Estimation of absolute GNSS satellite antenna group delay variations based on those of absolute receiver antenna group delays

Susanne Beer,Lambert Wanninger,Anja Heßelbarth

doi:10.1007/s10291-021-01137-8

Abstract

GNSS satellite and receiving antennas exhibit group delay variations (GDV), which affect code pseudorange measurements. Like antenna phase center variations, which affect phase measurements, they are frequency-dependent and vary with the direction of the transmitted and received signal. GNSS code observations contain the combined contributions of satellite and receiver antennas. If absolute GDV are available for the receiver antennas, absolute satellite GDV can be determined. In 2019, an extensive set of absolute receiver antenna GDV was published and, thus, it became feasible to estimate absolute satellite antenna GDV based on terrestrial observations. We used the absolute GDV of four selected receiver antenna types and observation data of globally distributed reference stations that employ these antenna types to determine absolute GDV for the GPS, GLONASS, Galileo, BeiDou, and QZSS satellite antennas. Besides BeiDou-2 satellites whose GDV are known to reach up to 1.5 m peak-to-peak, the GPS satellites show the largest GDV at frequencies L1 and L5 with up to 0.3 and 0.4 m peak-to-peak, respectively. They also show the largest satellite-to-satellite variations within a constellation. The GDV of GLONASS-M satellites reach up to 25 cm at frequency G1; Galileo satellites exhibit the largest GDV at frequency E6 with up to 20 cm; BeiDou-3 satellites show the largest GDV of around 15 cm at frequencies B1-2 and B3. Frequencies L2 of GPS IIIA, E1 of Galileo FOC, and B2a/B2b of BeiDou-3 satellites are the least affected. Their variations are below 10 cm.

Highlights

Most of the precise positioning applications of global navigation satellite systems (GNSS) are based on phase observations and, among other things, on the knowledge of the exact positions of the antenna phase centers (APC) of the transmitting and receiving antenna for all frequencies used
An extensive correction set of absolute receiver antenna group delay variations (GDV) was published (Wübbena et al 2019)
By applying these corrections to observations of four types of receiver antennas, we were able to estimate a set of absolute satellite antenna GDV for five GNSS with the code-minus-carrier (CMC) approach

Summary

Introduction

Most of the precise positioning applications of global navigation satellite systems (GNSS) are based on phase observations and, among other things, on the knowledge of the exact positions of the antenna phase centers (APC) of the transmitting and receiving antenna for all frequencies used. Haines et al (2015) determined nadir-dependent GDV for the entire GPS constellation of 2002–2004 They reach up to 1 m for the ionospheric-free linear combination (IF) of the frequencies L1 and L2 and show block-specific differences and satellite-to-satellite variations in Blocks IIR-A and IIR-B/M. These nadir-dependent GDV were used as corrections for the realization of a terrestrial reference frame with GPS. The German company Geo++, which calibrates receiver antennas with their robot device (Wübbena et al 1997, 2000), presented multi-GNSS and multi-frequency GDV corrections for 36 receiver antenna types They comprise ten GPS, GLONASS, Galileo, and BeiDou frequencies. The L1 PCO has to be applied to the code observations of all frequencies to obtain the overall correction

Method

Summary