The pilot episode of Solarnauts was titled; Cloud of Death, and was made in 1967 with a view to becoming a series.
The show was never picked up and to the best of my knowledge the one and only episode never even got a public viewing. Which is a bit of a shame really because apart from some cheap looking model effects there seems to be a lot of style and colour to the production and there’s an interesting enough set up to imagine that it might have developed into quite a good show for its time, if it had have been given the chance.
Thanks to the magic of the internet it’s viewable online in any number of places. Go check it out