Commissioning of AOT PHT50 for P2 in P_25 filter 15/10/97 U. Klaas 0 Summary The analysis presented here which is based on a limited data set, restricted to instrumental polarisation measurements, has provided some information about the feasibility of P2 polarisation measurements. 1) All necessary infrastructure is available: a) A PGA like interface is provided by the PHT AOT simulator program PHTAOT. This program produces directly the COB file which has to be converted into the deliverable COIF via the CUS set-up on the PIDT calibration account. Modifications as recommended in the following are already implemented. b) Signal processing can be done using PIA. This comprises interactive modes of baseline drift correction. c) A FORTRAN program (POLCALC_2) is available for the derivation of all polarisation values incl. uncertainties. Adjustments to special P2 data processing are easily to be implemented. 2) From the results of the commissioning cases which were done in the early mission the following proposals for improvement of the measurement set-up can be made: a) The minimum time per polariser should be 128 s. This gives sufficient signal stabilisation during the individual measurements. b) For assessment of signal uncertainties a minimum of 2 cycles is mandatory. Due to long term drifts, affecting the signals of the second cycle to be always higher than the ones of the first cycle, it is suggested to add a final measurement in the "0 orientation polariser" at the end of the cycles before the open measurement. This will help to correct for a long term baseline drift and decrease the signal uncertainty significantly. c) For higher signal reliability 3 to 4 cycles are recommended. 3) The instrumental polarisation for P2 is considerably low. Preliminary derivation from 8 individual measurements yields 1.5% with a 1 sigma uncertainty of 1.25%. Applying a simple baseline drift correction suggests that the instrumental polarisation is actually somewhat higher, 2.75% with a 1 sigma uncertainty of 0.25%. The aperture used for these measurements was 79" which is well matched for point source measurements. From a limited set of P1 measurements no dependence on aperture was found. However, in case the 180" aperture would be requested for extended source measurements, some confirmation for the P2 25 micron filter would be needed. This investigation does not need extra measurements, if a sufficiently large background position data base would be established from science observations. 4) No measurements on polarised sources are available for P2. Also no measurements in the optimised observing mode were done to probe the limits by observations. Assuming that the baseline drift correction works, 0.5% uncertainty for brighter sources is achievable and the S/N results are comparable to the C200 results. Taking the fact that P2 and C200 are quite similar in fastness of signal transients and detector stability, this analogy leads to the prediction that 5% polarisation of 3 Jy sources on a lower level background is measurable. 5) The total time request for PHT50 polarisation observations using P2 is: TDT OTT 2 cycles 1581 s 1387 s 3 cycles 1996 s 1802 s 4 cycles 2411 s 2217 s This includes already the extra "0 polariser measurement" at the end of the polariser cycles. 