The Global Earth Observation System of Systems ... - PMOD/WRC

The Global Earth Observation System of 

Systems (GEOSS) and Metrological Support 

for Measuring 

Radiometric 

Properties 

of Objects 

of Observations 

V. Krutikov - Federal Agency on Technical Regulating and Metrology, Russia; 

V. Sapritsky, B. Khlevnoy, B. Lisiansky, S. Morozova, S. Ogarev, A. Panfilov, 

M. Sakharov, M. Samoylov – All-Russian Institute for Opto-Physical Measurements 

(VNIIOFI), Russia; 

G. Bingham, T. Humpherys, A. Thurgood - Space Dynamics Laboratory, USA; 

V. Privalsky - Vega International, Inc, USA 

NEWRAD’2005 

1

GEOSS and Metrological Support for MeasuringM 

Radiometric 

Properties of Objects 


This report deals with the future of radiometric 

calibration of space-borne electro-optical optical sensors 

as applied to the Global Earth Observation System 

of Systems (GEOSS) 

The following topics will be briefly discussed: 

• General information about GEOSS 

• Formulation of the problem of metrological assurance for the GEOSS 

measurements 

• Potential solutions for the spectral regions from 0.2 µm m to 3 µm m and 

from 3 µm to 15 µm 

• An in-flight monitoring suggestion 

• Conclusions 

2


Radiometric 



The Global Earth Observation System of Systems 

(GEOSS) Milestones 

• First Earth Observation Summit, Washington, D.C., August 31, 2003 

• Declared the need for an information system that would help to make m 

well- 

based decisions in the interests of the entire mankind. 

• A decision is made to develop a 10-yr GEOSS plan. 

• A Group for Earth Observation (GEO) is subsequently established. 

• Second Earth Observation Summit, Tokyo, April 25, 2004 

• A framework is approved that describes major GEOSS 10-yr plan ideas. 

• Third Earth Observation Summit , Brussels, February 16, 2005 

• The 10-yr GEOSS plan approved with a possibility for future corrections. 

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Radiometric 



GEOSS Application Areas in accordance with 

the internationally approved 

10-year Implementation Plan 

• Reducing loss of life and property from natural and human-induced 

disasters. 

• Understanding environmental factors affecting human health and 

well-being. 

• Improving management of energy resources. 

• Understanding, assessing, predicting, mitigating, and adapting to t 

climate variability and change. 

• Improving water resource management through better 

understanding of the water cycle. 

• Improving weather information, forecasting, and warning. 

• Improving the management and protection of terrestrial, coastal, 

and marine ecosystems. 

• Supporting sustainable agriculture and combating desertification. 

• Understanding, monitoring, and conserving biodiversity. 

4


Radiometric 



GOESS Structure: 

GEOSS will be built as a “system of systems” 

• Will embrace both the existing and future Earth 

observation systems for jointly using the acquired 

data. 

• Global observation strategy will include 

complimentary use of space-borne, air-borne, and 

ground-based observation systems. 

Major functional parts of GEOSS: 

• Components of observation facilities 

• Coordinated data processing systems 

• Archiving 

• Cataloging 

• Dissemination systems for data, metadata, and final data 

products. 

5


Radiometric 



Coordinating Earth Observing Systems 

Vantage Points 

Capabilities 

Deployable Permanent 

Far- 

Space 

Near- 

Space 

Airborne 

Terrestrial 

L1/HEO/GEO 

TDRSS & 

Commercial 

Satellites 

LEO/MEO 

Commercial 

Satellites 

and Manned 

Spacecraft 

Aircraft/Balloon 

Event Tracking 

and Campaigns 

Forecasts & Predictions 

User 

Community 

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The 10-yr Plan GEOSS Idea 

7


Radiometric 



GEOSS Requirements 

• High quality of data 

• Global scale observations 

• No spatial or temporal gaps in the data 

• Accumulating real time data over decades 

8


Radiometric 



Formulation of the problem - 1 

Optical sensors present a major part of the GEOSS program. 

• Providing imaging data 

• Measurements of radiance, reflective properties, and radiation 

temperature of observation objects. 

Measurements can be trusted only if the instruments are metrologically 

robust. 

The task of the universal use of data acquired with the GEOSS 

subsystems can be solved only on the basis of common standards 

(data formats, geolocation, etc.). 

• For a number of applications such as climatology, meteorology, and a 

environmental monitoring, assuring the uniformity of radiometric 

measurements obtained by all subsystems and at an unusually high 

accuracy and stability levels is of extreme importance. 

