Abstract
I calculated force-diagonalization coefficient for the observed strange coupled pitch and yaw (or, again, vertical and horizontal) signals in the two QPDs at TMSX. Here "force" means that I'm not sure the phyical interpretation yet. The data and the time used for this calculation is listed in the end of this post.
What I did
What I did is to do the following simple arithmetic. First, I download the time-series signals from every segement of QPD1 and 2. Then, compose simple pitch and yaw signals by
- Simple_Pitch := (SEG4+SEG3) - (SEG1+SEG2)
- Simple_Yaw := (SEG4+SEG1) - (SEG2+SEG3)
Then, compose modified pitch and yaw signals as follows
- Mod_Pitch := Simple_Yaw + A * Simple_Pitch
- Mod_Yaw := B * Simple_Yaw + Simple_Pitch
And then determined the A and B by looking at spectra of them to zero the corresponding peaks; this time, 0.1Hz excitation to P and Y of ITMX were used for the marker peaks, as described in 11827.
- For QPD1: A = 0.346, B= 0.487
- For QPD2: A= -0.916, B= -0.5535
And the actual time series and the spectra are attached; Fig 1 and 2 are for QPD1 with pitch excitation, and the spectra in Fig 2 were estimated from the data shown in Fig 1. In the acquired data, there were several times locklosses, so I selected "suitable" time window. As shown in the both figures, the 0.1 Hz fluctuation in Modified_Yaw disappears. Fig 3 and 4 are for QPD1 with yaw excitation. And the similar manner stands for the remaining Figures.
Discussion
- When I plot the excitation signals as well, I can find some phase delay's difference for each case, and it is interesting to see.
- Note that I did not divid the ouputs by the sum, but the important behaviors were not smeared out.
- As shown in above, the coupling coefficient A and B have the opposite signs between QPD1 and 2.
- Especially, QPD2's coefficient "A" is almost -1, which means Mod_Pitch2 = Simple_Yaw - Simple_Pitch = 2 (SEG1 - SEG3); those segments are aligned in diagonal... it is strange. Rotated in 45 deg?? But Mod_Yaw2 is not (SEG4 - SEG2)...Software is ok?
- What's else???
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Used data
- To find the excitation --> K1:VIS-ITMX_MN_LOCK_{P,Y}_EXCMON
- And the conformation --> K1:VIS-ITMX_MN_DRIVEALIGN_{P,Y}_OUTMON
- Signal channels --> K1:AOS-TMSX_IR_QPDA{1,2}_SEG{1,2,3,4}_OUT16
- start time = Nov 28 2019 7:00:00 UTC (16:00 JST)
- stop time = Nov 28 2019 10:00:00 UTC (19:00 JST)
- GPStime = (Start = 1258959618.0, Stop = 1258970418.0)
- Pitch excitation: relative GPS time (Start to be 0): 7200 to 8500 sec
- Yaw excitation: relative GPS time (Start to be 0): 8700 to 9000 sec
