COSMO Large Coronagraph (COSMO LC) is a telescope dedicated to the measurement of the Sun magnetic field. This project is currently at a design phase funded by the National Science Foundation under the technical direction of the High Altitude Observatory.
COSMO LC is a refractive telescope whose objective lens has a clear aperture of 1.4m, it will be the largest refractive telescope in the world. This telescope can observe the Sun corona thanks to the internal occulter which is able to obscure the solar disk. This device needs to accomplish two main functions: 1) adapt its diameter to the Sun apparent size, 2) reject all the incoming heat to not start any air turbulence which leads to the degradation of image quality (seeing).
Diameter change is accomplished by means of a cam mechanism which actuates 14 petals arranged azimuthally while the occulter cooling is obtained through cold water running through internal channels and forced air convection.
This article describes the mathematical models employed to quantify the seeing effect on image resolution and the technical solutions adopted to implement the above-mentioned functions. In addition, the tests performed on this device are described along with the results.
HYPSOS (HYPerspectral Stereo Observing System, patented) is a novel remote sensing instrument able to extract the spectral information from the two channels of a pushbroom stereo camera; thus it simultaneously provides 4D information, spatial and spectral, of the observed features. HYPSOS has been designed to be a compact instrument, compatible with small satellite applications, to be suitable both for planetary exploration as well for terrestrial environmental monitoring. An instrument with such global capabilities, both in terms of scientific return and needed resources, is optimal for fully characterizing the observed surface of investigation. HYPSOS optical design couples a pair of folding mirrors to a modified three mirror anastigmat telescope for collecting the light beams from the optical paths of the two stereo channels; then, on the telescope focal plane, there is the entrance slit of an imaging spectrograph, which selects and disperses the light from the two stereo channels on a bidimensional detector. With this optical design, the two stereo channels share the large majority of the optical elements: this allowed to realize a very compact instrument, which needs much less resources than an equivalent system composed by a stereo camera and a spectrometer. To check HYPSOS actual performance, we realized an instrument prototype to be operated in a laboratory environment. The laboratory setup is representative of a possible flight configuration: the light diffused by a surface target is collimated on the HYPSOS channel entrance apertures, and the target is moved with respect to the instrument to reproduce the in-flight pushbroom acquisition mode. Here we describe HYPSOS and the ground support equipment used to characterize the instrument, and show the preliminary results of the instrument alignment activities.
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