  In this correspondence, we propose a joint mechanical and electrical
adjustment of intelligent reflecting surface (IRS) for the performance
improvements of low-earth orbit (LEO) satellite multiple-input multiple-output
(MIMO) communications. In particular, we construct a three-dimensional (3D)
MIMO channel model for the mechanically-tilted IRS in general deployment, and
consider two types of scenarios with and without the direct path of LEO-ground
user link due to the orbital flight. With the aim of maximizing the end-to-end
performance, we jointly optimize tilting angle and phase shift of IRS along
with the transceiver beamforming, whose performance superiority is verified via
simulations with the Orbcomm LEO satellite using a real orbit data.
