Speckle Tracking for 2-Dimensional Ice Motion Studies in Polar Regions: Influence of the Ionosphere.

• Main Authors: Laurence Gray, Karim Mattar, Naomi Short
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Antarctic; Antarc*
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.205.3178; http://earth.esa.int/pub/ESA_DOC/fringe1999/Papers/gray.pdf

Speckle tracking can be used to estimate glacial ice motion in coherent pairs of SAR images. The technique is particularly appropriate when either the ice motion or temporal separation of the data acquisitions are large. Examples of ice motion derived from speckle tracking analysis of the NASA/CSA Antarctic Mapping Mission interferometric data are shown. In this, and in earlier work, it has been shown that occasionally streaks are observed in interferograms acquired at polar latitudes. Usually the effect is observed in the coherence, but associated modulation has also been observed in the phase. This affect arises from a km scale modulation in the optimum azimuth registration. The streaks in azimuth registration, or azimuth ‘shift’, could not be caused by terrain motion and were treated previously as an ‘artifact ’ of unknown origin. We present evidence that the effect is caused by small scale ionospheric disturbances associated with polar auroral regions. We propose that imagery of the azimuth shift streaks is related to a 2-dimensional ‘shadow ’ of the along-track gradient of the integrated electron density.