It is not possible to have true remote sensing persistence without a constellation of space-based radar imaging satellites. Radar illumination penetrates clouds, haze, dust and smoke. It also works at night.
With a planned launch in 2020, the XpressSAR constellation will guarantee collection in the cloud-persistent regions of the globe between 40°N and 40°S. XpressSAR will collect and deliver your remote sensing data within hours, guaranteed.
XpressSAR will operate a constellation of four small radar satellites with an average revisit rate of just a few hours. XpressSAR will act as a watchful eye in space over any location in its coverage area. It will be able to monitor harbors, airfields, active volcanoes, spreading floods, oil spills, ship traffic, and other sites and activities, with a periodicity of days or even hours.
And because radar illumination is consistent image-to-image, XpressSAR collections of pairs, triplets or large stacks of images can be used for automated change detection. XpressSAR can monitor the location you care about and change detection apps will alert you when something significant has occurred.
XpressSAR will use the most advanced radar imaging technology available. It is based on existing radar imaging technology used on satellites that have been taking high quality, low-noise radar images for several years.
XpressSAR will have a range of collection modes, from small-area spotlight images with resolutions under one meter, to large-area stripmap images with resolutions of 2 to 3 meters, to an ocean scan mode that can be as large as 300 km across and 2000 km long with resolutions of 10 to 30 meters.
Radar imaging does not have a fixed resolution and swath width; it is far more flexible than optical imaging. Pick the mode you need and XpressSAR can handle your variable requirements.
Radar measurements are naturally precise. When radar data are combined with commodity GPS orbit-determination processes, they are used to form images that are in line with the geolocation revolution. XpressSAR images will provide ground coordinates that match the pixel scale of the image. No post-processing needed - you get precision with the image.
In addition to its core advantages of cloud penetration and day or night collection, radar imaging has other interesting capabilities. Radar sensors illuminate the ground using pulses of microwave radiation. The sensors emit thousands of pluses each second and record the resulting echoes. They measure the time it takes each pulse to travel from the sensor to the ground and back, as well as other characteristics of the return wave. From these raw measurements, the SAR technique is used to form images. SAR was a breakthrough in radar imaging because it synthesizes a large virtual antenna from a small physical antenna, allowing imaging from a small platform that can be put into orbit.
In addition, radar’s microwave pulses are coherent. They are controlled and consistent in structure from pulse to pulse. This contrasts to the random illumination of sunlight. The coherent nature of SAR enables high resolution from great distances. In fact, the resolution of a SAR sensor has the remarkable characteristic that it is not dependent on the distance between the sensor and the ground. Coherence also enables special image processing techniques like the precise measurement of surface structure changes over time. Commercial SAR systems have been used, for example, to measure ground subsidence in oil fields at a level of a few millimeters per year.
SAR imaging is not constrained by a fixed focal length like optical telescopes. Therefore imaging can be done in various modes with differing resolution and coverage. Another benefit of SAR is that the images have a natural geometric fidelity and accuracy. Multiple radar images taken over the same location can be managed so that they are all alike with consistent illumination and geometric characteristics. This makes change detection very reliable and one of SAR’s principal applications.
XpressSAR leverages all these technologies to provide the world's best commercial SAR data.