in-flight performance of the tansat atmospheric carbon ......atmospheric carbon dioxide grating...

IntroductionPerformance specifications of the TanSat ACGS

In-flight performance of the TanSat ACGSValidation of ACGS XCO2

Summary

In-Flight Performance of the TanSat Atmospheric Carbon DioxideGrating Spectrometer

Zhong-Dong Yang, Yan-Meng Bi, Qian Wang, Cheng-Bao Liu, Song-Yan Gu,Yu-Quan Zheng, Chao Lin, Zeng-Shan Yin, Long-Fei Tian

National Satellite Meteorological Center/CMA, CHINA15th International Workshop on Greenhouse Gas Measurements from

Space@Hokkaido University

Yang, Zhongdong etc.: [email protected]

National Satellite Meteorological Center, CMA

May 28, 2019

Yang, Zhongdong etc.: [email protected] In-Flight Performance of the TanSat Atmospheric Carbon Dioxide Grating Spectrometer



Summary

1 Introduction

2 Performance specifications of the TanSat ACGS

3 In-flight performance of the TanSat ACGSSpectroscopic performanceRadiometric performance

4 Validation of ACGS XCO2

5 Summary




Summary

Introduction

Figure: Physical photograph of the in-flight ACGS

1 TanSat is the first Chinese satellite missiondedicated to measuring the column-averagedCO2 dry-air mole fraction (XCO2 ); for thispurpose, TanSat is equipped with theAtmospheric Carbon Dioxide GratingSpectrometer (ACGS), a major spacebornegrating hyperspectral spectrometer suite.

2 TanSat was successfully launched into orbit fromJiuQuan Base in Gansu Province, China, on 22December 2016.

3 The ACGS has been providing globalmeasurements of CO2 and O2 spectral bands inreflected sunlight since early February 2017.




Summary

Introduction...

1 The ACGS measurements are calibrated and geolocated to produce level 1 (L1)products that are analyzed to retrieve spatially resolved estimates of XCO2 .

2 It is important that the radiometric and spectroscopic accuracies of the ACGS bemeticulously validated.

3 These demanding applications represent the motivation for the characterization ofthe ACGS radiometric and spectroscopic accuracies provided in this presentation.

4 In addition to understanding the physical basis of the uncertainties in ACGSmeasurements, it should be possible to achieve even higher accuracies inspace-based atmospheric CO2 measurements in the near future.

5 Since TanSat was launched in 2016, a team of subject matter experts from thegovernment, academic, and industrial sectors has been engaged in in-flight TanSaton-orbit checks that include ACGS calibration and validation activities.Consequently, an on-orbit check was completed in September 2017.




Summary

Performance specifications of the TanSat ACGS

ItemBand

O2A WCO2 SCO2

Spectral Range (nm) 758 - 778 1594 - 1624 2042 - 2082Spectral Resolution (nm) 0.033 - 0.047 0.120 - 0.142 0.160 - 0.182Spectral Resolving (λ/∆λ) ∼19000 ∼12800 ∼12250Spectral Sampling Per FWHM > 2Dynamic Range(ph/sec/m2/sr/um)

SNR=1 a©1.2 × 1017 ∼1.4 × 1021

SNR=1 a©5.7 × 1016 ∼4.9 × 1020

SNR=1 a©6.0 ×1016 ∼ 1.6×20

SNR @ (ph/sec/m2/sr/um) 360 a©5.8 × 1019 250 a©2.1 × 1019 180 a©1.1 × 1019Abs/Rel Calibration Error(%)



Summary

Spectroscopic performanceRadiometric performance

In-flight performance of the TanSat ACGS

1 The in-flight performance and absolute accuracy of any remote sensing satelliteinstrument are based on the optimal design of the optics, electricity andthermotics systems, ground laboratory calibration, and in-flight refinement of thecalibration parameters.

2 The performance of the ACGS was carefully characterized and calibrated twiceprior to launch, and the results met the mission requirements [?].

3 The ACGS has performed as expected on orbit. During the first month followingits launch in 2016, the spacecraft team completed a functional check of theplatform and instruments.




Summary


Spectroscopic performance

1 During the flight of TanSat, we used the available Fraunhofer lines of the solarspectrum acquired during solar calibration observations of the ACGS aftercorrecting for the Doppler effect and performed a comparison with the moreprecise solar spectra database used by OCO-2 as references to validate thespectral accuracy of the centroid wavelength.

