Welcome to our Thunderbirds Deep Dives! As we celebrate International Rescue's 60th anniversary, we asked you to pick your favourite episodes of Gerry and Sylvia Anderson's classic 1965 sci-fi adventure series that should receive in-depth, analytical retrospectives. Based on your picks, we've collated a top 10 selection of Thunderbirds greatest episodes to receive a review - as voted for by you!

We're continuing our Thunderbirds Deep Dives with International Rescue's first ever space-based mission - Sun Probe! From the eerie depths of outer space to the treacherous snowy terrain of Mount Arkan, Sun Probe blends cinematic production values with well-balanced character interplays. Let's investigate Alan Tracy's debut mission for International Rescue!

Operation Sun Probe

Thunderbirds' in-universe progression can be viewed by how the early episodes introduce each of the core five Thunderbird vehicles and their respective Tracy brothers. Trapped in the Sky, Sun Probe and The Mighty Atom, in which all five Thunderbirds and Tracy brothers are introduced, greatly emphasis the ensemble nature of the series. Almost none of these episodes particularly tune into the status of each Tracy brother, instead content to focus on the mechanical appeal of the Thunderbird craft that's at the centre of each rescue disaster.

Sun Probe partially breaks this rule with its determined emphasis on Alan Tracy as leading International Rescue's daring efforts to rescue the runaway Sun Probe when its expedition to capture a fragment of the sun nearly ends in disaster. But the episode is at its most enjoyable when it creatively balances its characters and rescue scenarios. Thunderbirds would come to rely heavily on the appeal of individual characters, particularly Lady Penelope, Parker, and Brains. But in Sun Probe, the framing is firmly on the family-run nature of International Rescue and their efforts as a collective, not as a collection of individuals.

Introducing Thunderbird 3

Following on from Trapped in the Sky, Pit of Peril, and City of Fire, Thunderbirds by now had well and truly honed its routines of Earth-based disaster scenarios. Viewers are hardened to the functionality and appeal of Scott and Virgil Tracy piloting Thunderbirds 1 and 2 to the danger zone and saving the day. With Sun Probe, a combination of the series' first space-based rescue and the demands put upon by AP Films to expand the series from half-hours to 50-minutes crafts a uniquely compelling early entry in the series that marvellously breaks away from the established order to riveting effect, more out of production necessities than creative choice. 

From sky-based terror to fiery infernos, the tense grandeur of the Sun Probe rocket's blast off and accompanying haunting isolation of deep space swells into an enthralling backdrop of rescue adventure. The earnestness of Sun Probe's depiction of a manned exploratory mission to capture a fragment of the sun eschews any close scientific analysis in terms of safeguarding of the three-man rocket crew. The world of Thunderbirds is one of scientific wonder and advancement, however nonsensical those advancements may be!

As Thunderbirds' first outer space adventure, Sun Probe proves its worth by hardwiring an abundance of mechanical grandeur of the Sun Probe rocket launch, which dominates the episode's opening scenes. This is our first view of space exploration since Fireball XL5, placing further importance on Sun Probe within the wider context of the history of Supermarionation. 

Even the half-hour version of this episode still would have communicated this significance effectively, with the earlier incarnation depicting Thunderbird 3 being dispatched to rescue the stricken Sun Probe when its retros fail and risks colliding with the sun. That's about as tricky as the earlier episode gets, but by stretching the episode out, the episode pleasantly highlights the operational functionality of International Rescue and dramatically exploits its core players.

Matt Zimmerman, who made his debut as Alan Tracy an episode earlier in Pit of Peril, has his chance to shine as the baby-faced Alan shared by the unexpected additional focus on Brains. His comical master versus servant dynamic with his robotic creation, Braman, is amusingly set up in the episode's early scenes of his disinterest in Operation Sun Probe. The Brains who would rather play with Braman is not the same Brains we later see in Day of Disaster. Evidence of this being bolted-on material is found simply in the fact that Brains and Braman's relationship isn't really explored further on in the series, despite the distinct feeling that something is being set-up here. 

Sun Probe's creative deployment of Thunderbirds 2 and 3 to tackle the rescue of the Sun Probe when its mission goes awry was not a feature of the original premise. Where Pit of Peril simply recycled the failed first rescue effort of Trapped in the Sky, Sun Probe's extra material comes off as an inspired afterthought. We never see this combination of IR craft anywhere else in the series, and it provokes further complications when TB2 is forced to save TB3 in a decidedly surreal manner, neatly tying together Brains and Braman's earlier interactions. 

