Earthdata Forum

I encountered a problem while using l2gen to process the collection2 level 1 product of Landsat 5 7. Because V2025.1 currently does not support collection 2 for Landsat 57, the source code is still related to collection 1. Therefore, is the formula for converting DN values to Lt applicable to collection 2 products for Landsat 57 in the source code. Because the conversion formula for Landsat 8's collection 2 product is not the same as these two.
For example:
Landsat7： Lt = (DN * scale + offset) / 10.0
But
Landsat8: Lt = (DN * refl_scale + refl_offset) * FoBAR / PI
These two scales are completely different, one is RADIONCE.MULTIBAND_ and the other is REFELECANCE.MULTIBAND

Support for Landsat in l2gen is on an "as available basis. When time and resources are available we may update the L5/7 reader to support the Collection 2 data. The conversion from DN to radiance is properly handled at least for the Collection 1 data.

Regards,
Sean

However, in the l1_oli.c file, the conversion of the Landsat 8 DN value to radiance(Lt) uses the following formula:
l1rec->Lt[ipb] = (data->buf[ip] * data->refl_scale[ib] + data->refl_offset[ib]) * l1rec->Fo[ib] / PI;

Due to the fact that the first half of this formula converts DN values to reflectance(data->buf[ip] * data->refl_scale[ib] + data->refl_offset[ib]) , but the second half does not seem to be multiplied by the sine value of the solar elevation angle