Optimal estimation of ionosphere-induced group delays of global positioning satellite signals during launch, orbit and re-entry

There are many sources of range error in a Global Positioning Satellite (GPS) signal that has traveled to a receiver near the earth's surface. Among these is the ionospheric group delay. In the past, a single-state, dual-frequency filter has been used to estimate the ionospheric delay for authorized users. Although sufficient for terrestrial receivers for which the ionospheric delay changes very slowly, such a filter is inadequate for space-based missions in which a receiver passes rapidly through the ionosphere. Various Kalman filters are examined and simulation results presented. The most robust Kalman filter considered was a seven-state filter. This filter utilizes four measurements: dual-frequency pseudo-range differencing, dual-frequency delta-range differencing, and single-frequency rate measurements for both frequencies (LI and L2). Two states are necessary for the model dynamics plus five constant states necessary for processing rate measurements. The process model selected for the seven-state filter was the integral of a first-order Markov process. The filter was used to estimate both the ionospheric group delay and the deviation of the delay from a given reference model. When used to estimate the deviation of the delay from a reference model, the group delay transitioned from "estimated" to "modeled" smoothly in the absence of measurements. In the absence of measurements, the estimated group delay tends to a bias from the reference model provided.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2007

Author dc:creator

• Johnson, Andrea Marie, S.M. Massachusetts Institute of Technology

Advisor dc:contributor.advisor

• J. Arnold Soltz, Thomas A. Herring and George T. Schmidt.

• Aeronautics and Astronautics.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/62968

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/62968