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LYRA Calibration, Data Products, and FITS Files

This document provides information on the calibration, data products, and FITS files for LYRA, including the file structure and various levels of data processing. It also includes details on the LYRA output, calibration issues, and the procedure for data conversion and correction.

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LYRA Calibration, Data Products, and FITS Files

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  1. LYRA Calibration, Data Products, and FITS Files PROBA2 SWT, CESRA La Roche 14-15 June 2010

  2. First… … some hints where to find our raw data:

  3. Summary: FITS File Structure • lyra_20100609_000000_lev1_***.fits • where: *** = met, std, cal, rej, (bst, bca, bre) • generally: header + binary extension table(s) • extension = header + data (variable length) • Lev1 met = HK, STATUS, VFC • Lev1 std = uncalibr. irradiance (counts/ms) • Lev2 std = calibr. irradiance (W/m²) • Lev3 std = calibr. aver. irradiance (W/m²) • per line: time, ch1, ch2, ch3, ch4, qual.

  4. Product Definition • Level 1 = full raw data (LY-EDG output) • Level 2 = calibrated physical data (LY-BSDG output) Caution: preliminary status. Require versioning. • Level 3 = processed products (e.g. averages) • Level 4 = plots of products • Level 5 = event lists (optionally with plots)

  5. Further Data Products… …“Level 4”, “Level 5” (still preliminary):

  6. Calibration… …incl. problems

  7. before & after (& still later) LYRA output, in kHz, incl. dark currents Ch1-1Ch1-2Ch1-3Ch1-4 700 500 20 30 expected 950+ 620 16+ 37 begin Jan 2010 650+ 520 16+ 37 end Apr 2010 Ch2-1Ch2-2Ch2-3Ch2-4(nominal unit) 260 580 19 42 expected 470 700 23 45 begin Jan 2010 100 100 12 40 end Apr 2010 Ch3-1Ch3-2Ch3-3Ch3-4 685 470 232 29 expected 900 550 280 35 begin Jan 2010 800 500 250 35 end Apr 2010

  8. Model t = time {1,…,T} T = number of days s(t) = solar data l(t) = LYRA data c(t) = s(t)/l(t) conversion factor => s(i) = c(t)*l(i) {1,…,8 000 000} simple expansion?? c(t) = b*d(t) degradation correction and conversion?? solar = a + b*lyra more realistic, see LRM, thus s(i) = a + b*d(t)*l(i) s(t) – a = b*d(t)*l(t) => T equations for T+2 variables

  9. Procedure (instead of LRM) • Get daily SORCE and TIMED data from the web • Calculate degradation correction d(t) and expand with splines • Calculate conversion parameters a and b • Estimate dark current from past measurements, or from temperatures • Estimate missing days with linear extrapolation of d(t) - currently only possible for channels 3 and 4

  10. * sigh * Any suggestion for better solutions or other feedback is very welcome.

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