Point and focus algorithms

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    Version as of 07:21, 17 May 2025

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    Low-pass filtering point scans from 3/21

    total_power_psd.png

    total_power_1hz_filtered.pngtotal_power_0.5hz_filtered.png

    Measuring total power at VLBI backend

    • Measure total power using Mark6 recorded 2-bit data by checking 2-bit occupancy
    • There is a time offset (4.1s) between the scan time and that reported in the total power files (leap seconds?)
    • Assumed every packet was exactly 8 microseconds, and used 31250 = 0.25s per integration.
    • Same time offset in A and B channels (IF0 and IF1)
    • IF0 and APower are both noisy
      mark6_totalpower.png
    • Measure total power using Mark6 eht3 and eth5 packets by checking 2-bit occupancy
    • Measure total power using R2DBE regular 8-bit snapshots as fast as possible
    • Measure total power using custom R2DBE bitcode

    Forward model fitting into time domain

    • useful for dealing with regions of spectrum that have both signal and noise contributions
    • starting beam width of 10 (arcsec, FWHM?)
    • can characterize noise as stationary?
    • how to get good local estimate of power spectrum?

    Averaging multiple scans

    Detrending with splines

    Detrending with high-pass filter


     
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