  This paper investigates downlink power adaptation for the suborbital node in
suborbital-ground communication systems, which are subject to extremely high
reliability and ultra-low latency communications requirements. The problem is
formulated as a power threshold-minimization problem, where interference from
satellites is modeled as an accumulation of stochastic point processes on
different orbit planes, and hybrid beamforming (HBF) is considered. To ensure
Quality of Service (QoS) constraints, the finite blocklength regime is adopted.
Numerical results show that the required transmit power of the suborbital node
decreases as the elevation angle at the receiving station increases.
