GADEM

Abstract:

The WegCenter/UniGraz Team has summarized scientific applications and defined scientific requirements for GADEM K band radio signals, and performed an end-to-end scientific performance analysis for both space-to-space and space-to-ground links.

The performance analysis addresses the quality of atmospheric data products expected by a GADEM-type measurement configuration. The performance analysis covers a Galileo-LEO part (occultation measurements of temperature and humidity profiles) as well as a Galileo-GS part (space-to-ground slant column integrated water vapor measurements). Based on a comprehensive end-to-end simulation software (End-to-end Generic Occultation Performance Simulator, EGOPS), the performance of both these measurement configurations was simulated and analyzed for a typical set of instrumental errors, using realistic orbital and ground-station geometries and using as a realistic atmospheric model a high resolution global weather analysis field, including also liquid water and ice water clouds. An operational analysis of the ECMWF (European Centre for Medium-Range Weather Forecasts) was taken for the purpose. In addition, turbulent atmospheric conditions were taken into account for Galileo-LEO links.

The main conclusion is that the GADEM system requirements as laid out in the GADEM scientific applications document are just adequate to achieve the observational requirements (summarized in the same document) for both the Galileo-LEO part and the Galileo-GS part, respectively. This confirms that those requirements, in many aspects drawing from heritage from previous study of similar systems (e.g., LEO-LEO K band occultation) provide a sound basic set of specifications for GADEM system design.

Based on the encouraging results of the performance analysis a GADEM demonstration experiment is strongly recommended.