What are the disadvantages of cassini-huygens?

Answer 1

Any long-duration space probe is going to have some compromises.

Size: we'd like to have sent along some extra fuel, added additional instruments, perhaps another lander - but there's a hard limit to how much weight we can launch into space.

Power: If we use solar power panels, then we lose power as the spacecraft goes away from the Sun, and Cassini is in orbit around Saturn - 9.5 times farther from the Sun as the Earth is. If we use radioisotope power cells, then the probe will lose power as the radioactive elements decay over time.

Huygens: The Huygens lander was a one-shot deal; it only survived for about 90 minutes after landing on Titan, and only one photograph of the surface was transmitted. There was no second chance. Only half of the hoped-for data was received because one of the two communication channels failed.

Additionally, robot space probes are only capable of finding answers to known questions; we can't ask follow-up questions that we hadn't anticipated. The Cassini probe was designed in the early 1990's and launched in 1997; it didn't arrive in the vicinity of Saturn until late 2004. Sometimes stuff breaks during the course of a several-year journey.