  The climate crisis we are facing calls for significant improvements in our
understanding of natural phenomena, with clouds being identified as a dominant
source of uncertainty. To this end, the emerging field of 3D computed cloud
tomography (CCT) aims to more precisely characterize clouds by utilizing
multi-dimensional imaging to reconstruct their outer and inner structure. In
this paper, we propose a future Earth observation mission concept, driven by
the needs of CCT, that operates constellation of NanoSats to provide
multi-angular, spectrally-resolved, spatial and temporal scientific
measurements of natural atmospheric phenomena. Our proposed mission, GEOSCAN,
will on-board active steering capability to rapidly reconfigure networked swarm
of autonomous Nanosats to track evolving phenomena of interest, on-demand, in
real-time. We present the structure of the GEOSCAN constellation and discuss
details of the mission concept from both science and engineering perspectives.
On the science side, we outline the types of remote Earth observation
measurements that GEOSCAN enables beyond the state-of-the-art, and how such
measurements translate to improvements in CCT that can lead to reduction in
uncertainty of the global climate models (GCMs). From the engineering side, we
investigate feasibility of the concept starting from hardware components of the
NanoSat that form the basis of the constellation. In particular, we focus on
the active steering capability of the GEOSCAN with algorithmic approaches that
enable coordination from new software. We identify technology gaps that need to
be bridged and discuss other aspects of the mission that require in-depth
analysis to further mature the concept.
