evan.goetz@LIGO.ORG - posted 16:33, Thursday 23 March 2023 - last comment - 13:04, Thursday 30 March 2023(68139)
Re-running 'Where not to dither - avoiding known pulsars with accessible spindown limits'
As O4 approaches, it is prudent to revisit the "where not to dither" in order to avoid known pulsars that have accessible spindown limits. Similar analysis has happened before (see LHO aLOG 44892). I suggest that the SUS and PCAL calibration lines are revisited to make sure that we are not interfering with important, high value astrophysical targets. Any other dither lines that are in-band (f>10 Hz) should also be assessed so that they can be placed in cleaner bands. I have updated the Matlab script to run in python. It can be found here. The two additional changes are to update the pulsar catalog (see query as of March 22 2023) and the MJD reference time: MJDref = 60065 ==> May 1 2023 00:00:00 UTC. This analysis uses the same aLIGO design sensitivity curve in T1800044. In order to stay conservatively away from any known pulsar with an accessible spindown limit at either once or twice the known spin frequency: Non-vetoed bands for veto half-band = 1.000000 (one or two times pulsar frequency) [33.42, 37.29) Hz (3.87 Hz) [42.88, 43.68) Hz (0.80 Hz) [46.94, 49.58) Hz (2.64 Hz) [51.59, 54.69) Hz (3.10 Hz) [56.70, 58.13) Hz (1.43 Hz) [62.89, 63.10) Hz (0.21 Hz) [65.11, 87.10) Hz (21.99 Hz) [89.11, 90.87) Hz (1.76 Hz) [92.88, 102.21) Hz (9.33 Hz) [104.22, 122.77) Hz (18.55 Hz) [124.78, 172.68) Hz (47.90 Hz) [174.69, 181.11) Hz (6.42 Hz) [183.12, 238.51) Hz (55.39 Hz) [240.52, 346.37) Hz (105.85 Hz) [348.38, 363.23) Hz (14.85 Hz) [365.24, 365.57) Hz (0.33 Hz) [367.58, 478.03) Hz (110.45 Hz) [480.04, 1999.99) Hz (1519.95 Hz) Notice that this restricts all frequencies below 33.42 Hz. Taking a slightly less conservative approach, allowing for a 0.5 Hz band and only twice the spin frequency: Non-vetoed bands for veto half-band = 0.500000 (two times pulsar frequency) [10.99, 11.04) Hz (0.05 Hz) [15.46, 15.49) Hz (0.03 Hz) [16.67, 16.76) Hz (0.09 Hz) [32.92, 37.79) Hz (4.87 Hz) [40.45, 40.64) Hz (0.19 Hz) [42.38, 44.18) Hz (1.80 Hz) [45.19, 50.08) Hz (4.89 Hz) [51.09, 55.19) Hz (4.10 Hz) [56.20, 58.63) Hz (2.43 Hz) [59.64, 60.44) Hz (0.80 Hz) [61.45, 63.60) Hz (2.15 Hz) [64.61, 87.60) Hz (22.99 Hz) [88.61, 91.37) Hz (2.76 Hz) [92.38, 102.71) Hz (10.33 Hz) [103.72, 123.27) Hz (19.55 Hz) [124.28, 346.87) Hz (222.59 Hz) [347.88, 363.73) Hz (15.85 Hz) [364.74, 478.53) Hz (113.79 Hz) [479.54, 1999.99) Hz (1520.45 Hz)
Non-image files attached to this report
Comments related to this report
Changed frequency of 56.39 Hz line to 53.67 Hz as of 2023 Mar 30 18:00 UTC, see newly updated summary of lines in LHO:68289.
Comparing this list against the current calibration lines, (all numbers in [Hz]): Freq (Hz) Actuator Purpose Channel that defines Freq Since O3 15.6 ETMX UIM (L1) SUS \kappa_UIM excitation H1:SUS-ETMY_L1_CAL_LINE_FREQ No Change 16.4 ETMX PUM (L2) SUS \kappa_PUM excitation H1:SUS-ETMY_L2_CAL_LINE_FREQ No Change 17.1 PCALY actuator kappa reference H1:CAL-PCALY_PCALOSC1_OSC_FREQ No Change 17.6 ETMX TST (L3) SUS \kappa_TST excitation H1:SUS-ETMY_L3_CAL_LINE_FREQ No Change 33.43 PCALX Systematic error lines H1:CAL-PCALX_PCALOSC4_OSC_FREQ New since Jul 2022 (LHO:64214, LHO:66268) 56.39 | | H1:CAL-PCALX_PCALOSC5_OSC_FREQ | 77.73 | | H1:CAL-PCALX_PCALOSC6_OSC_FREQ | 102.13 | | H1:CAL-PCALX_PCALOSC7_OSC_FREQ | 283.91 V V H1:CAL-PCALX_PCALOSC8_OSC_FREQ V 410.2 PCALX PCALXY comparison H1:CAL-PCALX_PCALOSC2_OSC_FREQ New since Jan 2023 (LHO:66967) 410.3 PCALY f_cc and kappa_C H1:CAL-PCALY_PCALOSC2_OSC_FREQ No Change 1083.7 PCALY f_cc and kappa_C monitor H1:CAL-PCALY_PCALOSC3_OSC_FREQ No Change n*500+1.3 PCALX Systematic error lines H1:CAL-PCALX_PCALOSC1_OSC_FREQ No Change (n=[2,3,4,5,6,7,8]) Currently -- above 33.42 Hz -- only the new 56.39 Hz PCALX systematic error line is in the veto region; it's between the following non-veto regions (by only 0.5 Hz): [51.59, 54.69) Hz (3.10 Hz) [56.70, 58.13) Hz (1.43 Hz) So, we can easily move that line frequency up without dramatic consequence. Note the low frequency actuator kappa lines at 15.6, 16.4, 17.1, and 17.6 Hz are now ALL in one of these veto regions. At the moment, LHO can't update the calibration line frequencies and simultaneously update the "epics records" that support the TDCF calculation (see the last attempt to change 410.3 to 450.13 Hz in January LHO:66268). So, the best we can do quickly is reduce the amplitude of these lines, and we'll do so which will also reduce coupling to 3.4 Hz mentioned in LHO:68003.
Thanks for summarizing the current situation, Jeff. We've noted that even during O3, we knew that we couldn't find a clean band for the low frequency calibration lines, so I don't suggest you should move them from where they currently are in frequency. The 56.39 Hz calibration monitor line is in the "clean band 0.5 Hz from a 2 x pulsar frequency": [56.20, 58.63) Hz (2.43 Hz) So I do not think that you need to change this either, but I am also not opposed to moving it to a "clean band 1.0 Hz from a 1 x or 2 x pulsar frequency": [56.70, 58.13) Hz (1.43 Hz)