Calibration of Microwave Radiometer
Geoscience and Remote Sensing Society
IGARSS 2010 Honolulu, Hawaii Friday, July 30
CALIBRATION OF MICROWAVE RADIOMETERS: AN OVERVIEW Andreas Colliander Jet Propulsion Laboratory, California Institute of Technology [email protected] Darren McKague U. of Michigan [email protected] This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
Geoscience and Remote Sensing Society
Outline •
Introduction to IFT MRWG – Instrumentation and Future Technologies Technical Committee (IFT) Overview – Microwave Radiometer Working Group (MRWG) Introduction
•
Microwave radiometer calibration – – – – – – –
Definition of calibration Calibration requirements and budget Brightness temperature calibrations Fully polarimetric calibration Synthetic aperture interferometer calibration Natural targets and inter-calibration Future outlook
This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
2
Geoscience and Remote Sensing Society
Microwave Radiometer Working Group
This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
3
Geoscience and Remote Sensing Society
What is the IFT? •
Instrumentation and Future Technologies (IFT) is technical committee of the IEEE Geoscience and Remote Sensing Society (GRSS)
•
Vision: “To foster international cooperation in advancing the state-of-the-art in geoscience remote sensing instrumentation and technologies that improve knowledge for the betterment of society and the global environment”
•
Mission: – To facilitate, engage and coordinate GRSS members and the communities-at-large to: • Assess the current state-of-the-art in remote sensing instruments and technology • Identify new instrument concepts and relevant technology trends • Recognize enabling technologies for future instruments
– To promote and provide insight to institutions and industry on remote sensing instrument and technology development
•
Co-Chairs: – Eastwood Im, JPL – Martin Suess, ESA ESTEC
•
Senior Advisors: – Mark Drinkwater, ESA ESTEC – George Komar, NASA ESTO
This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
4
Geoscience and Remote Sensing Society
Microwave Radiometer Working Group (MRWG) •
Address issues related to passive remote sensing in the microwave, millimeter wave and sub-millimeter wave – Covers all aspects of area including: • Trends in instrumentation, new instruments concepts, new calibration concepts • Specific technology challenges • New technologies, scientific and commercial applications (technology push and market pull)
– Provide forum for discussion of relevant topics for: • Discussion amongst experts in field • Highlighting key developments and issues for decision makers in general community
– Format of interaction: • Web: http://www.grss-ieee.org/community/technical-committees/instrumentationand-future-technologies/ – Download MRWG content – Discussion forum / Wiki – Advertise for future activities
• White papers • Conference sessions – Previously: MicroRad10 special session on Microwave Radiometer Technology This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
5
Geoscience and Remote Sensing Society
Calibration of Microwave Radiometer
This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
6
Geoscience and Remote Sensing Society
Definition of Calibration
•
“A set of operations that establish, under specified conditions, the relationship between sets of values of quantities indicated by a measuring instrument or measuring system and the corresponding values realized by standards.”
•
International vocabulary of metrology — Basic and general concepts and associated terms (VIM), Joint Committee for Guides in Metrology JCGM (includes ISO), 2008 “Recommended Terminology for Microwave Radiometry”, J. Randa et al., National Institute of Standards and Technology Technical Note 1551, August 2008.
•
IGARSS’10 sessions • • • •
TUP1.PI: “Microwave Radiometer Calibration and Advanced Instrument Design” FR1.L07: “Microwave Radiometer Calibration I” FR2.L07: “Microwave Radiometer Calibration II” FR2.L08: “Calibration and Performance Evaluation of Advanced Passive Microwave Instruments”
This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
7
Geoscience and Remote Sensing Society
Calibration Requirements and Budget • •
To set the calibration requirements for a radiometer the entire mission system needs to be analyzed The analysis usually follows subsequent general philosophy: 1. 2. 3. 4.
