Jaedong Seong, Korea Aerospace Research Institute (KARI); Okchul Jung, Korea Aerospace Research Institute (KARI); Daewon Chung, Korea Aerospace Research Institute (KARI)
Keywords: Space Debris, Conjunction Summary Data, Orbital Accuracy
Abstract:
Now KARI is operating 4 LEO satellites and 2 GEO satellites and preparing operation plan for several new satellites. To operate these satellites safely, SSA & STM activities are essential and thus KARI has performed various SSA & STM activities including collision risk mitigation (i.e., conjunction assessment and collision avoidance maneuver). In the collision risk mitigation activities, the CDM is main information with precise orbit information of KARI satellites and external tracking measurements for secondary objects. In this paper, we analyzed the accuracy of CDM (Conjunction Data Message), which is provided from CSpOC for KARI constellation satellites. Around 40,000 CDM data in 2019 were analyzed for 4 LEO satellites by two strategies. First, CDM accuracy for primary object was analyzed. Primary object means KARI constellation satellite and KARI has the most accurate orbit information from precise orbit determination using onboard GPS raw measurements of satellites. The CDM accuracy for primary object can be determined from difference between KARI orbit and CDM data. Next, secondary object accuracy was analyzed. Reference orbit information of secondary object are hard to obtain without world-wide space surveillance network. Thus, we assumed that last CDM is true data because CDM revised almost every 8 hours for same conjunction event and the orbit uncertainty is getting smaller with new measurement data. We analyzed the CDM accuracy with respect to prediction duration, object type and altitude (i.e., primary satellite orbit). In case of payload, CDM orbit accuracy was 200~300m for 7 days prediction, 100m for 3 days prediction and 50m for 1 day prediction. Rocket body represented similar results with payload. But debris and unknown, which are small objects, represented 1~4km difference for 7 days prediction, 1~3km difference for 3 days prediction and 0.6~1.2km difference for 1 day prediction. This analysis result can be useful for decision-making process of collision avoidance maneuver and risk identification for the close approach events.
Date of Conference: September 15-18, 2020
Track: Astrodynamics