- "Oh no! Virgil! We brought the wrong box!"
The retro rockets fail on a manned mission to retrieve matter from a solar prominence, putting the spaceship on collision course with the Sun. Thunderbird 3 and Thunderbird 2 are sent on a dual mission to transmit a radio signal that will remotely activate the Sun Probe's retros.
- Main article: Sun Probe/Storyline
- Main article: Sun Probe/Transcript
International Rescue Equipment Used
Non-International Rescue Equipment Used
- This episode marks the first appearance of Brains' robot Braman.
- The Sun Probe from The Perils of Penelope returns in this episode. It later returns again in Security Hazard, albeit as a flashback.
- This episode, along with Ricochet, were edited together in the compilation film, In Outer Space.
- Jeff states that this is Tin-Tin's first mission, which means this episode must take place before The Uninvited and Desperate Intruder.
- Music from 'Fireball XL5' can be heard as the Probe Rocket recovers the Solar Module.
- Camp reveals that Harris’s first name is Frank when the Colonel asks him for the radiation figures (“I have them, Frank”).
- This is the first out of three episodes in which Alan and Scott pilot Thunderbird 3, the other two being The Impostors and Ricochet.
- Outside of the opening titles, this is the first episode where Thunderbird 1 does not appear. However, it is The Perils of Penelope that marks the first time it does not take part in a rescue mission.
- This is only episode that has Tin-Tin directly participating in a rescue mission, again not counting her involvements in Desperate Intruder and The Uninvited.
- Alan reveals that Thunderbird 3 has at least one escape capsule when he suggests that Tin-Tin should abandon ship (“Just give the word, and we’ll put you in a release capsule and get you to safety.”).
- This episode marks the first time Thunderbird 3 is used on a rescue mission, as well as the first time Alan is seen in command of one.
- This episode marks the first appearance of guest voice actor John Tate, who voices Camp.
- Main article: Sun Probe/Goofs
- When broadcast in the 2-part 'cliff-hanger' format, the first instalment concludes with two external shots of Sun Probe successfully turning around and moving away from the Sun.
- However, in the Australian version, part 1 ends after Thunderbirds 2 launches, and then the camera zooms in on the Sun, then screen fades to black.
- French: Vers le Soleil
- German: Unternehmen Sonnensonde
- Italian: Missione sole
- Spanish: La Sonda del Sol; Sonda solar (DVD)
- Dutch: Zonnesonde (VHS, DVD); Gevaarlijke koers (TV 1991)
- Portuguese: Sonda Solar
- Japanese: ロケット”太陽号”の危機