<p>Satellites provide wide coverage by connecting the unconnected through high-capacity data links. These high-capacity satellite signals require large channel bandwidth for the data to be transmitted and free space optical (FSO) communication fulfils this requirement of large bandwidth while using license free spectrum for the transmission. High altitude platform station (HAPS) acts as a relay node between satellite and ground and converts single hop satellite-ground link to dual hop satellite-to-HAPS-to-ground link. Here, we assume that the low earth orbit (LEO) satellite is transmitting signal to the HAPS to establish a point-to-point link, so, FSO is a good candidate to provide connectivity on this link. In this work, we optimize the divergence angle of FSO beam for the satellite–HAPS downlink transmission to reduce the link outage probability which in turn reduces the transmit power requirement, thus, improving the performance of the satellite. We also consider several parameters such as the receiver aperture diameter, threshold SNR, jitter standard deviation and zenith angle and numerically estimated the effects of these parameters on the FSO link outage probability considering the optimized beam divergence angle.</p>