The HYPSO-1 satellite, a 6U CubeSat carrying a hyperspectral imager, was launched on 13 January 2022, with the Goal of imaging ocean color in support of marine research. This article describes the development and current status of the mission and payload operations, including examples of agile planning, captures with low revisit time and time series acquired during a campaign. The in-orbit performance of the hyperspectral instrument is also characterized. The usable spectral range of the instrument is in the range of 430 nm to 800 nm over 120 bands after binning during nominal captures. The spatial resolvability is found empirically to be below 2.2 pixels in terms of Full-Width at Half-Maximum (FWHM) at 565 nm. This measure corresponds to an inherent ground resolvable resolution of 142 m across-track for close to nadir capture. In the across-track direction, there are 1216 pixels available, which gives a swath width of 70 km. However, the 684 center pixels are used for nominal captures. With the nominal pixels used in the across-track direction, the nadir swath-width is 40 km. The spectral resolution in terms of FWHM is estimated to be close to 5 nm at the center wavelength of 600 nm, and the Signal-to-Noise Ratio (SNR) is evaluated to be greater than 300 at 450 nm to 500 nm for Top-of-Atmosphere (ToA) signals. Examples of images from the first months of operations are also shown.
In this paper, we explore the use of maximum hands-off control for attitude control of a spacecraft actuated by reaction wheels. The maximum hands-off, or L0-optimal, controller aims to find the sparsest control signal among all admissible control signals. L0-optimal problems are generally hard to solve as L0-cost functions are discontinuous and nonconvex. Previous research have investigated methods to approximate the L0-norm in the cost function, for instance by using an L1-norm. We propose an approach to the maximum hands-off control problem for spacecraft attitude control involving an L0cost function relaxed through complementarity constraints. The controller is applied to the spacecraft attitude control problem, and the performance of the maximum hands-off controller is compared to that of the L1-optimal controller. Simulations of a 6U CubeSat were conducted using CasADi as the primary optimization tool, and the L1-and L0-optimal control problems were discretized using direct multiple-shooting and solved using the IPOPT solver. In addition to these results, we propose a new control scheme, called moving maximum hands-off control, which lets the user specify in which time interval the control should occur, and then aims to find the sparsest control among all admissible controls based on this information. The moving maximum hands-off controller is demonstrated to be as sparse as the maximum hands-off controller for some spacecraft maneuvers.
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