NISAR Provisional Range Doppler Wrapped Interferogram Product (Version 1)

The NASA-ISRO Synthetic Aperture Radar (NISAR) Range Doppler Wrapped Interferogram (RIFG) product represents the ellipsoid and topography flattened wrapped interferogram generated from two Level 1 Range-Doppler Single Look Complex (RSLC) products in the range-Doppler geometry of the earlier reference acquisition. The WGS84 ellipsoid is used as the reference surface for flat earth correction.

The RIFG product contains a binary raster layer of complex numbers, i.e., the wrapped interferogram; its phase represents the wrapped interferometric phase in radians. The product also contains a binary raster layer of floating-point numbers representing the normalized interferometric correlation, i.e., the interferometric coherence magnitude. The wrapped interferogram and the interferometric coherence magnitude are multi-looked to a nominal posting of 30 m on the ground. No ionospheric phase screen correction layers are available with this product.

The interferometric workflow producing RIFG products coregisters a pair of RSLC products using a Digital Elevation Model and the best available orbit ephemeris. This coregistration is refined using incoherent cross-correlation on the pair of coarsely coregistered RSLCs. The RIFG product includes the slant range and along-track sub-pixel offsets obtained from incoherent cross-correlation and used to generate the complex wrapped interferogram. If a Range Doppler Pixel Offsets (ROFF) product is available for the processed frame, the sub-pixel offset layers included in RIFG are obtained by optimally blending the multi-resolution offset layers included in ROFF.

The products in this collection are considered Provisional products and are intended to facilitate data exploration and process studies that do not require rigorous validation. These data are partially validated, and improvements are continuing; quality may not be optimal since validation and quality assurance are ongoing.