Low Earth orbit satellite navigation errors and vertical total electron content in single‐frequency GPS tracking

Abstract

[1] In the context of space applications, the GPS system is presently a well-established and accepted tracking system. To meet the basic navigation requirements, most satellites in a low Earth orbit are equipped with single-frequency GPS receivers that measure the coarse acquisition code as well as the L1 phase. However, the resulting kinematic navigation solutions exhibit systematic position errors caused by elevation-dependent ionospheric path delays. In this study a simple analytical model is established, which quantitatively relates the position error to the vertical electron content and the mapping function. This model substantiates the empirical evidence of a mean radial offset that increases in proportion to the total electron content above the satellite. It is furthermore shown that the ratio between this offset and the vertical ionospheric path delay depends on the applied elevation mask angle. Representative ratios of 3-5 are obtained for the mapping function of the Lear ionosphere model and elevation cutoff angles of 10°, 5°, and 0°. This analytical result has further been confirmed by signal simulator tests as well as flight data of the CHAMP satellite.Citation: Garcia-Fernàndez, M., and O. Montenbruck (2006), Low Earth orbit satellite navigation errors and vertical total electron content in single-frequency GPS tracking, Radio Sci., 41, RS5001,

NeQuick-G performance assessment for space applications

“…As described in Garcia-Fernàndez and Montenbruck (2006), the Lear mapping function closely matches the STEC/VTEC ratio at 450 km altitude for a Chapman density profile with 75 km scale height and peak electron density at 300 km altitude. Like the more generic F&K mapping function, the Lear mapping function has been widely employed for ionospheric correction of GPS observation from individual spacecraft as well as satellite formations (Garcia-Fernàndez and Montenbruck 2006;Tancredi et al 2011).…”

“…The model is particularly beneficial for the radial component, which is most sensitive to uncorrected path delays. As a rule of thumb, SPP solutions of orbiting receivers exhibit a mean radial bias of 5-7 times the uncompensated vertical delay for typical mask angles and elevation dependencies of the ionospheric delay (Garcia-Fernàndez and Montenbruck 2006). For the given test data set, a mean radial bias of + 4 m can be observed, which changes to −1 m upon correction.…”

Morphology of high‐latitude plasma density perturbations as deduced from the total electron content measurements onboard the Swarm constellation

“…We use the obliquity function of Garcia‐Fernàndez and Montenbruck [, equation (15)], which originates from Lear []: where θ is the elevation angle toward a GNSS satellite: it is 90° when the GNSS satellite is at the zenith of Swarm. The minimum elevation angle of the Swarm TEC data product is 20°.…”

Autonomous and Precise Navigation of the Proba-2 Spacecraft

“…To study the influence of key error sources, ionospheric path delays and broadcast ephemeris errors have been considered in most of the tests. The "spacecraft ionosphere model" (which implements the Lear mapping function 36 ) and a constant total electron content (TEC) of 5•10 16 electrons/m 2 (=5 TECU) have been selected for the simulation of ionospheric effects. The impact of broadcast ephemeris and clock errors on the navigation solution has been modeled by considering constant offsets between the modeled GPS spacecraft position and the one described by the GPS navigation message.…”