Abstract
Low Earth orbit (LEO) satellites play an important role in human space activities, and market demands for commercial uses of LEO satellites have been increasing rapidly in recent years. LEO satellites mainly consist of Earth observation satellites (EOSs), the major commercial applications of which are various sorts of Earth observations, such as map making, crop growth assessment, and disaster surveillance. However, the success rates of observation tasks are influenced considerably by uncertainties in local weather conditions, inadequate sunlight, observation dip angle, and other practical factors. The available time windows (ATWs) suitable for observing given types of targets and for transmitting data back to ground receiver stations are relatively narrow. In order to utilize limited satellite resources efficiently and maximize their commercial benefits, it is necessary to evaluate the overall effectiveness of satellites and planned tasks considering various factors. In this paper, we propose a method for determining the ATWs considering the influence of sunlight angle, elevation angle, and the type of sensor equipped on the satellite. After that, we develop a satellite effectiveness evaluation (SEE) model for satellite observation and data-downlink scheduling (SODS) based on the Availability–Capacity–Profitability (ACP) framework, which is designed to evaluate the overall performance of satellites from the perspective of time resource utilization, the success rate of tasks, and profit return. The effects of weather uncertainties on the tasks’ success are considered in the SEE model, and the model can be applied to support the decision-makers on optimizing and improving task arrangements for EOSs. Finally, a case study is presented to demonstrate the effectiveness of the proposed method and verify the ACP-based SEE model. The obtained ATWs by the proposed method are compared with those by the Systems Tool Kit (STK), and the correctness of the method is thus validated.
Highlights
Earth observation satellites (EOSs) use Earth-observing sensors to detect the Earth’s surface and lower atmosphere to obtain information [1]
We firstly describe the motion of a low Earth orbit (LEO) satellite in an Earth-centered inertial (ECI) coordinate frame and provide a method for generating the available time windows (ATWs) considering sunlight angles, elevation angles, and sensor types
A procedure for obtaining available time windows with multiple constraints is presented, and an Availability–Capacity–Profitability (ACP)-based satellite effectiveness evaluation (SEE) model is provided for evaluating the effectiveness of a given satellite observation and data-downlink scheduling (SODS)
Summary
Earth observation satellites (EOSs) use Earth-observing sensors to detect the Earth’s surface and lower atmosphere to obtain information [1]. By using many kinds of remote sensing systems, such satellites can measure a wide range of spatial, spectral, and temporal parameters [2]. Spectral measurements from satellite remote sensors have been applied in many fields, including national defense construction, economic development, national security, environmental protection, disaster assessment, and land resource surveys [3,4]. Among the satellites active on 30 November 2018, 1232 of them (63%) were low Earth orbit (LEO) satellites, i.e., those orbiting at an altitude of less than 2000 km above the Earth’s surface. Since LEO satellites have the property of low propagation delay, they are very suitable for use in multimedia technology, as they should be able to deliver a large amount of information such as image and video signals at a higher data rate, as well as audio signals at a relatively low data rate [7,8]
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