Spacewave is a very small part of the synthwave community (and rarely officially called that). It focuses on futuristic, science fiction-based themes of planetary exploration in both the visual aesthetic and also in the spacey sounding music and track titles. There’s enough musicians on the Aphasia Records label and elsewhere that are the innovators of this particular style.  

Of course Spacesynth has existed for several decades now and is not related although there are some similarities.  They are two separate terms and communities.

Lazerhawk Tommy ’86 Lueur Verte DYNATRON STARFORCE Droid Bishop Kalax Volkor X Syntax Zombie Hyperdrive Tonebox Waveshaper Nightcrawler Moskva-Kassiopeya Stilz LVX Isidor