TEMPO Instrument Update Dennis Nicks TEMPO PM May

TEMPO Instrument Update Dennis Nicks, TEMPO PM May 21 -22, 2014 (303) 939 -4467 dnicks@ball. com

TEMPO Instrument Status Ø Instrument design is maturing with PDR in July 2014 • Performance estimates have been updated based on design maturity • Updated operating parameters to optimize instrument performance Ø At NASA KDP-B Instrument cost risk is perceived to be too high • Ball, La. RC, and SAO worked closely to evaluate current instrument performance and science performance • SAO and La. RC are able to accept the current instrument performance with little impact to science • SNR, Spectral Stability, dark current • Issues remain with stray light – need to work with La. RC/SAO on definitions and resolution Ø Mission Level INR requirements have been allocated to subsystems • Instrument pointing performance has been rolled up into Mission Level INR – everything closes 5/21/2014 2

TEMPO Design Maturation Since Last Science Meeting Design Presented at 7/2013 Science Team Meeting 5/21/2014 Pre-PDR Design as of 5/2014 3

Detector Update 5/21/2014 4

TEMPO Parameter Evolution Parameter SRR Value PDR Baseline Notes Frame Integration Time 95. 83 ms 118 ms A longer frame integration time marginally improves SNR performance and gives flexibility for seasonable variations in lighting conditions. Image Frame Rate 10 Hz 8. 19 Hz Includes frame integration time and frame transfer time of 4. 17 ms. 10 Hz is the maximum frame rate. Image Frame Time 2. 70 s 2. 69 s Includes integration time, frame transfer time, and coadds. Number of Coadds 27 22 Number of coadds must adjust with integration time to meet the coverage time requirement. 114 µrad The measure of E/W overlap and the requirement has changed since SRR. New requirement will be 6µrad based on INRWG analysis presented by Benton Ellis on 4/30/2014. Scan Mirror Step Size Number of Scan Mirror Steps Coverage Time 5/21/2014 115 urad 1267 59. 14 min 1278 59. 39 min Number of scan mirror steps increased slightly due to the slightly smaller scan mirror step size. A more careful accounting of coverage time is now being done, courtesy of Roger Drake. Coverage time includes book keeping for flight software timing margin from the end of a scan to the beginning of a scan (10 seconds), scan mirror move time at the end and beginning of a scan (4. 75 s), scan mirror step/settle (50 ms), ICE commanding step/settle (50 ms). 5

SNR Ø Previous SNR model assumed aggressive mirror reflectivity and grating efficiencies • Dielectric coatings for mirrors allow for high performance over a broad spectral range • However they often increase spectral features and polarization Ø TEMPO design has more optical elements • Polarization wave plate and corrector lens in front of FPA Ø New TEMPO SNR estimates assume “as manufactured” grating efficiency of 55% (was 60%) and mirror reflectivity curves – based on Geo. TASO • Lower risk posture is highly desirable given the Earth Venture cost cap • Allows adequate design space between SNR requirement (minimum optical throughput) and saturation requirement (maximum optical throughput) • Worked with SAO and La. RC to assess impacts to science • Impact to primary chemical species is negligible • Secondary chemical species that have been removed can be added back when cost risk is less of a concern 5/21/2014 6

Original TEMPO Requirements: Total System Optical Throughput Ø The margined curves (red) indicate that no system throughput will meet the SNR requirement with 20% margin and the saturation requirement with 10% margin Ø Having a gap between curves of less than 10% translates to coating tolerances that are likely not achievable 5/21/2014

Dark Current Ø Dark Current requirement at 290 -300 nm affects the SNR requirement (need for higher optical throughput) • Dark current is within requirements for the rest of the spectral range Ø After discussions – the Dark Current requirement has been dropped for wavelengths below 300 nm. 5/21/2014 8

New SNR Requirements vs Performance Ø New SNR requirements are result of BATC/SAO/La. RC negotiations • • 5/21/2014 Utilizes the new operating parameters Allows for manufacturability of optical elements and coatings Uses new retrieval assumptions from SAO / Xiong Reduces instrument project cost risk 9

