Final answer:
The Cassini orbiter and its Huygens probe, which landed on Saturn's moon Titan, represent the only spacecraft to send a probe into the atmosphere of a jovian planet's moon.
Step-by-step explanation:
The only spacecraft to send a probe into the atmosphere of a jovian planet's moon is the Cassini orbiter with its Huygens probe. The Huygens probe was built by the European Space Agency and successfully landed on Titan, Saturn's largest moon, on January 14, 2005. This remarkable feat marks it as the first and only landing on a moon in the outer solar system. The Cassini orbiter, equipped with cameras, spectrometers, and a radar imaging system, made close flybys of Titan, providing valuable radar and infrared images of the moon's surface.