Spaceborne InSAR Technique for Study of Himalayan Glaciers using ENVISAT ASAR and ERS Data

An endeavor is made for the study of movement of Himalayan glaciers using Spaceborne InSAR technique, which is based on preserving the coherence between two acquisitions of the same scene. Gangotri, Siachen, Bara Shigri and Patsio are major glaciers in the Himalayan region, which are showing retreat, and their respective tributary glaciers completely disconnected from main body of glaciers. ERS-1/2 observations show high correlation on glacier area and hence movement of Siachen and Gangotri glacier are measured. Information about dynamism of glaciated terrain can be retrieved by counting differential interferograms. Displacement of Gangotri glacier in the radar look direction has been observed as 8.4 cm represented by 3 fringes. Siachen glacier exhibits a displacement of 22 cm represented by 8 fringes. ERS-1/2 tandem data over all these glaciers show highest correlation over glacier areas but ENVISAT ASAR data shows coherence loss over glacier area due to decorrelation. Coherence loss is usual phenomena in glaciated terrain as repeativity of sensor is high (35 days for ENVISAT). Among all these, Siachen glacier shows highest coherence and then Gangotri, respectively. A tandem pair of ERS-1&2 acquired on April 1 and 2, 1996 in descending pass over Siachen shows high coherence than the ascending pair acquired on May 2 and 3, 1996. It is due to change in climate between two acquisitions at glacier locations. A systematic monitoring of dynamism of Himalayan glaciers can be done using Permanent Scatterer Interferometric SAR (PSInSAR) if we place a corner reflector on the glaciers.