Spectral Stability Requirement ISD 6. 7. 7 Spectral Stability The instrument shall have a spectral stability better than 0. 02 nm (1 -sigma) for all data collected that mets the requirements in Section 6. 6. 1 and Section 6. 7. 1 over any 24 -hour time period New: ISD 6. 6. 7 Spectral Stability of Radiances versus Irradiances The Instrument shall have a spectral stability of radiances compared to irradiances of better than 0. 2 nm (1 -sigma) for all data collected that meet the requirements in Section 6. 6. 1 and Section 6. 7. 1 over any 24 -hour time (midnight-midnight) period. ISD 6. 6. 8 Spectral Stability of Radiances The Instrument shall have a spectral stability for radiances of better than 0. 1 nm (1 -sigma) for all data collected that meet the requirements in Section 6. 6. 1 and Section 6. 7. 1 over any 24 hour time (midnight-midnight) period. ISD 6. 6. 9 Spectral Stability of Irradiances The Instrument shall have a spectral stability for irradiances of better than 0. 1 nm (1 -sigma) for all data collected that meets the requirements in Section 6. 6. 1 and Section 6. 7. 1 over any 24 -hour time (midnight-midnight) period. 5/21/2014 10

Spectral Stability Ø The single Spectral Stability requirement over a 24 hour period was extremely challenging • The design already had a low-CTE structure, athermal optics and an active thermal design • Would require extremely precise thermal control over all solar geometries Ø Worked with science team to rephrase the requirement to allow for easier compliance while still meeting science requirements • Specify spectral stability for radiance measurements (Earth View), irradiance measurements (solar cal) and allowable shifts between radiance and irradiance Ø Change allows for smart instrument design / operational trades with no impact to science 5/21/2014 11

Stray Light Requirement ISD 6. 6. 7 Stray Light The Instrument shall have a stray light response less than 2% of the Instrument response over the spectral range of 290 to 740 nm for the hemispherical angle of incidence for the nominal radiances in Table 1. The definition of stray light is the ratio of the sum of contributions from sources (e. g. , scatter, ghosts from lenses, windows, and focal plane reflections) originating from outside the point source function being evaluated to the signal inside the point source image area of interest. For the purposes here, inside the point source image area is defined as a box on the focal plane 15 x 15 pixels centered on the point source. 5/21/2014 12

Stray Light Status Ø Design / Trade Studies • Includes baffling design iteration • Scatter from surface roughness/particulate contamination • Waveplate angle of rotation Ø Ghosting contributors Ø New analysis indicates that the largest stray light contributor for TEMPO is the grating • Used BRDF measurements of “as manufactured” grating • BRDS model fitting • Grating efficiency / orders Ø Requirement is worded as Point Spread Function (PSF) stray light • Less than 2% of the instrument response over the spectral range of 290 -740 nm 5/21/2014 13

System Stray Light Compliance System Level Requirement < 2% Goal Allocations Wavelength (nm) 303 400 497 Grating Model ZW_base ZW_1 Optical Surface Scatter/Ghosting Grating Scatter/Artifacts < 0. 75% < 1. 0% A B C Optical Ghosting Optical Surf. Grating SL SL (%) Scatter SL (%) 0. 05 0. 43 0. 75 0. 05 0. 43 1. 13 0. 25 0. 40 0. 95 0. 25 0. 40 1. 40 0. 07 0. 30 1. 00 0. 07 0. 30 1. 39 Mechanical Surface Scatter < 0. 25% D Mechanical Surf. SL* (%) 0. 25 Model Contingency** (%) 1. 01 1. 26 1. 24 Total (%) 1. 48 1. 87 1. 85 2. 30 1. 62 2. 01 Total w/Contingency (%) 2. 49 2. 87 3. 10 3. 56 2. 86 3. 25 * Stray light contributions from mechanical surfaces have not been analyzed – 0. 25% allocation is assumed ** Model contingency = 5/21/2014 Preliminary Results from F. Grochocki

