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Calibration of PPTA Data

Calibration of PPTA Data. R. N. Manchester. Australia Telescope National Facility, CSIRO Sydney Australia. Summary. Effect of calibration on timing Non-linearities in system response Time stability of calibration parameters. Uncalibrated Rms Residual: 1.23  s.

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Calibration of PPTA Data

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  1. Calibration of PPTA Data R. N. Manchester Australia Telescope National Facility, CSIRO Sydney Australia Summary • Effect of calibration on timing • Non-linearities in system response • Time stability of calibration parameters

  2. Uncalibrated Rms Residual: 1.23 s • Calibrated instrumental gain and phase Rms Residual: 0.74 s • Jump around H-OH data Rms Residual: 0.65 s • PCM calibration - no jump Rms Residual: 0.72 s • PCM Cal with jump Rms Residual: 0.59 s PSR J1744-1134 Timing Residuals • 20cm Multibeam Receiver • PDFB1, June 05 - Nov 07 • Mostly 1-h observations

  3. Raw Calibration Amplitudes • PDFB1, June 05 - Nov 07 • Cal amplitudes in counts (obtained using pdv -c) • Initially operating with input levels too high • Levels further reduced after linearity tests • Apart from non-linear effects, absolute levels don’t matter provided cal and psr observations done with same settings

  4. Effect of Non-Linearities Vela Pulsar, 20cm band Plotted profiles truncated at 5% of peak WBC, H-OH Receiver 2-bit digitisation effects, feed resonances, correlator artifacts PDFB1, MB Receiver Saturation effects

  5. System Linearity • PDFB2, MB receiver • Pulsed calibration used as test signal • Adjust input signal levels using down-converter attenuators • Measure digitiser rms, cal amplitudes and apparent fractional linear polarisation of calibration • System reasonably linear over input rms range of 6 - 60, i.e. 20 db range of input power • Operating point of rms = 10 chosen • Similar level tests done for PDFB1

  6. Linearity with Current Settings for Input Levels Vela Pulsar, MB Receiver 5% truncation of profiles PDFB2 PDFB1

  7. Pulsed Cal Mean Flux Densities • Centre beam Multibeam receiver, 1369 MHz • Mean values from pacv

  8. Calibration Flux Density Spectra • Multibeam Receiver - based on observations of Hydra A WBC: 22 Dec 2005 PDFB1: 16 June 2007 PDFB2: 11 Sept 2007 PDFB2: 01 Oct 2007

  9. Feed Cross-Coupling Parameters • PDFB1, Multibeam Receiver • 1369 MHz • Polarisation ellipse orientation and ellipticity 09 May 2006 16 June 2007 04 Aug 2007

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