FRS11679 I verified that it was possible to load filters into other ISS filter-modules (FM), so there appears to be something special about the ISS_SECONDLOOP_REFERENCE_DIFFRACTION_CAL FM. Gabrielle confirmed that for the past 6 months no filter was shown on this FM, and he was surprised to find filters defined for this FM in H1PSLISS.txt.

The first thing which struck us was the long name length. Of the 12,733 filter modules in H1, only 3 have name lengths of 40 characters. The FM list below is sorted by name length (last few lines shown).

To test, I tried to load a filter into CS_DARM_TDEP_CORR_DELTAL_RESIDUAL_WHITEN, which also failed.

WP7881 covers shortening the names of these three FMs and verifying filters can then be loaded.

37 SIM_ITMY_SUB_DEFOCUS_FULL_SINGLE_PASS
39 CS_DARM_TDEP_CORR_DELTAL_CTRL_L1_WHITEN
39 CS_DARM_TDEP_CORR_DELTAL_CTRL_L2_WHITEN
39 CS_DARM_TDEP_CORR_DELTAL_CTRL_L3_WHITEN
39 CS_DARM_TDEP_CORR_DELTAL_CTRL_M0_WHITEN
39 VAULT_SEIS_1030X195Y_STS2_X_BLRMS_INPUT
39 VAULT_SEIS_1030X195Y_STS2_Y_BLRMS_INPUT
39 VAULT_SEIS_1030X195Y_STS2_Z_BLRMS_INPUT
40 CS_DARM_TDEP_CORR_DELTAL_CTRL_SUM_WHITEN
40 CS_DARM_TDEP_CORR_DELTAL_RESIDUAL_WHITEN
40 ISS_SECONDLOOP_REFERENCE_DIFFRACTION_CAL