20000515: McIDAS calibration issues VISR BRIT

>From: Craig Motell <address@hidden>
>Organization: University of Hawaii
>Keywords: 200005150845.e4F8js417747 McIDAS GVAR calibration VISR BRIT

Craig,

>I was asking you about McIDAS files a little while ago.
>
>You helped with the navigation. I have been told by the National
>Weather Service we are getting the McIdas data directly from Madison.

This is an interesting comment.  Can you tell me how you are getting
the images from UW-Madison?  Just curious.

>This may not be true. Attached I have some output from the AREA header
>block. In this block it say the data type is:
>
>word 52-53:VISRBRIT
> 
>I suspect that data, represents raw visible counts scaled to 8 bits.

That is what VISR means: two-byte count values have been scaled to 8
bit values.  BRIT means that the data is not raw, it is
pre-calibrated.

>The calibration block probably does not exist (see AREA header block).

Right.  The data has been pre-calibrated.

>I have the following questions:
>1) Does 8 bit visible data from SSEC make sense
>   to you (versus, say 10 bit or other).

Yes.  McIDAS programs can be directed to ask for a 2-byte to 1-byte
conversion (i.e,, to VISR) on-the-fly.

>2) Can you tell me where to look for converting
>   from counts to radiance.

Try browsing through the calibration routines for the satellite you
are interested in.  If you are dealing with GVAR data, the module
would be kbxgvar.dlm.  This will be located in the 'src' directory
for the McIDAS distribution you are using (e.g.,
~mcidas/mcidas7.6/src/kdxgvar.dlm).

>Presently, I'm using Table 2 from NESDIS which shows how to convert 10
>bit data into counts for each of the 8 PRT of the visible sensor.

Can you tell me the document you are referring to?  I could then check
out Table 2 in that document.   This reference would be good to have
available in our tracking system.

>Each
>of the 8 PRTs are pretty much the same so I just take the average, and
>I also assume that the 8 bit data is scaled linearly from 10 bit.

Yes, the 8-bit data is scaled linearly from 10-bit data.

>Thank you, Tom,

You are welcome.  I would appreciate you giving providing me the
information I request above so that I can add useful references to our
tracking system.  Thanks in advance...

>Sincerely,
>Craig Motell

Tom

>From address@hidden Mon May 15 13:56:24 2000
>Subject: Re: 20000515: McIDAS calibration issues VISR BRIT

>I better start proof reading, the statment below should say "Table 2
>from NESDIS which shows how to convert 10 bit data in radiance"

>I meant to say radiance, I guess I air balled here!

re: Table 2 from where

>I am going to forward you the email I got from NESDIS
>concerning visible calibration.

>I will check out the code you suggested. Thanks again.

>From address@hidden Mon May 15 13:57:44 2000
>Subject: Fwd: GOES-10 Imager Visible Channel Calibration

--- Dejiang Han <address@hidden> wrote:
> From: "Dejiang Han" <address@hidden>
> To: <address@hidden>
> CC: <address@hidden>
> Subject: GOES-10 Imager Visible Channel Calibration
> Date: Mon, 15 May 2000 10:13:21 -0400
> 
> Dear Dr. Craig Motell,
> 
> All the documents both on the GOES calibration web site
> (http://www.oso.noaa.gov/goes/goescal.htm) and its
> affiliated are the latest.
> 
> Regarding the GOES-10 imager calibration for visible channels, there are two
> approached as follows. One approach is to apply the pre-launch calibration
> coefficients. As you might know, Table 2 (visible-channel calibration
> coefficients for GOES-10 imagers) on
> http://www.nnic.noaa.gov/SOCC/vis_ch_calibration.html
> contains the pre-launch calibration coefficients for all eight
> imager detectors. The other approach is in-orbit star-based. For the
> detailed information, please take a look at "GOES Imager Visible Channel
> Responsivity Trending", which is located on
> http://www.oso.noaa.gov/goes/visible_trending.htm.
>
> The way dealing with GOES-10 imager visible channel is
> expected to be similar to those for GOES-8 and -9, although at this moment
> there are no coefficients released due to insufficient data. However, in the
> near future, we will release them and will keep you informed.
> 
> Thank you for your interest in the GOES calibration.
> 
> Sincerely,
> 
> Dejiang Han
>