Abstract
This paper proposes an approach for impulsive formation maintenance tailored to distributed synthetic aperture radar, i.e., a spaceborne system composed by several antennas working together to provide enhanced remote sensing capabilities. The analyzed configuration is designed to guarantee the presence of a safety tube surrounding each satellite as the dynamics evolve. Formation requirements are related to general constraints on the acceptable along-track and radial/cross-track separations. The paper introduces an adaptive maintenance logic which fulfills these constraints. Specifically, the formation is adaptively redesigned around the chief every time geometry constraints are violated by means of a procedure developed by the authors in previous works and based on relative orbit parameters. Once these parameters are defined, the optimal impulsive burns required for orbit transfer are computed using state-of-the-art approaches. Performance in terms of delta-v and maneuver frequency is analyzed for a two-spacecraft formation exploiting a simulation environment based on MATLAB and GMAT. In ideal conditions, it is shown that maintenance costs are limited, while close proximity requires fine sensitivity on the applied impulses. A first assessment of the impact of relative navigation and maneuvering execution errors indicates that they play an important role in defining the overall control effort.
Highlights
It is widely agreed that many upcoming space missions will rely on distributed systems exploiting co-flying, cooperating platforms to replace current monolithic systems, and to implement missions otherwise impossible or extremely complex [1].Unleashing the potential of such evolution requires the addressing of challenges both at a payload and at a system level, which are closely related to each other
This paper proposes an approach for impulsive formation maintenance tailored to distributed synthetic aperture radar, i.e., a spaceborne system composed by several antennas working together to provide enhanced remote sensing capabilities
distributed synthetic aperture radar (DSAR) is defined as a synthetic aperture radar in which the signal emitted by the transmitter and scattered from the area of interest is not collected by a single receiver, but by many conveniently distributed formation flying receivers
Summary
It is widely agreed that many upcoming space missions will rely on distributed systems exploiting co-flying, cooperating platforms to replace current monolithic systems, and to implement missions otherwise impossible (e.g., those requiring very large sensor apertures) or extremely complex [1]. The concept of distributed aperture is a generalization of the conventional synthetic aperture radar (SAR) principle [5], and of standard interferometric SAR (InSAR) techniques [6], towards a flexible system able to implement a wide range of different working modes As these different working modes require specific observation geometries, formation flying represents a key technology for DSAR implementation, and aspects such as relative navigation accuracy, control accuracy, and ∆v expense are key factors for mission design and feasibility. Within this framework, this paper proposes a formation maintenance approach that is tailored to DSAR applications.
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