J. Kissel

Some good news, at least -- I've been periodically taking PCAL 2 DELTAL broad band transfer functions as a quick check of the stability/reproducibility of the interferometer's response. Over the past few days, and several lock stretches, the systematic error in DELTAL (as reported by PCAL) is very stable/reproducible., and remains within 1% / 1 deg between 20 Hz and 100 Hz, and shows the the same frequency dependence (probably within the uncertainty of the PCAL, 0.5%) every time this is measured.

We're trying our darnedest to wrestle with the sensing function systematic error (see LHO aLOGs 48083, 48080, 48057) because we believe this is one (if not *the*) source of the problem for the time-dependent correction factors -- if you don't have all elements of the model with low systematic error, then you can't produce the reference DARM loop model values at all frequencies that are needed to correct for (known) frequency dependence between calibration lines.

But -- maybe it's not so urgent that we correct for time dependent correction factors.

Remember -- we always will re-calibrate the data for computer communication drop-outs between the real world and LDAS. So, there will be a re-calibrated data stream available once we have all of this non-sense figured out, and we can re-recorrect the data if need be.