Photocurrent values set to zero in the LSPD file indicate that the photocurrent for this ramp was not calculated or was discarded. Photocurrents may not be calculated because all of the readouts in the ramp have been discarded because of glitches, saturation, etc. Photocurrents may also be discarded because of glitches in the previous ramps. The LSPD status word can be used to confirm that this is an invalid point and give extra information about what happened during the processing of this point. See section 8.2.5 for a description of the LSPD status word.
Flux values in the LSAN file will also be set to zero when no value could be calculated. This is usually because the value read from the LSPD file was zero, but it can also be caused by a failure to find the spectral responsivity value for this point. The LSAN status word contains a flag which indicates if the point is valid or not. It also contains other flags which give more information about what has happened to this point. See section 8.2.8 for a description of the LSAN status word.
Note that the LSPD file also contains a copy of the photocurrents with no deglitching applied.