******************
doc marmotte
Il manque une reference (demander a laurent Laguerre
j'ai recupere un fichier ascii derive de Word d'ou le format etrange
des tableaux.
il faudrait les reformatter ou demander a laurent de le faire
merci
Yann
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1
TITLE
GROUND PASSIVE MICROWAVE MEASUREMENTS
1.1
Data Set Identification
Ground passive microwave maesurements (4.3 GHz) and surface
data at the East Central Supersite.
1.2
HAPEX SAHEL Data Base Table Name
1.3
CD-ROM File Name
1.4
Revision Date of this Document
August 1993
2
INVESTIGATORS
2.1
Investigators Name and Title
PI : Dr Yann H. Kerr LERTS
Co-Is : Laurent Laguerre LERTS
Dr Abdelghani Chehbouni ORSTOM
Jean Christophe Calvet CNRM
Dr Andr Chanzy INRA
Dr Thomas Schmugge (USDA)
2.2
Title of Investigation
Passive Microwaves and soil moisture estimation
2.3
Contacts (For Data Production Information)
Contact 1
Contact 2
2.3.1 Name
2.3.2 Address
2.3.3 Tel.
2.3.4 Email
2.3.5 Fax
Laurent LAGUERRE
LERTS
18 avenue Edouard Belin
31055 TOULOUSE Cedex
(+33) 61 28 14 16
Laguerre@lerts.cnes.fr
(+33) 61 28 14 10
Yann H. KERR
LERTS
18 avenue Edouard Belin
31055 TOULOUSE Cedex
(+33) 61 27 44 72
Kerr@lerts.cnes.fr
(+33) 61 28 14 10
2.4
Requested Form of Acknowledgement.
It is expected from the user to contact the PI before
submitting a paper offering the possibility of being co-author or
simply acknowledge. The PI will decide the most appropirate way of
referencing as well as the member of the team to be eventually named.
3
INTRODUCTION
3.1
Objective/Purpose
The study was performed with several applications in mind:
* collect ground measurements of brightness temperature and
relevant surface characterisation to make and validate a roughness
model for soil in the passive microwaves;
* Make measurements over several types of surfaces to sample
the different types of contributions within a PORTOS or PBMR
footprint;
* provide ground data for the validation of inverse
algorithms in the microwave (soil moisture and biomass, taking into
account surface roughness
3.2
Summary of Parameters
The measurements are related to 4.3 GHz brightness
temperatures at various incidence angles and polarizations, surface
temperature, temperature and humidity profiles, surface roughness
measurements, vegetation ccover characterisation, sky brightness
temperatures.
3.3
Discussion
The microwave brigthness temperature measurements have been made over
bare soil , medium rough , grass , grass cut, guiera targets, at a
local scale. Each target surface parameter have been
characterized.(soil moisture, soil temperature, surface roughness,dry
bulk density, texture,vegetation parameters) .
4
THEORY OF MEASUREMENTS
Understanding of the influence of parameters such as surface soil
moisture, surface roughness, and vegetation characteristics on the
microwave brightness temperature. Use of multi-angular and
bi-polarisation measurements to extract relevant parameters. The
different calibrations made (twice per day) is to ensure the
stability of the response of the radiometer.
5
EQUIPMENT
The instrumentation used can be divided in two parts:
- Radiometric instrumentation
Weight
7Kg
Dimensions
0.23x0.25x0.54m
Type
Dicke noise added
Aperture
23
(-3dB)
Antenna
horn
Frequency
4.2- 4.4 GHz (C Band)
Polarization
Horizontal, Vertical
Range
0- 330K
Power supply
12 V DC
Output
0-10 V analog
9600 Bauds, 12 bits Digital
One portable thermal infra-red radiothermometer
Type HEIMANN KT17
Spectral band
8-14 *m
Detector
Type A
- Instrumentation for surface characteristics
-Soil temperature profile
thermocouples.
-Surface roughness:
one soil profile meter with a needle density of 1 needle per 5 mm;
the needles are mounted on a one-meter long bar .
Bulk density:
one gamma-ray probe for in situ measurements of dry bulk density.
5.1.1 Platform (Satellite, Aircraft, Ground, Person..)
The microwave and infra-red radiomers are mounted on the same device
which allows microwave measurements at different zenithal angles, and
thermal infra-red measurements at nadir. It consists of a rotating
arm on which is mounted Marmotte (height 2.5m) and a fixed arm on
which is mounted the Infra red radiothermometer.