2 These figures illustrate remarkable consistencies among the footprints andagreements with the reference spectrum. The spectral calibration accuracy of theO2 A-band is 0.19 pm, that of the WCO2 band is 0.27 pm, and that of the SCO2band is 4.75 pm, all of which meet the 0.05 FWHM requirement. Thespectroscopic performance of the ACGS therefore surpasses mission requirementswith a margin.




Summary


Spectroscopic performance of the ACGS O2 A-band

758 760 762 764 766 768 770 7721.8

2.0

2.2

2.4

2.6

2.8

3.0(P

h/S/m2/sr/um)

1e20 Solar Diffuser Measurement of ACGS O2 A band Radiance

758 760 762 764 766 768 770 7721.8

2.0

2.2

2.4

2.6

2.8

3.0

(Ph/S/m2/sr/um)

1e20 Toon O2 A band Solar Radiance

758 760 762 764 766 768 770 772(nm)

−1.00

−0.75

−0.50

−0.25

0.00

0.25

0.50

0.75

1.00

Diff. (Ph

/S/m

2/sr/um)

1e19 Difference between ACGS and Toon spectrum radiance of O2 A band

FP1 FP2 FP3 FP4 FP5 FP6 FP7 FP8 FP9Yang, Zhongdong etc.: [email protected] In-Flight Performance of the TanSat Atmospheric Carbon Dioxide Grating Spectrometer



Summary


Spectroscopic performance of the ACGS WCO2 band

1595 1600 1605 1610 1615 16201.1

1.2

1.3

1.4

1.5

1.6

(Ph/S/m2/sr/um)

1e20 Solar Diffuser Measurement of ACGS WCO2 band Radiance

1595 1600 1605 1610 1615 1620

1.2

1.3

1.4

1.5

(Ph/S/m2/sr/um)

1e20 Toon WCO2 band Solar Radiance

1595 1600 1605 1610 1615 1620(nm)

−1.00

−0.75

−0.50

−0.25

0.00

0.25

0.50

0.75

1.00

Diff. (Ph

/S/m

2/sr/um)

1e19 Difference between ACGS and Toon spectrum radiance of WCO2 band




Summary


Spectroscopic performance of the ACGS SCO2 band

2045 2050 2055 2060 2065 2070 2075 2080

7.8

8.0

8.2

8.4

8.6

8.8

9.0

9.2

9.4

(Ph/S/m2/sr/um)

1e19 Solar Diffuser Measurement of ACGS SCO2 band Radiance

2045 2050 2055 2060 2065 2070 2075 2080

7.8

8.0

8.2

8.4

8.6

8.8

9.0

9.2

(Ph/S/m2/sr/um)

1e19 Toon SCO2 band Solar Radiance

2045 2050 2055 2060 2065 2070 2075 2080(nm)

−3

−2

−1

0

1

2

3

Diff. (Ph

/S/m

2/sr/um)

1e18 Difference between ACGS and Toon spectrum radiance of SCO2 band




Summary


Dark current

1 Dark current constitutes the response of an instrument detector when it is notactively being irradiated, It is the baseline of instrument radiometric response.

2 For the HgCdTe detectors of the WCO2 and SCO2 bands of the ACGS, theresponse component is sensitive to tiny changes in the ambient temperature,although the temperature is controlled to within 0.3 K in-flight, and thus, it mustbe corrected routinely on orbit.

3 Preliminary dark current responses as a function of the ambient temperature wereestablished for the two CO2 bands during the thermal-vacuum (TVAC) testing ofthe ACGS [Yang2018].

4 The response models of each channel in the two CO2 bands were rebuilt usingin-flight data measured in real time during the first phase of orbital checkoutthrough a few days of continuous full-orbit, in-flight dark current response testing.

5 These models have been used in the preprocessing algorithm of the ACGS L1products, and the performance has been validated in our XCO2 retrievalprocessing. After the corrections used in these models, the dark current error wasbelow 5 counts in the two CO2 bands of the ACGS.




Summary


Dark current model of WCO2(left) and SCO2(right) band




Summary


SNR and gain coefficient

1 The SNR is a measurement that compares the level of desired signal to the levelof background noise, that is, the SNR measures the ratio between an arbitrarysignal level and noise.