• These exact requirements have not yet been properly reflected in the 

10-yr plan. 

• The solution of the problem requires joint efforts both in supporting this 

idea and in implementing it at the international level. 

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Within the wide area of GEOSS data application, the highest requirements for 

the long-term stability of the data and for the accuracy of optical sensors are 

imposed by climatology which needs time series extending over decades. 

Required accuracies and stabilities of satellite instruments 

No 

1 

2* 

3* 

4* 

5* 

6 

7 

8 

9 

Ozone 

Vegetation 

Surface albedo 

Ocean color 

Sea surface temperature 

Atmospheric temperature 

Water vapor 

Climate variable 

Total solar irradiance 

Cloud parameters 

* Requirements to radiance measurements 

Accuracy 

0.1 % 

1 % 

2 % 

5 % 

5 % 

0.1 K 

0.5 K 

1 K 

1 K 

[Satellite Instrument Calibration for Measuring Global Climate Change. C 

NISTIR 7047. 

US Department of Commerce. 2004. ] 

Stability 

(per decade) 

0.02 % 

0.1 % 

0.8 % 

1 % 

1 % 

0.01 K 

0.04 K 

0.03 K 

0.2 K 

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Radiometric 




Maximum Requirements 

Onboard 

instrumentation 

Spectral region, µm 

0.2 – 3 3 – 15 

Calibration 

systems 

(ground) 

accuracy 

1 % 0.1 K 

accuracy 

stability 

0.1 % per 

decade 

0.01 K per 

decade 

reproducibility 

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Radiometric 




The accuracy requirements can be met even today but we still 

cannot satisfy the requirements for the long-term stability of 

our instruments. Those requirements transformed into 

respective requirements for the national scale reproducibility 

are: 

Ground calibration 

Spectral region 0.2 – 3 µm ≤ 0.1 % 

Spectral region 3 - 15 µm ≤ 0.01 K 

As for the in-flight stability monitoring, the requirement is 

satisfied for the spectral s region 0.2 - 3 µm (see T.C. Stone, H.H. 

Kieffer. . Proc. CALCON 2005. Logan, Utah, 2005 ) 

Inside the spectral region 3 - 15 µm we need to ensure the 

stability within 0.01 K. 

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Radiometric 




The necessary conditions for the implementation of these 

requirements and for the assurance of uniformity of measurements 

include: 

•High-quality methodological basis, and 

•High-quality systems for both ground and in-flight radiometric calibration of 

the measuring devices. 

The methodological basis includes such components as: 

•Definitions of measurands and respective measurement units, 

•Methods and techniques of calibration, and 

•Estimation of the accuracy of measurement results during the calibration 

process. 

With regard to the ground calibration systems, we need: 

•To improve our calibration standards as well as methods and devices used 

to transfer the dimensions of radiometric quantities from standards to the 

instrument that is being calibrated 

•Better calibration installations and international comparisons of calibration 

standards. 

These efforts should result in universal, stable and accurate scales s 

of radiometric quantities, with a mandatory participation of respective 

national metrological institutions. 

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Radiometric 



SOLUTION 

We believe that a necessary condition for the solution of 

the above-formulated problem is the use of newly- 

developed ground calibration facilities: 

• Highly accurate blackbody sources on the basis of phase 

transitions of eutectic alloys and pure metals that 

possess very high reproducibility; such sources on 

eutectic alloys were first advanced by the National 

Institute of Metrology of Japan. 

• Improved calibration installations 

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Radiometric 



Eutectic alloys and pure metals to be used and their 

phase transition temperatures 

High-temperature 

Medium-temperature 

Low-temperature 

Substance 

Temperature, K 

Substance 


Substance 


HfC-C 

3458 

Cu 

1357.8 

In 

429.7485 

ZrC-C 

3154 

Au 

1337.3 

Ga 

302.9146 

TiC-C 

3034 

Ag 

1234.9 

GaZn 

298.5 

Re-C 

2748 

GaSn 

293.5 

Ir-C 

2563 

GaIn 

288.5 

This phenomenon ensures a high level of reproducibility 

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Radiometric 



Solution for the 0.2 µm – 3 µm m region 

Transferring the spectral radiance unit dimension 

Traditional approach 

Filament tungsten 

Primary 

standard 

incandescence lamps 

Reproducibility ~ 1 % 

Integrating 

sphere 

Imager 

Suggested approach 

Eutectic alloy fixed-point 

blackbodies 

Reproducibility ≤ 0.03 % 

Integrating 

sphere 

Imager 

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Radiometric 



Blackbody BB3200pg and a crucible with a eutectic 

placed inside a pyrographite radiator (VNIIOFI) 