5.1.2
Mission Objectives
The objective of this equipment is to collect data for
modelling purposes. It is portable and has been used in several field
experiments.
5.1.3 Key Variables
-Microwave brightness temperature (4.3 GHz, H&V, 0-60 deg)
-Thermal infra-red brightness temperature to assess surface temperature
-Soil temperature profile
- Surface soil moisture
- Surface roughness
- Bulk density
5.1.4 Principles of Operation
The instrument Marmotte is a noise added radiometer operating between
4.2 and 4.4 GHz. It measures the radiation from the target which can
be linearly related to the brightness temperature (See Skou et al.)
5.1.5 Instrument Measurement Geometry
The device {microwave radiometer+infra-red radiothermometer} is
located on surfaces characteristic of the site (bare soil, grass,
guiera). Both measurements are made from a 2.5 m height. Microwave
measurements can be performed at any angle between 0 and 60 for
both polarizations (the radiometer is simply rotated 90 ) and thermal
infra-red measurements are made at nadir. Both radiometers watch the
same target.
5.1.6 Manufacturer of Instrument
MARMOTTE prototype manufacturer:
Centre Hyperfr quences et Semi-conducteurs (CHS Lille)
Scientific staff: Y.Leroy, J.C. Van de velde.
5.2
Calibration
Microwave radiometer calibration:
We have primarily carried out routine in situ calibrations over
specific targets such as microwave absorbing materials (eccosorb)
whose temperature is measured by themocouples embedded in, and
natural targets through space views to get the cold reference. Some
calibrations are performed over liquid nitrogen. Calibration was
twice performed simultaneously to that of PORTOS.
Thermal infra-red thermometer calibration:
In-door measurements are performed over a blackbody made up of a
copper cylinder immersed in a thermal-controlled water.
5.2.2 Frequency of Calibration:
Eccosorb and sky microwave calibrations are made before and after a
an entire serie of measurements is conducted. The calibration over
eccosorb immersed in liquid nitrogen are made only twice at Niamey
airport using PORTOS calibration device. The precision on the output
values (brightness temperature) can be fixed estimated at +/-2K.
Infra-red radiothermometer calibration were made before the campaign.
6. PROCEDURE
6.1.
Data Acquisition Methods.
A radiometric measurement is the average over one minute of an analog
output (representing a microwave or thermal infra-red brightness
temperature) sampled every second, for a given configuration
(zenithal angle, polarization), over a given surface. Typically, a
serie of measurements represents, for a given polarization, microwave
radiometric measurements from 0 to 60 (this system can not allowed
simultaneous polarizations measurements) Microwave and infra-red
recordings are made simultaneously. In the same way, soil
temperature profile is recorded, soil moisture samples are collected.
6.2
Spatial Characteristics
6.2.1 Spatial Coverage
Each working characteristic surfaces (bare soil,grass,guiera)
represents a 5m by 5m area. Central East Site near Banizoumbou "Wab
jachere"
13 33'417N 2 40'913E
6.2.2 Spatial Resolution
Dimensions of MARMOTTE footprint, between 1 and 2 m depending on
height and viewing angle.
6.3
Temporal Characteristics
6.3.1 Temporal Coverage
measurements were made from 05/09/1992 until 05/10/1992 (IOP)
6.3.2 Temporal Resolution
Every day or two days.
The time needed to perform the measurements was about 2 hours
7
OBSERVATIONS
8
DATA DESCRIPTION
8.1
Table Definition With Comments
8.2
Type of Data
RADIOMETRIC.TAB contains the microwave and infra-red brightness
temperatures
and soil temperature profile, for each characteristic surfaces.
Column 3 indicates the nature of the target:
1
Smooth Bare Soil 1
2
Medium Rough Bare Soil 1
3
Grass
4
Grass Cut
5
Smooth Bare Soil 2
6
Medium Rough Bare Soil 2
Column 4 indicates the position of each serie.
Column 5 indicates the polarization:
1
Horizontal
2
Vertical
Column 7 and 8 represent respectively the microwave brigthness
temperature and the
thermal infra-red brightness temperature measured by the radiometers.
Column 9,10,11 and 12 represent respectively the soil temperature
(thermocouples) at
the surface, 1cm (T1), 5 cm (T5), 10 cm (T10).
