ORFEO 
plementing it 
ich will serve 
ional levels. 
r comparison, 
ents. 
by COSMO- 
R, developed 
of resolution 
ound Control 
cts for easier 
cquisition of 
r to develop 
Il décrit les 
util adapté à 
ire la plupart 
n, aussi bien 
radar seront 
lution seront 
seulement en 
ique : même 
ifiées seront 
éographique 
'réoscopique 
teurs finaux 
ptique. 
| resolution 
Quick Bird 
t policy. 
ty of small 
Observation 
) has been 
n (about 80 
h 3S2) with 
vious SPOT 
ind cheaper 
nono-sensor 
lite; 
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B1. Istanbul 2004 
Developing dual systems which could be used by 
Defenses as well by Civilian bodies; 
Finding new and important European partners; 
Developing the use of Earth Observation by scientists 
and institutional bodies. 
This paper presents how Pléiades HR has been decided, 
describes its characteristics and performances and indicates 
which actions are undertaken for preparing the users to the 
best use of Pléiades data combined with other space, airborne 
and ground sources of information. 
Chapter 2 presents the mission analysis from which 
several systems have been proposed, 
Chapter 3 explains how Pléiades HR has been chosen 
among the previous candidates 
Chapter 4 details the Pléiades HR system and its 
performances. 
- Chapter 5 presents, as a conclusion the ORFEO 
Preparatory Program and international initiatives which 
should help users to better benefit from Earth 
Observation. 
2 MISSION ANALYSIS 
2.1 User's needs assessment 
In order to identify which space systems should be developed 
users were consulted, within a dedicated expert group and 
through several meetings with the different user 
communities. Results from other European studies, such as 
ERSIS, made by major European industries for ESA, were 
also taken into account. ; 
For each of the main application domains information needs 
had been evaluated and possible sensors to get these 
information identified. 
SAR and optical sensors are both required for most of the 
applications, the first one mainly for its all weather capacity, 
the second one for its better visual interpretation. It is also 
acknowledged that external data from ground or airborne 
surveys are in most cases needed to get reliable and accurate 
information from space imagery. 
2.1.1: Cartography: For basic mapping, land use planning, 
urban surveys or telecommunication the use of space imagery 
is already mature and well known (Konecny, 1999), even if 
the complementarities and competition with aerial 
photographs are still evolving quickly. 
Three types of data are requested: high-resolution (metric or 
sub metric) optical imagery, wide field imagery for medium 
scale mapping of large areas and radar acquisition when all 
weather capabilities are needed. 
2.1.2 Agriculture: Precision farming, agricultural control 
and crop statistics are application with great potentialities for 
Earth observation if efficient methodologies could be used to 
extract useful and accurate end users’ information. From 
current experiments this appears to be feasible but has still to 
be confirmed and operationally implemented. 
Several types of data are needed but the key parameters are 
the number (6 to 20) and choice of spectral bands with a very 
good revisit time (to provide weekly information). 
2.1.3 Forest: Space imagery (SPOT, ERS, Landsat, ..) is 
already used for forest inventories but new application areas 
could be envisaged for timber management or ecological 
surveys. Many Earth Observation data are needed, from very 
high optical photograph (relevant to airborne sensors) to 
multi/superspectral data, radar imagery (P or L band) and 
thermal data (especially for forest fires) 
2.4 Hydrology: Water is considered to be one of the most 
important issues for the future. Its management, either to 
provide fresh water or to avoid catastrophic floods could be 
facilitated using Earth Observation data, such as metric 
optical or radar imagery and especially accurate Digital 
Elevation Models derived from stereoscopic or 
interferometric data. Most of the potential users (insurance 
companies, water providers, civil protection, ..) are not yet 
familiar with such remote sensing data and they should be 
involved as soon as possible in the development of the 
applications. 
2.1.5 Geological prospects: Geology was one of the first 
application domains of Earth Observation and remains an 
important one, with a very diverse need of data, at several 
resolutions, with as many spectral bands as possible, and with 
always stereoscopic and/or interferometric demands. 
It is noted that for mining surveys there is a special interest 
for hyper spectral data. 
2.1.6 Dynamic geology and associated risks: As for 
hydrology the potential interest of Earth Observation for 
dynamic geology and associated risks (earthquakes, 
volcanoes, landslides, ..) is far to be fully exploited and 
GMES initiative could help to develop the use of space data, 
coupled with continuous ground surveys, for such 
applications. The needs for high resolution, either optical or 
radar (X band), and for fast services (within few hours or 
days) have been identified as well as complementary sensors 
(wide field, thermal, SuperSpectral and C or L. SAR). 
2.1.7 Marine applications: Even if Pléiades has not been 
designed to fulfill marine applications, some of these 
applications could be envisaged, either for oceans, sea ice or 
littoral surveys, especially with wide field imagery and C 
band data. 
2.2 Sensor assessment 
As a result of these mission analysis 10 sensors (or 
acquisition techniques) have been identified to fulfil most of 
the users’ needs. The required parameters are described in 
Table I. 
  
  
  
  
  
  
  
  
  
  
  
  
  
Component Resolut Swath Band | Revisit 
ion (m) | width (km) number time 
T (days) 
WF: Wide Field 2-5 40-100 3-4 3-7 
HR: Optical HR =] 10-30 3-4 1-2 
SS: SuperSpectral | 3-10 100-300 6-20 1-2 
HS: Hyperspectral | 5-20 50-300 30-200 2-7 
TH: Thermal 1-40 100 TBD «] 
C:SAR C 2-4 50-300 1-2 1-5 
X: SAR X 1-5 10-300 1-4 «] 
L: SAR L 2-10 50-100 1-4 1-7 
P: SARP 5-10 70-100 1-4 1-7 
IF: Interferometry 1-5 70-100 NA NA 
  
  
  
  
  
* For SAR the number of bands is the number of polarisation 
channels 
Table 1: Sensors requirements