Gravity field processing with enhanced numerical precision for LL-SST missions

Abstract

On their way to meet the augmenting demands of the Earth system user community concerning accuracies of temporal gravity field models, future gravity missions of low-low satellite-to-satellite tracking (LL-SST) type are expected to fly at optimized formations and make use of the latest technological achievements regarding the on-board sensor accuracies. Concerning the main measuring unit of an LL-SST type gravity mission, the inter-satellite measuring instrument, a much more precise interferometric laser ranging system is planned to succeed the K-band ranging system used by the Gravity Recovery and Climate Experiment (GRACE) mission. This study focuses on investigations concerning the potential performance of new generation sensors such as the laser interferometer within the gravity field processing chain. The sufficiency of current gravity field processing accuracies is tested against the new sensor requirements, via full-scale closed-loop numerical simulations of a GRACE Follow-On configuration scenario. Each part of the processing is validated separately with special emphasis on numerical errors and their impact on gravity field solutions. It is demonstrated that gravity field processing with double precision may be a limiting factor for taking full advantage of the laser interferometer’s accuracy. Instead, a hybrid processing scheme of enhanced precision is introduced, which uses double and quadruple precision in different parts of the processing chain, leading to system accuracies of only 17 nm in terms of geoid height reconstruction errors. Simulation results demonstrate the ability of enhanced precision processing to minimize the processing errors and thus exploit the full precision of a laser interferometer, when at the same time the computational times are kept within reasonable levels.