2 Measuring the SNR requires the selection of a reference signal source. In theprelaunch calibration of the ACGS, we used a National Institute of Standards andTechnology (NIST)-traceable integrating sphere as the reference signal source tocharacterize the SNR successfully[Yang2018].

3 In flight, we used measurements of the calibration lamp devices and solar diffuserto evaluate the SNR of the ACGS. In our work, the SNR is defined as the ratio ofthe mean to the standard deviation of a measured signal.




Summary


In-flight performance stability of O2 A-band(left: from calibration lamp,right: from solar diffuser)

1.05

1.06

1.07

1.08

1.09

Mea

n(Ph

/S/m

2/sr

/um

)

1e19 Mean Value of O2A from Lamp

FP1 FP2 FP3 FP4 FP5 FP6 FP7 FP8 FP9

1

2

3

NEdR

(Ph/

S/m

2/sr

/um

)

1e17 Noise of O2A from Lamp


201702

10

201703

10

201704

10

201705

10

201706

10

201707

10

201708

10

201709

10

201710

11

201711

10

201712

10

201801

10

201802

11

201803

10

201804

10

201805

11

201806

10

200

400

600

SNR

SNR of O2A from Lamp

2.95

3.00

3.05

3.10

3.15

3.20

Mea

n(Ph

/S/m

2/sr

/um

)

1e20 Mean Value of O2A from Solar Diffuser


1

2

3

4

NEdR

(Ph/

S/m

2/sr

/um

)

1e17 Noise of O2A from Solar Diffuser


201702

10

201703

10

201704

10

201705

10

201706

10

201707

10

201708

10

201709

10

201710

11

201711

10

201712

10

201801

10

201802

11

201803

10

201804

10

201805

11

201806

10

1000

2000

3000

4000

SNR

SNR of O2A from Solar Diffuser




Summary


In-flight performance stability of WCO2 band(left: from calibrationlamp;,right: from solar diffuser)

3.0

3.1

3.2

3.3

Mea

n(Ph

/S/m

2/sr

/um

)

1e19 Mean Value of WCO2 from Lamp


1

2

3

NEdR

(Ph/

S/m

2/sr

/um

)

1e17 Noise of WCO2 from Lamp


201702

10

201703

10

201704

10

201705

10

201706

10

201707

10

201708

10

201709

10

201710

11

201711

10

201712

10

201801

10

201802

11

201803

10

201804

10

201805

11

201806

10200

400

600

800

1000

SNR

SNR of WCO2 from Lamp

1.500

1.525

1.550

1.575

1.600

1.625

Mea

n(Ph

/S/m

2/sr

/um

)

1e20 Mean Value of WCO2 from Solar Diffuser


1

2

3

4

NEdR

(Ph/

S/m

2/sr

/um

)

1e17 Noise of WCO2 from Solar Diffuser


201702

10

201703

10

201704

10

201705

10

201706

10

201707

10

201708

10

201709

10

201710

11

201711

10

201712

10

201801

10

201802

11

201803

10

201804

10

201805

11

201806

101000

2000

3000

4000

5000

6000

SNR

SNR of WCO2 from Solar Diffuser




Summary


In-flight performance stability of SCO2 band(left: from calibration lamp,right: from solar diffuser)

2.3

2.4

2.5

2.6

Mea

n(Ph

/S/m

2/sr

/um

)

1e19 Mean Value of SCO2 from Lamp


1

2

3

NEdR

(Ph/

S/m

2/sr

/um

)

1e17 Noise of SCO2 from Lamp


201702

10

201703

10

201704

10

201705

10

201706

10

201707

10

201708

10

201709

10

201710

11

201711

10

201712

10

201801

10

201802

11

201803

10

201804

10

201805

11

201806

10

200

400

600

800

SNR

SNR of SCO2 from Lamp

8.6

8.8

9.0

9.2

9.4

Mea

n(Ph

/S/m

2/sr

/um

)

1e19 Mean Value of SCO2 from Solar Diffuser


1

2

3

4

NEdR

(Ph/

S/m

2/sr

/um

)