Alan's remarks of 'Gee whiz' and 'I just don't dig him' at Brains' apparent disinterest in the solar mission signify his usefulness as the modern (as much as you can be looking back to 1965!) youth character for Thunderbirds' child audiences to latch onto. But where future episodes would portray Alan as petulant and impulsive, he's remarkably mature in leading his elder brother Scott and romantic interest, Tin Tin, in leading Thunderbird 3 to rescue the Sun Probe. 

It's odd then that Thunderbird 3's grand debut rescue operation should come off as rather underwhelming in its execution. The vast canvas of outer space doesn't appear to lend itself well to inspired filming techniques of International Rescue's space rescue vessel. Throughout the journeys of both craft, TB3 and the Sun Probe are filmed nearly consistently in two-dimensional profile against a rolling space backdrop, which struggles to convey the dramatic jeopardy of the situation when either craft fall victim to the Sun's tremendous power.

Barry Gray's shimmering electronic music is used as if to compensate, enlivening the ethereal atmosphere of TB3's pursuit of the Sun Probe. Where the underwater escapades of Stingray were mostly shorn of electronic music, Gray's trademark pre-digital tinerkings hark back to the earlier days of Fireball XL5. Not helping matters is TB3's lack of apparent tangible rescue apparatus compared to Thunderbirds 1 and 2, despite its wondrously imposing design and memorably prolonged launch sequence, seen in full display for the first time here. More visually stimulating is Virgil and Brains' dual rescue operation from Thunderbird 2, battling the hazardously snowy Mount Arkan as the best vantage point to launch their own neutralising transmitter beam from Earth toward the Sun Probe's location. Perhaps Earth-based locations simply lent themselves better to more imaginatively tactile landscapes.

Characterful rescue operations

Ironically, only when Alan, Scott and Tin Tin manage to intercept the Sun Probe's trajectory and enable the rocket to swerve out of its path of destruction, Sun Probe enlivens itself into a classic nail-biter finale. We can safely presume that the original half-hour incarnation of Sun Probe, however finished it may have been, would have ended on the triumph of TB3 saving the day and safely returning to Earth. However, with remaining time to fill, we receive our first instance of International Rescue forced to rescue its own team members when its own rescue efforts go awry.

Even International Rescue's state-of-the-art technology isn't enough to prevent Thunderbird 3 itself eventually becoming ensnared by the sun. Failing to pull out of its sun-trapped trajectory, it falls to Virgil and Brains to rescue the increasingly decimated TB3 crew, who succumb to the sun's encroaching heat. The combined jeopardy of the TB3 crew in horrific peril and Virgil and Brains' they'd believed to have packed with them injects Sun Probe with a rather grimly faced energy to climax with.

The family-focused nature of Thunderbirds shines through in these climactic scenes. The drama of Scott, Alan and Tin Tin's collapse aboard TB3 and the tension of Virgil and Brains' efforts to utilise Braman's mechanical intelligence to compute how to trigger TB3's retros and drag the flailing craft away from the jaws of solar death are a compelling juxtaposition of moods to bring the episode to a rousing finale. The highlight of these scenes however is the shared fatherly worry of Jeff Tracy and Kyrano in being so helpless to intervene in rescuing their children. 

It's a testament to the editorial craftmanship of Thunderbirds, in both its scripting and its directing, that this hastily composed extra material feels far from aggressively bolted on. They're vital story beats to the cosmic danger that makes Thunderbird 3's debut rescue operation so thrillingly memorable, and all the more triumphant when Virgil, Brains, and Braman eventually succeed in recovering TB3, allowing Alan, Scott, and Tin Tin safe passage back to Earth.

Awe-infused terror 

It's always impressive to be reminded of Thunderbirds' ability to juxtapose the epic with the intimate. For all of the cinematic reach of the episode, its most muscular value emerges when it thrusts the dangers of its characters into view. For all of the focus on Alan and Brains, Jeff and Kyrano are arguably the secret stars of the episode. Kyrano's subtle reveal that he and his daughter owe their lives to Jeff is an intriguing slice of backstory that goes unfulfilled for the remainder of the series.

Jeff and Kyrano's palpable concern for their children is a heartfelt encapsulation of how Thunderbirds navigates its characterisations. The family-run nature of International Rescue proves to be a rich source of emotional material to dig into when writing and performing the Tracy's as a believable family unit. That, deftly welded with the awe-infused terror of what is surely Thunderbirds' largest disaster threat, enables Sun Probe to stand as one of the series' greatest episodes.

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