1. VIS/NIR sub-group discussion
GSICS annual meeting, Shanghai, China, March 19-23, 2018

2. The GSICS VIS/NIR group will be using NPP-VIIRS as the calibration reference
Most of the new 3rd generation GEOs will have similar band spectral response functions as VIIRS.
There will be four more VIIRS instruments on JPSS-1 through JPSS-4
JPSS-1 launched late last year (operational Jack?)
Aqua-MODIS is ageing and will be de-orbited by 2023
Unlike MODIS, VIIRS has many calibrated datasets and archive centers
The NOAA IDPS VIIRS data has not been recalibrated
The NASA LandPEATE, is currently processing version 5000 (about the 5th version)
The NOAA and NASA ocean and other retrieval teams are all optimizing the calibration

3. Proposed NPP-VIIRS calibration reference dataset
Download the IDPS VIIRS dataset and apply the NASA-VCST correction factors that are referenced to the latest LandPEATE Version radiances.
Rather than continuously downloading LandPEATE VIIRS versions
I heard IDPS is recalibrating the VIIRS dataset for public release

4. MODIS and VIIRS solar band constants
• Both MODIS and VIIRS absolute calibration on orbit is the earth view radiance divided by the solar diffuser radiance, otherwise known as a scaled radiance or reflectance (no solar zenith angle term)
• The radiances provided on the MODIS and VIIRS datasets are the reflectances multiplied by the MCST and MODTRAN Thullier 2003 solar spectra, respectively
• To go from reflectance to radiance or back to reflectance, simply use the band solar constant
MCST=509.3
IDPS=518.3

5. MODIS and VIIRS solar band constants
These are the MODIS/VIIRS radiance ratio difference, due to solar constant and SRF differences
These are the MODIS/VIIRS radiance ratio difference, due to SRF differences using IDPS solar spectra µm
MODIS/VIIRS ratio
MODIS MCST
VIIRS IDPS
SC RATIO
0.48
B3/M3
664.70
636.54
+4.4%
0.55
B4/M4
593.73
595.13
-0.2%
0.65
B1/I1
509.34
518.34
-1.7%
B1/M5
487.08
+4.1%
0.86
B2/M7
315.73
306.36
+3.1%
1.24
B5/M8
151.16
145.44
+3.9%
1.37
B26/M9
116.20
114.57
+1.4%
1.61
B6/I3
76.58
78.20
-2.1%
B6/M10
78.08
-1.9% µm
MODIS/VIIRS ratio
SC RATIO
IDPS
0.48
B3/M3
+3.2
+3.6
0.55
B4/M4
+0.2
-0.2
0.65
B1/I1
-2.1
-1.7
B1/M5
+4.2
+4.8
0.86
B2/M7
+1.2
+0.7
1.24
B5/M8
-0.3
1.37
B26/M9
-1.0
-0.8
1.61
B6/I3
-4.1
-3.1
B6/M10
-3.9
-1.1

6. VIIRS 0.65µm reference channel, M5 or I1
VIIRS I bands have a higher spatial resolution, than M bands. But analyzed at the same resolution as M5 or collectively, would that matter?
The M5 band has a very narrow spectral band response function (SRF) and the I1 band has a SRF very similar to many 3rd generation GEOs
The calibration difference between M5 and I1 bands is about 1.5%
0.65µm

7. VIIRS 0.86 or1.6µm reference channel, M or I
The 0.86 µm I2 and M7 bands have very similar SRFs
The 1.61µm I2 and M10 bands have very similar SRFs.
0.86 µm
1.6 µm

8. Rethinking L1B calibrated radiance datasets
Currently, every time the L1B imager data is reprocessed, which can be yearly, you have to download the whole dataset (TB’s) all over again
If the user could only download the dataset once and apply calibration modules, could save reprocessing and storage requirements
Must ensure accurate calibrated radiances when applying calibration module
The remote sensing instrument community would release a level 1b dataset that contains all of the required on orbit instrument measurements.
The calibration module can then be downloaded and applied to update calibration, for example the Terra-MODIS WV detector striping anomaly
The instrument providers would then provide a calibration module and test dataset to ensure proper implementation, similar to GOME-2 and SCIAMACHY
I have presented this at the 2017 CALCON and November CLARREO meeting
Two reservations, the users do not want to apply a post calibration (if only grabbing small amounts of the data
The onboard calibration parameters are too extensive and perhaps the instrument calibration team loss of control of the dataset
When reviewing papers that use dataset, make sure the authors attribute the project name, product name, version number and doi.

9. CLARREO PATHFINDER GSICS requirements
The CLARREO PATHFINDER instrument will fly on the international space shuttle (ISS) around 2021
Instrument to be operationally for at least one year
Only the solar instrument will flyThe PATHFINDER mission will not have any requirements for climate monitoring and be strictly available for inter-calibration events
The ISS is in a precessionary orbit is ~63 days with an inclination of ~51°
While the ISS is in the sun-synchronous orbit of Aqua, Terra, it will be dedicated to inter-calibrate in these orbit.
The remainder of the time it can inter-calibrate with GEOs using the PATHFINDER pointing capability
Or to characterize ground targets under differing angular configurations

11. CLARREO PATHFINDER GSICS requirements
Here is the projected sampling activities
What sites and GEOs should be sampled and priorities?

12. GSICS DCC GEO calibration paper
To document the GSICS DCC GEO calibration approach and to provide a reference for the calibration community
Similar to the GSICS IR calibration paper
Would like input from GPRC members
The DCC VIS/NIR methodology will mostly be in common with some variation due to the GEO domain

13. VIS/NIR 2018 web meeting agenda
Rayleigh scattering approach
Implementation of the DCC method for SWIR bands
GSICS DCC paper web meeting

14. GPRC VIS/NIR priorities discussion