InSAR Application for mapping Ice Sheets Akhilesh Mishra Dec 04, 2015

Figure 1: [1]InSAR review- Path length between two signals received by the antennas is a function of the elevation of mapped terrain InSAR Review where a = 1 for single-pass a = 2 for multipass a = 2 for single-pass, ping-pong mode

RADAR Specification Figure 2: [2]Geometry of the RADAR Two Tx channels and 8 Rx channels Baseline between Tx is 3.658m,  =0 Mode of operation -> Ping Pong mode with alternating PRI between two transmitters i.e. Height above the reference plane ~2500m Figure 3: [2]Mode of operation

Ground based MultiChannel Coherent Radar Depth Sounder Center freq = 150 MHz BW= 30MHz Pulse Duration = 10  s Sampling freq = 120MHz Tx channels = 2 Rx channels = 8 Figure 4: [3]Image of the RADAR

Steps for InSAR processing for this project - Pulse Compress the Raw data Bandpass filter, coherently integrate and decimate data in range dimension Bandpass filter, coherently integrate and decimate data in azimuth dimension SAR process data using Time Domain Back Propagation Steer beam +/- 20 Degrees off nadir Create Side looking SAR complex images Coherence measurements Image registration Create Interferogram

Pulse Compression and SAR processing- TDP Range resolution = 3m Azimuth resolution = 4m Figure 5: Small fragment of the data

Estimation of the bed depth – Reference Height as we move in the along track direction, taken in two way propagation time for applying the firn refraction correction Figure 6: Detection of the reference Height in along track Figure 7: Dielectric constant profile of ice to model refraction

Animation for demonstration of beam steering for generating side looking RADAR image Steering of beam off nadir Figure 8: Animation for side looking RADAR

Steering of beam off nadir Steer the beam to image scene off nadir 300m -900m and avoid the grating lobes ice = (3e08/sqrt(  r )) /fc = 1.13m d= 0.857m Figure 9 : Beam steered to 15 o off nadir Figure 9: [2]Applying Hanning window for steering

Results of steering the beam off nadir by 15 degrees for two paths Figure 10: Steered beam for path 1Figure 11: Steered beam for path2

Calculation of the coherence in the two images for registration of images Figure 12: Absolute power plot of cross track swath 1 Figure 13: Absolute power plot of cross track swath 2

Figure 14: Absolute power –mean power cross track swath 1Figure 14: Absolute power –mean power cross track swath 2

Plots and results of Dr. William Blake Figure 15: [2]Coherence value with pixel shift of -1.3 for 15 o off nadir beam

Figure 16: [2] Constructed Interferogram Figure 17: DEM

References 1. InSAR slides, Dr. Allen 2. INTERFEROMETRIC SYNTHETIC APERTURE RADAR (INSAR) FOR FINE- RESOLUTION BASAL ICE SHEET IMAGING, Dissertation Dr. William Blake 3. DataProducts and Images from CReSIS