Earthdata Forum

Hello,

I'm processing OLCI/Sentinel-3A with SeaDAS 7.5, 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

Vicarious calibration....or rather the lack thereof. Once properly calibrated, the result is more like what you would expect: 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

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

OK, I probably got the answer in viewtopic.php?f=7&t=1273&sid=257aa1fe29 ... 3&start=10

Yes, that would be the answer
Sean