Stray Light Summary Ø Current estimates based on PSF show some areas of noncompliance Ø Further discussions with Science Team at La. RC and SAO indicated that PSF interpretation may not be correct • 15 x 15 pixel box confuses the interpretation of the requirement and may be deleted • May be more correctly interpreted in a broadband sense, where measured stray light needs to be <2% of signal electrons • Most challenging at the 290 – 300 nm range where there is low signal Ø Ball / SAO / La. RC are working stray light requirement interpretation • Discussions are on-going regarding the wording of the stray light requirement 5/21/2014 15

KTP Summary: Science Performance (1 of 3) KTP Reqt Current Est Long Term Radiometric Drift < 0. 9% over mission Not yet available RAD Spectral Stability < 0. 1 nm (1 -sigma) over 24 hrs Preliminary analysis – to be verified by STOP analysis IRD Spectral Stability < 0. 1 nm (1 -sigma) over 24 hrs Preliminary analysis – to be verified by STOP analysis RAD-IRD Spectral Stability < 0. 2 nm (1 -sigma) over 24 hrs Preliminary analysis – to be verified by STOP analysis < 0. 6 nm 0. 575 nm Based on expected slit width, slit width variability, and optical spot size specification < 6% ≤ 6% < 4% (1 -sigma) 2. 8% (1 -sigma) Radiance / 3. 2% (1 -sigma) Irradiance < 0. 5 (RMS) / Required SNR Not yet available Bandwidth Symmetry Radiometric Calibration Accuracy Relative Radiometric Uncertainty 5/21/2014 Notes Expect estimate next month with finalized pointing requirements Holding 9% reserve against requirement. Performance estimates are not yet available. Error budget holds 10% reserve against requirement. Performance estimates are not yet available. 16

KTP Summary: Science Performance (2 of 3) KTP Reqt Current Estimate FOR GNA, between 58° N and 18° N Compliant Allocated for worst-case orbit GSD ≤ 2. 22 km, ≤ 5. 15 km @ C. F. * 2. 21 km, 5. 11 km @ C. F. * Allocated for worst-case orbit 5% (3 -sigma) 5% > 0. 16 @ 0. 5 cyc/N-S GSD > 0. 3 @ 0. 5 cyc/E-W GSD 0. 19 @ 0. 5 cyc/N-S GSD 0. 36 @ 0. 5 cyc/E-W GSD Trend ≥ 2. 7 pixels / FWHM 2. 9 pixels / FWHM Consistent with nominal slit width and dispersion E/W Step Overlap MTF Spectral Sampling ISD Requirement update LPS 290 – 490 nm: < 5% (1 -sigma) 540 – 690 nm: < 20% (1 -sigma) SNR See SNR chart < 2% 2. 0 – 2. 9% Stray Light Notes 290 – 490 nm: < 4% (1 -sigma) Current design estimate 540 – 690 nm: < 15% (1 -sigma) See SNR chart Preliminary analysis results of PSF stray light modelling * C. F. = Chance Farm at Geodetic 36. 5° N, 100° W 5/21/2014

KTP Summary: Science Performance (3 of 3) SNR Wavelength SNR Requirement SNR Performance This Month 290 19. 6 24 Significant updates based 300 46. 1 56 on realistic optical and 305 161. 9 196 QE information. 310 377 456 320 1220 1473 330 2003 2419 340 2013 2431 350 1414 2299 420 836 1734 430 675 1401 450 733 1423 490 1176 1411 540 1109 1340 600 987 1193 650 898 1085 690 820 975 5/21/2014 Notes 450 nm is a new reqmt.

Summary Ø Instrument design is maturing quickly • Instrument is designed for high structural / thermal stability • Instrument performance is based on “as-manufactured” optical components based on Geo. TASO experience Ø Some changes to TEMPO performance requirements were required to reduce perceived cost risk • Worked closely with Science Team to relax requirements without severely impacting science • Science analysis / algorithm development descopes can be added back if cost risk allows • Low risk posture highly desirable at NASA HQ 5/21/2014 19