1e17 Noise of SCO2 from Solar Diffuser


20170210201703

10201704

10201705

10201706

10201707

10201708

10201709

10201710

11201711

10201712

10201801

10201802

11201803

10201804

10201805

11201806

10

1000

2000

3000

4000

SNR

SNR of SCO2 from Solar Diffuser




Summary


Normalized to AU Radiance of ACGS Solar Diffuser Measurement

0 2 4 6 8 10 12 14 162.95

3.00

3.05

3.10

3.15

3.20

Mea

n(Ph

/S/m

2/sr

/um

)

1e20 Solar Diffuser Measurement of O2 A band Normalized to AU Radiance


0 2 4 6 8 10 12 14 161.50

1.52

1.54

1.56

1.58

1.60

1.62

Mea

n(Ph

/S/m

2/sr

/um

)

1e20 Solar Diffuser Measurement of WCO2 band Normalized to AU Radiance


20170210

20170310

20170410

20170510

20170610

20170710

20170810

20170910

20171011

20171110

20171210

20180110

20180211

20180310

20180410

20180511

20180610

8.58.68.78.88.99.09.19.29.39.4

Mea

n(Ph

/S/m

2/sr

/um

)

1e19 Solar Diffuser Measurement of SCO2 band Normalized to AU Radiance




Summary

Validation of ACGS XCO2 Using Target Observation Model of TanSat

39.3°N

39.8°N

40.3°N

40.8°N

115.52°E 116.02°E 116.52°E 117.02°E

FY3D/MERSI-II: 20180531_0450 20180531_0455TanSat/ACGS : 20180531_0514 20180531_0521

SampleNum.=7761μ=406.2200σ=0.0446Num3σ/Num.=0.9937

0.0 0.03 0.05 0.08

406.10

406.15

406.20

406.25

406.30

XCO2(ppm

)

39.3°N

39.8°N

40.3°N

40.8°N

115.52°E 116.02°E 116.52°E 117.02°E

FY3D/MERSI-II: 20180620_0510 20180620_0515TanSat/ACGS : 20180620_0501 20180620_0508

SampleNum.=5960μ=404.0303σ=0.0660Num3σ/Num.=0.9854

0.0 0.08 0.17403.8

403.9

404.0

404.1

404.2

XCO2(ppm

)




Summary

Validation to ACGS XCO2(3σ) at Beijing Ground Station in 2018

Date FTS125HR (ppm) ACGS(ppm) Precision(ppm) Bias(ppm) Samples(n) Confidence

Mar. 08 407.71 408.00 1.15 -0.29 9074 95.54%

Apr. 16 409.87 408.62 2.22 +1.25 11250 98.74%

May 04 408.74 409.49 0.91 -0.75 10843 96.27%

May 31 407.09 405.78 2.88 -1.31 11602 99.81%

June 20 403.30 404.89 1.76 -1.59 10912 97.13%

Aug. 20 402.32 400.00 0.11 +2.32 11597 98.05%

Nov. 21 408.01 408.05 1.13 -0.04 10242 99.52%

Dec. 04 408.15 409.52 0.53 -1.38 10174 96.64%

Average / / /

Validation to ACGS XCO2 using FTS 125HR Measurement




Summary

Summary

1 In this study, we evaluated the in-flight spectroscopic and radiometric performanceof the ACGS using measured data from solar diffuser and halogen tungsten lampdevices.

2 In-flight calibration and validation work of the ACGS has achieved success, andthe radiometric and spectral performance specifications have met the missionrequirements.

3 The Ver 2.0 L1 products were released to the world on 1 February 2018(http://satellite.nsmc.org.cn/portalsite/default.aspx).

4 The estimated absolute spectral calibration uncertainty is less than one-tenth ofthe spectral resolution, and the estimated radiometric uncertainty is less than 5%in the O2 A-band, WCO2 and SCO2 band.

5 In February 2018, the NSMC TanSat team completed the research and softwaredevelopment phase of a full physical inversion algorithm for XCO2 . The softwarehas since been put into operation, the initial accuracy verification has beencompleted, and large-scale batch processing and validation efforts are underway.




Summary

THANK YOU FOR YOUR ATTENTION!

THANK YOU FOR YOUR ATTENTION!


IntroductionPerformance specifications of the TanSat ACGSIn-flight performance of the TanSat ACGSSpectroscopic performanceRadiometric performance

Validation of ACGS XCO2Summary

in-flight performance of the tansat atmospheric carbon ......atmospheric carbon dioxide grating...

Documents