•
•
Accuracy requirement for the retrieved parameter Geophysical retrieval algorithms Required instrument performance Calibration approach with calibration budget
The calibration budget details the uncertainty components of the calibration and together with instrument performance constitute the measurement error budget Therefore, calibration essential part of the radiometer measurement; new instruments and measurement concept continuously call for new calibration techniques and methodologies
IGARSS’10 • •
TUP1.PI.4: Miao Tian et al., “Optimal Calibration of Radiometers Using System Identification Techniques” FR2.L07.3: J. Bobak et al., “Error Budgeting for Radiometer Thermal Vacuum Test”
This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
8
Geoscience and Remote Sensing Society
Basic Radiometer Calibration Philosophy
•
•
•
Traditionally microwave radiometers are calibrated using two known targets and assuming (close to) linear response Calibration targets ideally have brightness temperatures at the extremes of the measurement range Implementation of the targets depends on wavelength, beam width and antenna aperture (and deployment constraints)
r
Linearity assumption
rhot
Brightness temperatures of hot and cold loads
rcold
Tcold
Thot
This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
T
9
Geoscience and Remote Sensing Society
Brightness Temperature Calibration (1/2) •
First choice in designing calibration is to trade-off between internal and external calibration – Internal: frequent and accurate, but does not include whole antenna and whole front-end – External: less frequent (due to constraints) and not necessarily as accurate, but end-to-end
•
External (antenna) targets:
AMSR-E
– Commonly pyramid shaped absorbers; in ambient, heated or cooled
PSR
IGARSS’10 • • •
FR2.L07.4: D. Walker et al., “Comparison of Microwave Black-Body Target Radiometric Measurements” TUP1.PI.1: I. Cherny et al., “In-Orbit Calibration of the “Meteor-M” Microwave Imager/Sounder” TUP1.PI.7: D. Gu et al., “Reflectivity Studies of Passive Microwave Calibration Targets and Absorptive Materials”
This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
10
Geoscience and Remote Sensing Society
Brightness Temperature Calibration (2/2) •
Internal targets: – Matched loads; in ambient, heated or cooled – Noise sources – Recently Active Cold Loads utilized
•
The non-linearity of the radiometer detector becomes an issue for very accurate measurements – Accurate measurement techniques demanding • Changing known input level vs. output level • Relative level change approaches most reliable
– In general, digitalization of the back-end has the potential to reduce this effect to negligible
IGARSS’10 •
FR1.L07.3: J. Piepmeier et al., “On-Board Calibration Noise Sources for the Global Precipitation Measurement (GPM) Microwave Imager (GMI)”
This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
11
Geoscience and Remote Sensing Society
Fully Polarimetric Calibration •
Calibration of 3rd and 4th Stokes parameter depends on the measurement technique: – In incoherent case traditional calibration of the different channels can be applied – For correlating case calibration of the phase detection is needed
•
AMSR-E
Challenges: – In incoherent case the alignment of the channels important for the error budget – Added complexity in implementing phase reference, external targets also more complex
IGARSS’10 •
J. Lahtinen, 2003
TUP1.PI.2: Y-H Kim et al., “Analysis and Verification of Calibration Methods for Fully Polarimetric W-Band Radiometer”
This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
12
Geoscience and Remote Sensing Society
Synthetic Aperture Interferometer Calibration •
•
Calibration of the synthetic aperture interferometric radiometers inherently (number of elements, processing requirements) very complex The issue can be divided in different components – Phase – Amplitude – Antenna patterns
• •
Phase and amplitude can utilize internal and external sources: same trade-off with inclusiveness Natural ‘flat’ targets extremely valuable
SMOS
IGARSS’10 • • • • •
TUP1.PH.7: D. Fenigstein et al., “Analysis of Anechoic Chamber Testing of the Hurricane Imaging Radiometer” FR1.L07.2: I. Corbella et al., “SMOS Results on SMOS-MIRAS Calibration and Imaging” FR1.L07.5: A. Tanner et al., “New Architecture for the Geostationary Synthetic Thinned Array Radiometer (GeoSTAR)” FR2.L07.2: K. Srinivasan et al., “Phased Array Radiometer Calibration Using a Radiated Noise Source” TU2.L10: Session on SMOS instrument performance
This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
13
Geoscience and Remote Sensing Society
Natural Targets and Inter-Calibration • • •
For completing external calibration on orbit many instruments require offplatform targets Additionally, terrestrial targets at the same geometry and ‘plane’ as the measurement object Several targets have been studied and identified; accuracy (homogeneity, stability, etc) depends on frequency, footprint – Oceans, Antarctica, deserts, rain forests, …
• • •
The cosmic microwave background offers a very accurate target (celestial objects an error source) Inter-calibration of instrument a valuable tool for tracking validity of calibration For scientific long time series inter-calibration is crucial!
