aLIGO LHO Logbook

H1 SEI

hugh.radkins@LIGO.ORG - posted 14:05, Wednesday 08 October 2014 - last comment - 14:41, Wednesday 08 October 2014(14373)

LHO SEI Cartesian Basis Status

The local sensors, both positional and inertial, are converted to Ligo Global Frame (assuming the Z_L & Z_G are collocated, which they are not, quite) via calibration filters and local to cartesian transformation matrices; this is done using the right hand rule, RHR. Many of the platforms for H1 were commissioned before much thought and diligence was put into these matrices. The seismic group has finalized these transforms and we can now correct the long standing errors. However, this will require taking platforms off line to load the matrices as well as new cartesian basis controllers and Position Targets for many of the platforms. We'll attempt to do this systematically during maintenance days and other opportunities.

Meanwhile, as I just finished an update to the state of these matrices, I thought a tabulation of the platforms was in order.

	HEPI	Impact	ISI	Impact
HAM1	Wrong	Magnitudes are correct so displacements are right but the rotational dofs have the wrong sign wrt RHR.	NA	iLIGO Platform
HAM2	Wrong	Ditto	Wrong	Rotational dof signs are wrong for RHR
HAM3	Wrong	Ditto	Wrong	Ditto
HAM4	Correct	Signs & Amplitudes are right for examining platform movement	Wrong	CPS & GS13 matrices are good, correcting L4C2CART will not impact platform or alignment
HAM5	Correct	Ditto	Wrong	Ditto
HAM6	Correct	Ditto	Wrong	Ditto
ITMY	Wrong	X & Y dof mags wrong. ~x2	Wrong	All good sans HEPI L4C Sencorr--no impact on use of sensors.
BS	Wrong	Rotation dof mags are incorrect, RZ x4, RX & RY x2	Wrong	X Y RX & RY signs are wrong putting positional study in jeopardy
ITMX	Correct	Signs & Amplitudes are right for examining platform movement	Wrong	All good sans HEPI L4C Sencorr--no impact on use of sensors.
ETMX ETMY	Correct Correct	Ditto Ditto	Wrong Wrong	X Y RX & RY signs are wrong putting positional study in jeopardy Minor errors in off diag elements, basic study use okay but fixing will require completesweep through system.

Comments related to this report

jeffrey.kissel@LIGO.ORG - 14:41, Wednesday 08 October 2014 (14374)

Link

Awesome summary, thanks Hugh!

For everyone else, 
- The document where we define the local-to-cartesian basis transformation that Hugh refers to is T1000388. 
- Orientations of Cartesian bases with respect to the global IFO coordinates are defined in G1000125. 
- Finally, the document that defines the calibration of each sensor is D1001575.

For the record, when Hugh says "Mags," "Magnitude," or "Amplitude," he means the same thing, and that's the value of the elements in the above mentioned matrices. Also "displacements" means translations, i.e. X, Y, Z, and "positional study," "platform movement," and "platform" and means performance of the given stage. Rotational DOFs, and "alignment" are the same thing: RX, RY, and RZ.

(These are all linked together in E1300815, "the SEI Controls Document Hub," E1100703, and also "Useful Documents for SEI Testing and Commissioning," both linked from the aLIGO, SEI document tree E1200684.)