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LYRA Calibration

LYRA Calibration. DRB Meeting ESTEC 15 June 2007. Contents. 1. Radiometric Model 2. Calibration Software 3. Flatfields 4. Off-Pointing 5. LEDs, Dark Currents 6. Integration Time 7. Stability Conclusions. 1. Radiometric Model: Calibration Procedure. Telemetry from spacecraft: LUMPS

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LYRA Calibration

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  1. LYRA Calibration DRB Meeting ESTEC 15 June 2007

  2. Contents • 1. Radiometric Model • 2. Calibration Software • 3. Flatfields • 4. Off-Pointing • 5. LEDs, Dark Currents • 6. Integration Time • 7. Stability • Conclusions

  3. 1. Radiometric Model: Calibration Procedure Telemetry from spacecraft: LUMPS unpacking, decompression => [cnt] exposure time => [Hz] fixed --------------------------------------------------------------------------------------------------- Instrumental effects: variable Voltage-Frequency-Converter (VFC) => [V] resistance => [A] off-pointing, degradation, drift, dark current, dead time (+/- %) => [A] Conversion to (solar) physical units: absolute radiometric calibration => [Wm-2]

  4. 1. Radiometric Model: Selected Configurations filter detector nominal FWHM measured 1-1 Ly XN + MSM12 121.5 +/- nm 116-126 nm 1-2 Herzberg + PIN10 200-220 nm 197-218 nm 1-3Aluminium + MSM11 17-80 nm (1)-2.4, 17-35 nm 1-4Zr (300nm) + AXUV20D 1-20 nm (1)-1.3, 6-15 nm 2-1 Ly XN + MSM21 121.5 +/- nm 116-126 nm 2-2 Herzberg + PIN11 200-220 nm 199-219 nm 2-3 Aluminium + MSM15 17-80 nm (1)-1.4, 17-27 nm 2-4 Zr (150nm) + MSM19 1-20 nm (1)-1.3, 6-12 nm 3-1 Ly N+XN + AXUV20A 121.5 +/- nm 116-126 nm 3-2 Herzberg + PIN12 200-220 nm 198-219 nm 3-3 Aluminium + AXUV20B 17-80 nm (1)-2.4, 17-35 nm 3-4 Zr (300nm) + AXUV20C 1-20 nm (1)-1.3, 6-15 nm

  5. 1. Radiometric Model: Measured Responsivity

  6. 1. Radiometric Model: Simulation of Sample Spectra

  7. 2. Calibration Software: Example Lyman-alpha Channel 1-1 [LYRA 1-1 rest signal / nA] = 0.015 * [LYRA 1-2 total signal / nA] [LYRA 1-1 pure signal / nA] = [LYRA 1-1 total signal / nA] - [LYRA 1-1 rest signal / nA] ["Lyman-alpha" solar signal / (W m-2)] = 0.0975 * [LYRA 1-1 pure signal / nA]

  8. 2. Calibration Software: Example Zirconium Channel 1-4 [LYRA 1-4 pure signal / nA] = [LYRA 1-4 total signal / nA] ["Zirconium" solar signal / (W m-2)] = interp[LYRA 1-4 pure signal / nA]

  9. 3. Flatfields: Orientation

  10. 3. Flatfields: Solar Beam on Detector Plane

  11. 4. Off-Pointing: Simulation e.g. spatial responsivity channel 1-3:

  12. 4. Off-Pointing: Consequences • Simulation of off-pointing effects • -25% with 1 degree off-pointing • -1% with 5 arcmin off-pointing (jitter?) • Negligible with 10 or 20 arcsec off-pointing • Generalize for possible roll TBD • Details TBD • Commissioning phase • Confirm simulation results with off-pointing tests • Establish nominal pointing together with SWAP • Determine functional relationship between off-pointing and necessary deduction for calibration (fixed table)

  13. 5. LEDs, Dark Currents: Sample Pulses from test with heads 1 and 2. Visual LEDs commanded approx. every 270 ms, data sampled with 20 ms integration time

  14. 5. LEDs, Dark Currents: Estimates Averaged pulses, and fits of their decay phase, from test with heads 1 and 2 MSM and AXUV detectors can all be fitted well; time constants are similar. PIN detectors cannot be fitted this way. Final averages or fitted plateau values can be used to estimate dark current or LED response, resp.

  15. 6. Integration Time: Fluctuations Long integration times (> 0.2 s): (Ir)regular fluctuations, 0.05% - 0.1% around trend

  16. 6. Integration Time: Random Noise Short integration time (0.01 s): Gaussian fit, st.dev. (4.75) / signal (1675) = 0.28% e.g. channel 3-3: 15.29 / 10249 = 0.15%

  17. 6. Integration Time: Dead Time Correction dead time: 10.5807 microseconds max. correction (at 0.01 s integration time): 0.1%

  18. 7. Stability: Drift in (MSM-) Channel 1-3

  19. Conclusions • Calibration concept, software: basically ready • Updates: latest test results, new sample spectra, details • Cross-calibration during commissioning phase, degradation?

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