Transcript PowerPoint

TEMPO Instrument Update
Dennis Nicks, TEMPO PM
May 21-22, 2014
(303) 939-4467
[email protected]
TEMPO Instrument Status
 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
 At NASA KDP-B Instrument cost risk is perceived to be too high
• Ball, LaRC, and SAO worked closely to evaluate current instrument
performance and science performance
• SAO and LaRC 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 LaRC/SAO on
definitions and resolution
 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
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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
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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).
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SNR
 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
 TEMPO design has more optical elements
• Polarization wave plate and corrector lens in front of FPA
 New TEMPO SNR estimates assume “as manufactured” grating efficiency of 55%
(was 60%) and mirror reflectivity curves – based on GeoTASO
• 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 LaRC 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
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Original TEMPO Requirements:
Total System Optical Throughput
 The margined curves (red) indicate that no system throughput will meet the SNR requirement with
20% margin and the saturation requirement with 10% margin
 Having a gap between curves of less than 10% translates to coating tolerances that are likely not
achievable
5/21/2014
Dark Current
 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
 After discussions – the Dark Current requirement has been dropped for wavelengths
below 300 nm.
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New SNR Requirements vs
Performance
 New SNR requirements are result of BATC/SAO/LaRC
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
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Spectral Stability Requirement
ISD 6.7.7
Spectral Stability
The instrument shall have a spectral stability better than 0.02nm (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 24hour 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 24hour time (midnight-midnight) period.
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Spectral Stability
 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
 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
 Change allows for smart instrument design / operational trades
with no impact to science
5/21/2014
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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
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Stray Light Status
 Design / Trade Studies
• Includes baffling design iteration
• Scatter from surface roughness/particulate contamination
• Waveplate angle of rotation
 Ghosting contributors
 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
 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
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System Stray Light Compliance
System Level
Requirement
< 2%
Goal Allocations
Wavelength
(nm)
303
400
497
Grating
Model
ZW_base
ZW_1
ZW_base
ZW_1
ZW_base
ZW_1
Optical Surface
Scatter/Ghosting
Grating
Scatter/Artifacts
< 0.75%
< 1.0%
A
B
C
Optical
Optical Surf. Grating SL
Ghosting 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
0.25
0.25
0.25
0.25
0.25
Model
Contingency** (%)
1.01
1.01
1.26
1.26
1.24
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
0.5 𝐴 + 𝐵 + 𝐷
2
+
𝐶𝑚𝑎𝑥 + 𝐶𝑚𝑖𝑛
2
2
Preliminary Results from F. Grochocki
Stray Light Summary
 Current estimates based on PSF show some areas of noncompliance
 Further discussions with Science Team at LaRC 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
 Ball / SAO / LaRC are working stray light requirement
interpretation
• Discussions are on-going regarding the wording of the stray light requirement
5/21/2014
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KTP Summary: Science Performance (1 of 3)
KTP
Reqt
Current Est
< 0.9% over mission
Not yet available
RAD Spectral Stability
< 0.1 nm (1-sigma) over 24
hrs
< 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
< 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
< 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
Long Term Radiometric
Drift
Bandwidth
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.
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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
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
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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
 Instrument design is maturing quickly
• Instrument is designed for high structural / thermal stability
• Instrument performance is based on “as-manufactured” optical
components based on GeoTASO experience
 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
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