ISO/TS 19159-4:2022

Geographic information - Calibration and validation of remote sensing imagery sensors and data - Part 4: Space-borne passive microwave radiometers

This document defines the calibration of space-borne passive microwave radiometers and the validation of the calibrated information.

Information géographique — Calibration et validation de capteurs de télédétection — Partie 4: Radiomètres spatiaux à micro-onde passive

General Information

• Status: Published
• Publication Date: 23-Nov-2022
• ICS: 35.240.70 - IT applications in science
• Technical Committee: ISO/TC 211 - Geographic information/Geomatics
• Drafting Committee: ISO/TC 211/WG 6 - Imagery
• Current Stage: 9020 - International Standard under periodical review
• Start Date: 15-Oct-2025
• Completion Date: 15-Oct-2025

Overview

ISO/TS 19159-4:2022 - Geographic information: Calibration and validation of remote sensing imagery sensors and data - Part 4 covers the calibration of space-borne passive microwave radiometers and the validation of the calibrated information. It is a technical specification from ISO/TC 211 that standardizes procedures, models and metadata needed to ensure traceable, repeatable calibration of microwave radiometers on satellites. The document focuses on sensor calibration and validation processes rather than end‑product data validation.

Key topics and technical requirements

• Scope and normative references: Defines the calibration domain for space‑borne passive microwave radiometers and references related parts of ISO/TS 19159 and ISO 19103.
• Terms and definitions: Standardized vocabulary for antenna pattern, antenna temperature (TA), brightness temperature (TB), blackbody loads, boresight, efficiency and related microwave radiometry concepts.
• Calibration model: A top‑level model for sensor calibration including geometric position, TA calibration, antenna pattern calibration and antenna sidelobe/main‑beam characteristics.
• TB calibration/validation: Methods and class diagrams for calibrating and validating brightness temperature (TB) measurements, and modelling of TB true values.
• Auxiliary data and satellite specifics: Requirements for supporting data (auxiliary data), attitude/position information and satellite microwave radiometer characteristics.
• Conformance and notation: UML notation, identifiers, symbols, conventions and conformance statements to support consistent implementation.
• Normative annexes: Includes an abstract test suite, a data dictionary, and informative annexes with an XML schema implementation and a formula for specification calculation.

Applications and practical value

• Ensures traceable calibration of space radiometers used in Earth observation missions.
• Supports consistent brightness temperature (TB) products for climate monitoring, oceanography, soil moisture retrieval, cryosphere studies, and atmospheric sounding.
• Enables interoperability between satellite missions and consistent long‑term data records by standardizing calibration metadata, test suites and data dictionaries.
• Facilitates quality assurance in satellite ground segments, calibration laboratories, and scientific data processing centers.

Who should use this standard

• Satellite instrument engineers and system integrators working with space‑borne passive microwave radiometers
• Calibration laboratories and metrology teams responsible for in‑orbit and pre‑launch calibration
• Remote sensing data producers, processing centers and data users needing to assess calibration traceability and uncertainty
• Agencies and standardization bodies harmonizing remote sensing products across missions

Related standards

• ISO/TS 19159-1 (Optical sensors)
• ISO/TS 19159-2 (Lidar)
• ISO/TS 19159-3 (SAR/InSAR)
• ISO 19103 (Conceptual schema language)

Keywords: ISO/TS 19159-4:2022, space-borne passive microwave radiometers, calibration, validation, brightness temperature, TB calibration, antenna pattern, remote sensing, geographic information.

Standards Content (Sample)

