Abstract
Making use of dual-frequency (DF) global navigation satellite system (GNSS) observations and good dynamic models, the precise orbit determination (POD) for the satellites on low earth orbits has been intensively investigated in the last decades and has achieved an accuracy of centimeters. With the rapidly increasing number of the CubeSat missions in recent years, the POD of CubeSats were also attempted with combined dynamic models and GNSS DF observations. While comprehensive dynamic models are allowed to be used in the postprocessing mode, strong constraints on the data completeness, continuity, and restricted resources due to the power and size limits of CubeSats still hamper the high-accuracy POD. An analysis of these constraints and their impact on the achievable orbital accuracy thus needs to be considered in the planning phase. In this study, with the focus put on the use of DF GNSS data in postprocessing CubeSat POD, a detailed sensitivity analysis of the orbital accuracy was performed w.r.t. the data continuity, completeness, observation sampling interval, latency requirements, availability of the attitude information, and arc length. It is found that the overlapping of several constraints often causes a relatively large degradation in the orbital accuracy, especially when one of the constraints is related to a low duty-cycle of, e.g., below 40% of time. Assuming that the GNSS data is properly tracked except for the assumed constraints, and using the International GNSS Service (IGS) final products or products from the IGS real-time service, the 3D orbital accuracy for arcs of 6 h to 24 h should generally be within or around 1 dm, provided that the limitation on data is not too severe, i.e., with a duty-cycle not lower than 40% and an observation sampling interval not larger than 60 s.
Highlights
Combining strong dynamic models and observations of global navigation satellite system (GNSS) collected onboard, the processing strategies used for the low Earth orbit (LEO) reduced-dynamic precise orbit determination (POD) have been intensively investigated in the last decades [1,2,3,4,5]
Compared to the dynamic orbits based on the dynamic models only and the kinematic orbits based on the GNSS observations only, the reduced-dynamic orbit determination has the advantage that it is more robust against model deficiencies for the former case, and possible data constraints, e.g., data in-continuity for the latter case
As an important step at the planning phase of the CubeSat missions, a proper compromise needs to be carefully considered between these constraints and the orbital accuracy, so that limited resources can be better managed and saved for other tasks of CubeSat missions under the required POD accuracy
Summary
Combining strong dynamic models and observations of global navigation satellite system (GNSS) collected onboard, the processing strategies used for the low Earth orbit (LEO) reduced-dynamic precise orbit determination (POD) have been intensively investigated in the last decades [1,2,3,4,5]. For undifferenced POD, the highest accuracy is often realized in postprocessing mode applying good dynamic models, precise GNSS satellite orbits, and clocks, and under the condition that the GPS dual-frequency phase and code data are tracked and collected with a good continuity and completeness. The collected GNSS observations are most likely to be temporarily stored onboard and transferred back to the ground processing centre (GPC) every orbital cycle or a few cycles during a limited ground contact time, while information of tasks other than positioning is required to be stored and transferred at the same time. With the expectation that in future CubeSat missions, dual-frequency measurements can be properly tracked in each duty-cycle by geodetic receivers with a mean average satellite number of at least 5 to 6, this study performs a sensitivity analysis of different limitations on the data availability, continuity, resources, latencies, and arc lengths with respect to the orbital accuracy. In addition to CubeSats, the analysis should benefit the POD of other small satellites that need to bare similar constraints on data, power, and resources
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