IGARSS’10 •
TUP1.PI.3: D. McKague et al., “Development of a Microwave Radiometer Inter-Calibration Transfer Function for the GPM Constellation” • TUP1.PH.4: J. Dall’Amico et al., “Comparing Data of Two Airborne L-Band Radiometers with Different Spatial Resolution over a Heterogeneous Land Surface” • FR1.L10.4: G. Macelloni et al., “Ground-Based L-Band Emission Measurements at Dome-C Antarctica: DOMEX-2 A Contribution to SMOS Calibration” 14 This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
Geoscience and Remote Sensing Society
Future Outlook to Calibration Challenges • • • • • • •
New missions and new instruments present new challenges for radiometer calibration SMOS and calibration of interferometric radiometers will continue for a long time The achievement of the precision required for SSS measurement (SMOS, Aquarius) will be on the table for some time NASA SMAP introduces a large reflector which needs to be accounted for Development of new technologies at higher frequencies require new calibration approaches Interferometers at higher frequencies are not directly scalable from L-band (GeoSTAR) Inter-calibration will increase in importance in lock-step with desire for climate studies/use of constellations of radiometers
SMAP
IGARSS’10 •
TH3.L10.2: M. Spencer et al., “The Soil Moisture Active Passive (SMAP) Mission L-Band Radar/Radiometer Instrument”
This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
15
Geoscience and Remote Sensing Society
Conclusions •
IFT MRWG: We hope to grow the IFT: – Hope to make it a place relevant to community – Want it to be a place to: • Share thoughts on emerging technologies and issues • Highlight advances for dissemination of information within and beyond microwave radiometer community • Complain because we didn’t cover your topic in our most recent presentation
– We need you to get involved • Contact a MRWG lead Andreas Colliander: [email protected] Darren McKague: [email protected]
•
Calibration: Progress on all fronts on-going as demonstrated by the presentations of this conference!
This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
16
IGARSS 2010 Honolulu, Hawaii Friday, July 30
CALIBRATION OF MICROWAVE RADIOMETERS: AN OVERVIEW Andreas Colliander Jet Propulsion Laboratory, California Institute of Technology [email protected] Darren McKague U. of Michigan [email protected] This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
Geoscience and Remote Sensing Society
Outline •
Introduction to IFT MRWG – Instrumentation and Future Technologies Technical Committee (IFT) Overview – Microwave Radiometer Working Group (MRWG) Introduction
•
Microwave radiometer calibration – – – – – – –
Definition of calibration Calibration requirements and budget Brightness temperature calibrations Fully polarimetric calibration Synthetic aperture interferometer calibration Natural targets and inter-calibration Future outlook
This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
2
Geoscience and Remote Sensing Society
Microwave Radiometer Working Group
This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
3
Geoscience and Remote Sensing Society
What is the IFT? •
Instrumentation and Future Technologies (IFT) is technical committee of the IEEE Geoscience and Remote Sensing Society (GRSS)
•
Vision: “To foster international cooperation in advancing the state-of-the-art in geoscience remote sensing instrumentation and technologies that improve knowledge for the betterment of society and the global environment”
•
Mission: – To facilitate, engage and coordinate GRSS members and the communities-at-large to: • Assess the current state-of-the-art in remote sensing instruments and technology • Identify new instrument concepts and relevant technology trends • Recognize enabling technologies for future instruments
– To promote and provide insight to institutions and industry on remote sensing instrument and technology development
•
Co-Chairs: – Eastwood Im, JPL – Martin Suess, ESA ESTEC
•
Senior Advisors: – Mark Drinkwater, ESA ESTEC – George Komar, NASA ESTO
This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
4
Geoscience and Remote Sensing Society
Microwave Radiometer Working Group (MRWG) •
Address issues related to passive remote sensing in the microwave, millimeter wave and sub-millimeter wave – Covers all aspects of area including: • Trends in instrumentation, new instruments concepts, new calibration concepts • Specific technology challenges • New technologies, scientific and commercial applications (technology push and market pull)
– Provide forum for discussion of relevant topics for: • Discussion amongst experts in field • Highlighting key developments and issues for decision makers in general community
– Format of interaction: • Web: http://www.grss-ieee.org/community/technical-committees/instrumentationand-future-technologies/ – Download MRWG content – Discussion forum / Wiki – Advertise for future activities
• White papers • Conference sessions – Previously: MicroRad10 special session on Microwave Radiometer Technology This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
5
Geoscience and Remote Sensing Society
Calibration of Microwave Radiometer
This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
6
Geoscience and Remote Sensing Society
Definition of Calibration
•
“A set of operations that establish, under specified conditions, the relationship between sets of values of quantities indicated by a measuring instrument or measuring system and the corresponding values realized by standards.”
