The Arctic and Nordic Imager as sensor concept for optical imaging in highly elliptical orbits with applications to polar meteorology

摘要

This paper presents the Arctic and Nordic Imager as a concept investigated by the European Space Agency (ESA) and the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT). The concept addresses a recognized gap in the near-real-time coverage at high latitudes (above 55 degrees) from geostationary satellites, due to viewing geometry over polar areas. The paper recalls the context, summarises the requirements customized for it, describes the main trades, features and sizing parameters of the mission and sensor, and illustrates potential implementations. The requirements are similar to those of geostationary systems. They call for near-real-time multispectral optical observations in the Visible, Near Infrared, Short Wave Infrared, Water Vapour, and Thermal Infrared bands, at moderate spatial resolution. The mission profile proposed uses Highly Elliptical Orbits (HEO). The sensor concept is largely derived from GEO imagers in operation or in development, due to very similar requirements. In the current instrument concepts, the area of interest is covered using a scanning mirror in two directions. A telescope and complementing optics then redirect the optical beam to focal plane assemblies and optical detectors. The instrument also includes calibration subsystems and all necessary equipment i.e. cryocoolers for infrared detectors and electronics for data handling. The major trades are to do with meeting the very demanding optical performance, and to a lesser degree with the radiometric one. These include aperture sizing, definition of scanning law and principle, telescope concept, cryostat design, and image registration. The resulting concepts yield state-of-the-art large space optical instruments.