Sampling of cloud and clear-sky radiances over Arctic from two-satellite system on Molniya orbit

The highly-elliptical orbit (HEO) offers a unique opportunity for quasi-geostationary observations of Polar Regions. Two-satellite system on 12 hrs Molniya-type HEO orbit with inclination 63.4 deg could be configured to provide continuous coverage of entire Arctic region north of 50deg. In combination with a set of geostationary satellites, this system potentially can provide observations of weather at any point and any time over the Northern hemisphere, and entire globe if complemented by a similar system for the Southern hemisphere. The observations from HEO orbit are more complicated than observations from geostationary and polar orbiting satellites flying on circular orbits, due to constantly changing altitude and orbit precession. The study will present analysis of spatio-temporal sampling of observations from two-satellite system on Molniya orbit, currently considered for the Polar Communications and Weather (PCW) system being developed in Canada. An example of simulations of spectral radiances and radiative fluxes for planned PCW imager bands in solar and thermal domain as well as sampling of cloud cover will be presented based on output from the global circulation model of Canadian Meteorological Center with 15-min temporal resolution. The suitability of these observations for radiation budget and Arctic cloudiness applications will be discussed. The orbital properties of HEO Molniya orbit can provide very rich information in terms of temporal coverage and angular sampling, which makes these observations very beneficial also for surface bi-directional studies, surface albedo, snow/ice and vegetation property mapping. To ensure adequate quality of PCW data and derived products, it is anticipated that PCW data will be calibrated using comprehensive onboard calibration system and will be included as part of Global Space-Based Inter-Calibration System (GSICS).