TECHNICAL ISO/TS
SPECIFICATION 19159-4
First edition
2022-11
Geographic information — Calibration
and validation of remote sensing
imagery sensors and data —
Part 4:
Space-borne passive microwave
radiometers
Information géographique — Calibration et validation de capteurs de
télédétection —
Partie 4: Radiomètres spatiaux à micro-onde passive
Reference number
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols, abbreviated terms and conventions .12
4.1 Abbreviated terms .12
4.2 Symbols .12
4.3 Conventions . 15
5 Conformance .15
6 Notation .16
6.1 UML notation. 16
6.2 Identifiers . 16
7 General microwave radiometer sensor and data calibration and validation model .16
7.1 Introduction . 16
7.2 Top-level model . 18
7.3 Sensor calibration . 19
7.3.1 General description . . 19
7.3.2 Geometric position . 19
7.3.3 TA calibration .20
7.3.4 Antenna pattern calibration . 22
7.4 Auxiliary data . 23
7.5 TB calibration/validation . 24
7.5.1 TB calibration/validation class diagram . 24
7.5.2 TB calibration/validation methods . 26
7.5.3 TB true value class diagram . 27
7.6 Satellite microwave radiometer .29
Annex A (normative) Abstract test suite .30
Annex B (normative) Data dictionary .33
Annex C (informative) XML schema implementation .47
Annex D (informative) Formula for specification calculation .48
Bibliography .50
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 211, Geographic information/Geomatics.
A list of all parts in the ISO 19159 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
Introduction
Imaging sensors are one of the major data sources for geographic information. The image data captures
spatial and spectral measurements and has numerous applications ranging from road/town planning
to geological mapping. Typical spatial outcomes of the production process are vector maps, digital
elevation models and 3-dimensional city models.
In each case the quality of the end products fully depends on the quality of the measuring instruments
that have originally sensed the data. The quality of measuring instruments is determined and
documented by calibration.
Calibration is often a costly and time-consuming process. Therefore, a number of different strategies
are in place that combine longer time intervals between subsequent calibrations with simplified
intermediate calibration procedures that bridge the time gap and still guarantee a traceable level of
quality.
This document standardizes the calibration of remote sensing imagery sensors and the validation of the
calibration information and procedures. It does not address the validation of the data and the derived
products.
Many types of imagery sensors exist for remote sensing tasks. In addition to the different technologies,
the need for standardization of the various sensor types takes into account different priorities. In order
to meet such needs, the ISO 19159 series has been split into several parts. ISO/TS 19159-1 addresses
the optical sensors. ISO/TS 19159-2 addresses the airborne lidar (light detection and ranging)
sensors. ISO/TS 19159-3 addresses synthetic aperture radar (SAR) and interferometric SAR (InSAR).
ISO/TS 19159-4 (this document) covers space-borne passive microwave radiometers.
In accordance with the ISO/IEC Directives, Part 2, 2018, Rules for the structure and drafting of
International Standards, in International Standards the decimal sign is a comma on the line. However,
the General Conference on Weights and Measures (Conférence Générale des Poids et Mesures) at its
meeting in 2003 passed unanimously the following resolution:
“The decimal marker shall be either a point on the line or a comma on the line.”
In practice, the choice between these alternatives depends on customary use in the language concerned.
In the technical areas of geodesy and geographic information it is customary for the decimal point
always to be used, for all languages. That practice is used throughout this document.
v
TECHNICAL SPECIFICATION ISO/TS 19159-4:2022(E)
Geographic information — Calibration and validation of
remote sensing imagery sensors and data —
Part 4:
Space-borne passive microwave radiometers
1 Scope
This document defines the calibration of space-borne passive microwave radiometers and the validation
of the calibrated information.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 19103, Geographic information — Conceptual schema language
ISO/TS 19159-1, Geographic information — Calibration and validation of remote sensing imagery sensors
and data — Part 1: Optical sensors
ISO/TS 19159-2, Geographic information — Calibration and validation of remote sensing imagery sensors
and data — Part 2: Lidar
ISO/TS 19159-3, Geographic information — Calibration and validation of remote sensing imagery sensors
and data — Part 3: SAR/InSAR
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
antenna beam width
half-power full width
half-power beam width
full angle at which the antenna's pattern (in power units) is at half its maximum value
Note 1 to entry: In engineering convention, this is also known as the "3 dB beam width."
3.2
antenna main-beam efficiency
η
M
fraction of the total radiant energy that is received from the main beam (3.29), which is defined as the
ratio of the power received within the "main lobe" to that of the total power received by the antenna
Note 1 to entry: η is calculated using the following formula:
M
Fdθφ, Ω
()
n
∫∫
Y
η =
M
Fd()θφ, Ω
4π n
∫∫
where
F is the antenna pattern;
n
θ is the elevation angle;
ϕ is the azimuth angle;
dΩ is the differential solid angle;
Y is the main lobe value.
Note 2 to entry: Main beam (3.29) is also referred as main lobe.
3.3
antenna output temperature
T
A,out
physical temperature of correctional impedance that delivers to the receiver the same noise power as
the antenna collects
Note 1 to entry: This includes two terms: the noise coming from the environment attenuated by the antenna
Ohmic efficiency and the thermal noise added by the antenna Ohmic losses. In the Rayleigh-Jeans approximation,
the following formula applies:
TTΩΩ=ηη+−1 T
() () ()
A,outA00Ω Ω p
