Ground Tracking Support Condition Effect on Orbit Determination for Korea Pathfinder Lunar Orbiter (KPLO) in Lunar Orbit

Abstract

The ground tracking support is a critical factor for the navigation performance of spacecraft orbiting around the Moon. Because of the tracking limit of antennas, only a small number of facilities can support lunar missions. Therefore, case studies for various ground tracking support conditions are needed for lunar missions on the stage of preliminary mission analysis. This study analyzes the ground supporting condition effect on orbit determination (OD) of Korea Pathfinder Lunar Orbiter (KPLO) in the lunar orbit. For the assumption of ground support conditions, daily tracking frequency, cut-off angle for low elevation, tracking measurement accuracy, and tracking failure situations were considered. Two antennas of deep space network (DSN) and Korea Deep Space Antenna (KDSA) are utilized for various tracking conditions configuration. For the investigation of the daily tracking frequency effect, three cases (full support, DSN 4 pass/day and KDSA 4 pass/day, and DSN 2 pass/day and KDSA 2 pass/day) are prepared. For the elevation cut-off angle effect, two situations, which are 5 deg and 10 deg, are assumed. Three cases (0%, 30%, and 50% of degradation) were considered for the tracking measurement accuracy effect. Three cases such as no missing, 1-day KDSA missing, and 2-day KDSA missing are assumed for tracking failure effect. For OD, a sequential estimation algorithm was used, and for the OD performance evaluation, position uncertainty, position differences between true and estimated orbits, and orbit overlap precision according to various ground supporting conditions were investigated. Orbit prediction accuracy variations due to ground tracking conditions were also demonstrated. This study provides a guideline for selecting ground tracking support levels and preparing a backup plan for the KPLO lunar mission phase.

Observational Arc-Length Effect on Orbit Determination for KPLO Using a Sequential Estimation Technique

“…In this section, the results of OD and OP analysis are discussed. The OD for the one-month period using 48-hr arc-length tracking delivered the results of total position uncertainty under 140 m (3-sigma) and orbit overlaps precision under 35 m (Kim et al 2018b). For OP analysis, Kim et al (2018b) demonstrated that the performance of 72hr OP with tuning was under 270 m. In this study, OD and OP performance variation by tracking arc length duration for 10 days was investigated.…”

“…In this study, the basic OD strategy for KPLO was based on a daily schedule using a fixed arc length by three ground stations. Kim et al (2018b) performed preliminary OD and OP analysis based on a 48-hr arc-length strategy during one month, which has total 26 arcs. In the consecutive daily 48-hr-based OD strategy, a 24-hr orbit overlap period was arranged for orbit precision assessment.…”

“…In the consecutive daily 48-hr-based OD strategy, a 24-hr orbit overlap period was arranged for orbit precision assessment. We followed the same OD strategy of Kim et al (2018b). Estimated parameters were spacecraft position and velocity, solar radiation pressure coefficient Cr, transponder bias, and measurement bias of each station.…”

“…Estimated parameters were spacecraft position and velocity, solar radiation pressure coefficient Cr, transponder bias, and measurement bias of each station. For the arc length effect on the OD investigation, we selected ten days (including face-on geometry) in the middle of the total one-month arc results of Kim et al (2018b). "Face-on geometry" is the case where the line of sight from ground stations and the orbit plane of a lunar orbiter is perpendicular.…”

Autonomous and Earth-Independent Orbit Determination for a Lunar Navigation Satellite System

“…A key performance criterion is an orbit determination accuracy of below 30 m [6], with each satellite transmitting a pseudo-like ranging signal to ground users, to deliver a surface positioning accuracy of 40 m. This performance target is feasible through the use of Earthbased tracking stations, where lunar pathfinder missions have delivered performances below 40 m in three dimensions [8]. However, the use of deep-space tracking networks is expensive, and they have infrequent visibility and a high user demand.…”