8.2.2a Parameter/Variable
Description
8.2.3a
Range
8.2.4a
Units
8.2.5a
Source
Microwave brightness
temperature
min = 206.27
max = 301.39
Kelvin
Radiometric.tab
Thermal infra-red
temperature
min = 307.2
max = 328.08
Kelvin
Radiometric.tab
Surface Temperature
min = 308.06
max = 329.78
Kelvin
Radiometric.tab
Temperature 1 cm
T1
min = 307.87
max = 326.5
Kelvin
Radiometric.tab
Temperature 5 cm
T5
min = 307.61
max = 320.5
Kelvin
Radiometric.tab
Temperature 10 cm
T10
min = 306.97
max = 324.27
Kelvin
Radiometric.tab
RADIOMETRIC.TAB Data Record example
Julian Local Surface Serie Polar
Microwave
Infra-Red
Day
Time Type
Angle
brightness
brightness
(degree) temperature (K) temperature(K)
252
1306
1
1
Tsurf(K)
T1(K)
316.85
313.93 309.5
2
53.55
288.02
T5 (K) T10 (K)
ATMOSPHERIC.TAB contains atmospheric caracterisations such as upward and
donwnwardatmospheric attenuation and sky radiometric temperature.
These results are obtained using Niamey airport radio-sondings
8.2.2b Parameter/Variable
Description
8.2.3b
Range
8.2.4b
Units
8.2.5b
Source
Sky radiometric temperature
min = 4.63
max = 7.40
Kelvin
Atmospheric.tab
ATMOSPHERIC.TAB Data Record example
Julian Zenithal Upward
Downward
Sky
day
angle
atmospheric atmospheric radiometric
(degree) attenuation attenuation temperature(K)
249
249
249
0
10
20
0.999996
0.999996
0.999996
0.992409
0.992283
0.991888
4.80
4.84
4.95
MOISTURE.TAB contains average soil moistures (weight percent) for
different
surface types. Each average is made with five samples collected as
near as
possible of
the radiometer footprint.
P1
0-0.5 cm
P2
0-1 cm
P3
0.5-1 cm
P4
1-2 cm
P5
2-3 cm
P5
4-6 cm
P6
6-10 cm
P7
10-15 cm
8.2.2c Parameter/Variable
Description
8.2.3c
Range
8.2.4c
Units
8.2.5c
Source
Soil moisture
min = 0
max = 0.0745
%weight
Moisture.tab
MOISTURE.TAB Data Record example
Julian Surface P1
P2
day
type
weight weight
weight
percent percent
Percent
249
251
1
1
0.0032
0.0117
0.0075
0.0291
P3
weight
P4
weight
P5
weight
P6
weight
P7
P8
weight
percent percent percent percent percent
0.0146
0.0443
0.0224
0.0531
0.0360
0.0515
0.0402
0.0577
0.0522
0.0529
ROUGHNESS.TAB contains surface roughness informations , at a local
scale, such as surface height standard deviation and correlation
length
8.2.2d Parameter/Variable
Description
8.2.3d
Range
8.2.4d
Units
8.2.5d
Source
Surface height standard
deviation
min = 2.2
max = 9.4
missing =
surface type 1
mm
Roughness.tab
Correlation Length
min = 10.65
max = 79.25
missing =
surface type 1
mm
Roughness.tab
ROUGHNESS.TAB
Data Record example:
Julian
Day
Surface Surface standard
Correlation
Type
height deviation (mm) Length (mm)
255
274
2
4
6.1
4.2
10.65
61.56
DENSITY.BAT only contains dry bulk density for bare smooth soil
(surface type 1)
Surface 3cm
type
1
5 cm
1.76 1.74
7.5 cm
10 cm
12.5 cm
15 cm
1.71
1.66
1.61
1.58
8.4
Data Format
9
DATA MANIPULATIONS
The sky radiometric temperatures in table ATMOSPHERIC.TAB is
calculated with Y. Kerr algorithm (EVA), using vertical profiles of
air density, pressure, temperature, and water-vapor density from
radio-sondings.
10
ERRORS
11
NOTES
12
REFERENCES
Y.H. Kerr, Y. Leroy, L. Laguerre, P. Bertuzzi, J.C. Van de Velde
Marmotte: a portable microwave field radiometer
*rad 92 Proceedings of Specialist Meeting on Microwave radiometry and
Remote
Sensing Applications
Kerr & Njoku , E.G 1990 (EVA)
A semiempirical model for interpreting microwave emission from semi arid
land surfaces as seen from space.
IEEE Transactions on Geoscience and Remote Sensing, 28, page 384-393