A framework for orbital performance evaluation in Distributed Space Missions for earth observation

Abstract

Abstract-Distributed Space Missions (DSMs) are gaining momentum in their application to earth science missions owing to their unique ability to increase observation sampling in angular, spatial, spectral and temporal dimensions simultaneously. DSM architectures have a large number of design variables and since they are expected to increase mission flexibility, scalability, evolvability and robustness, their design is a complex problem with many variables and objectives affecting performance. There are few open-access tools available to explore the tradespace of variables which allow performance assessment and are easy to plug into science goals, and therefore select the most optimal design. This paper presents a software framework developed on the MATLAB engine interfacing with STK, for DSM orbit design and selection. The associated tool is capable of generating thousands of homogeneous constellation or formation flight architectures based on pre-defined design variable ranges and sizing those architectures in terms of pre-defined performance metrics. The metrics can be input into observing system simulation experiments, as available from the science teams, allowing dynamic coupling of science and engineering designs. Design variables include constellation type, formation flight type, instrument view, altitude and inclination of chief orbits, differential orbital elements, leader satellites, latitudes or regions of interest, planes and satellite numbers. Intermediate performance metrics include angular coverage, number of accesses, revisit coverage, access deterioration over time at every point of the Earth's grid. The orbit design process can be streamlined and variables more bounded along the way, owing to the availability of low fidelity and low complexity models such as corrected HCW equations up to high precision STK models with J2 and drag. The tool can thus help any scientist or program manager select pre-Phase A, Pareto optimal DSM designs for a variety of science goals without having to delve into the details of the engineering design process. This paper uses cases measurements for multi-angular earth observation to demonstrate the applicability of the tool.

Subsystem support feasibility for formation flight measuring Bi-directional Reflectance

“…temporal, angular, sp ectral and radiometric [5]. DSMs encompass a diverse family of spacecraft configurations.…”

“…The mission will not only need precise relative fo rmation flight but also strict attitude control, orbit maintenance, onboard processing for the mUlti-spectral data, inter-satellite calibration and a good communication channel to downlink the collected data. Parallel studies have demonstrated availability of fe asible orbits and their performance trade offs [5], payload development [22] to support such a mission, science models to quantify the performance of such DSMs [2], [12], [13] as well as open-source flight software to continually update satellite capability for staged, scalable deployment [25]. This paper fo cuses on quantitative methods to evaluate such a mission's development and operational fe asibility within achievable COTS (Commercial Off-The Shelf) technologies identified in Reference [26], satellite vendor websites and mission-tested components.…”

“…The architecture generating modules, orbits [5] and imaging modes [24] and payload [22] have been described in previous literature. Reference [29] has described the cost sizing modules.…”

“…Instantaneous VZA is calculated as the angle subtended under one satellite by another while A as the angle subtended at the Earth centre by both satellites. From geometry and the trigonometric sine law, VZA, h and ISL are related as [5]:…”

“…Attitude control analysis on the 4-satellite baseline configurations is performed in the L VLH frame, by adapting the analemma equations [5]. They are used for baseline analysis because they have been shown to provide required science performance by using appropriate imaging modes.…”