SEARCH

SEARCH BY CITATION

Abstract

  1. Top of page
  2. Abstract
  3. References

The effect of equatorial ionospheric scintillations on the operation of GPS receivers is investigated, with special attention given to the effect of scintillation timescales on the code division multiple access (CDMA) protocol used by GPS. We begin by examining the timescales of scintillation fades modeled as a horizontally drifting pattern whose timescales are determined by the Fresnel length and the drift speed. The model is tested by comparing the speed, determined by dividing the Fresnel length by the autocorrelation time (width), with the speed estimated using spaced receivers, and the two independent estimates of speed are shown to possess a linear relationship. Next we show that the scintillation pattern drift speed is given by the difference of the ionospheric drift and the speed of the GPS signal F region puncture point. When the ionosphere and GPS signal puncture point speeds match, the fade timescales lengthen. Additionally, if the fade depth is adequate, during periods of longer fade times the loss of receiver lock on GPS signals is more likely, as shown in several examples; that is, both larger fade depths and longer fade timescales are required to produce loss of tracking. We conclude by demonstrating that speed matching or resonance between the ionosphere and receiver is most likely when the receiver is moving from west to east at speeds of 40–100 m/s (144–360 km/h). This is in the range of typical aircraft speeds.

References

  1. Top of page
  2. Abstract
  3. References
  • Aarons, J., Global morphology of ionospheric scintillations, Proc. IEEE, 704, 360378, 1982.
  • Aarons, J., The longitudinal morphology of equatorial F-layer irregularities relevant to their occurrence, Space Sci. Rev., 63, 209243, 1993.
  • Aarons, J., J. P. Mullen, H. E. Whitney, E. M. MacKenzie, The dynamics of equatorial irregularity patch formation, motion, and decay, J. Geophys. Res., 85A1, 139149, 1980.
  • Basu, S., S. Basu, Equatorial scintillations: Advances since ISEA-6, J. Atmos Terr. Phys., 47, 753768, 1985.
  • Basu, S., S. Basu, Ionospheric structures and scintillation spectra, Wave Propagation In Random Media (Scintillation)V. I. Tatarskii, A. Ishimaru, V. U. Zavorotny, 139155, Soc. for Opt. Eng., Bellingham, Wash., 1993.
  • Basu, S., E. MacKenzie, S. Basu, Ionospheric constraints on VHF/UHF communications links during solar maximum and minimum periods, Radio Sci., 233, 363378, 1988.
  • Basu, S., et al., Scintillations, plasma drifts, and neutral winds in the equatorial ionosphere after sunset, J. Geophys. Res., 101A12, 26,79526,809, 1996.
  • Coker, C., D. Coco, G. J. Bishop, A. J. Mazzella Jr., How bad are the effects of ionospheric scintillation on GPS?: An initial bench-test, Space Weather Effects on Propagation of Navigation & Communication Signals, Abstracts of Invited Review Talks and Contributed Papers, 24, COMSAT Corp., Bethesda, Md., 1997.
  • Fejer, B. G., M. C. Kelley, Ionospheric irregularities, Rev. Geophys., 18, 401454, 1980.
  • Kelley, M. C., Equatorial spread F: Recent results and outstanding problems, J. Atmos Terr. Phys., 47, 745752, 1985.
  • Kelley, M. C., The Earth's Ionosphere: Plasma Physics and Electrodynamics, Int. Geophys. Ser., 43, Academic, San Diego, Calif., 1989.
  • Kil, H., P. M. Kintner, E. R. dePaula, I. J. Kantor, Global Positioning System measurements of the ionospheric zonal apparent velocity at Cachoeira Paulista in Brazil, J. Geophys. Res., 105A3, 53175327, 2000.
  • Koster, J. R., Ionospheric studies using the tracking beacon on the Early Bird synchronous satellite, Ann. Geophys., 22, 435445, 1966.
  • Mazzella Jr., A. J., E. J. Fremouw, J. A. Secan, C. H. Curtis Jr., G. J. Bishop, An algorithm for simulating scintillation, Space Weather Effects on Propagation of Navigation & Communication Signals, Abstracts of Invited Review Talks and Contributed Papers, 42, COMSAT Corp., Bethesda, Md., 1997.
  • Ossakow, S. L., Spread F theories; A review, J. Atmos. Terr. Phys., 43, 437452, 1981.
  • Sahai, Y., J. Aarons, M. Mendillo, J. Baumgardner, J. A. Bitten-court, H. Takahashi, OI 630 nm imaging observations of equatorial plasma depletions at 16 degree S dip latitude, J. Atmos. Terr. Phys., 56, 14611475, 1994.
  • Salpeter, E. E., Interplanetary scintillations, I, Theory, Astrophys. J., 147, 433448, 1967.
  • Spatz, D. E., S. J. Franke, K. C. Yeh, Analysis and interpretation of spaced receiver scintillation data recorded at an equatorial station, Radio Sci., 233, 347361, 1988.
  • Spilker Jr., J. J., GPS signal structure and theoretical performance, Global Positioning System: Theory and Applications, 1B. W. Parkinson, J. J. Spilker Jr., 57119, Am. Inst. of Aeronaut. and Astronaut., New York, 1996.
  • Sultan, P. J., Linear theory and modeling of the Rayleigh-Taylor instability leading to the occurrence of equatorial spread F, J. Geophys. Res., 101A12, 26,87526,891, 1996.
  • Wernik, A. W., C. H. Liu, K. C. Yeh, Modeling of spaced-receiver scintillation measurements, Radio Sci., 185, 743764, 1983.
  • Yeh, K. C., C.-H. Liu, Radio wave scintillations in the ionosphere, Proc. IEEE, 704, 325378, 1982.