SOFIE Spectral Response Mark Hervig, GATS Inc. 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 TR 14 = R 17  T 19  R 13  T 14  DR 14 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 CSM layout

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

Filter Part and Data list, bands 1-4 BandPart #Bandpass Data Angle / temperature Out-of-band Data Angle / temperature / wavelength (  m) Comment 114?14? 15°/ 260K No part # 223?23? 15°/ 260K No part # 324?24? 15°/ 260K No part # 414?14? 15°/ 260K 15°/ 260K / No part # Underlined bandpass data were used the in following OOB analysis Amb = ambient temperature (? K) *part received by SDL

Filter Part and Data list, bands BandPart #Bandpass Data Angle / temperature Out-of-band Data Angle / temperature / wavelength (  m) Comment °/ 260K Underlined bandpass data were used the in following OOB analysis Amb = ambient temperature (? K) *part received by SDL

Filter Part and Data list, bands 9-12 BandPart #Bandpass Data Angle / temperature Out-of-band Data Angle / temperature / wavelength (  m) Comment °/ 260K (wit) 2* 3* ? 0°/ amb, 15°/ 260K, 15°/amb 0°/ amb 15°/ 260K/ 2.0– °/ 260K/ 1.0–2.0, 15°/ 260K/ 3.42–5.5No part # 127* * 11(wit) ? 0°/ amb 0°/ 260K, 15°/ 260K, 15°/amb 15°/ 260K/ 1.0–2.0, 15°/ 260K/ 2.0–3.44, 15°/ 260K/ 3.54–6.0No part # Underlined bandpass data were used the in the following analysis Amb = ambient temperature (? K) *part received by SDL

Filter Part and Data list, bands BandPart #Bandpass Data Angle / temperature Out-of-band Data Angle / temperature / wavelength range (  m) Comment 131 2* 3 4* 5 wit ? 0°/ amb, 15°/ 260K, 15°/200K 0°/ amb 15°/ 260K, 15°/ 200K 15°/ 260K/ 1.0–2.0, 15°/ 260K/ 2.0–4.2, 15°/ 260K/ 4.6–6.0 No part # 142* 3* 5 15°/ 260K, 15°/ amb 15°/ 260K/ 2.0–3.26, 15°/ 260K/ 4.79–6.0no OOB 3.3-cuton 152 3* 5* ? 15°/ 260K, 15°/ amb 0°/ amb 15°/ amb/ 1.0–2.0, 15°/ 260K/ , 15°/ 260K/ No part # 162* 3* 5 Wit 0°/ amb 15°/ 260K 0°/ amb, 15°/ amb, 15°/ 260K15°/ 260K/ , 15°/ 260K/ No part # Underlined bandpass data were used the in following analysis Amb = ambient temperature (? K) *part received by SDL

SOFIE Bandpass Performance BandMeasurement Center (  m) spec / actual filter Width (%) spec / actual filter Cuton – Cutoff (  m) spec / actual filter Cuton – Cutoff (cm -1 ) spec / actual filter 1O 3 strong0.290 / / / / – O 3 weak0.328 / / / 0.320– / particle strong0.862 / / / / particle weak1.03 / / / / H 2 O weak2.45 / / / / H 2 O strong2.60 / / / / CO 2 strong2.77 / / / / CO 2 weak2.94 / / / / particle strong3.06 / / / / particle weak3.19 / / / / CH 4 strong3.37 / / / / CH 4 weak3.51 / / / / CO 2 strong4.35 / / / / CO 2 weak4.68 / / / / NO weak4.98 / / / / NO strong5.32 / / / / 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.

SOFIE Bandpass Performance BandMeasurementFilter Transmission (%) Average in-band spec / predicted / actual Detector Response (%) Average in-band actual (part #) Total Response (%) Average in-band predicted / actual filter Out of Band Solar Energy (%) (Spec is < 1%) predicted / actual filter 1O 3 strong>80 / 95.2 / (G07)17.6 / / O 3 weak>80 / 93.4 / (G07)9.0 / / particle strong>80 / 97.7 / (J540)5.1 / / particle weak>80 / 98.4 / (J550)20.1 / / H 2 O weak>80 / 92.9 / (J562)34.8 / / H 2 O strong>80 / 93.0 / (J541)32.2 / / CO 2 strong>80 / 93.0 / (J554)41.6 / / CO 2 weak>80 / 93.0 / (J553)41.3 / / particle strong>80 / 92.9 / (J559)44.4 / / particle weak>80 / 93.0 / (J561)42.9 / / CH 4 strong>80 / 93.0 / (J560)46.3 / / CH 4 weak>80 / 93.0 / (J552)53.1 / / CO 2 strong>75 / 94.0 / (J546)60.9 / / CO 2 weak>75 / 92.7 / (J544)66.0 / / NO weak>75 / 92.3 / (J542)66.6 / / NO strong>75 / 92.6 / (J547)54.3 / / Total response includes all preceding optical elements & detector response

Band 1 analysis

Band 2 analysis

Band 3 analysis

Band 4 analysis

Band 5 Analysis Notes:

Band 6 Analysis

Band 7 Analysis

Band 8 Analysis

Band 9 Analysis

Band 10 Analysis

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.

Band 11 Analysis Notes: Filter location shift

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.

Band 12 Analysis Notes: Filter location shift

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

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.

Band 13 Analysis

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

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

Band 15 Analysis Notes: Filter location shift

Band 16 Analysis Notes: Filter location shift, broader

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

Extra slides follow

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 2 nd filter  Bands 1 & 2 now use SiC solar source  detector response

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

Backup slides follow

SOFIE Out of Band Performance 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 BandMeasurement Center (  m) Out of Band Solar Energy (%), Predicted Out of Band Solar Energy (%), Actual Filter & Detector 1O 3 strong O 3 weak particle strong particle weak H 2 O weak H 2 O strong CO 2 strong CO 2 weak particle strong particle weak CH 4 strong CH 4 weak CO 2 strong CO 2 weak NO weak NO strong Here, in-band is defined as a region 3 filter widths wide centered on the band center wavelength

SOFIE Bandpass Performance, Continued BandMeasurementFilter Transmission (%) Average in-band spec / predicted or actual Detector Response (%) Average in-band predicted or actual (part #) Total Response (%) Average in-band predicted or actual filter 1O 3 strong>80 / O 3 weak>80 / particle strong>80 / (J540)21.0 4particle weak>80 / (J550)33.2 5H 2 O weak>80 / (J562)37.2 6H 2 O strong>80 / (J541)43.2 7CO 2 strong>80 / (J554)46.8 8CO 2 weak>80 / (J553)48.5 9particle strong>80 / (J559) particle weak>80 / (J561) CH 4 strong>80 / (J560) CH 4 weak>80 / (J552) CO 2 strong>75 / (J546) CO 2 weak>75 / (J544) NO weak>75 / (J542) NO strong>75 / (J547)50.4 In-band is wavelengths between the  half-power points Total response includes all preceding optical elements & detector response