Fast satellite imagery of lengthy territories with complex configuration

Abstract

When solving a number of remote sensing problems, there arose a need for fast satellite imagery of arbitrarily-spaced lengthy territories with complex configuration (borders, roads, rivers, coastlines, etc.), The distinctive features of Earth remote sensing satellites equipped with optical-electronic scanners providing sub-meter spatial resolution are a narrow swath width, which does not allow to take images of arbitrarily-spaced lengthy territories in one-orbit period, and a small pixel size of CCD photocells (i.e., low sensitivity), which does not allow to take images of low-contrast objects, as well as take pictures from neighbouring orbits at low angles of the Sun. An effective technique for controlling the high-resolution remote sensing spacecraft orientation in the process of retargeting (i.e., with non-zero angular velocities) is proposed, which allows to choose the best scan mode and take images of arbitrarily-spaced lengthy territories with complex configuration in one-orbit period, i.e. much faster. Moreover, non-zero angular velocities allow to increase the exposure time and take pictures of low contrast, low light or camouflaged objects. The main characteristics and disadvantages of Earth remote sensing satellites equipped with optical-electronic scanners providing sub-meter spatial resolution are shown in the article. The features of planning high-resolution satellite imagery and remote sensing data processing require consideration of a larger number of additional influencing factors than when using traditional imagery with optical-electronic scanners characterized by sub-meter spatial resolution. The main stages of modeling and planning ultra-fast satellite imaging of lengthy territories, as well as the basic design formulas are considered in the article. To approximate a lengthy object defined by the nodal points on the map, smoothing with a cubic interpolating spline is used. For short forecast periods and low earth circular orbits, sufficient accuracy is achieved with the propagator SGP4, which allows to work with the initial conditions in TLE files generated by NORAD.