where
T is the antenna aperture temperature;
A
T is the physical temperature of the antenna;
p
Ω is the Ohmic loss;
η is the Ohmic efficiency of the antenna.
Ω
Note 2 to entry: The antenna output temperature (T ) is related to the input noise temperature of the receiver
A,out
as shown in the following formula:
hv
T =
rec,in
hkvT/
A,out
e −1
where
T is the input noise temperature of the receiver;
rec,in
-34
h is the Plank’s constant (6.626 07×10 J·s);
v is the frequency in Hz;
-23
k is the Boltzmann’s constant (1.380 648 52×10 J/K);
e is the base of natural logarithm.
3.4
antenna pattern
ratio of the electronic-field strength radiated in the direction θ to that radiated in the beam-maximum
direction
Note 1 to entry: In microwave radiometry, this is the spatial distribution of a quantity (usually proportional to or
equal to power flux density or radiation intensity) that characterizes the electromagnetic field generated by an
antenna.
[SOURCE: ISO/TS 19159-3:2018, 3.2, modified — Note 1 to entry added.]
3.5
antenna radiation efficiency
η
l
ratio of the total radiated power divided by the total power accepted by the antenna
Note 1 to entry: This is also equivalent to the ratio of the antenna radiation resistance (R ) divided by the sum
rad
of the antenna radiation resistance and the antenna Ohmic resistance (R ), as described in the following formula:
Ω
P R
rad rad
η ==
l
P RR+
in rad Ω
where
P is the total radiated power;
rad
P is the total power accepted by the antenna;
in
R is the antenna radiation resistance;
rad
R is the antenna Ohmic resistance.
Ω
Note 2 to entry: Antenna radiation efficiency (η ) is also called as Ohmic efficiency (η ).
l Ω
3.6
antenna sidelobe
antenna radiation pattern away from its main beam (3.29), or defined as part of an antenna response
pattern which is not contained in the main beam
3.7
antenna temperature
T
A
temperature (K) equivalent of the power received with an antenna, or physical temperature (K) of the
‘antenna radiation resistance’ that delivers to a matched receiver the same noise power as the antenna
collects
3.8
attitude
orientation of a body, described by the angles between the axes of that body’s coordinate system and
the axes of an external coordinate system
[SOURCE: ISO 19116:2019, 3.3, modified — Note 1 to entry removed.]
3.9
blackbody load
microwave load with characteristics very close to those of a perfect blackbody (3.30) within a certain
frequency range
3.10
blackbody radiance
I
bb,v
physical radiance of an absorber determined by applying Planck’s function (either in wavelength space
or in terms of frequencies) to absorber temperature, T , as shown in the following formula (in frequency
w
space):
21hv
I =
bb,v
2 hv
c
kT
w
e −1
where
T is the temperature of the absorber;
w
-34
h is the Plank’s constant (6.626 07×10 J·s);
v is the frequency in Hz;
c is the velocity of light (2.997 925×10 m/s);
-23
k is the Boltzmann’s constant (1.380 648 52×10 J/K);
e is the base of natural logarithm.
Note 1 to entry: The constants are defined in terms of a perfect blackbody (3.30).
3.11
boresight
calibration of a lidar sensor system, equipped with an inertial measurement unit (IMU) and a global
navigation satellite system (GNSS), to accurately determine or establish its position and orientation
Note 1 to entry: In microwave radiometry, the boresight is usually used to characterize the beam-maximum
direction of a highly directive antenna.
[SOURCE: ISO/TS 19159-2:2016, 4.4, modified — Original note 1 to entry deleted and replaced with new
note 1 to entry.]
3.12
brightness temperature
T
B
descriptive measure of radiation in terms of the temperature (K) of a hypothetical blackbody emitting
an identical amount of radiation at the same wavelength, which can be derived from the Planck's
radiation law
Note 1 to entry: In the Rayleigh-Jeans limit, the microwave power per unit bandwidth received by a radiometer,
P, (3.33) is:
Note 2 to entry: P=k·T
B
-23
Note 3 to entry: where k is the Boltzmann’s constant (k= 1.380 648 52×10 J/K).
Note 4 to entry: For the frequency range of microwave, Planck's radiation law can be well approximated by
the Rayleigh-Jeans formula. Usually the microwave radiometers use the Rayleigh–Jeans equivalent brightness
temperature, which is defined as:
c
()RJE
T = I
v
b,v
2v k
where
()RJE
is the Rayleigh–Jeans equivalent brightness temperature;
T
b,v
v is the frequency in Hz;
c is the velocity of light (2.997 925×10 m/s);
-23
k is the Boltzmann’s constant (1.380 648 52×10 J/K);
I is the radiance.
v
3.13
brightness temperature sensitivity
minimum detectable change of the brightness temperature (3.12) incident at the antenna-collecting
aperture
Note 1 to entry: For the purpose of this document, the noise equivalent delta temperature (NEDT) values shall
be defined as the standard deviation of the radiometer (3.33) output in K when the antenna is viewing a 300 K
uniform and stable target. For microwave radiometer, this is also called radiometric resolution (3.34).
Note 2 to entry: The formula relative to sensitivity is shown in D.2.
3.14
calibration
process of quantitatively defining a system’s response to known, controlled signal inputs
[SOURCE: ISO/TS 19101-2:2018, 3.2]
3.15
calibration equation
equation relating the primary measure and that of the radiometer (3.33), for example the brightness
temperature (3.12), to subsidiary measurands, such as powers, and to calibration quantities, such as
standard values
3.16
co-polarization
fraction of total power within the main beam (3.29) that is detected in the main polarization (3.31)
3.17
cosmic microwave background
CMB
isotropic radiation in the microwave region that is observed almost completely uniformly in all
directions
Note 1 to entry: This radiation is understood to be the radiation emitted by the universe at an early period of its
history.
Note 2 to entry: In order to use CMB for calibrating a microwave radiometer operating at microwave to sub-
millimetre band, it should be converted into brightness temperature (3.12), T , according to the following formula:
B
hv
 