1 Introduction This report cannot be a full commissioning report of AOT PHT50, as so far only measurements on unpolarised sources have been performed. The investigations are based on a very limited data set from the earlier mission. Therefore, some analogy considerations with the well understood C200 polarisation properties have to be made. 2 Implementation The observations can be implemented using the PHT AOT simulator program PHTAOT which provides a user interface similar to PGA. PHTAOT produces automatically a COB file which can be converted into a COIF file for import into the Mission Data Base using the CUS. The COB file can contain a whole proposal consisting of up to 99 IONs. For simplification of the measurement analysis, the cold read-out electronics setting for the final FCS measurement in the observation sequence is forced to have the same set-up as the sky measurement. This is implemented in PHTAOT V4.4. Also the latest switch-on mode for P2 to prevent occurrence of latch-ups is implemented. 3 Measurement strategy 3 out of the 4 instrumental polarisation measurements used the old sequence starting with an open polariser measurement. Also no FCS measurements were included in the dedicated sequences for assessment of instrumental polarisation. Measurement times had been 64 s in the first 3 observations, but changed to 128 s per measurement in the latest one. As the transmission factor for the NIR/MIR polariser is around 0.3 drift effects are introduced in the open measurement, as the flux jump is a factor of 3. Also the first measurement in the cycle shows some initial drift. Inspection of the drift curves shows that the transients settle after 50 to 60 s, so that a measurement time of 128 s is recommended for future implementations. The P2 detector is similar to the C200 detector in fastness w.r.t. flux changes. 4 Signal Processing PIA was used to process the ERD to average signals per chopper plateau (SCP). 5 Polarisation Calculation We refer to the PHT51 commissioning report for a description of the relevant analysis steps. The polariser efficiency used for the NIR/MIR polariser, as derived from ground calibration facility measurements, is 93%. We apply an uncertainty of 3%. 6 Instrumental Polarisation Instrumental polarisation for the P_25 filter was derived from a data set of 4 observations with two independent measurements each. The measurements were performed with the 79" aperture. The measurement on rev. 230 had twice the measurement time per polariser (128 s) than the measurements on revs. 74 and 147. Log of observations: no. rev. target comment -------------------------------------------- 1 074 HR 6705 HR 6705 star 2 147 HR 6705 HR 6705 star 3 147 HR 6705 HR 6705 star 4 230 HR 5340 HR 5340 star -------------------------------------------- The data sheets of these measurements are contained in Appendix A. The resulting instrumental polarisation was obtained by computing the weighted mean, using the individual uncertainties as weighting factors. The currently best values for P_25 instrumental polarisation are: P(inst) dP(inst) Theta(inst) dTheta(inst) [%] [%] [deg] [deg] -------------------------------------------------- 1.42 1.26 -31.7 19.5 -------------------------------------------------- P(inst,debias) = 0.65% The quoted errors are the standard deviation of the mean. We can confirm the quite low instrumental polarisation reported for P2 earlier. Note that with correction for a baseline drift, as discussed in section 7, the instrumental polarisation will be somewhat higher, but better confined: P(inst) dP(inst) Theta(inst) dTheta(inst) [%] [%] [deg] [deg] -------------------------------------------------- 2.76 0.25 -9.24 5.16 -------------------------------------------------- P(inst,debias) = 2.75% Future background measurements will be used to increase the data base of instrumental polarisation measurements. 