VIIRS issues
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Adam Dybbroe
Dec 19, 2012, 6:23:09 AM12/19/12
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Hi,
I don't know about you, but we have stumbled over quite some features or
issues with VIIRS over the past autumn where we have started looking
more regularly at the data. We are yet unable to say how much is onboard
related and how much is related to the SDR processing using CSPP. But it
would be nice if you could share your experience as well.
Some of the issues we have seen so far:
* DNB: Quite strong "smile effect" observed, that is the radiance
increases with scan angle, and you get a nice smile-shape, as in the
figure here attached. We have experimented a bit applying a correction,
and it does improve the RGB imagery somewhat. But there is still some
bow-tie-like effects left on the edges, and still some along-track lines
left.
* Christelle told me that this "smile effect" is actually observed on
all M-bands, but I haven't investigated myself.
* We do observe occasional jumps in radiance levels across track in the
DNB. Usually it is just right in the middle of the swath, but the shift
is not sharp (from one line to another) but rather takes place over
several lines.
* Occasional problems in geolocation. We have seen this on at least one
scene a few weeks ago. Unfortunately I don't remember at the moment
exactly when. I talked to Herve about this and he said that Pascal had
observed similar problems, and had looked into the CSPP logs indicating
that there was indeed a problem with geolocation in the actual scene.
* Now today we have seen a strange shift in IR calibration, a sharp
"jump" in intensity in the RGB images, also affecting PPS, so apparently
a real shift in Tb. Not nice! I will try analyze this further, but it
would be nice if you could comment if you had seen something similar.
I am sure there is more to the list, but this is what I recall just now.
Best regards
Adam
--
Adam Dybbroe,
Satellite Remote Sensing Scientist,
Numerical models and Remote Sensing,
Core Services, Swedish Meteorological and Hydrological Institute (SMHI)
www.pytroll.org
nwcsaf.smhi.se
www.smhi.se
I don't know about you, but we have stumbled over quite some features or
issues with VIIRS over the past autumn where we have started looking
more regularly at the data. We are yet unable to say how much is onboard
related and how much is related to the SDR processing using CSPP. But it
would be nice if you could share your experience as well.
Some of the issues we have seen so far:
* DNB: Quite strong "smile effect" observed, that is the radiance
increases with scan angle, and you get a nice smile-shape, as in the
figure here attached. We have experimented a bit applying a correction,
and it does improve the RGB imagery somewhat. But there is still some
bow-tie-like effects left on the edges, and still some along-track lines
left.
* Christelle told me that this "smile effect" is actually observed on
all M-bands, but I haven't investigated myself.
* We do observe occasional jumps in radiance levels across track in the
DNB. Usually it is just right in the middle of the swath, but the shift
is not sharp (from one line to another) but rather takes place over
several lines.
* Occasional problems in geolocation. We have seen this on at least one
scene a few weeks ago. Unfortunately I don't remember at the moment
exactly when. I talked to Herve about this and he said that Pascal had
observed similar problems, and had looked into the CSPP logs indicating
that there was indeed a problem with geolocation in the actual scene.
* Now today we have seen a strange shift in IR calibration, a sharp
"jump" in intensity in the RGB images, also affecting PPS, so apparently
a real shift in Tb. Not nice! I will try analyze this further, but it
would be nice if you could comment if you had seen something similar.
I am sure there is more to the list, but this is what I recall just now.
Best regards
Adam
--
Adam Dybbroe,
Satellite Remote Sensing Scientist,
Numerical models and Remote Sensing,
Core Services, Swedish Meteorological and Hydrological Institute (SMHI)
www.pytroll.org
nwcsaf.smhi.se
www.smhi.se
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