Imaging Ionospheric Density and Height Gradients from Geosynchronous Orbit

The capability to image ionospheric density and height gradients globally from a geosynchronous platform will provide new information critical to understanding the development and evolution of ionospheric structures and gradients. Eventually, such a system will also provide a forecasting capability that will permit mitigation of the effects of ionospheric structures and steep ionospheric gradients on systems that rely on trans-ionospheric radio frequency propagation, such as satellite communication systems and global positioning system navigation. The Naval Research Laboratory and the Office of Naval Research have been developing an instrument for flight on a geosynchronous platform (altitude ~36000 km). This instrument, called the Ionospheric Mapping and Geocoronal Experiment (IMAGER), is designed to image a selectable 1000 km field-of-view at 10 km resolution in ~100 seconds. The instrument will image in one of four selectable extreme- and far-ultraviolet passbands centered at 83, 130.4, 135.6, and 148.0 nanometers, which will allow it to measure the dayside and nightside ionosphere and the N2 and O column densities in the dayside thermosphere on the Earth’s disk. The instrument can also image the Earth’s limb to observe atmospheric altitude profiles and ion outflow. We present and discuss our instrument concept and the algorithm developments that permit us to image F-region ionospheric density and height gradients during the daytime and at night.