Bright band in middle of VIIRS DNB swath

[Adam Dybbroe]

Hi,

I have recently observed that the DNB RGB images we generate here almost
all the time has a bright band in the middle of the swath/scene. At
first I thought it was related to the straylight correction, but I am
surprised that it seems to appear in almost every single image, and
generally always in the approximate same position. Is it something you
have observed?

Check the few images here:

https://www.dropbox.com/sh/o877k0vbwz8st42/AACQSWPYZNB3li2P6rTWwk6aa?dl=0

It is visible in four out of the five images.

-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

[Atkinson, Nigel]

Adam,

My understanding is that it is the straylight correction, when the satellite goes from sun to shadow. A back-of-the-envelope calculation shows that this will happen at 62N at equinox. We are now 3 weeks after equinox which will push it further north. The NOAA correction algorithm is pretty good, but not perfect and you have got quite high contrast on your image (the effect is barely visible on our standard image product).

Regards,

Nigel

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[Trygve Aspenes]

Hii

I have seen the same, and guessed it is some kind of straylight.

Other explanations?

Trygve Aspenes

On 10/15/2015 10:44 AM, Adam Dybbroe wrote:
> Hi,
>
> I have recently observed that the DNB RGB images we generate here
> almost all the time has a bright band in the middle of the
> swath/scene. At first I thought it was related to the straylight
> correction, but I am surprised that it seems to appear in almost every
> single image, and generally always in the approximate same position.
> Is it something you have observed?
>
> Check the few images here:
>
> https://www.dropbox.com/sh/o877k0vbwz8st42/AACQSWPYZNB3li2P6rTWwk6aa?dl=0
>
> It is visible in four out of the five images.
>
> -Adam
>
>

--

Trygve Aspenes - Senioringeniør/Senior Engineer
Fjernmåling Utvikling/Remotesensing development Telefon/Phone: 22963133
Fjernmålingsavdelingen/Remotesensing department Postboks 43, Blindern
Metklim 0313 OSLO
Meteorologisk Institutt
/Norwegian Meteorological Institute NORWAY

[Atkinson, Nigel]

Correction, 62N would be if the satellite pass was at midnight. It's after midnight which will shift the transition further south, but the 3 weeks will shift it north. So a band at 63N on your image seems about right!

[Adam Dybbroe]

Nigel,

Thanks. I can buy that. 62 deg indeed it is (on my envelope). Where do
we have a description of the straylight correction algorithm? Guess I
have to look back at the presentations from last spring?

-Adam