The launch of the Sun Probe at the start of the "The Perils of Penelope" is the same event that was seen in flashback at the start of this episode. The events of that episode take place one week after the launch, so this episode takes place immediately before. Indeed, "The Perils of Penelope" and "Sun Probe" can be viewed as Thunderbirds' only two-part story, although they have never been broadcast as consecutive episodes.
Jeff states that this is Tin-Tin's first mission, which means this episode must take place before The Uninvited and Desperate Intruder.
The Solarnauts uniform feature a number of badges, one of which is that of the Supercar Fan Club badge. It can be seen as a shoulder patch.
Tin Tin and Alan are seen briefly touching several times, a subtle indication of their evolving relationship.
A slightly modified Robert the robot, who was a regular character in Gerry a previous Gerry Anderson series, Fireball XL5 (1962-63,) makes a guest appearance in this episode. Although his voice is completely different as it has been processed through a ring modulator rather than the artificial larynx used by the film makers in the earlier show.