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Christophe,There is no band integration involved. Currently, the HICO reader in our processing codesimply selects the HICO bands nearest to the MERIS bands. Yes, this is done prior to atmospheric correction.We are not currently processing HICO beyond L1 browse imagery and have made no attemptyet at calibrating the instrument for doing so. On our exceptionally long list of things to do isto modify our processing code to be able to handle hyperspectral instruments like HICO.If you want to see how we're currently handling HICO, the reader code is available in the source package for SeaDAS or just for web browsing, here.
The L1B HICO reader selects the band closest to the center wavelength of each of the 15 MERIS bands. This is done prior to the atmosphere correction as you suspected. We started out VERY simple to get started. I am in the process of modifying l2gen to be able to accept 128 (probably not 384 though) bands. That might take a while...
by bryanfranz » Tue Jan 21, 2014 1:12 pm America/New_York
I'd add that the HICO bands are at 6-nm intervals and spectral smoothing is performed with a gaussian filter in the calibration process such that the band widths are nominally overlapping 10-nm FWHM gaussians (much like MERIS bands).
Hi Sean, I am processing HICO L1b data using Seadas 7, and an IDL code as a wrapper from L1 to L3. I understand that HICO processing "simulates" the MERIS bands. However, I would wish to clarify the following:
1. Is the HICO processing set up under SEADAS 7 meant to generate exactly the same products list like MERIS. 2. I have noted that requesting for processing of some OC products with the HICO bands fails (actually Seadas 7 halts), e.g. tsm_clark, chl_gsm; is it possible to generate such products from HICO bands?
HICO has 128 bands (or 384, but we'll not go there...), but our processing code currently only supports multispectral instruments. SO, we only read in the bands that match the MERIS band set. This means that we can produce the same products with HICO that we can produce with MERIS - although there may be some products that are not "HICO" aware and may not work (although technically they could - e.g. par).
tsm_clark was removed as a product with 7.0.1 (although seems not completely enough, as it's selectable, but not produceable) chl_gsm works for me...
Hi Sean, Thanks, thats great info, I wish would actually go ahead and explain the 384, I am keen to understand a little bit more about HICO. Let me know what you would suggest as a thorough read on this.
Well, nice to meet you the other day at Cornell. Regards, R
HICO can be commanded into a special calibration mode where it will record 384 spectral bands. There are only a few scenes like this. I don't think the version of the code in the current SeaDAS release will handle these files, although our current development code does. When we modify our code to be able to deal with hyperspectral data, we are likely to only handle the 128 band files.
by jasmine » Wed Jun 11, 2014 12:58 pm America/New_York
To add to Sean's reply ...The HICO sensor collects data from 350 to 1080 nm at 1.91 nm spectral resolution (384 bands). In normal operating mode, these bands are binned spectrally by three at read-out, yielding the final 128 bands (at 5.7 nm spectral resolution) that are found in the data files. Binning the bands increases the signal-to-noise ratio.As Sean mentioned, a high-resolution mode is used periodically for calibration purposes. This mode retains the original 1.91 nm resolution.Further details about the HICO sensor are available from the HICO website://hico.coas.oregonstate.edu/You may particularly be interested in this page://hico.coas.oregonstate.edu/datasets/datacharacteristics.shtmlRegards,Jasmine