OLCI 709 nm band

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jstum
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Joined: Mon Jul 04, 2005 4:54 am America/New_York

OLCI 709 nm band

by jstum » Tue Oct 05, 2021 7:03 am America/New_York

Hello,

I'm processing OLCI/Sentinel-3A with SeaDAS 7.5
Seadas_OLCI_Spectrum.PNG
Seadas_OLCI_Spectrum.PNG (15.63 KiB) Not viewed yet
, and I don't understand why the surface reflectance (rhos) at 709 nm is always depleted as compared to the two nearby wavelengths (681 and 754). I speak about ocean spectrum, far from sunglint or clouds, with no vicarious gain applied. See enclosed png file. I expected a 709 nm rhos value approximately given by a linear interpolation between 681 and 754 rhos values. Is there some correction missing in Seadas for this particular wavelength ?

Thanks

Jacques

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OB.DAAC - SeanBailey
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Re: OLCI 709 nm band

by OB.DAAC - SeanBailey » Tue Oct 05, 2021 4:15 pm America/New_York

Vicarious calibration....or rather the lack thereof. Once properly calibrated, the result is more like what you would expect:
Screen Shot 2021-10-05 at 4.11.34 PM.png
Screen Shot 2021-10-05 at 4.11.34 PM.png (82.39 KiB) Not viewed yet
The above was generated from a scene using the following gains:
gain=[0.9795,0.9953,0.9796,0.9675,0.9697,0.9695,0.9750,0.9750,0.9744,0.9788,1.0060,0.9834,1.0,1.0,1.0755,0.9908,1.0,1.0174,1.0,1.0,1.0]

Keep in mind these are not likely to be the set of gains we apply when we finally get around to distributing L2 data...but they're probably close.

Sean

jstum
Posts: 56
Joined: Mon Jul 04, 2005 4:54 am America/New_York

Re: OLCI 709 nm band

by jstum » Wed Oct 06, 2021 8:20 am America/New_York

Thanks Sean. Is there some internal report about the method used to derive these coefficients ?

jstum
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Joined: Mon Jul 04, 2005 4:54 am America/New_York

Re: OLCI 709 nm band

by jstum » Wed Oct 06, 2021 9:01 am America/New_York


OB.DAAC - SeanBailey
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Re: OLCI 709 nm band

by OB.DAAC - SeanBailey » Wed Oct 06, 2021 10:00 am America/New_York

Yes, that would be the answer :D
Sean

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