LM uu $1 1 LIS Ll 
racterized by several different land covers and complex morpho- 
logy. 
This paper is intented to give a short description of a 
simulation program which, taking into account the orbit dynamics, 
the satellite attitude, the sensor viewing geometry, the sun illu- 
mination and a digital terrain model (DIM), amalyzes the geometric 
and radiometric characteristics of a space remote sensing mission. 
Furthermore different aspects of the procedure are described par- 
ticularly by means of flow charts. Finally some considerations 
are given due to & preliminary analysis of the results obtained 
on the island of Capri. 
A SHORT DESCRIPTION OF THE SIMULATION PROGRAM 
A deeper description of the simulation program can be 
found in ref. 8, 
The program takes into account: a) the orbital geometry, 
in order to compute the principal orbital parameters, the sub-sa- 
tellite and Doppler track and the local time; b) the remote sen- 
sing system with satellite pointing accuracy and drift to obtain 
each instantaneous line of sight or slant range and its interac- 
tion with illumination and atmospheric conditions due to the 
Earth-Sun motion. 
. The orbital dynamics is derived by the Kepler equation 
and is described as a function of a mean anomaly stop. The sub-sa- 
tellite point longitude and latitude are related to the satellite 
position vector; the local time is computed from the difference 
between Greenwich mean time and zone time. 
The ground location of the line of sight is integrated 
with the orbital dynamics and a DIM in order to get, on a pixel 
by pixel basis, a "geographic" images The interactive DIM program 
uses bicubic polynomials on each square mesh of a grid that can 
be subdivided in subgrids. The intersection of the line of sight 
with the DTM is then found considering the segment from the nadir 
to the geoid point previously found. This intersection allows also 
the atmospheric path lenght evaluation. Finally the Sun elevation/ 
zenith and the Sun shining direction angles are computed descri- 
bing the Earth-satellite motion around the Sun. 
This method takes into account contemporarely the errors 
due to the Earth's morphology, the Earth-satellite dynamics, the 
platforn attitude, the sensor characteristics, the sun illurina- 
tion and the ztmosphere (tab. 1). 
DIFFERENT ASPECTS OF THE SIMULATION PROGRAM 
Besides the possibility of studying the general cha- 
racteristics of a remote sensing mission when the user require- 
ments are given (fig.1 ), the simulation program allows the ana-— 
24 
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