7 Signal uncertainties of polarisation measurements The signal uncertainties have been derived per pixel from the reproducibility of the measurements of the two cycles in all three polariser settings. dI(0) = dI(120) = dI(240) = 1/sqrt(3*Ncyc-1) * sqrt(SUM(i=1..Ncyc) (I(0)i - I(0)av)^2 + SUM(i=1..Ncyc) (I(120)i - I(120)av)^2 + SUM(i=1..Ncyc) (I(240)i - I(240)av)^2) In the following we list the average signals, the derived uncertainties and the resulting signal-to-noise ratios for the 3 measurements on HR 6705 and the 1 measurement on HR 5340. 1) HR 6705, rev. 74, 64 s per polariser average signals of all polariser cycles: pixel pol. orientation source signal background signal [deg] [mV/s] [mV/s] 1 0 261.1115 0.0000 1 120 257.8170 0.0000 1 240 257.8500 0.0000 standard deviation of source and background signal pixel dsig dback [mV/s] [mV/s] 1 8.8556 0.0000 S/N ratios for on- and off-position and source and source-to-background contrast pixel S/N_on S/N_off S/N_sour source/back contrast 1 29.24 0.00 0.00 0.0000 2) HR 6705, rev 147, 64s per polariser average signals of all polariser cycles: pixel pol. orientation source signal background signal [deg] [mV/s] [mV/s] 1 0 275.9475 0.0000 1 120 278.8005 0.0000 1 240 278.0630 0.0000 standard deviation of source and background signal pixel dsig dback [mV/s] [mV/s] 1 12.0153 0.0000 S/N ratios for on- and off-position and source and source-to-background contrast pixel S/N_on S/N_off S/N_sour source/back contrast 1 23.10 0.00 0.00 0.0000 3) HR 6705, rev. 147, 64s per polariser average signals of all polariser cycles: pixel pol. orientation source signal background signal [deg] [mV/s] [mV/s] 1 0 304.0625 0.0000 1 120 301.8265 0.0000 1 240 296.3465 0.0000 standard deviation of source and background signal pixel dsig dback [mV/s] [mV/s] 1 7.4488 0.0000 S/N ratios for on- and off-position and source and source-to-background contrast pixel S/N_on S/N_off S/N_sour source/back contrast 1 40.37 0.00 0.00 0.0000 4) HR 5340, rev. 230, 128 s per polariser average signals of all polariser cycles: pixel pol. orientation source signal background signal [deg] [mV/s] [mV/s] 1 0 1011.9091 0.0000 1 120 993.8660 0.0000 1 240 999.5270 0.0000 standard deviation of source and background signal pixel dsig dback [mV/s] [mV/s] 1 40.4281 0.0000 S/N ratios for on- and off-position and source and source-to-background contrast pixel S/N_on S/N_off S/N_sour source/back contrast 1 24.78 0.00 0.00 0.0000 From these 4 examples it can be inferred that in general the derived S/N ratio is poorer than the corresponding one derived for C200. Also 128 s per polariser does not seem to bring any gain. The reason for that is that the derived standard deviation of the signal is systematically increased by an underlying drift during the measurement sequence. The signals of the second cycle are always higher than the signals of the first cycle. For the internal measurement stability a factor of 2 to 4 higher S/N ratios are derived. In order to investigate the effect by a baseline drift correction or an increase of the number of polariser cycles we did the following simple test: We set the signal of the first polariser setting of the first cycle equal to the correponding one of the second cycle and scaled the 2nd and 3rd polariser setting signals accordingly by linear interpolation. In the calculation of the signal deviation we reset the scaling factor from sqrt(3*Ncyc-1) to sqrt(2*Ncyc-1). The resulting data sheets are listed in Appendix B. By this method we achieve the following gain in S/N: target rev. t_polariser S/N_uncorr S/N_corr ------------------------------------------------------- HR 6705 74 64 s 29.2 52.7 HR 6705 147 64 s 23.1 37.1 HR 6705 147 64 s 40.4 56.3 HR 5340 230 128 s 24.8 161.1 ------------------------------------------------------- >From the table it can be seen that in particular the long measurement gains significantly in S/N and the two cycles give very consistent results. With some caution, due to the limited number of measurements, we conclude that the drift may be in the order of a full long cycle of 3*128 s = 384 s. As a considerable improvement in the measurement set-up we therefore recommend to include an additional "0 polariser measurement" at the end of the cycles in order to assess the drifts. This is much better than an open measurement at the beginning which has three times the brightness of the polariser measurements and introduces signal transients in the following. Using then the "0 polariser measurement" as reference will lead to considerable improvement of the signal reproducibility. This will cost about 150 s extra time. 8 Achievable polarisation degrees Only limited information can be provided, as no polarised source measurement was performed yet. For instrumental polarisation assessment reasonably bright sources were selected in order to get sufficient S/N ratio. At 25 micron HR 5340 has flux density of 163 Jy, and HR 6705 of 38 Jy. As the instrumental polarisation is quite low, these measurements are already quite hard in order to achieve accurate signal differences. In the discussion of the signal reproducibility we have seen the poorness of the uncorrected results which give 1 sigma polarisation uncertainties of 2 to 4%. Correcting for the systematic P2 drift by an improved measurement set up an uncertainty of 0.5% is achievable for brighter sources. Concerning the achieved S/N the P2 results become then comparable to the C200 results. The background at 25 micron is relatively bright. In the 79" aperture 30 MJy sr^-1, a moderate ZL background, correspond to 3.4 Jy. In analogy to C200 the detection of 5% polarisation of a 3Jy source seems to be feasible. All the P2 instrumental polarisation measurements have been done with the 79" aperture which is matched to point source measurements. For extended source polarimetry the 180" aperture may be desirable. There is not much information available about the aperture dependence of the instrumental polarisation. We have performed some tests with P1 in the 16 micron filter with 52" and 180" apertures for which no significant differences (inside the uncertainties due to drift effects) were found. Depending on the observer requests, this issue may need some follow-up. However, a reliable basic data base can be build up from the background measurements, if there will be a sufficient number of them. Appendix A: Instrumental polarisation results data sheets from unpolarised sources obtained with POLCALC_2 file = HR6705INS_074_25.pol polarisation calculation done for detector P2 derivation of INSTRUMENTAL POLARISATION source name: HR 6705 signal file used: HR6705INS_074_25.DAT number of polariser cycles: 2 INPUT SIGNALS: polariser cycle no. 1: pixel pol. orientation source signal background signal [deg] [mV/s] [mV/s] 1 0 252.7580 0.0000 1 120 250.4130 0.0000 1 240 249.3970 0.0000 polariser cycle no. 2: pixel pol. orientation source signal background signal [deg] [mV/s] [mV/s] 1 0 269.4650 0.0000 1 120 265.2210 0.0000 1 240 266.3030 0.0000 average signals of all polariser cycles: pixel pol. orientation source signal background signal [deg] [mV/s] [mV/s] 1 0 261.1115 0.0000 1 120 257.8170 0.0000 1 240 257.8500 0.0000 standard deviation of source and background signal pixel dsig dback [mV/s] [mV/s] 1 8.8556 0.0000 S/N ratios for on- and off-position and source and source-to-background contrast pixel S/N_on S/N_off S/N_sour