Assessment of the performance of the TOPGNSS and ANN-MB antennas for ionospheric measurements using low-cost u-blox GNSS receivers

Low-cost GNSS receivers have recently been gaining reliability as good candidates for ionospheric studies. In line with these gains are genuine concerns about improving the performance of these receivers. In this work, we present a comprehensive investigation of the performances of two antennas(the u-blox ANN-MB and the TOPGNSS TOP-106) used on a low-cost GNSS receiver known as the u-blox ZED-F9P. The two antennas were installed on two identical and co-located u-blox receivers. Data used from both receivers cover the period from January to June 2022. Results from the study indicate that the signal strengths are dominantly greater for the receiver with the TOPGNSS antenna than for the receiver with the ANN-MB antenna, implying that the TOPGNSS antenna is better than the ANN-MB antenna in terms of providing greater signal strengths. Summarily, the TOPGNSS antenna also performed better in minimizing the occurrence of cycle slips on phase TEC measurements. There are no conspicuous differences between the variances(computed as 5-min standard deviations) of phase TEC measurements for the two antennas, except for a period around May-June when the TOPGNSS gave a better performance in terms of minimizing the variances in phase TEC. Remarkably, the ANN-MB antenna gave a better performance than the TOPGNSS antenna in terms of minimizing the variances in pseudorange TEC for some satellite observations. For precise horizontal(North and East) positioning, the receiver with the TOPGNSS antenna gave better results, while the receiver with the ANN-MB antenna gave better vertical(Up) positioning. The errors for the receivers of both antennas are typically within about 5 m(the monthly mean was usually smaller than 1 m) in the horizontal direction and within about 10 m(the monthly mean was usually smaller than 4 m) in the vertical direction.

Characteristics of solar-irradiance spectra from measurements,modeling,and theoretical approach

An accurate solar-irradiance spectrum is needed as an input to any planetary atmosphere or climate model.Depending on the spectral characteristics of the chosen model,uncertainties in the iradiance may introduce significant differences in atmospheric and climate predictions.This is why several solar spectral-irradiance data sets have been published during the last decade.They have been obtained by different methods:either measurements from a single instrument or a composite of different spectra,or they are theoretical or semi-empirical solar models.In this paper,these spectral datasets will be compared in terms of iradiance,power per spectral interval,their derived solar-atmosphere brightness temperature,and time series.Whatever the different sources of these spectra are,they generally agree to within their quoted accuracy.The solar-rotation effect simultaneously observed by SORCE and PREMOS-PIC ARD is accurately measured.The 11-year long-term variability remains a difficult task,given the weak activity of solar cycle 24 and long-term instrument aging.