Left: avoidance angles for CubeSpec. The grey shaded spacecraft is displayed at three positions along its orbit, assuming the optical axis is pointing in the anti-Sun direction. The green shades illustrate the regions of the sky accessible from each of those locations. The Moon is seen partly obstructing one of those regions. The zones of avoidance imposed by the Sun, the Earth, and CubeSpec’s radiator are shown in yellow, blue, and red, respectively. Right: simulated evolution of visibility window duration over 6 months of visibility of the star τ Lib, involving lunar interruptions. The vertical lines show the start (blue) of the observational campaign and the ends of 90 d (red) and 30 d (black) observational campaigns defined for the observing scenarios described in the main text (Sect. 3). The inset panel zooms into the start of visibility to highlight visibility windows.