Lessons Learned from CERES
2nd ESA EarthCARE Validation Workshop
25-28 May 2021 (online)
Kory PriestleyNASA Langley Research Center
ESA UNCLASSIFIED - For Official Use

Lessons Learned From CERES
Clouds and the Earth’s Radiant Energy System
Clouds and the Earth’s Radiant Energy System

Radiation Budget Science Project Supported Missions

CERES

LiberaESA UNCLASSIFIED - For Official Use

2nd ESA EarthCARE Validation Workshop | 25-28/05/2021 | Slide 2

Radiometric Performance Requirements
Clouds and the Earth’s Radiant Energy System

CERES is defined as a class ‘B’ Instrument5-year design LifetimeSpectralRegions

Reflected Solar

Emitted Thermal

Atmospheric
Window

Wavelengths

0.3 - 5.0 µm

5.0 - 200 µm

8 - 12 µm

Scene levels<100 w/m2-sr>100 w/m2-sr<100 w/m2-sr>100 w/m2-sr

All Levels

Accuracy
Requirements

0.8 w/m2-sr

1.0 %0.8 w/m2-sr

0.5 %0.3 w/m2-sr

SOW Stability
Requirements< 0.14%/yr< 0.1%/yr

ClimateStability Goals< 0.6 w/m2/dec< 0.03 %/yr

< 0.2 w/m2/dec< 0.02%/yr• Requirements for CERES are more stringent than ERBE’s by a factor of 2
• Requirements per Ohring et. al. are more stringent than CERES by a factor of 3-5

Calibrate, Calibrate, Calibrate….
Evolve Observational Strategies via FSW Modifications
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2nd ESA EarthCARE Validation Workshop | 25-28/05/2021 | Slide 3

Why is ERB Climate Quality
Calibration so difficult?
Clouds and the Earth’s Radiant Energy System
A question of time scales, experience and balancing accuracy
with providing data products to the community.
- Calibrated Radiances have been released on ~6 month centers- 6 months is just a blink of an eye when analyzing decadal trends…
Same time scale as phenomena which influence instrument response- Beta Angle- Solar Zenith Angle
CERES is a Thermal instrument- Earth Sun Distance- Solar Cycle- Orbital shifts- Instrument Operational modes (e.g. RAPS vs. Xtrack)
Design weaknesses and unanticipated failures in onboard calibration hardware- full spectral range of observations not covered by cal subsystems
Complicates separation of instrument ‘artifacts’ from natural variability.
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2nd ESA EarthCARE Validation Workshop | 25-28/05/2021 | Slide 4

Beta Angle Annual Cycle
Clouds and the Earth’s Radiant Energy System
Clouds and the Earth’s Radiant Energy System

TRMM -Terra-Aqua-NPP Solar Beta Angles; Mission

3280

30

60
40

26202422020-20

18Angle (TRMM)

Angle (Terra/Aqua/NPP)

28-40

16-60

1412-80050

100

150200

250

300

350

DOY
Terra Solar
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Aqua SolarNPP Solar

TRMM Solar
2nd ESA EarthCARE Validation Workshop | 25-28/05/2021 | Slide 5

Aqua/NPP Flight Cal Locations
Clouds and the Earth’s Radiant Energy System
Clouds and the Earth’s Radiant Energy System- Lunar Observations- Solar Calibrations- Internal Calibration Sequence
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2nd ESA EarthCARE Validation Workshop | 25-28/05/2021 | Slide 6

Solar Calibration Results
Clouds and the Earth’s Radiant Energy System
Terra/Aqua/NPP In-Flight Solar Calibration Results

8Sensor Response, Percentage Change765

FM1_SW

FM1_TL

FM2_SW

FM2_TL

FM3_SW

FM3_TL

FM4_SW

FM4_TL

FM5_SW

FM5_TL

Si02 overcoat on theCERES FM1-FM4 Solar
diffusers not appliedproperly, and continued tooxidize on orbit

43210-1-20

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246Mission Year

81012

2nd ESA EarthCARE Validation Workshop | 25-28/05/2021 | Slide 7

Spectral Coverage of Cal Sources
Clouds and the Earth’s Radiant Energy System
Clouds and the Earth’s Radiant Energy System

Make certain the spectral content of yourcal sources adequately represent thecontent of your science targets….

Spectral Response,
Normalized Radiance

1.0
0.8
0.6
0.4
0.2
0.0

0ESA UNCLASSIFIED - For Official Use

123Wavelength (micron)

40

123
Wavelength (micron)4

2nd ESA EarthCARE Validation Workshop | 25-28/05/2021 | Slide 8

Cal-Val Approach
Clouds and the Earth’s Radiant Energy System

Pre-Launch- Implement a rigorous & thorough ground calibration/characterization program- Cal/Val role must be prominent in original proposal and SOW- System level characterization is typically last test performed prior to delivery of
the instrument- Cost and schedule constraints typically drive programs at that point

Post-Launch- Implement a protocol of independent studies to characterize on-orbitperformance- Studies should cover all spectral, spatial and temporal scales as well as data
product levels- Continuous development of new validation studies

Data Product Release Strategy- Develop a logical and well understood approach to data release.
- Minimize the number of Editions/Versions of Data
- Utilize Data Quality Summaries for the community

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2nd ESA EarthCARE Validation Workshop | 25-28/05/2021 | Slide 9

CERES Flight Radiometric Validation Activities
Clouds and the Earth’s Radiant Energy System

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2nd ESA EarthCARE Validation Workshop | 25-28/05/2021 | Slide 10

Lessons Learned / Future Direction
Clouds and the Earth’s Radiant Energy System
Programmatic Implementation- Increase weighting/influence of Radiometric Performance in cost/schedule trades- Maintain positive/open relationship with hardware provider. Avoid ‘Us’ vs. ‘Them’ mentality.
- LaRC/NGST Team has proven track-record and experience
Ground Characterization Procedures- Re-verify traceability of calibration targets- Establish collaborations with NIST, other international agencies- Implement automated Data Acquisition System on Calibration Chamber
Operational Mode- Do not point optics in ‘forward’ looking direction- Strong Correlation to spectral darkening of SW channel optics
Onboard Calibration Hardware- Provide additional SW spectral characterization capability- Stringent measurement requirements demand SW spectral capabilities
Handling Procedures- Minimize possibility of contamination- Develop Inspection and cleaning procedures

ESA UNCLASSIFIED - For Official Use

2nd ESA EarthCARE Validation Workshop | 25-28/05/2021 | Slide 11

Lessons Learned
Clouds and the Earth’s Radiant Energy System
Clouds and the Earth’s Radiant Energy System•••••••••••ESA UNCLASSIFIED - For Official Use

Establish a calibration team early and hold regular reviews/TIMS
Understand that the Science team has Lifecycle responsibility
Part science, part engineering, a lot of socialization
Understand requirement traceability
Be adept at responding to change
Be robust to withstand unknowns/change
Keep it simple
Don’t be afraid to evolve with technology
Don’t let Process replace sound judgment
Engineer knows long before the statistician
The only thing that is for certain is that if you don’t try, you won’t get it

2nd ESA EarthCARE Validation Workshop | 25-28/05/2021 | Slide 12