Orbit Determination Strategy Using Single-Frequency Global-Positioning-System Data

Abstract

Orbit determination results are presented for a low-Earth-orbiter (LEO) satellite carrying a single-frequency global-positioning-system (GPS) receiver. Various techniques to correct for errors induced by ionospheric refraction are compared. These include the Jet Propulsion Laboratory's (JPL) global ionosphere maps (GIM), which provide global maps of total electron content. The direct-calibration method, differenced range versus integrated Doppler (DRVID), which uses range differences of group delay and phase advance to compensate for the first-order ionospheric error, was also tested. The fidelity of the orbit solutions was compared using orbit overlaps and orbit differences from dual-frequency truth orbits computed using MicroCosm and JPL's Gipsy-Oasis-II program. Analyses showed that, with a single-frequency GPS receiver on the LEO satellite, the DRVID-corrected carrier phase can determine the orbit with accuracy below the meter level. JPL's GIM correction to pseudorange data also provided improved results over no ionospheric error correction. Nomenclaturec = speed of light, m/s E LEO = elevation angle of global-positioning-system (GPS) satellites at the low-Earth-orbit (LEO) satellite position H = scale height (=100 km), m h IPP = height from ground to the ionospheric pierce point (IPP), m h LEO = altitude of the LEO satellite, m h 0 = peak point of the ionospheric density, m N = integer ambiguity P1, P2 = pseudorange observable on GPS L1 and L2 frequency, respectively r IPP = distance from the Earth center to the IPP, m r LEO = LEO satellite radial position magnitude, m s f (E LEO ) = slant function t k , t 0 = tagging time of measurement for arbitrary epoch k and minimum range epoch 0 during the phase lock, respectively, s α = scale factor ρ ion = ionospheric range delay, m λ IPP , ϕ IPP = longitude and latitude of the IPP, respectively ρ S R = geometric range from the GPS satellite transmitter to the LEO receiver antenna, m 1 = carrier phase range observable on GPS L1 frequency

Near real time orbit detemination of BILSAT-1

“…In equations (11), (12), (13), (14,) G denotes the gradient matrix and t Δ is the time difference. I is the identity matrix.…”

“…In this context, orbit determination algorithms are studied by the various authors in order to supply orbit products within the scientific mission accuracy requirements, using GPS or GPS combined solutions (e.g. [3], [6], [7], [8], [9], [10], [11] ).…”

KOMPSAT-2 Precise Orbit Determination Using GPS Data

“…The drag coefficient is solved to lessen the deficiencies of the atmosphere density model and un-modeled dynamic forces instead of the constant along-track coefficient 6 . The integer ambiguity for carrier phase and GRAPHIC data are also estimated.…”

“…Thus, a direct calibration that combines phase and pseudorange data using range delay and phase advance and ionosphere model such as Global Ionosphere Model (GIM 2 ) can be used for single frequency GPS data to eliminate the ionosphere delay. To reduce the ionospheric error, a method based on ionosphere models or the use of Group and Phase Ionospheric Calibration (GRAPHIC 3 ) technique that averages carrier phase and pseudorange has been tried for single frequency GPS users [4][5][6][7][8][9][10] .…”

An Extended Propagation Ephemeris for GNSS

“…The IGS orbits would then be propagated forward to the epoch of interest. A high fidelity orbit propagator, such as MicroCosm (http://www.vmsi-microcosm.com/gps.html) or Gipsy-Oasys-II [33] could be applied for this purpose. The longer propagating ephemeris would then be fit to the predicted orbits.…”