NISAR Beta Range Doppler Pixel Offsets (Version 1)

The NASA-ISRO Synthetic Aperture Radar (NISAR) Range Doppler Pixel Offsets (ROFF) product contains a collection of dense pixel offset layers obtained from applying incoherent cross-correlation on a pair of coarsely coregistered Level 1 Range Doppler Single Look Complex (RSLC) products in the range-Doppler geometry of the earlier reference RSLC product. The pair of RSLCs used to produce ROFF is first coarsely aligned with geometrical coregistration using the best available sensor orbit ephemeris and a Digital Elevation Model (DEM).

The spacing, the window size, and the search radius used to generate the ROFF offsets layers for L-SAR data are organized by sensor mode and area of observation. Irrespective of the mode, the pixel offset layers are provided with a nominal posting of 90 m on the ground. It is assumed that pixel offset layers within ROFF share the same spacing and the same starting pixel along slant range and azimuth directions. Each pixel offset layer is distributed without performing any conventional post-processing operation, i.e., layers might contain offset outliers and are not low-pass filtered to reduce noise in the data.

The products in this collection are considered Beta products and are intended to enable users to gain familiarity with the parameters and the data formats. Beta products are not intended for use in scientific research.

NASA-ISRO合成孔径雷达（NISAR）距离多普勒像素偏移（ROFF）产品集，收录了一系列高密度像素偏移图层。此类图层通过对两幅经粗略配准的一级距离多普勒单视复数（RSLC）产品，在参考RSLC产品原有的距离多普勒几何框架下执行非相干互相关处理得到。用于生成ROFF产品的两幅RSLC数据，首先会借助当前最优的传感器轨道星历与数字高程模型（DEM），通过几何配准完成初步对齐。

针对L波段合成孔径雷达（L-SAR）数据生成ROFF偏移图层时所采用的采样间距、窗口尺寸与搜索半径，均按照传感器工作模式与观测区域进行分类组织。无论采用何种工作模式，所有像素偏移图层的地面标称采样间距均为90米。ROFF产品集中的各像素偏移图层，默认在斜距与方位向均采用统一的采样间距与起始像素位置。需特别说明的是，本产品的像素偏移图层未经过任何常规后处理操作：图层中可能存在偏移异常值，且未通过低通滤波去除数据中的噪声。

本数据集的所有产品均属于测试版（Beta）产品，仅用于帮助用户熟悉相关参数与数据格式，不建议用于正式科学研究工作。