Of all the challenges found by the new Hayabusa space probe (and there were lots), none involved lugging giant instruments around the Solar System. The entire craft weighed just over 500 kg, and a quarter of that was propellants. Scientifically, the investigations aboard Hayabusa were sufficient, not bleeding-edge. Things like high-resolution telescopes were left on Earth, as they should. Instead, particles of 25143 Itokawa were taken to our giant instruments- a sample return mission. Such were the open questions left by the Galileo mission, NEAR, etc.
Hayabusa did not visit 4660 Nereus as first planned. That would have been nice, but a C-type body was left to Hayabusa 2. Itokawa is, rather, an S-type; a sample would settle the issue of ordinary chondrite meteorites and S-types in a way that Galileo and NEAR only inferred. We see lots of S-type asteroids in our telescopes- they’re the number one type in the inner Solar System. And we have plenty of ordinary chondrites that fall to Earth- again, they’re the most common. Yet S-types don’t look like OCs, but like stony-iron meteorites.
Itokawa flew past Earth in 2001. Telescopes around the globe got observing runs, if for no other reason to lower risks for Hayabusa operations. Jun 2004, as Hayabusa was in flight, Itokawa made its next Earth pass. It came within two million km, under half its 2001 range. This was part of the logic for Itokawa: an easy target, with a favorable, Earth-crossing orbit (“low ΔV”). Even if Hayabusa failed, mustering the astronomy world was an achievement.
Hayabusa did not fail, but got over 1500 particles from a known body. The craft’s (lightweight) instruments also rendered data (and knowledge) of the sampling site. We know how our samples fit into contexts- of Itokawa as one example of asteroid diversity, and the site as one example over Itokawa’s surface. Not some random outlier, from some random body.
Ground telescopes, flight probes, and sample examination combine in complementary ways. Let’s look at not just a space body, but the investigation process: Solar System science.