GLONASS Data Analysis: Interim Results

Abstract

A satellite navigation data collection and analysis facility, comprising GPS and GLONASS receivers and the supporting computer systems, has been established at Lincoln Laboratory under the sponsorship of the Federal Aviation Administration. In this paper, we present results based on an analysis of the measurements from GLONASS collected at this facility over a 6 month period (FebruaryJuly 1991). While our main interest is in the positioning results obtained from GLO-NASS, we also examine some important issues related to the system operations. The findings are generally consistent with the technical data provided by the Soviets. The GLONASS positioning results are comparable to those provided by the GPS Standard Positioning Service (SPS) when the Selective Availability (SA) feature of the latter is off. When the GPS signal is degraded via SA, the GLONASS position estimates will clearly be better. Of course, the positioning accuracy reflects directly on the quality of the system upkeep and control. We have analyzed the navigation messages in order to understand the nominal patterns of data uploads, changes in parameter values at uploads, and the handling of system anomalies. We discuss these findings and identify some issues requiring further clarification.