Long range airborne SAR imaging with very high resolution is appealing in many applications for protecting the sensor aircraft or for avoiding its interference with existing air traffic. Extending range to imaged area yields several difficulties: First the increase in propagation loss is mitigated by increasing the transmitted power and using an high gain antenna (more directive). But, unlike satellite borne case, an highly directive antenna requires active steering for compensating aircraft attitude variations during signal acquisition. It may also require slowing or stopping antenna footprint sweeping on the ground in order to allow long integration time hence high azimuth resolution. Second, increased radio wave flight time imposes to have several pulses simultaneously in flight in order to keep pulse repetition frequency above antenna pattern Doppler width. Thus, in case frequency agility is used (for very high range resolution), received sub-band may not match the just transmitted one, which has an impact on the system design. Third, as integration time increases, the required accuracy on the trajectory for focusing the image is also increased. Trajectory measurement can be improved with autofocus, however, as antenna is more directive, this requires a tie-point coverage with an higher angular density thus cancelling the beneficial effect of range increase in that matter. Last, as aircraft operational altitude is limited, incident angle is more grazing some landscape may not be appropriated to random tie-point sampling. These issues are illustrated with signals from the X-band radar on the ONERA new RAM- SES SAR system.


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    Titel :

    Very high resolution airborne synthetic aperture radar imaging at long range


    Beteiligte:


    Erscheinungsdatum :

    2013


    Format / Umfang :

    6 Seiten, 5 Bilder, 4 Quellen



    Medientyp :

    Aufsatz (Konferenz)


    Format :

    Datenträger


    Sprache :

    Englisch




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