kT
 
c
hev +1
 
 
 
T =
B
hv
 
kT
 
c
21ke −
 
 
 
where
-34
h is the Planck’s constant (6.626 07×10 J·s);
v is the frequency in Hz;
-23
k is the Boltzmann’s constant (1.380 648 52×10 J/K);
T is the cosmic background temperature (2.736 ± 0.017 K);
c
e is the base of natural logarithm.
3.18
cross-calibration
process of relating the measurements of one instrument to another instrument which is usually well-
calibrated, serving as a reference
Note 1 to entry: Cross-calibration of instruments operating during the same period requires careful collocation
wherein instrument outputs are compared when the instruments are viewing the same Earth scenes, at the same
times, from the same viewing angles.
3.19
cross-polarization
fraction of total power within the main beam that is detected in the orthogonal polarization
3.20
effective blackbody brightness temperature
physical temperature of a perfect absorber that would produce the same spectral brightness density or
spectral radiance density as that under consideration
3.21
emissivity
ratio of the energy radiated by an emissive surface relative to that of an ideal blackbody source at the
same temperature
3.22
end-to-end calibration
calibration of the entire radiometer (3.33) system as a unit, achieved by
observing the values of output quantities (e.g. voltage, power) for known values of incident radiance at
the antenna aperture
3.23
experimental standard deviation
for a series of n measurements of the same measurand, the quantity, s(q ), characterizing the dispersion
k
of the results and given by the formula
n 2
qq−
()
j
∑
j=1
sq =
()
k
n−1
where
q is the result of the kth measurement;
k
q
is the arithmetic mean of the n results considered;
n is the number of the measurements.
Note 1 to entry: Considering the series of n values as a sample of a distribution, q is an unbiased estimate of the
2 2
mean μ, and s is an unbiased estimate of the variance σ of that distribution. The expression s/ n is an estimate
of the standard deviation of the distribution of q and is called the experimental standard deviation of the mean.
[SOURCE: ISO/IEC Guide 98-3:2008 B.2.17, modified — Notes 3 and 4 to entry have been removed.]
3.24
external calibration
calibration method that applies reference signals from targets that lie outside the radiometer (3.33)
Note 1 to entry: If these targets illuminate the antenna of the radiometer, an end-to-end calibration (3.22) is
obtained.
3.25
half-power bandwidth
frequency range at which the power response is half the maximum value
3.26
incident angle
vertical angle between the line from the detected element to the sensor and the local surface normal
(tangent plane normal)
[SOURCE: ISO/TS 19130-1:2018, 3.13]
3.27
instantaneous field of view
IFOV
instantaneous region seen by a single detector element, measured in angular space
[SOURCE: ISO/TS 19130-2:2014, 4.36, modified — Admitted term added.]
3.28
linearity
property of a mathematical relationship or function which means that it can be graphically represented
as a straight line
Note 1 to entry: The formula relative to the linearity is shown in D.1.
3.29
main beam
main lobe
major part of the radiated field where maximum radiated energy exists (region around the direction of
maximum radiation)
Note 1 to entry: The main beam is also defined as 2.5 times 3 dB beamwidth for mathematical computation of
antenna main beam efficiency.
Note 2 to entry: The width of main beam (which is commonly called "null to null beamwidth") is defined as the
angular span between the first pattern nulls (the magnitude of the radiation pattern decreases to zero, negative
infinity dB) adjacent to the main lobes.
3.30
perfect blackbody
perfect absorber (and therefore the best possible emitter) of thermal electromagnetic radiation, whose
spectral radiance density (or spectral brightness density, L ) is given by the Planck formula
f
2hv
L =
f
2 h/vTk
ce −1
()
where
v is the frequency in Hz;
-34
h is Planck’s constant (6.626 07×10 J·s);
-23
k is Boltzmann’s constant (1.380 648 52×10 J/K);
T is physical temperature of the blackbody in K;
c is velocity of light (2.997 925×10 m/s).
e is the base of natural logarithm.
3.31
polarization
restricting radiation, especially light, vibrations to a single plane
Note 1 to entry: In microwave radiometry, the direction of the polarization is defined by the direction of the
electric field (E, in most cases) or magnetic field (H) in a propagating electromagnetic wave.
Note 2 to entry: A general, elliptically polarized electromagnetic plane wave propagating in the rˆ direction can
have its electric field expressed in phasor form as:

− jw r
n
ˆˆ
Ep=+EqE e
()
pq
where
ˆ ˆ
p and q
ˆ ˆˆ ˆ
are unit vectors oriented perpendicular to r and satisfying pq×= r = rr/ ;
are the complex amplitudes of the electric field in the pˆ and qˆ directions, respectively;
E and E
p q
w
n is the wavenumber of the propagating wave, and rr= .
Note 3 to entry: Vertical polarization and horizontal polarization are specific cases of elliptical polarization.
[SOURCE: ISO 19115-2:2019, 3.24, modified — Notes to entry added.]
3.32
radiance
I
v
point on a surface and in a given direction, the radiant intensity of an element of the surface, divided
by the area of the orthogonal projection of this element on a plane perpendicular to the given direction
Note 1 to entry: In microwave radiometry, radiance can be expressed as the radiated power per unit solid angle
per unit area normal to the direction defined by the solid angle Ω:
dP
I =
v
ddΩ A
⊥
where
dP is the differential radiation power;
dΩ is the differential solid angle;
′
′
in which θ is the angle between the direction defined by the solid angle and the
dA = cosθ dA
⊥
normal to the area element dA.
3.33
radiometer
very sensitive receiver, typically with an antenna input, used to measure radiated electromagnetic
power
3.34
radiometric resolution
smallest change in input brightness temperature (3.12) or radiance (3.32) that can be detected in the
system output
Note 1 to entry: This is often estimated by using the ideal equation for a total-power radiometer (3.33), as shown
in the following formula.
T
sys
ΔT =
min
Bτ
where
ΔT is the radiometric resolution;
min
T is the radiometer system temperature;
sys
B is the bandwidth of the radiometer system;
τ
is the integral time.
Radiometric resolution can be also estimated from the variant of this equation that is appropriate for
the particular radiometer (3.33) in question.
3.35
spatial resolution
length of the major and/or minor axes diameters of the 3 dB contour of the antenna pattern (3.4)
projected onto the Earth’s surface
Note 1 to entry: The diameter of the two axes may differ.
Note 2 to entry: See also IFOV (3.27).
3.36
spectral response function
SRF
relative sensitivity of the sensor to monochromatic radiation of different wavelengths
Note 1 to entry: For microwave radiometer (3.33), SRF refers to the receiver's band-pass, B(v), which can be
determined by performing two measurements per frequency at different input power levels, as shown in the
following formula:
ΔVv
()
out
Bv =
()
ΔPv()
in
where
ΔV is the output voltage difference;
out
ΔP
is the input power difference;
in
v is the frequency in Hz.
3.37
spillover
condition where radiation from the feed antenna falls outside the edge of the dish and does not
contribute to the main beam (3.29)
Note 1 to entry: Spillover factor is written as 1−Λ and can be measured in the field, where Λ is the ratio of
P P
antenna pattern (3.4) within the Earth to all space of 4π.
ΛΩ=+dF F
()
PPnn,,PPQ
∫
Z
where
F
is the co-polarization antenna pattern;
n,PP
F
is the cross-polarization antenna pattern;
n,PQ
dΩ is the differential solid angle;
Z is the Earth.
3.38
stability
ability of a measuring instrument or measuring system to maintain its metrological characteristics
constant with time
3.39
Stokes parameters
set of four real quantities, which completely describe the polarization (3.31) state of monochromatic or
quasi-monochromatic radiation
Note 1 to entry: The parameters are, collectively, known as the Stokes Real {ordered}, a 4 × 1 Real {ordered}.
Note 2 to entry: The Stokes parameters were introduced as a mathematically convenient alternative by Sir
[14,17]
George Stokes. These four parameters are related to the horizontally and vertically polarized components
of electric field by:
2 2
 