•
International vocabulary of metrology — Basic and general concepts and associated terms (VIM), Joint Committee for Guides in Metrology JCGM (includes ISO), 2008 “Recommended Terminology for Microwave Radiometry”, J. Randa et al., National Institute of Standards and Technology Technical Note 1551, August 2008.
•
IGARSS’10 sessions • • • •
TUP1.PI: “Microwave Radiometer Calibration and Advanced Instrument Design” FR1.L07: “Microwave Radiometer Calibration I” FR2.L07: “Microwave Radiometer Calibration II” FR2.L08: “Calibration and Performance Evaluation of Advanced Passive Microwave Instruments”
This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
7
Geoscience and Remote Sensing Society
Calibration Requirements and Budget • •
To set the calibration requirements for a radiometer the entire mission system needs to be analyzed The analysis usually follows subsequent general philosophy: 1. 2. 3. 4.
•
•
Accuracy requirement for the retrieved parameter Geophysical retrieval algorithms Required instrument performance Calibration approach with calibration budget
The calibration budget details the uncertainty components of the calibration and together with instrument performance constitute the measurement error budget Therefore, calibration essential part of the radiometer measurement; new instruments and measurement concept continuously call for new calibration techniques and methodologies
IGARSS’10 • •
TUP1.PI.4: Miao Tian et al., “Optimal Calibration of Radiometers Using System Identification Techniques” FR2.L07.3: J. Bobak et al., “Error Budgeting for Radiometer Thermal Vacuum Test”
This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
8
Geoscience and Remote Sensing Society
Basic Radiometer Calibration Philosophy
•
•
•
Traditionally microwave radiometers are calibrated using two known targets and assuming (close to) linear response Calibration targets ideally have brightness temperatures at the extremes of the measurement range Implementation of the targets depends on wavelength, beam width and antenna aperture (and deployment constraints)
r
Linearity assumption
rhot
Brightness temperatures of hot and cold loads
rcold
Tcold
Thot
This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
T
9
Geoscience and Remote Sensing Society
Brightness Temperature Calibration (1/2) •
First choice in designing calibration is to trade-off between internal and external calibration – Internal: frequent and accurate, but does not include whole antenna and whole front-end – External: less frequent (due to constraints) and not necessarily as accurate, but end-to-end
•
External (antenna) targets:
AMSR-E
– Commonly pyramid shaped absorbers; in ambient, heated or cooled
PSR
IGARSS’10 • • •
FR2.L07.4: D. Walker et al., “Comparison of Microwave Black-Body Target Radiometric Measurements” TUP1.PI.1: I. Cherny et al., “In-Orbit Calibration of the “Meteor-M” Microwave Imager/Sounder” TUP1.PI.7: D. Gu et al., “Reflectivity Studies of Passive Microwave Calibration Targets and Absorptive Materials”
This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
10
Geoscience and Remote Sensing Society
Brightness Temperature Calibration (2/2) •
Internal targets: – Matched loads; in ambient, heated or cooled – Noise sources – Recently Active Cold Loads utilized
•
The non-linearity of the radiometer detector becomes an issue for very accurate measurements – Accurate measurement techniques demanding • Changing known input level vs. output level • Relative level change approaches most reliable
– In general, digitalization of the back-end has the potential to reduce this effect to negligible
IGARSS’10 •
FR1.L07.3: J. Piepmeier et al., “On-Board Calibration Noise Sources for the Global Precipitation Measurement (GPM) Microwave Imager (GMI)”
This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
11
Geoscience and Remote Sensing Society
Fully Polarimetric Calibration •
Calibration of 3rd and 4th Stokes parameter depends on the measurement technique: – In incoherent case traditional calibration of the different channels can be applied – For correlating case calibration of the phase detection is needed
•
AMSR-E
