1. Progress of Lunar Calibration Using INSAT- 3D Meteorological Satellite Imager at IMD, New Delhi
A.K. Mitra, Shailesh Parihar, S.K. Peshin
Ministry of Earth Sciences
India Meteorological Department, New Delhi

2. INSAT-3D Spectral Response Function
The Earth’s surface and clouds have been observed for many years by meteorological satellites operating in geostationary Earth orbit (GEO), distributed in longitude around the globe. Images from solar-band channels (visible and shortwave infrared, 0.4–2.5 μm) have been used to monitor important climate variables such as surface insulation, surface albedo, aerosol optical depth, and cloud optical properties.

3. The Moon in INSAT-3D images
In INSAT-3D satellite the Moon appears regularly in full-disk operational images of the Earth acquired by meteorological instruments with a rectangular field of regard, several times each month, which provides an excellent opportunity for radiometric calibration.
The Moon is being observed from INSAT-3D regularly in the of full-disk operational image of earth with rectangular field of regard in IMDPS New Delhi.
INSAT-3D measurements of lunar surface observed in Visible ( µm), Short Wave Infrared µm, Mid Wave Infrared ( µm), Water Vapor (WV) µm, Thermal Infrared (TIR) 1 & 2, µm & µm wavelength regions.
The visible and infrared wavelengths region provide a new and intriguing methodology of distinguish in sensitivities of Earth observing radiometers.

4. INSAT-3D visible channel full-disk image acquired 2016 August 22
INSAT-3D visible channel full-disk image acquired 2016 August 22. The Moon is captured in northwest corner on 0858 UTC.

5. Input template.ncl file to generates netCDF file by ncgen utility
Methodology
Find the Moon in INSAT-3D full frame image and then collect L1B data and decode VIS and SWIR channels
Consider only lunar pixels for specific channels and make template.ncl file
Input template.ncl file to generates netCDF file by ncgen utility
.nc file is the input format of GIRO model, Run that model and get output files
Compare the results of irradiance of GIRO model and INSAT-3D satellite lunar imagette irradiance and other scientific analysis
Generate calibration coefficients
This template.ncl file having information of OSF, Satellite Cartesian Coordinates, Pixel Solid Angle, Time & date of satellite image at the time of Moon acquired , Satellite Position References, Spectral lunar pixel radiance converted to irradiance and Spectral Response Function of INSAT-3D

6. GSICS Implementation of ROLO Model: GIRO
The USGS RObotic Lunar Observatory (ROLO) project has developed the capability for on-orbit calibration using the Moon via a GSICS (Global Space based Inter calibration System) Implementation of ROLO Model (GIRO)
Lunar spectral irradiance that accommodates the geometries of illumination and viewing by a spacecraft. ROLO model is work on lunar spectral irradiance that accounts for phase and libration explicitly.
In general the same face of the Moon is always turned toward Earth, the optical librations result in about 59% of the lunar surface being viewable from Earth.
ROLO Model (GIRO) model has been installed at NSMC, IMDPS, IMD New Delhi. The version of GIRO model is GIRO_v1.0.0 has been downloaded from
(Courtesy by Sebastien Wagner and Tim Hewison EUMETSAT)

7. Step by step method for GIRO input
First, Identification of lunar pixels and calculate the sum of the lunar pixels (which included digital counts and radiances)
Make template.ncl file for lunar pixels, it is input for generates netCDF file.
Radiances observed of lunar pixels are converted to the irradiance, this is input of GIRO model.
Lunar data (irradiance) converted to netCDF using IDL code with Compulsory inputs:
Lunar observation imagette time(hour, minute, second), Date (year, month, date)
Satellite Position References
Satellite Cartesian Coordinates at the time of Moon acquired
Over Sampling Factor
DC observations

8. From these processes and ephemeris calculations for the Moon and INSAT-3D, the following values were found for visible channel only:
Over Sampling Factor
IFOV μrad
Pixel Solid Angle steradian
Scan Rate 20o/sec + 0.2sec turn around
Nominal Altitude km (GEO)
Satellite Position References J2000
Lunar observation time(hr, min, sec)&
Date (year, month, date) --
Satellite Cartesian Coordinates , ,
Irradiance Observation of Moon ( )W/m2/um
Irradiance GIRO ( )W/m2/um
Spectral Response Function of INSAT-3D for visible band only, the central wavelength is 0.65um.

