Presentation Overview Ref:LunarCalibWS_Guideline_Presentations -General description of the sensor (spectral bands, orbit, resolution, etc.) - Description of the Moon acquisition (manoeuvre) - Example of an image: how does the Moon look like? - Dark signal correction - Absolute calibration (calibration methods) - Integration step - Oversampling consideration - Satellite position - Operation of the GIRO: status and calibration results - Feedback for discussions
Bandwidth per band (nm) = 20, 20, 20, 20, 20, 20, 30, 40; General description of the sensor (spectral bands, orbit, resolution, etc.) Parameters Specifications Instantaneous geometric field of view (meters) 360 (m) across track (at nadir) 236 (m) along track Number of Detectors in array 6024 Active pixels 3730 Integration time 34.75 m sec Swath 1420 km Spectral band (micron) B1 0.402 – 0.422 B2 0.433 – 0.453 B3 0.480 – 0.500 B4 0.500 – 0.520 B5 0.545 – 0.565 B6 0.610 – 0.630 B7 0.725 – 0.755 B8 0.845 – 0.885 Saturation radiance (mW/cm2/sr/μm) B1 60.4 B2 35.7 B3 22.8 B4 22.5 B5 22.1 B6 14.9 B7 07.3 B8 10.1 Camera MTF (at Nyquist) > 0.2 SWR at Nyquist > 0.26 Band to Band Registration 0.25 pixels Quantization 12 Bits SNR (at saturation) > 512 Along track steering 200 Central wavelengths per band (nm) = 412, 443, 490, 510, 555, 620, 740, 865; Bandwidth per band (nm) = 20, 20, 20, 20, 20, 20, 30, 40; Instantaneous field-of-view = 1.5835 mrad; Pixels per scan = 3730; Scan rate = 28.78/sec; Sample rate= 190215.8/sec
Description of the Moon acquisition (manoeuvre) Step1 : Target the Center CCD to a point 2.0deg (Pitch bias 2.0 deg) Above the Moon center Step2 : Provide Pitch Scan Rate of -0.05 d/s for 80 secs Step 3 : Reverse Rotation to Earth
( Full operation in eclipse) Time Line Diagram ( Full operation in eclipse) Eclipse Entry AOS Scan start Scan End Start of Reverse Rotation Normalization Eclipse exit LOS 18:00:03 18:01:00 18:09:30 18:11:00 18:12:20 18:12:30 18:22:30 18:23:00 18:35:18 18:43:03
Example of an image: how does the Moon look like?
--Oversampling factor (OSF consideration) - Integration step Identification of lunar pixels by including all pixels with a specified number of standard deviations outward from the mean of the centrally selected area. Get the weighted sum of radiance from the histogram of selected lunar pixels Convert radiance (L) to irradiance (I) as I=L*pi()*(theta)as*(theta)xs Where theta = Altitude/GIFOV in along scan(as) and across scan (xs) direction --Oversampling factor (OSF consideration) OSF=(pixels)as /(pixels)xs assuming moon as circle - Satellite position Orbital vector in J2000 for moon central scanline
OCM-2 Lunar Irradiance calculation Sum Radiance I = L*Omega I (for GIRO) mW/cm2/um/sr mW/cm2/um W/m2/um 13177.09734 0.00678452 0.067845202 19934.41129 0.010263673 0.102636728 20882.54979 0.010751843 0.107518429 20094.50745 0.010346102 0.103461018 20654.8518 0.010634608 0.106346075 19274.10738 0.009923701 0.099237007 16051.40875 0.008264423 0.08264423 12038.59283 0.006198336 0.061983359 Solid Angle calculation Direction IGFOV (m) IFOV (rad) Omega AS 360 0.0005 5.14872E-07 XS 236 0.000328 Altitude 720000
- Operation of the GIRO: status and calibration results Lunar data converted to netCDF using IDL code with Compulsory inputs and some additional information GIRO (2nd release) could be run successfully Yet to be done: Including imagette in netCDF format Testing GIRO (4th) release
Thanks for your kind attention My Special thanks to -Sebastien Wagner and the team working behind-the-scene for ensuring this workshop -Masaya Takahashi, specially for prompt netCDF related support -Director, Space Applications Centre (ISRO), for his whole hearted support Thanks for your kind attention