LIGO-G DM. Landry – Hanover LSC Meeting, August 18, 2003 LIGO S2 Calibration Michael Landry LIGO Hanford Observatory Representing the calibration team: Rana Adhikari, Peter Fritschel, Gabriela Gonzalez, Luca Matone, Brian O’Reilly, Hugh Radkins, Patrick Sutton, Akiteru Takamori

LIGO-G DM. Landry – Hanover LSC Meeting, August 18, 2003 Current status Online calibration with accuracy of ~20% was available with 1 hour latency Interim calibration issued with corrected DC calibration Final calibration to include hardware measurements: accurate representation of the actuation function Additional Wednesday talks relating to calibration include: Brian O’Reilly, Patrick Sutton, Xavier Siemens, and Soumya Mohanty

LIGO-G DM. Landry – Hanover LSC Meeting, August 18, 2003 Calibration Basics I R(f): Response Function  Scale Factor (from Calibration Line) G(f): Open Loop Gain = C(f)  D(f)  A(f) X i / AS_Q(f i,t) = R(f i,t) = [1 +  (t)  (t) G(f i ) ] /  (t) C(f i ) X i = AS_Q(f i,t). R(f i,t)

LIGO-G DM. Landry – Hanover LSC Meeting, August 18, 2003 Calibration Basics II We choose a time t 0 and measure  0,G 0 and R 0. This allows us to extrapolate to any time t using the amplitude of the calibration line (or lines). The amplitude  (t) is a function of the alignment, dependent on the carrier power in the arms and the sideband power in the recycling cavity.  (t) is tracked throughout the science segments. R(f i,t) = [ 1 +  (t)  (t) G(f i ) ] /  (t) C(f i )

LIGO-G DM. Landry – Hanover LSC Meeting, August 18, 2003 DC calibrations Have redundant measurements, including sign toggling, fringe counting, free- swinging and PZT fine actuator Gained confidence with multiple methods during S2; excellent agreement Will limit the number of redundant measurements during the S3 run; making some of these beforehand Concentrate on reducing error

LIGO-G DM. Landry – Hanover LSC Meeting, August 18, 2003 L1 anti-imaging filter

LIGO-G DM. Landry – Hanover LSC Meeting, August 18, 2003 New model comparison

LIGO-G DM. Landry – Hanover LSC Meeting, August 18, 2003 LHO open loop gains

LIGO-G DM. Landry – Hanover LSC Meeting, August 18, 2003 Propagating the calibration:  LLO

LIGO-G DM. Landry – Hanover LSC Meeting, August 18, 2003 Propagating the calibration:  LHO H1

LIGO-G DM. Landry – Hanover LSC Meeting, August 18, 2003 Contributions to the Error Magnitude: Phase: R(f i,t) = 1 +  (t)  (t) G(f i )  (t) C(f i )

LIGO-G DM. Landry – Hanover LSC Meeting, August 18, 2003 Estimating errors in L1  ’s

LIGO-G DM. Landry – Hanover LSC Meeting, August 18, 2003 Violins in H1 Independent check by Rachel Berkowitz (SURF), and Fred Raab – modelling of violin modes in H1

LIGO-G DM. Landry – Hanover LSC Meeting, August 18, 2003 S2 strains

LIGO-G DM. Landry – Hanover LSC Meeting, August 18, 2003 LLO epoch comparsion

LIGO-G DM. Landry – Hanover LSC Meeting, August 18, 2003 Conclusions Necessary to incorporate more realistic filters in model, i.e. measurements instead of as-designed filter Final calibration with errors to be issued by next Monday Expectations for S3: same 1hr latency for online calibration, with accuracy as per existing (final) calibration – we learn more each time