9. Time Series of Irradiance Observed INSAT-3D and GIRO
Calibration Strategy of INSAT-3D Meteorological Satellite Imager Using the Moon at IMD, New Delhi by
Shailesh Parihar and A.K. Mitra, et all., “Proceedings of SPIE Vol , doi: / ”.

10. Summary of past work
Although, this is four days observation comparison and the result is consistent with INSAT-3D visible-channel underestimate over time period.
The GIRO (ROLO) model output irradiance is found to be 15-20% higher with INSAT-3D observed irradiance.
This study demonstrates the capability for calibration of INSAT-3D imager that has viewed the Moon.
However, conformity of result requires a long time observation of INSAT-3D lunar images to compare with GIRO model irradiance for better precision levels.

11. The One year data need to be analyzed…
It was great contribution and suggestions by Sebastien Wagner and Tim Hewison in last Lunar Web Meeting held on 30 August 2016.
Comparisons of on-orbit lunar irradiance of INSAT-3D imager measurements against GIRO (ROLO) model.
In this context, collected one year moon data from only for imager payload of INSAT-3D visible channel.
The comparisons are given as the percent difference of the satellite measurements from the model generated lunar irradiances.

12. Moon Images in INSAT-3D Full Frame Imagery
23Oct2015_0130, 23Oct2015_0230
02Sep2015_1000
27Oct2015_0531, 27Oct2015_0630

13. Moon captured in INSAT-3D imagery
Note: Time is in Universal Time Coordinate (UTC)

14. Analysis of data
The sum of the radiance and observed irradiance of Moon have been calculated for one year data. In this context, we have a script that considered only lunar pixels in full frame INSAT-3D image.
For making .ncl file using lunar pixels, for this we put manually Lunar observation imagette time(hour, minute, second), Date (year, month, date), Satellite Position References, Satellite Cartesian Coordinates at the time of Moon acquired, Over Sampling Factor, DC observations, these are input for generates .netCDF file.
Then make .netCDF file this is essential input for GIRO model.
Now according to this procedure, we have been ran the GIRO model, observed the irradiance of output model for 2-4 month data.
In this regard, we got GIRO output irradiance as independent data sets with each covering only a limited range of phase angles.

15. INSAT-3D Observed and GIRO Output Irradiance
Note: Irradiance is W/m2/micron

16. Time Series of Irradiance Observed INSAT-3D and GIRO

17. Conclusion
Although, this is 2-4 month observation comparison and the result is consistent and follow the same pattern with INSAT-3D visible-channel.
The GIRO (ROLO) model output irradiance is underestimate with INSAT-3D observed irradiance. INSAT-3D observed irradiance found to be 30-40% higher with GIRO (ROLO) model output irradiance.
This study demonstrates the capability for calibration of INSAT-3D imager that has viewed the Moon.
However, conformity of result requires a long time observation of INSAT-3D lunar images to compare with GIRO model irradiance for better precision levels. Therefore, we have to follow the same methodology for one year data.

18. Future Work
Must have long time observation at least one year of INSAT-3D lunar images to compare with GIRO model irradiance for better precision levels
To improve quality of the derived products, we need to check calibration coefficients should be performed on past visible radiance data.
Calculate the calibration coefficient and then we will get the actual sensor response for VIS/SWIR channel of INSAT-3D. And also, we can get the conclusion for best method for INSAT-3D Cal/Val.
Suggestions if any for future work using INSAT-3D/3DR……..

19. My Special thanks to…
K.G. Ramesh, DGM providing us the facilities for complete this project.
Sebastien Wagner and Tim Hewison, EUMETSAT for provided GIRO model as well as supporting this work.
Masaya Takahashi (JMA, Japan) for operate understand GIRO model netCDF related support and GSICS members for his support regarding INSAT-3D lunar calibration.
Satish Kulkarni, ISRO Bangalore for provided us L1B data for particular dates.
SAC (ISRO), Ahmedabad.

20. Thank You..
Thanks for your kind attention. Suggestions and feedbacks are welcome.