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SPECTRAL SIGNATURE MEASUREMENT TECHNIQUES EMPLOYED AT THE 
JeR.C. : MAJOR PROBLEMS AND BASIC CONSIDERATIONS 
Ge Maracci 
Commission of the European Communities 
Joint Research Centre - ISpra Establishment 
I-21020 Ispra (Va), Italy 
INTRODUCTION 
Measurements of spectral signatures of several targets 
have been performed by the J.R.C. ISpra remote sensing 
experimental team with different instruments and unger 
different field conditions for the AGRESTE!, TELLUS 
and EURASEP3 projects. This paper gives a short review 
of the employed techniques but in particular a descrip- 
tion of the experimental difficulties and some of the 
considerations relevant to spectral signature probiems. 
INSTRUMENTS 
The J.R.C. remote sensing measurements for the radio- 
metric ground truth in the visible (VIS) and near in- 
frared (NIR) have made use of the following instruments 
during the past few years: 
a) EXOTECH 100 Radiometer with the four LANDSAT bands. 
Interchangeable optics allow to have 1°, 15° Or 27 
sterradian field of view (FOV). Output levels for 1° 
and 15° FOV are calibrated in terms of radiation 
source Equivalent Radiant Emittance (w/cm2). Output 
levels for the 2m sterradian FOV are calibrated in 
terms of total incident power at the diffuser surface 
(W/cm2). 
b) An OPTRONIC model 740 spectroradiometer which is 
calibrated to measure spectral irradiance (w/cm? nm) 
over the 300 to 1050 nm vavelength region with a 
bandpass of 5 nm with a rectangular FOV. 
c) An EG&G model 580/85 spectroradiometer calibrated to 
measure spectral irradiance (w/cm? nm) and spectral 
radiance (w/cm? nm sr) over the range of 0.35 /um to 
1.2 m. This range can be extended to 2.4 /um. A 
telescope modulus and interchangeable input optics al- 
low different conical field of viewse