Imaging the Ionosphere with the Global Positioning System
Observing the Global Positioning System by a satellite in low earth orbit in an occulting geometry provides a powerful means of imaging the ionosphere.
tomographic↗
Engineering topics
Hajj, G.
Publications and source records attributed to Hajj, G..
Accuracies of Atmospheric Profiles Obtained from GPS Occultations
Radio occultation studies of the terrestrial atmosphere are possible through use of signals transmitted by satellites of the Global Positioning System (GPS) and received by one or more other satellites in low earth orbit (LEO). The perturbed phase of the occulted signal gives direct information on the refractivity profile in the region of occultation, from which vertical profiles of density, pressure, and temperature can be retrieved. Based on model simulations the capability of GPS to provide atmospheric profiles is assessed.
atmospheric↗
Ionospheric Imaging From a Low Earth Orbiter Tracking GPS
Tomographic imaging of the ionosphere is examined using singular value decomposition analysis. The interdependency of the obtainable resolution, the accuracy of the solution and the noise data is explained. A simulation is illustrated where a true 2-D ionospheric structure is generated, and a tomographic inversion of the structure is carried out. Inclusion of data taken in an occultation geometry reveals the strength that is added by these data. The effect of the ionosphere on a GPS signal as viewed by a user in space is examined. Under somewhat strong solar conditions, the absolute bending of the signal is of the order of 0.01 degrees for the L1 signal; the phase advance can be as large as 90 meters.
ionosphere↗
Atmospheric Profiles from Radio Occultation Measurements of GPS Satellites
Atmospheric profiles can be retrieved with techniques utilizing measurements of the propagation delay of signals from Global Positioning System satellites observed by one or more receivers in low earth orbit.
limb-sounding↗
Higher-Order Ionospheric Effects on the GPS Observables and Means of Modeling Them
Based on realistic modeling of the electron density of the ionosphere and using a dipole moment approximation for the earth magnetic field, we are able to estimate the effect of the ionosphere on the GPS signal for a ground user. Our study implies reduction of the second-order ionospheric error to less than 2 mm on the average and, therefore, potential improvement of orbit determination and baseline solutions.
ionosphere↗