Cost Effective One-Way Doppler Measurements Correction of NOAA Satellites Using GPS Dissemination

Abstract

This paper describes a new low cost method implemented in Bremen university ground station for correcting Doppler measurements based on GPS techniques. The facilities of the tracking ground station to determine the one-way Doppler shift of the NOAA weather satellites are described. Using an open source GPS platform, frequency bias in the measurement and receiving devices was measured. The performance of the low cost instruments with antennas, rotor controller, receiver, frequency counter and open source GPS terminal will be explained. This station is a reassembly of the same ground station used previously in 1994 to support the BREM-SAT mission, with the addition of the GPS terminal in order to measure the reference oscillator's error. Incorporating all the processed measurements, a corrected Doppler shift curve will result which differs from the original measured Doppler curve by the fact that the frequencies now are the absolute values. The results are compared with the expected nominal predictions. Finally, the least square algorithm was implemented for orbit determination using the uncorrected and corrected measurements. Nomenclaturec = speed of light f d = Doppler frequency f 0 = nominal frequency f synth = synthesizer frequency f measured = measured frequency H = transition matrix R = covariance matrix x, y, z = coordinates of state vector ρ = range ρ = range rate ρ ′ = estimated range rate

Recepción de Imágenes Meteorológicas de Colombia con una Antena de Dipolos Cruzados

“…La figura 6 corresponde a una imagen meteorológica del centro y norte de Colombia con resolución de 72 dpi. En el momento de la recepción se observó en el analizador de espectros una desviación de frecuencia de portadora de ±10KHz, atenuación por efecto de cables utilizados en el proceso de medición (Suarez-Fajardo et al, 2017) y reducción del ancho de banda de la señal modulada influenciados por el efecto Doppler, que hizo que la amplitud de la portadora disminuyera y la frecuencia variara rápidamente mientras el satélite pasaba sobre la estación receptora (Mahmood et al, 2016;Qaise et al, 2008). La figura 7 corresponde a la segunda imagen meteorológica de la misma zona del país, pero con una resolución de 72 dpi y una desviación de frecuencia de ±12KHz.…”