International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B1. Istanbul 2004
The tenth acquisition technique has been added to fulfil the
need of 3D information mainly requested for cartography,
hydrology and risk management. Radar interferometry (IF)
has been found the best technical way, from space, to provide
such information with a metric accuracy, improving current
altimetric information given by SPOT 5 with its HRS
instrument. Such data could be provided by 3 micro satellites
placed almost on the same orbit as a SAR satellite, according
to the Interferometric Cartwheel concept created by D.
Massonnet (Massonnet, 1999).
These 10 sensors have been compared in terms of user’s
interest, operational maturity, compliance with National and
European space policy (innovation, industrial impact,
sovereignty, ..) and cost. The user’s interest is shown in
table 2.
Application Sensor needs for the application domain
Mapping HR, WF, X ,IF
Agriculture SS, WF. C
Forests SS WE
Geology HR, 1, WF, CIF
Marine C X
Risks X,C WF TH,IF
Table 2. Sensor needs for application domains
3 PLÉIADES HR DECISION
3.1 Several possible programmatic frameworks
Even if all these sensors have an interest for some users it
could not be possible for CNES to develop them all together.
Cooperation(s) and/or partnership(s) had to be identified to
develop the most important Pléiades components (a
component is a constellation of small satellites associated
with a single sensor)
Three types of co-operative framework had been identified:
- multi-national cooperation under ESA
responsibility, whenever possible, especially for
developing new systems;
- PPP, public private partnership when the market
could be sufficient to cover the recurrent costs.
- bilateral cooperation for components with a strong
Defense interest;
Among all the possible components two of them have been
considered with the highest priority: Optical High Resolution
and SAR X for which a bilateral co-operative framework has
been searched as those systems have a strong Defense
interest. As it will explain in the next paragraph such
cooperation has been found with Italy, to share the
development of these two high resolution systems.
In spite its great interest the Wide Field component has not
been considered with the highest priority, as SPOT-5 fulfill
perfectly this mission for the time being (as ENVISAT is
currently fulfilling the SAR C mission). Nevertheless the
continuity of these missions should be guaranteed and
follow-on systems have to be decided soon.
For the Interferometric Cartwheel which has a great technical
interest several programmatic and cooperation frameworks
are still possible and evaluated, but no decision is expected in
the near future.
Due to its potential market interest, especially for precision
farming, the superspectral system has been proposed through
a Public Private Partnership (PPP) but up to now such
solution could not be implemented.
Other systems considered as less operational in a near future
time scale (L and P band SAR, thermal and hyper spectral
imagery) are not envisaged to be developed by CNES.
3.2 An agreement found with Italy
Since beginning 1999 possible co-operations were envisaged
and the most fruitful co-operation scheme was found with
Italy, as its approach for its COSMO-SkyMed program was
very similar to Pléiades, with a its dual oriented objectives
and multi-sensors approach.
An intergovernmental Agreement was signed by France and
Italy in January 2001. It is an Umbrella Memorandum of
Understanding, which gives the overall objectives and
implementation rules of the co-operation. Its main purpose is
the development and exploitation of a Dual System, ORFEO,
with two high resolution components, one with two optical
satellites under the leadership of France, the other with four
SAR-X satellites under the leadership of Italy. The extension
of the co-operation to other countries can be envisaged, and
France has already set up co-operation agreements with
Belgium, Sweden, Spain and Austria.
3.3 Pléiades HR realization confirmed
The agreement with Italy has allowed CNES to concentrate
its studies on the optical high resolution system whereas SAR
data should be acquired from COSMO-SkyMed. Definition
studies have confirmed the main technical choices and the
possibility to develop and launch the two satellites within the
foreseen cost envelop. Therefore the C/D phase was
confirmed by the CNES Board mid 2003. Cooperation
Agreements have been signed with some European partners:
Sweden, Belgium, Spain and Austria. Now the two satellites
are under construction with Astrium as prime contractor and
Alcatel Space as a major sub-contractor.
The first satellite should be ready by mid 2008 and the
second one by end 2009.
4 PLÉIADES HR CHARACTERISTICS AND
PERFORMANCES
4.1 Main Mission Requirements
Pléiades HR is designed to fulfill civilian and Defense needs
which implies confidentiality and security constraints from
one side as well as easy and quick access through Internet
from the other side. At system level optical data from
Pléiades HR should be, as much as possible, easily
combined with other types of data and especially SAR from
COSMO-SkyMed.
Pléiades HR will provide Earth observations in black and
white (panchromatic band) with a 0.7 m resolution at nadir,
and in color (four spectral bands in the visible and near infra
red range) with a 2.8 m resolution at nadir.
The image swath will be larger than 20 km.
The Pleiades HR satellites will orbit the Earth during at least
5 years on a quasi-circular, sun-synchronous orbit of 695 km
altitude, with a 10h30 descending node local time.
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