Challenges: – In incoherent case the alignment of the channels important for the error budget – Added complexity in implementing phase reference, external targets also more complex
IGARSS’10 •
J. Lahtinen, 2003
TUP1.PI.2: Y-H Kim et al., “Analysis and Verification of Calibration Methods for Fully Polarimetric W-Band Radiometer”
This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
12
Geoscience and Remote Sensing Society
Synthetic Aperture Interferometer Calibration •
•
Calibration of the synthetic aperture interferometric radiometers inherently (number of elements, processing requirements) very complex The issue can be divided in different components – Phase – Amplitude – Antenna patterns
• •
Phase and amplitude can utilize internal and external sources: same trade-off with inclusiveness Natural ‘flat’ targets extremely valuable
SMOS
IGARSS’10 • • • • •
TUP1.PH.7: D. Fenigstein et al., “Analysis of Anechoic Chamber Testing of the Hurricane Imaging Radiometer” FR1.L07.2: I. Corbella et al., “SMOS Results on SMOS-MIRAS Calibration and Imaging” FR1.L07.5: A. Tanner et al., “New Architecture for the Geostationary Synthetic Thinned Array Radiometer (GeoSTAR)” FR2.L07.2: K. Srinivasan et al., “Phased Array Radiometer Calibration Using a Radiated Noise Source” TU2.L10: Session on SMOS instrument performance
This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
13
Geoscience and Remote Sensing Society
Natural Targets and Inter-Calibration • • •
For completing external calibration on orbit many instruments require offplatform targets Additionally, terrestrial targets at the same geometry and ‘plane’ as the measurement object Several targets have been studied and identified; accuracy (homogeneity, stability, etc) depends on frequency, footprint – Oceans, Antarctica, deserts, rain forests, …
• • •
The cosmic microwave background offers a very accurate target (celestial objects an error source) Inter-calibration of instrument a valuable tool for tracking validity of calibration For scientific long time series inter-calibration is crucial!
IGARSS’10 •
TUP1.PI.3: D. McKague et al., “Development of a Microwave Radiometer Inter-Calibration Transfer Function for the GPM Constellation” • TUP1.PH.4: J. Dall’Amico et al., “Comparing Data of Two Airborne L-Band Radiometers with Different Spatial Resolution over a Heterogeneous Land Surface” • FR1.L10.4: G. Macelloni et al., “Ground-Based L-Band Emission Measurements at Dome-C Antarctica: DOMEX-2 A Contribution to SMOS Calibration” 14 This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
Geoscience and Remote Sensing Society
Future Outlook to Calibration Challenges • • • • • • •
New missions and new instruments present new challenges for radiometer calibration SMOS and calibration of interferometric radiometers will continue for a long time The achievement of the precision required for SSS measurement (SMOS, Aquarius) will be on the table for some time NASA SMAP introduces a large reflector which needs to be accounted for Development of new technologies at higher frequencies require new calibration approaches Interferometers at higher frequencies are not directly scalable from L-band (GeoSTAR) Inter-calibration will increase in importance in lock-step with desire for climate studies/use of constellations of radiometers
SMAP
IGARSS’10 •
TH3.L10.2: M. Spencer et al., “The Soil Moisture Active Passive (SMAP) Mission L-Band Radar/Radiometer Instrument”
This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
15
Geoscience and Remote Sensing Society
Conclusions •
IFT MRWG: We hope to grow the IFT: – Hope to make it a place relevant to community – Want it to be a place to: • Share thoughts on emerging technologies and issues • Highlight advances for dissemination of information within and beyond microwave radiometer community • Complain because we didn’t cover your topic in our most recent presentation
– We need you to get involved • Contact a MRWG lead Andreas Colliander: [email protected] Darren McKague: [email protected]
•
Calibration: Progress on all fronts on-going as demonstrated by the presentations of this conference!
This presentation was prepared at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
16
