An EO-1 ALI filter function for ENVI

This Help Article provides an ENVI filter function (spectral response file) for the EO-1 ALI sensor in ENVI's spectral library format. It also describes how an ascii file should be formatted to create the filter function in ENVI, and provides the spectral response ascii file for EO-1 ALI, as an example.
 
An EO-1 ALI filter function in ENVI spectral library format was created for use with ENVI tools such as FLAASH Atmospheric Correction and Spectral Resampling. The spectral response of each ALI band was taken from the document:

"Earth Observing-1 Advanced Land Imager: Spectral Response Calibration". Mendenhall, J.A., and Ryan-Howard, D.P., September 20, 2000.

Filter function files can be generated from an ascii file using ENVI's Spectral Library Builder. The format of the file should be a column of wavelengths that spans all wavelengths measured by any band of the sensor followed by one column of the spectral response at each of the wavelengths for each band. A value of 0.0 should be entered where there is no spectral response recorded for that wavelength. For example, let's say I have a 3 band sensor with bands centered at 450, 550 and 650nm. My full spectral response wavelength range may be from 350nm (for band 1) to 750 (for band 3). If my first band response spans from 350 to 500nm, then values of 0.0 should be entered for all wavelengths beyond 500nm. In addition, each band spectral response should begin and end with at least two 0.0 values. So in this example, you should add two wavelengths before 350nm and two wavelengths after 750nm and enter values of 0.0 as the spectral response for these wavelengths. For reference, the ascii file used to create the filter function for EO-1 ALI can be downloaded here.

The EO-1 ALI filter function in ENVI spectral library format can be downloaded here.

The file is zipped and contains two files - the binary .sli file which contains the data and the .hdr which describes the file format so that ENVI can open it. These files can be placed in the \envixx\filt_func directory and used in ENVI processes that require a filter function file .

Review on 12/31/2013 MM