source/back contrast 1 29.24 0.00 0.00 0.0000 POLARISATION DEGREE AND ANGLE: first error = Gaussian error second error = maximum error polariser cycle no. 1 pixel 1 POL DEG: 0.85 +- 3.10 [%] POL ANG: -8.57 +- 104.08 [deg] +- 6.19 [%] +- 191.83 [deg] polariser cycle no. 2 pixel 1 POL DEG: 1.03 +- 2.91 [%] POL ANG: 7.10 +- 81.35 [deg] +- 5.69 [%] +- 145.01 [deg] average values pixel 1 POL DEG: 0.91 +- 3.00 [%] POL ANG: 0.25 +- 94.79 [deg] +- 5.00 [%] +- 135.43 [deg] debiased polarisation degrees pixel 1 DEBIASED POL DEG: 0.00 [%] file = HR6705INS1_147_25.pol polarisation calculation done for detector P2 derivation of INSTRUMENTAL POLARISATION source name: HR 6705 signal file used: HR6705INS1_147_25.DAT number of polariser cycles: 2 INPUT SIGNALS: polariser cycle no. 1: pixel pol. orientation source signal background signal [deg] [mV/s] [mV/s] 1 0 265.8690 0.0000 1 120 267.3610 0.0000 1 240 266.7280 0.0000 polariser cycle no. 2: pixel pol. orientation source signal background signal [deg] [mV/s] [mV/s] 1 0 286.0260 0.0000 1 120 290.2400 0.0000 1 240 289.3980 0.0000 average signals of all polariser cycles: pixel pol. orientation source signal background signal [deg] [mV/s] [mV/s] 1 0 275.9475 0.0000 1 120 278.8005 0.0000 1 240 278.0630 0.0000 standard deviation of source and background signal pixel dsig dback [mV/s] [mV/s] 1 12.0153 0.0000 S/N ratios for on- and off-position and source and source-to-background contrast pixel S/N_on S/N_off S/N_sour source/back contrast 1 23.10 0.00 0.00 0.0000 POLARISATION DEGREE AND ANGLE: first error = Gaussian error second error = maximum error polariser cycle no. 1 pixel 1 POL DEG: 0.35 +- 3.96 [%] POL ANG: -77.50 +- 325.05 [deg] +- 8.25 [%] +- 642.65 [deg] polariser cycle no. 2 pixel 1 POL DEG: 0.96 +- 3.66 [%] POL ANG: -84.57 +- 109.16 [deg] +- 6.91 [%] +- 186.03 [deg] average values pixel 1 POL DEG: 0.66 +- 3.80 [%] POL ANG: -82.80 +- 164.37 [deg] +- 7.40 [%] +- 293.00 [deg] debiased polarisation degrees pixel 1 DEBIASED POL DEG: 0.00 [%] file = HR6705INS2_147_25.pol polarisation calculation done for detector P2 derivation of INSTRUMENTAL POLARISATION source name: HR 6705 signal file used: HR6705INS2_147_25.DAT number of polariser cycles: 2 INPUT SIGNALS: polariser cycle no. 1: pixel pol. orientation source signal background signal [deg] [mV/s] [mV/s] 1 0 298.6440 0.0000 1 120 293.4340 0.0000 1 240 290.1080 0.0000 polariser cycle no. 2: pixel pol. orientation source signal background signal [deg] [mV/s] [mV/s] 1 0 309.4810 0.0000 1 120 310.2190 0.0000 1 240 302.5850 0.0000 average signals of all polariser cycles: pixel pol. orientation source signal background signal [deg] [mV/s] [mV/s] 1 0 304.0625 0.0000 1 120 301.8265 0.0000 1 240 296.3465 0.0000 standard deviation of source and background signal pixel dsig dback [mV/s] [mV/s] 1 7.4488 0.0000 S/N ratios for on- and off-position and source and source-to-background contrast pixel S/N_on S/N_off S/N_sour source/back contrast 1 40.37 0.00 0.00 0.0000 POLARISATION DEGREE AND ANGLE: first error = Gaussian error second error = maximum error polariser cycle no. 1 pixel 1 POL DEG: 1.82 +- 2.22 [%] POL ANG: -11.37 +- 35.08 [deg] +- 4.67 [%] +- 69.06 [deg] polariser cycle no. 2 pixel 1 POL DEG: 1.70 +- 2.13 [%] POL ANG: -32.52 +- 35.84 [deg] +- 4.29 [%] +- 75.69 [deg] average values pixel 1 POL DEG: 1.64 +- 2.17 [%] POL ANG: -21.82 +- 38.02 [deg] +- 4.79 [%] +- 83.37 [deg] debiased polarisation degrees pixel 1 DEBIASED POL DEG: 0.00 [%] file = HR5340INS_230_25.pol polarisation calculation done for detector P2 derivation of INSTRUMENTAL POLARISATION source name: HR 5340 signal file used: HR5340INS_230_25.DAT number of