Mapping Earth's Dust-EMITting Regions from the ISS with the EMIT Imaging Spectrometer

Abstract

The Earth Surface Mineral Dust Source Investigation (EMIT) is a Dyson-type imaging spectrometer which will operate from the EXPRESS Logistics Carrier (ELC) 1 platform of the International Space Station (ISS) starting in 2022 with the objective of mapping Earth's dust-EMITting land regions for the purpose of determining the composition of key constituent minerals and their impact on radiative forcing. Designed to operate for a minimum of one year, the EMIT instrument will collect over 50 Terabits of data representing billions of individual spectra for processing on the ground, significantly improving the state of knowledge about the composition and regional and global distribution of these key minerals. Acquiring, storing, processing and downlinking such large amounts of data requires a well-orchestrated planning effort in concert with an on-board high-performance computing embedded system. Adding to the challenge, and because the science requires a cloud-free measurement, significant effort has been expended in both attempting to predict the impact of clouds on the coverage as well as removing cloudy acquisitions on-board to reduce the pressure on the shared ISS downlink pipeline. In this paper we will explore the ways in which the EMIT mission design has been shaped by the performance requirements imposed by the science on data sufficiency and quality along with the constraints imposed by ISS operations and hardware limitations. Various sensitivity analyses are presented investigating the impact of ISS orbit altitude and seasonality on the coverage of the science target mask, along with data compression and throughput, cloudiness assumptions, and downlink data rate effects on on-board storage sizing and margins.