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Higher-order ionospheric effects on the GPS observables and means of modeling themBased on relaistic 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 Global Positioning Systems (GPS) signal for a ground user. The lowest-order (1/f(exp 2)) effect, which is of the order of .1 - 30 meters of zenith group delay, is subtracted out by forming a linear combination of the dual frequencies of the GPS signal. One is left with second- (1/f(exp 3)) and third-order (1/f(exp 4)) effects which are estimated typically to be approximately 0 - 2 cm, and approximately 0 - 2 mm at zenith respectively, depending on the time of day, time of year, the solar cycle and the relative geometry of the magnetic field and the line of sight. Given the total electron content along a line of sight, we derive an approximation to the second-order term which is accurate to approximately 90% within the magnetic dipole moment model; this approximation can be used to reduce the second-order term to the millimeter level, thus potentially improving precise positioning in space and on the ground. The induced group delay, or phase advance, due to second- and third-order effects are examined for two ground receivers located at equatorial and mid-latitude regions tracking several GPS satellites.
Document ID
19950049812
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Bassiri, Sassan
(Sharif Univ. of Technology, Tehran, Iran, United States)
Hajj, George A.
(Jet Propulsion Lab. California Inst. of Tech., Pasadena, CA, US, United States)
Date Acquired
August 16, 2013
Publication Date
January 1, 1993
Publication Information
Publication: In: Spaceflight mechanics, 1993; AAS(AIAA Spaceflight Mechanics Meeting, 3rd, Pasadena, CA, Feb. 22-24, 1993, Parts 1 & 2 . A95-81344
Publisher: American Astronautical Society (Advances in the Astronautical Sciences, Vol. 82, Pts. 1 & 2)
ISSN: 0065-3438
Subject Category
Communications And Radar
Accession Number
95A81411
Distribution Limits
Public
Copyright
Other

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