EE+
vh
 
I
 
 
2 2
 
EE−
 vh 
Q
 
=  
 
η *
U
 
2Re EE
 
v h
 
 
V
 
 
*
2Im EE
 v h 
 
where
E is the vertically polarized component of electric field;
v
E is the horizontally polarized component of electric field.
h
The units of the Stokes parameters are W/m . The first Stokes parameter (I) gives the total radiation
power density, and the second Stokes parameter (Q) represents the power density difference between
the two linearly polarized components. The third and fourth Stokes parameters (U and V) describe the
correlation between these two components.
Note 3 to entry: For microwave remote sensing, modified Stokes parameters are often used. Under the Rayleigh-
Jeans approximation, the modified Stokes parameters in brightness temperature (3.12) are given by the following
[19], [37]
formula:
 
E
v
 
T
 
v
 
 
E
T  h 
h λ
 
=  
 
kηB *
T
 
2Re EE
 
vh
 
 
T
 
 
*
2Im EE
 v h 
 
where T , T , T and T are, respectively, the vertically and horizontally polarized and the third and
v h 3 4
fourth Stokes parameters, and B is the radiometer system bandwidth.
[SOURCE: ISO 12005:2003, 3.11, modified — Original notes to entry have been removed and replaced.]
3.40
traceability chain
sequence of measurement standards and calibrations (3.14) that is used to relate a measurement result
to a reference
[SOURCE: ISO/IEC Guide 99:2007, 2.42, modified — Notes to entry have been removed.]
3.41
true value
value consistent with the definition of a given quantity
Note 1 to entry: This is a value that would be obtained by perfect measurement. However, this value is in principle
and in practice unknowable.
[SOURCE: ISO 17123-1:2014, 3.1.3]
3.42
two-point calibration
adjustment of the relationship between the input signal and the output response of a radiometer (3.33)
using two distinct input stimuli
Note 1 to entry: Assuming a linear receiver, all possible input signal levels can now be retrieved from the
radiometer output responses.
Note 2 to entry: In the case of an external end-to-end calibration (3.22), the input signal equals the antenna
temperature (3.7) of the radiometer.
3.43
uncertainty
parameter, associated with the result of measurement, that characterizes the dispersion of values that
could reasonably be attributed to the measurand
Note 1 to entry: When the quality of accuracy or precision of measured values, such as coordinates, is to be
characterized quantitatively, the quality parameter is an estimate of the uncertainty of the measurement results.
Because accuracy is a qualitative concept, one should not use it quantitatively, that is, associate numbers with it;
numbers should be associated with measures of uncertainty instead.
[SOURCE: ISO 19116:2019, 3.28]
3.44
validation
process of assessing, by independent means, the quality of the data products derived from the system
outputs
Note 1 to entry: In this document, the term validation is used in a limited sense and only relates to the validation
of calibration data in order to control their change over time.
[SOURCE: ISO 19101-2:2018, 3.41, modified — Note 1 to entry added.]
3.45
viewing angle
angle between the line-of-sight and the line orthogonal to the surface of the display at the point where
the line-of-sight intersects the image surface of the display
[SOURCE: ISO 9241-5:1998, 3.1]
3.46
vicarious calibration
post-launch calibration of sensors that make use of natural or artificial sites on the surface of the Earth
[SOURCE: ISO/TS 19159-1:2014, 4.41]
4 Symbols, abbreviated terms and conventions
4.1 Abbreviated terms
AMSR-E advanced microwave scanning radiometer for the Earth observing system
APC antenna pattern calibration
CMB cosmic microwave background
DSB double side band
GNSS global navigation satellite system
HPBW half-power beam width
HPFW half-power full width
IFOV instantaneous field of view
LSB lower side band
MR microwave radiometer
NEDT noise equivalent delta temperature
OMB observation field minus background field
SCF sensor constant file
SRF spectral response function
SSB single side band
SSM/I special sensor microwave/imager
TA antenna temperature
TB brightness temperature
UML unified modeling language
USB upper side band
XML extensible markup language
4.2 Symbols
B radiometer system bandwidth
B(v) spectral response function (receiver's band-pass)
Ci(), j hot target count of the ith scan, jth hot target
