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WBS Software Requirements

WBS Software Requirements. Frank Schmülling. The WBS requires software support to achieve full performance. ICU On Board Software: instrument tuning (attenuation) 16 bit data transfer timing constraints in fast chop mode ICC Data analysis software frequency calibration

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WBS Software Requirements

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  1. WBS Software Requirements Frank Schmülling The WBS requires software support to achieve full performance • ICU On Board Software: • instrument tuning (attenuation) • 16 bit data transfer • timing constraints in fast chop mode • ICC Data analysis software • frequency calibration • power correction (TBD) F. Schmülling; WBS Software Requirements; WBS CDR 2-3rd April 2003

  2. WBS data format F. Schmülling; WBS Software Requirements; WBS CDR 2-3rd April 2003

  3. ICU: Dark Pixel correction Dark pixels measure the variable offset that is introduced to reduce DNL effects of the ADC • Subtract dark pixels from data that is to be used for on board instrument tuning. • For rearranged (sorted) WBS data the corrected spectrum c is:c(2i) = p(2i) - de and c(2i+1) = p(2i+1) - dofor each CCD, i=0..2048/2 • Note: dark pixel correction is also necessary for ZERO scans that are used for on board instrument tuning F. Schmülling; WBS Software Requirements; WBS CDR 2-3rd April 2003

  4. ICU: WBS Attenuator tuning 3. Optimize (2 iterations) • Start integration, read scan, subtract ZERO and bin data • Optimize attenuator setting • Command new setting 1. Prepare • Read ZERO scan • Set attenuators to maximum attenuation (TBD) • Put HOT load into signal path 2. First Guess • Start integration, read scan, subtract ZERO and bin data • Calculate optimum attenuator setting • Command new setting F. Schmülling; WBS Software Requirements; WBS CDR 2-3rd April 2003

  5. ICU: WBS Attenuator tuning (cont.) • Fixed number of iterations • Total procedure takes in the order of 5 seconds • Robust against spikes • Store settings in the ICU so they can be reused after COMB/ZERO measurements F. Schmülling; WBS Software Requirements; WBS CDR 2-3rd April 2003

  6. WBS raw data (24 bit) 0.08s ≤ t ≤ 1.28s 1.28s ≤ t ≤ 2.56s 2.56s ≤ t ≤ 5.12s ICU: Convert data to 16 bit For integration times between 0.1 and 5 seconds the 24 bit WBS data can be converted to 16 bit F. Schmülling; WBS Software Requirements; WBS CDR 2-3rd April 2003

  7. ICU: Convert data to 16 bit (cont.) • Information how the data was shifted must be included in the data header • ZERO and COMB with 1 sec integration time • Maximum integration time is 5 seconds • Truncated data is guaranteed to • Cover full range of possible values:represent maximum pixel-count • Have enough precision to resolve RMS:make digitization noise negligible F. Schmülling; WBS Software Requirements; WBS CDR 2-3rd April 2003

  8. 10ms 10ms 10ms ICU: Timing constraints Fast chop timing of the WBS CCD readout frames Timing-Jitter of the start command affects the performance of the WBS (Memory effect of the CCD) start stop start Tstop-start=N•10ms + 5ms ± 0.5ms Tstart-start=(N+n)•10ms + 5ms ± 10µs F. Schmülling; WBS Software Requirements; WBS CDR 2-3rd April 2003

  9. ICU: Timing constraints (cont.) CCD memory effect: about 3% charges from the previous scan Maximum integration times in fast chop mode: Note: fast chop mode has 2 seconds dead-time for every read-out F. Schmülling; WBS Software Requirements; WBS CDR 2-3rd April 2003

  10. ICC: Data handling overview F. Schmülling; WBS Software Requirements; WBS CDR 2-3rd April 2003

  11. 2. Find exact peak position by fitting Gaussians 3. Fit frequencies (100MHz, 200MHz..) to Comb positions 1. Identify peaks ICC: generate frequency calibration polynomials Find coarse peak positions Fit polynomial. Plot showslinear fit - 100*residuals Fit exact (sub-pixel resolution) peak positions F. Schmülling; WBS Software Requirements; WBS CDR 2-3rd April 2003

  12. ICC: Frequency calibration • Use a Gaussian filter-curve to resample data: • The frequency fn for every pixel is computed using the frequency calibration polynomial • The resolution of the resampled spectrum can be defined (Q2) F. Schmülling; WBS Software Requirements; WBS CDR 2-3rd April 2003

  13. ICC: Power correction Platforming effects Raw data Corrected data Effects in uncorrected data due to non-linear behaviour of WBS components.Spectrum: (S-R)(R-Z), S≈2•R F. Schmülling; WBS Software Requirements; WBS CDR 2-3rd April 2003

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