I’m using the check_crtm.f90 and its 4 test profiles that came with v2.4.0 to learn how to run the CRTM. I need only the forward model, so I’ve removed the K-matrix material. The program runs, but the output from CRTM_RTSolution_Inspect has the (default) values of zero for “Up Radiance”, “Down Radiance”, “Down Solar Radiance”, and “Surface Planck Radiance”. What do I need to do to output the actual values for those components? Apart from removing the lines involving the K-matrix calculations, I did also switch out the original sensors to the ones I’m interested in: abi_gr, viirs-m_npp, v.modis_terra, and v.modis_aqua. In addition, I modifed the geometry arguments. I have: Sensor_Zenith_Angle=0.0, Sensor_Scan_Angle=0.0, Source_Zenith_Angle=30.0, Source_Azimuth_Angle=90.0, Longitude=90.0, and Latitude=45.0.

Hello Jack @JackD, welcome to the forum.
If you are interested in running the forward model at first, I suggest having a look at the CRTM tutorial instead:

check_crtm.f90 is part of the legacy build system and maintaining it is not a priority anymore.

Thanks for the welcome and the information. Would you please clarify of your statement about “having a look at the CRTM instead”? The program check_crtm.f90 does run the CRTM, both the forward model (my current interest) and k-matrix computations. The code to which you pointed appears to be k-matrix material only (I must say however that I may eventually be interested in weighting function generation). In fact, the program KMatrix_test.f90 looks a lot like check_crtm.f90, only focusing on just k-matrix calculations.

Aha. And apologies on my part as well. I looked at the two k-matrix examples, but not the Nakajima-King case, which has the forward model example I am interested in.