  We address the applicability of quantum key distribution with
continuous-variable coherent and squeezed states over long-distance
satellite-based links, considering low Earth orbits and taking into account
strong varying channel attenuation, atmospheric turbulence and finite data
ensemble size effects. We obtain tight security bounds on the untrusted excess
noise on the channel output, which suggest that substantial efforts aimed at
setup stabilization and reduction of noise and loss are required, or the
protocols can be realistically implemented over satellite links once either
individual or passive collective attacks are assumed. Furthermore, splitting
the satellite pass into discrete segments and extracting the key from each
rather than from the overall single pass allows one to effectively improve
robustness against the untrusted channel noise and establish a secure key under
active collective attacks. We show that feasible amounts of optimized signal
squeezing can substantially improve the applicability of the protocols allowing
for lower system clock rates and aperture sizes and resulting in higher
robustness against channel attenuation and noise compared to the coherent-state
protocol