polariser cycles: 2 INPUT SIGNALS: polariser cycle no. 1: pixel pol. orientation source signal background signal [deg] [mV/s] [mV/s] 1 0 962.7680 0.0000 1 120 960.2170 0.0000 1 240 976.3110 0.0000 polariser cycle no. 2: pixel pol. orientation source signal background signal [deg] [mV/s] [mV/s] 1 0 1061.0500 0.0000 1 120 1027.5150 0.0000 1 240 1022.7430 0.0000 average signals of all polariser cycles: pixel pol. orientation source signal background signal [deg] [mV/s] [mV/s] 1 0 1011.9091 0.0000 1 120 993.8660 0.0000 1 240 999.5270 0.0000 standard deviation of source and background signal pixel dsig dback [mV/s] [mV/s] 1 40.4281 0.0000 S/N ratios for on- and off-position and source and source-to-background contrast pixel S/N_on S/N_off S/N_sour source/back contrast 1 24.78 0.00 0.00 0.0000 POLARISATION DEGREE AND ANGLE: first error = Gaussian error second error = maximum error polariser cycle no. 1 pixel 1 POL DEG: 1.11 +- 3.67 [%] POL ANG: 55.76 +- 94.69 [deg] +- 7.11 [%] +- 194.41 [deg] polariser cycle no. 2 pixel 1 POL DEG: 2.50 +- 3.42 [%] POL ANG: -3.28 +- 39.23 [deg] +- 6.28 [%] +- 62.91 [deg] average values pixel 1 POL DEG: 1.14 +- 3.54 [%] POL ANG: 8.93 +- 88.76 [deg] +- 7.13 [%] +- 165.14 [deg] debiased polarisation degrees pixel 1 DEBIASED POL DEG: 0.00 [%] Appendix B: Instrumental polarisation results data sheets from unpolarised sources applying simple linear baseline correction to first polariser cycle file = HR6705INSBF_074_25.pol polarisation calculation done for detector P2 derivation of INSTRUMENTAL POLARISATION source name: HR 6705 signal file used: HR6705INSBF_074_25.DAT number of polariser cycles: 2 INPUT SIGNALS: polariser cycle no. 1: pixel pol. orientation source signal background signal [deg] [mV/s] [mV/s] 1 0 269.4650 0.0000 1 120 261.2660 0.0000 1 240 254.6610 0.0000 polariser cycle no. 2: pixel pol. orientation source signal background signal [deg] [mV/s] [mV/s] 1 0 269.4650 0.0000 1 120 265.2210 0.0000 1 240 266.3030 0.0000 average signals of all polariser cycles: pixel pol. orientation source signal background signal [deg] [mV/s] [mV/s] 1 0 269.4650 0.0000 1 120 263.2435 0.0000 1 240 260.4820 0.0000 standard deviation of source and background signal pixel dsig dback [mV/s] [mV/s] 1 5.0196 0.0000 S/N ratios for on- and off-position and source and source-to-background contrast pixel S/N_on S/N_off S/N_sour source/back contrast 1 52.67 0.00 0.00 0.0000 POLARISATION DEGREE AND ANGLE: first error = Gaussian error second error = maximum error polariser cycle no. 1 pixel 1 POL DEG: 3.52 +- 1.69 [%] POL ANG: -13.22 +- 13.72 [deg] +- 3.70 [%] +- 28.51 [deg] polariser cycle no. 2 pixel 1 POL DEG: 1.03 +- 1.65 [%] POL ANG: 7.10 +- 46.11 [deg] +- 3.24 [%] +- 82.39 [deg] average values pixel 1 POL DEG: 2.16 +- 1.67 [%] POL ANG: -8.73 +- 22.10 [deg] +- 3.41 [%] +- 41.49 [deg] debiased polarisation degrees pixel 1 DEBIASED POL DEG: 1.37 [%] file = hr6705ins1bf_147_25.pol polarisation calculation done for detector P2 derivation of INSTRUMENTAL POLARISATION source name: HR 6705 signal file used: hr6705ins1bf_147_25.dat number of polariser cycles: 2 INPUT SIGNALS: polariser cycle no. 1: pixel pol. orientation source signal background signal [deg] [mV/s] [mV/s] 1 0 286.0260 0.0000 1 120 280.6100 0.0000 1 240 273.2760 0.0000 polariser cycle no. 2: pixel pol. orientation source signal background signal [deg] [mV/s] [mV/s] 1 0 286.0260 0.0000 1 120 290.2400 0.0000 1 240 289.3980 0.0000 average signals of all polariser cycles: pixel pol. orientation source signal background signal [deg] [mV/s] [mV/s] 1 0 286.0260 0.0000 1 120 285.4250 0.0000 1 240 281.3370 0.0000 standard deviation of source