Remote sensing of the ionosphere from very low earth orbit

The charge density of the ionosphere peaks several hundred kilometers above the surface of the Earth and is responsible for both enabling and interfering with signals for radar, navigation, and communication. The ionosphere is caused by ionizing radiation from the Sun interacting with the Earth’s atmosphere. It is part of a complex network of charged particles and electromagnetic fields surrounding the Earth. Thus, understanding the variations and irregularities in the structure, strength, and position of the ionosphere is important to a number of pure and applied scientific and technical fields. The advent of Very Low Earth Orbit (VLEO) spacecraft allows us to make measurements of the region of ionospheric peak electron density from a spacecraft located in or near to the density peak. We describe the use of ultraviolet sensors on VLEO spacecraft to image the position and structure of the ionosphere near the ionospheric peak. When making in situ measurements there is always the risk that the presence of the sensor will alter the subject of the measurements. This is particularly true of a spacecraft traveling at a high Mach number through a charged medium like the ionosphere. Optical measurements avoid local effects by measuring the gas at a small, but significant distance from the spacecraft. We have modeled the response of the sensors and the expected results of a VLEO spacecraft with a pair of optical sensors observing optically thin emission such as the O I 1356 Å line. • VLEO spacecraft can be used for ionospheric remote sensing. • When used for ionospheric remote sensing optical sensors on VLEO spacecraft are sensitive to ionosphere structure. • Optical sensors on VLEO spacecraft are sensitive to ionospheric structure at both large and small scale, including such features as ionospheric plumes.