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Radiometric 



Summary of measurements of the melting / freezing 

temperatures of eutectics (VNIIOFI data) 

Metal 

Purity 

T, , K 

Repeatability, σ 

Radiance, % 

650 nm 

Re-C 

0.99995 

0.04 – 0.09 

0.01 – 0.022 

TiC-C 

0.9998 

0.05 

0.012 

ZrC-C 

0.9994 

0.09 

0.02 

HfC-C 

0.999 

0.30 

0.06 

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Radiometric 



Solution for the 3 µm – 15 µm m region 

Fixed-point blackbodies 

Reproducibility ≤ 0.01 K 

Variabletemperature 

blackbodies 

Imager 

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Radiometric 



Ga fixed-point blackbody BB29gl (VNIIOFI) 

1 - Body; 

2 - Pt resistance thermometers; 

3 - Copper heat-exchanger 

exchanger; 

4 - Gallium in a Teflon case 8; 

5 - Heat-exchanger exchanger tube; 

6 - Copper cavity covered by the Chamglaze Z-306 

7 paint; 

9 - “O” ring; 

10 - Sylphon; 

11 - Aperture. 

Reproducibility: 0.2 mК 

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Radiometric 



Medium Background Facility (VNIIOFI) 

for VTBB and fixed-point BB comparison 

The Medium Background 

Facility (MBF) was 

constructed to provide 

the absolute radiometric 

calibration of blackbody 

sources of thermal 

radiation, to compare 

radiometric scales with 

predictions for the 

measured temperatures, 

and to serve as a highly 

stable transfer standard 

for calibration of 

blackbody sources under 

the medium vacuum 

conditions (10 - 4 Torr) 

and medium background 

environment (liquid 

nitrogen cooled shroud) 

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Radiometric 



SDL Calibration Chambers 

22


Radiometric 



Calibration Domains 

A complete calibration will address five responsivity domains: 

 

 

 

 

 

Radiometric responsivity 

• Radiance and irradiance 

• Response linearity and uniformity corrections 

• Nominal/outlying pixel identification 

• Transfer calibration to internal calibration units 

Spectral responsivity 

• Sensor-level relative spectral response (RSR) 

Spatial responsivity 

• Point response function, effective field of view, optical distortion, 

tion, 

and scatter 

Temporal 

• Short, medium, and long-term reproducibility, frequency response 

Polarization 

• Polarization sensitivity 

23


Radiometric 



Top Level SDL Calibrator Specifications 

 

 

 

 

 

 

 

Provide complete calibration in a single test configuration 

20K (He) or 100K (LN2) radiometric background 

Up to 17.5 inch exit pupil diameter 

Long focal length collimator to simulate small angular divergent sources 

(i.e. point sources) 

Short focal length collimator for measurements requiring sources with 

angular divergence of ~1° 

Sensor specific extended source measurements for radiance calibration 

ation 

Capability for in situ monitoring of 

 

radiance, irradiance, calibrator focus/image quality, spectral 

throughput, and polarization 

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Radiometric 



In-flight monitoring 

Spectral region 3 - 15 µm 

Stability 

≤ 0.01 K 

The practice of the remote sensing of the Earth shows that the 

traditional in-flight monitoring techniques do not assure the required 

long-term stability. 

Approaches to problem solution 

• Develop and use onboard sources based upon phase transition of 

substances. 

Studies are required to 

- select suitable substances, 

- determine their properties under the space environment 

- design onboard sources. 

• Develop a space-borne radiometric calibration facility 

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Radiometric 



Conclusions 

The only way to achieve the goal of combining individual 

observation systems into a single Global Earth Observation System 

of Systems is solving the problems formulated here through joint 

efforts of all participants of the program, with a mandatory 

participation of respective national metrological institutions. 

The approach to the solution is seen through the use of fixed-point 

blackbody sources and better (more “powerful”)) ground calibration 

installations. 

New approaches are required for the in-flight monitoring of our 

instruments within the spectral region form 3 µm to 15 µm (the 

phase-transition phenomenon). 

A unification of metrological support on the basis of approaches 

advanced here will help us obtain intercomparable high-quality data 

sets. 

26

Thank you 

27

The Global Earth Observation System of Systems ... - PMOD/WRC

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