H
mean hot target counts of the ith scan
Ci
()
H
dA area element
dA
area element normal to the direction defined by the solid angle
⊥
dP differential radiation power
dΩ differential solid angle
E horizontally polarized component of electric field
h
ˆ
amplitude of the electric field in the p direction
E
p
amplitude of the electric field in the qˆ direction
E
q
E vertically polarized component of electric field
v
F antenna pattern
n
F co-polarization antenna pattern
n,PP
F cross-polarization antenna pattern
n,PQ
mean antenna gain of the ith scan
Gi
()
-34
h Plank’s constant (6.626 07×10 J·s)
I total radiation power density (first Stokes parameter)
I
blackbody radiance
bb,v
I radiance
v
j imagery unit
-23
k Boltzmann’s constant (1.380 648 52×10 J/K)
L spectral radiance density of a perfect blackbody
f
M number of hot targets viewed during each scan
N number of scans
n number of the measurements
P power per unit bandwidth received by a radiometer
P total power accepted by the antenna
in
P
total radiated power
rad
ˆ ˆˆ ˆ
ˆ unit vector oriented perpendicular to q and satisfying pq×= r
p
q result of the kth measurement
k
q
arithmetic mean of the n results considered
ˆ
q ˆ ˆˆ ˆ
unit vector oriented perpendicular to p and satisfying pq×= r
R
antenna radiation resistance
rad
R
antenna Ohmic resistance
Ω
rˆ
unit vector oriented in the wave propagating direction
s experimental standard deviation
T third modified Stokes parameters in brightness temperature
T forth modified Stokes parameters in brightness temperature
T antenna temperature
A
T antenna output temperature
A,out
()RJE
Rayleigh–Jeans equivalent brightness temperature
T
B,v
T physical temperature of the cold blackbody
C
T cosmic background temperature
c
T effective blackbody brightness temperature of the cold target
CC
T physical temperature of the hot blackbody
H
T second modified Stokes parameters in brightness temperature
h
T effective blackbody brightness temperature of the hot target
HC
T noise equivalent delta temperature
NED
T physical temperature
p
T effective input noise temperature
rec,in
T radiometer system temperature
sys
T first modified Stokes parameters in brightness temperature
v
T temperature of the absorber
w
U real part of the correlation between these two components (third Stokes parameter)
u nonlinearity coefficient
V imagery part of the correlation between these two components (forth Stokes parameter)
v frequency in Hz
V output voltage viewing the scene
A
V output voltage viewing the cold target
C
V output voltage viewing the hot target
H
w wavenumber of the propagating wave
n
Y main lobe value
Z Earth
ΔP input power difference
in
ΔT
nonlinear term of antenna temperature
BAC
ΔT
correction to the contribution of emissivity and the surroundings of the cold target
C
ΔT
correction to the contribution of emissivity and the surroundings of the hot target
H
ΔT radiometric resolution
min
ΔV output voltage difference
out
η wave impedance
η antenna radiation efficiency
l
η antenna main-beam efficiency
M
η Ohmic efficiency
Ω
θ elevation angle
θ′
angle between the direction defined by the solid angle and the normal to the area element dA
λ electromagnetic wavelength
1-Λ spillover
P
τ
integral time
φ azimuth angle
Ω
Ohmic loss
4.3 Conventions
In accordance with ISO 19103, the names of UML classes, with the exception of basic data type classes,
shall include a two-letter prefix that identifies the standard and the UML package in which the class
is defined. Table 1 lists the prefixes used in this document, the document in which each is defined
and the package each identifies. UML classes defined in this document belong to a package named
"Calibration Validation" and shall have the same two letter prefix as in ISO/TS 19159-1, ISO/TS 19159-2
and ISO/TS 19159-3: CA (see Table 1). The XML schema for the UML model defined in this document is
described in Annex C.
Table 1 — UML class prefixes prefix standard package
Prefix Document Package
CA ISO/TS 19159-1, ISO/TS 19159-2, ISO/TS 19159-3 and ISO/TS 19159-4 (this document) Calibration
Validation
5 Conformance
This document defines one conformance class:
— “Microwave Radiometer Sensors Calibration/Validation” (specification target: Microwave
Radiometer Sensors).
A specification, standard, test suite or test tool claiming conformance to this document shall implement
