This Python script converts Landsat TM digital numbers (DNs) to top-of-atmosphere (TOA) radiance values, producing output GeoTIFF files with units of W/(m2·ster·µm). It reads USGS metadata files to extract calibration constants (gain, bias, radiance limits, and quantization ranges) and applies them to each spectral band. The program uses GDAL (via `osgeo.gdal`) for raster I/O with block-based processing, NumPy for array operations, and supports LZW compression, tiling, and BigTIFF options. The example processes six bands (1–5 and 7) from standard USGS naming conventions, as shown in the sample run with LE7 scene data.