and background signal pixel dsig dback [mV/s] [mV/s] 1 7.6666 0.0000 S/N ratios for on- and off-position and source and source-to-background contrast pixel S/N_on S/N_off S/N_sour source/back contrast 1 37.08 0.00 0.00 0.0000 POLARISATION DEGREE AND ANGLE: first error = Gaussian error second error = maximum error polariser cycle no. 1 pixel 1 POL DEG: 2.84 +- 2.41 [%] POL ANG: -17.48 +- 24.28 [deg] +- 5.33 [%] +- 52.45 [deg] polariser cycle no. 2 pixel 1 POL DEG: 0.96 +- 2.33 [%] POL ANG: -84.57 +- 69.65 [deg] +- 4.42 [%] +- 118.82 [deg] average values pixel 1 POL DEG: 1.11 +- 2.37 [%] POL ANG: -26.62 +- 60.88 [deg] +- 5.06 [%] +- 132.79 [deg] debiased polarisation degrees pixel 1 DEBIASED POL DEG: 0.00 [%] file = HR6705INS2BF_147_25.pol polarisation calculation done for detector P2 derivation of INSTRUMENTAL POLARISATION source name: HR 6705 signal file used: HR6705INS2BF_147_25.DAT number of polariser cycles: 2 INPUT SIGNALS: polariser cycle no. 1: pixel pol. orientation source signal background signal [deg] [mV/s] [mV/s] 1 0 309.4810 0.0000 1 120 300.4830 0.0000 1 240 293.6040 0.0000 polariser cycle no. 2: pixel pol. orientation source signal background signal [deg] [mV/s] [mV/s] 1 0 309.4810 0.0000 1 120 310.2190 0.0000 1 240 302.5850 0.0000 average signals of all polariser cycles: pixel pol. orientation source signal background signal [deg] [mV/s] [mV/s] 1 0 309.4810 0.0000 1 120 305.3510 0.0000 1 240 298.0945 0.0000 standard deviation of source and background signal pixel dsig dback [mV/s] [mV/s] 1 5.4075 0.0000 S/N ratios for on- and off-position and source and source-to-background contrast pixel S/N_on S/N_off S/N_sour source/back contrast 1 56.28 0.00 0.00 0.0000 POLARISATION DEGREE AND ANGLE: first error = Gaussian error second error = maximum error polariser cycle no. 1 pixel 1 POL DEG: 3.28 +- 1.58 [%] POL ANG: -12.80 +- 13.77 [deg] +- 3.45 [%] +- 28.38 [deg] polariser cycle no. 2 pixel 1 POL DEG: 1.70 +- 1.55 [%] POL ANG: -32.52 +- 26.02 [deg] +- 3.13 [%] +- 55.14 [deg] average values pixel 1 POL DEG: 2.35 +- 1.56 [%] POL ANG: -19.51 +- 19.02 [deg] +- 3.49 [%] +- 41.82 [deg] debiased polarisation degrees pixel 1 DEBIASED POL DEG: 1.76 [%] file = HR5340INSBF_230_25.pol polarisation calculation done for detector P2 derivation of INSTRUMENTAL POLARISATION source name: HR 5340 signal file used: HR5340INSBF_230_25.DAT number of polariser cycles: 2 INPUT SIGNALS: polariser cycle no. 1: pixel pol. orientation source signal background signal [deg] [mV/s] [mV/s] 1 0 1061.0500 0.0000 1 120 1023.7500 0.0000 1 240 1007.4800 0.0000 polariser cycle no. 2: pixel pol. orientation source signal background signal [deg] [mV/s] [mV/s] 1 0 1061.0500 0.0000 1 120 1027.5150 0.0000 1 240 1022.7430 0.0000 average signals of all polariser cycles: pixel pol. orientation source signal background signal [deg] [mV/s] [mV/s] 1 0 1061.0500 0.0000 1 120 1025.6326 0.0000 1 240 1015.1115 0.0000 standard deviation of source and background signal pixel dsig dback [mV/s] [mV/s] 1 6.4179 0.0000 S/N ratios for on- and off-position and source and source-to-background contrast pixel S/N_on S/N_off S/N_sour source/back contrast 1 161.10 0.00 0.00 0.0000 POLARISATION DEGREE AND ANGLE: first error = Gaussian error second error = maximum error polariser cycle no. 1 pixel 1 POL DEG: 3.31 +- 0.56 [%] POL ANG: -8.62 +- 4.75 [deg] +- 1.21 [%] +- 9.31 [deg] polariser cycle no. 2 pixel 1 POL DEG: 2.50 +- 0.55 [%] POL ANG: -3.28 +- 6.23 [deg] +- 1.07 [%] +- 10.16 [deg] average values pixel 1 POL DEG: 2.89 +- 0.55 [%] POL ANG: -6.31 +- 5.41 [deg] +- 1.15 [%] +- 9.85 [deg] debiased polarisation degrees pixel 1 DEBIASED POL DEG: 2.84 [%]