I want to know How to transform the HICO hyperspectral image DN values to at-satellite reflectance ?
So, the HICO DN that you are likely to have are scaled radiances. There is information at http://hico.coas.oregonstate.edu/datasets/datacharacteristics.shtml. If you have scaled radiances, and you have a .hdr file, then divide the DN by the values associated with image_scale_factor, which is in the header. When you do that, you will get radiance values in units of W/m^2/sr/mircometer.
To go from radiance to at-satellite reflectance, divide this radiance by (the solar spectral irradiance above the atmosphere)*(cosine of the solar zenith angle). This will give you at-satellite reflectance.
Also, please see the page
http://hico.coas.oregonstate.edu/datasets/datacharacteristics.shtml
and the section of the page titled: "Level 2A : atmospherically corrected remote sensing reflectances". The top entry of the table in that section shows a way to get the quantity you want.
At one point there was an online tool at their web site that would allow processing to apparent reflectance I suspect you need to contact them to find out more details.
Thank you for your reply, it is very useful.
Will you please tell me "Where can I find the solar exoatmospheric spectral irradiances (ESUN) values for HICO data?"
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