The optomechanical design of Amon-Ra instrument

The EARTH-Sun-Heliosphere interactions Experiment (EARTHSHINE) is a novel space mission designed to answer key questions about how Earth's climate and space environment are influenced by the Sun¹. One of the four EARTHSHINE instruments called Amon-Ra is a unique Earth reflectance monitor and is a combination of two detectors; one imaging the photon fluxes over the visible wavelength range and the other bolo-metrically measuring global emissions while the satellite orbits about the LI Lagrange point. Both detectors view both the whole Sun and whole Earth. In order to minimise the differential degradation of front-end optics and detectors, the measurements of the Sun and Earth light are designed to be performed using as many common components of instrument as possible. As the ratio of the radiance emitted from the Sun to Earth's albedo is nearly a factor of 300,000:1, the optics for the Sun channel has to incorporate a smaller aperture and an attenuator. The instrument enclosure is designed to fit into a compact volume including electronics, all mounting feet, connectors, and fixings so that it is expected to make the entire satellite structure compact and cost-effective, whilst meeting the scientific measurement specifications. The optomechanical design we have developed for Amon-Ra is presented in this paper.