the conformance class relevant to that specification target.
Conformance with this document shall be assessed using all the relevant conformance test cases
specified in Annex A.
6 Notation
6.1 UML notation
In this document, conceptual schemas are presented in the Unified Modeling Language (UML). ISO 19103
conceptual schema language presents the specific profile of UML used in this document.
6.2 Identifiers
The complete document is identified by the following URI:
https:// standards .isotc211 .org/ iso19159/ -4/ 1
The normative provisions in this document are denoted by the following URI:
https:// standards .isotc211 .org/ iso19159/ -4/ 1
All requirements and abstract test cases that appear in this document are denoted by partial URIs
which are relative to this base.
The name and contact information of the maintenance agency for this document can be found at www
.iso .org/ maintenance _agencies.
7 General microwave radiometer sensor and data calibration and validation
model
7.1 Introduction
This document addresses the calibration of space-borne microwave radiometers and validation
of space-borne microwave radiometers calibration information [brightness temperature (TB) or
radiance]. It includes the detailed description of space-borne microwave radiometers performance and
parameters related to space-borne microwave radiometers calibration, which can be used for refined
space-borne microwave radiometers information processing.
Figure 1 depicts a package diagram that shows all parts of the ISO 19159 series at the time of this
document's publication. The calibration and validation of Optics, LIDAR and SAR/InSAR sensors and
data have been standardized in ISO/TS 19159-1, ISO/TS 19159-2 and ISO/TS 19159-3 respectively.
Figure 1 — Package diagram of the package Calibration/Validation
Radiometer calibration (which is used as the abbreviation of “space-borne microwave radiometers
calibration” in this document) is the process of quantitatively defining a microwave receiver’s outputs,
whether in voltages or their counts, to controlled or known TB inputs. The purpose of microwave
radiometer calibration is to characterize the performance of the end-to-end microwave radiometer
system so that the real radiometric parameters can be derived from the measurement of the microwave
radiometer.
Although on-board calibration is usually carried out on the microwave radiometer system, its post-
launch calibration/validation, usually called external calibration, can ensure the differences between
the measurements and the TB or radiance from simulations by microwave transfer models, and can
bridge the time gap between calibrations of the radiometer, as well as radiometers from other platforms,
and ensure a long-term confidence in the quality.
This subclause describes the general model of microwave radiometer sensor calibration and validation.
A flow chart for microwave radiometer calibration is shown in Figure 2.
Figure 2 — Flow chart for microwave radiometer calibration
Calibration of a radiometer begins with “sensor calibration” using “satellite microwave radiometer
raw data”, which usually include data and parameters for producing a two-point calibration equation.
The process of sensor calibration generally includes three stages named as “Geometric position”, “TA
calibration” of the receiver, and “Antenna pattern calibration” of the antenna. Sensor calibration is a
routine in the space-borne microwave radiometer operational system, which is used for producing the
data products of level 1. It is also necessary in “TB calibration/validation” after the differences outside
the given “Threshold”, to find the roots of mismatch.
In Figure 2, “TB True Value” serves as input for the module “TB calibration/validation” (defined
in the class “CA_TBCalibrationValidation” in 7.5.1) to calibrate “TB to be calibrated”, and the results
will be assessed. If the assessments are within the “Threshold”, the calibrated TB will be outputted
as “recalibrated TB". Otherwise, three main processes in the “Sensor calibration” will follow for
correcting the errors by “Geometric position” (defined in the class “CA_GeometricPosition” in 7.3.1), “TA
calibration” module (defined in the class “CA_TACalibration” in 7.3.2), and “Antenna pattern calibration”
(defined in the class “CA_AntennaPatternCalibration” in 7.3.3). T
...