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POLinSAR Workshop 2003

Session Title: Spaceborne SAR

Chair(s): A.Moreira, Y-L Desnos
Recommendations (Spaceborne SAR Systems)

1) Several spaceborne SAR sensor and system parameters like resolution, NESZ, baseline, cross-talk isolation, revisit time etc. can be optimized for the data acquisition with polarimetric SAR interferometry for each group of applications (sea ice, forestry, agriculture, etc.). There is a need to make a first iteration between the Pol-InSAR community and the SAR system designers in order to consider the parameter specification in the design of future spaceborne SAR systems. It has influence in the system design as well as in the orbit selection and mission planning.

2) Future spaceborne SAR missions like ALOS, TerraSAR-L will be able to deliver PolinSAR data in repeat pass mode. Future analysis and understanding of the temporal decorrelation is required in order to take into account this effect in the parameter inversion. The limitations posed by the temporal decorrelation must be also investigated. The understanding and modeling of the temporal decorrelation will be very important for the further development of both PolinSAR and interferometric applications.

3) There is a need to coordinate the activities in several countries in the development of future spaceborne SAR systems towards the vision of a sensor web. The organization of working groups and workshops is a first effective way in order to establish an interface between the users and to stimulate the application development.

4) The understanding of basic polarization effects in ENVISAT/ASAR imagery is necessary to support the product development and underlying applications. The Pol-InSAR science community can support this activity by submitting proposals in the scope of the ESA category 1 scheme (permanent AO for science and application development) at http://eopi.esa.int) ENVISAT/ASAR data in the alternating polarization (AP) mode may be used since it allows for the combination of polarimetry and interferometry data acquisition. To support this activity, ESA will invite PI’s having the polarimetric expertise to join the category 1 advisory group, evaluating and reviewing the submitted scientific and application development proposals.

5) Airborne sensors and data exploitation play an important role as a precursor for supporting the definition and development of future spaceborne SAR mission products and applications. In particular the development of user tools shall be supported and made available in a broad sense for the scientific and application development community.
 

Seed Questions:

Question 1
Future, planned SAR missions will allow repeat-pass Pol-InSAR imaging (e.g. ALOS, TerraSAR-L). Which limitations are posed comparing to a dedicated single-pass Pol-InSAR mission?

The revisit time of future systems is varying from 11 to 46 days. Temporal decorrelation is the major limitation which need to be further investigated (cf. recommendation # 2 for Spaceborne SAR Systems). A regularisation (e.g. assumption of a priori information of the extinction coefficient) for the inversion algorithms will be required which poses a limitation in the accuracy of the parameter inversion.

Question 2
There are two trends for future SAR instruments: 1) large complex SAR systems versus 2) small, application focused SAR missions. What would be an optimum configuration for a dedicated Pol-InSAR spaceborne system?

A bistatic configuration using an existing SAR satellite as master satellite and micro-satellites as receivers (e.g. cartwheel) will be very suitable for a future PolInSAR mission.

Question 3
There is a need to co-ordinate future SAR missions being developed by several space agencies. At the end of this decade there will be probably more than 10 SAR systems operating in space, most of them being polarimetric. How to coordinate the individual systems towards a vision of a "sensor web"?

The organization of working groups and workshops is a first effective way in order to establish an interface between the users and to stimulate the application development. In addition, technical coordination (e.g. concerning the definition of radar carrier frequency, bandwidth, orbit selection etc) is required. The protection of the frequency allocations done through CEOS is currently lead by ESA. On a long term, it could even become possible to have tandem missions and constellation of SAR satellite coming from different agencies/countries.

Question 4
What is the impact of the new applications derived from Polarimetric-Inteferometry (POLinSAR) on the specification for future SAR missions ?

Several spaceborne SAR sensor and system parameters like resolution, NESZ, baseline, cross-talk isolation, revisit time etc. can be optimized for the data acquisition with polarimetric SAR interferometry for each group of applications (sea ice, forestry, agriculture, etc.). There is a need to make a first iteration between the Pol-InSAR community and the SAR system designers in order to consider the parameter specification in the design of future spaceborne SAR systems. It has influence in the system design as well as in the orbit selection and mission planning.

Question 5
What is the specific R & D required in preparation of POLinSAR applications (e.g. for the development of new inversion algorithms)?

Three main items have been identified:
· ESA concerted actions (campaigns-study-mission, application study)
· Theoretical Modelling
· Further work on the basic theory of polarimetry

Question 6
What are the new Geophysical products required to be developed by the Space Agencies?

The presentations of the different sensors (Radarsat, TerraSAR-X, Cosmo Skymed and SAOCOM) in the session “Spaceborne SAR Systems” show several tables concerning the applications and products specification which are foreseen in each case. A comparison of these tables can lead to a representative summary of the geo-physical products to be derived in order to fulfil the specifications for the future missions product development.
 
 

 

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