SOFIE Spectral Response Mark Hervig, GATS Inc.

1. Drivers: • Filter Response • Preceding Optics • Detector Response • Solar Source • Out-of-band performance is critical • Requirement: Out of band exoatmospheric solar energy < 1% of total signal • Spectral performance is analyzed using total response based on predicted and measured characteristics of the optical elements and detectors. • The optical layout is shown on the following page. • For example, the total response (TR) for band 14 is • TR14 = R17 T19 R13 T14 DR14 • where R is reflection, T is transmission, DR is detector response, and subscript indicates optical element number. • Below “actual” means that the filter transmissions are measurements from real filters. In the case of “actual” total response a number of other optical elements could be based on predictions. SOFIE Spectral ResponseMark Hervig, GATS Inc.

2. SOFIE CSM layout

3. Notes and Definitions • Half-power points (HPP) are the wavelengths where the filter bandpass transmission is 50% of the peak transmission value. • The HPP on the short wavelength side of the bandpass is known as the cuton wavelength, or lower HPP (LHPP). The HPP on the long wavelength side is known as the cutoff wavelength, or upper HPP (UHPP). • The bandpass is generally defined as the wavelength region between cuton and cutoff. • Bandpass center is defined as the average of cuton and cutoff wavelengths • Bandpass (filter) width is given in percent as: • 200*(cutoff-cuton)/(cutoff+cuton). • For the out-of-band (OOB) analysis, the in-band region was defined as the wavelength region 3 filter widths wide centered on the band center wavelength

4. Filter Part and Data list, bands 1-4 Underlined bandpass data were used the in following OOB analysis Amb = ambient temperature (? K) *part received by SDL

5. Filter Part and Data list, bands 5 - 8 Underlined bandpass data were used the in following OOB analysis Amb = ambient temperature (? K) *part received by SDL

6. Filter Part and Data list, bands 9-12 Underlined bandpass data were used the in the following analysis Amb = ambient temperature (? K) *part received by SDL

7. Filter Part and Data list, bands 13-16 Underlined bandpass data were used the in following analysis Amb = ambient temperature (? K) *part received by SDL

8. SOFIE Bandpass Performance • All values based on total response curves, not just filter transmission curves. • Filter width is defined from the  half-power points (cuton to cutoff). • Band center is the average of the cuton and cutoff wavelengths.

9. SOFIE Bandpass Performance Total response includes all preceding optical elements & detector response

10. Band 1 analysis

11. Band 2 analysis

12. Band 3 analysis

13. Band 4 analysis

14. Band 5 Analysis Notes:

15. Band 6 Analysis

16. Band 7 Analysis

17. Band 8 Analysis

18. Band 9 Analysis

19. Band 10 Analysis

20. Band 11: part to part consistency Shown are the filter transmissions for individual parts, all measured at 0 deg angle of incidence and ambient temperature.

21. Band 11 Analysis • Notes: • Filter location shift

22. Band 12: part to part consistency Shown are the filter transmissions for individual parts, all measured at 0 deg angle of incidence and ambient temperature.

23. Band 12 Analysis • Notes: • Filter location shift

24. CH4 channel (bands 11 & 12), filters & gas spectra

25. Band 13: part to part consistency Shown are the filter transmissions for individual parts, all measured at 0 deg angle of incidence and ambient temperature.

26. Band 13 Analysis

27. Band 14 Analysis • Notes: • Missing OOB data from 3.3 microns to cuton. • Filter location shift

28. CO2 channel (bands 13 & 14), filters & gas spectra

29. Band 15 Analysis • Notes: • Filter location shift

30. Band 16 Analysis • Notes: • Filter location shift, broader

31. NO channel (bands 15 & 16), filters & gas spectra

32. Extra slides follow

33. Silicon Carbide Detectors, Bands 1 & 2 • Ozone measurements originally used UV-enhanced silicon detectors The spectral response of UV-Si detectors is less than ideal: • UV-Si response combined with solar spectrum = amplified out-of-band energy • Can be addressed with stacked filters, difficult to verify, questionable stability • A new option: Silicon Carbide (SiC) detectors • Ideal spectral response • twice as rad-hard as Si • Space flight heritage • Eliminates 2nd filter • Bands 1 & 2 now use SiC solar source  detector response

34. Band 1 Spectral Response with SiC detector Predictions indicate excellent performance using silicon carbide detector Solar out-of-band = 0.02%

35. Backup slides follow

36. As hardware arrives at SDL, the measured characteristics are used to predict performance and ensure that all parts meet our requirements. Requirement: Out of band exoatmospheric solar energy < 1% of total signal SOFIE Out of Band Performance Here, in-band is defined as a region 3 filter widths wide centered on the band center wavelength

37. SOFIE Bandpass Performance, Continued • In-band is wavelengths between the  half-power points • Total response includes all preceding optical elements & detector response