MODIS_C_KCGS_ _01.nc
Quantity User Imgt Processing
Observed Irradiance
Observed DC
DC Offset
Total number of pixels
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)

23. 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_ bpc
earth_070425_370426_predict.bpc
earth_assoc_itrf93.tf
Moon orientation description
moon_ tf
moon_pa_de421_ bpc
moon_assoc_me.tf

24. 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.

25. 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)

26. 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.

27. 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 = µm) sum of the Solar Irradiance Spectrum within a reach of 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.

28. 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)

29. 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

30. 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.

31. 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!

32. 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)

33. Back-up slides

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

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

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