Hayabusa - The Return To Earth, The voyage home Options

[odave]

...starting a new thread for Hayabusa's sampling feedback and the return voyage.

After its nail-biting success in November, will there be enough fuel for the Falcon to make it home?

[edstrick]

Holder of the Two Leashes:
"...One other thing I don't understand, though, is what your whole point is. ..."

I guess my points is that NEAR was the first of the Smaller, Cheaper, Faster, Better missions, but there is an ongoing debate on whether it was even good enough to accomplish what I thought was it's primary mission objective: determining whether S-type asteroids are or are not the parent bodies of ordinary chondrite meteorites. While the indications of a space-weathering modified surface were at least somewhat expected to cause potential problems in linking the two, the mission that was flown carried instruments that simply did not have the signal-to-noise ratio AND the resolution to clearly sort out what appear to be end-members of the weathering sequence. It was good, but like Boris, it wasn't good-enough.

Where NEAR really shined is in photo-geology, where it mostly made up for it's dinky camera with scads and scads of images that can be mosaiced into global coverage, and revolutionized our understanding of geologic processes on asteroids.

[Holder of the Tw...]

I guess my points is that NEAR was the first of the Smaller, Cheaper, Faster, Better missions, but there is an ongoing debate on whether it was even good enough to accomplish what I thought was it's primary mission objective: determining whether S-type asteroids are or are not the parent bodies of ordinary chondrite meteorites. 

Hmmm. Okay.

You'll please forgive my earlier lashing out. NEAR was a mission I had a great fondness for. I perceived some slights directed at John Hopkins APL and the NEAR team, whom I thought pulled off a remarkable mission given the resources at hand, and reacted defensively. I believe the merits of Hayabusa can stand on their own without much comparision to specific previous missions, but rather what was gained in comparison to everything we had before.

NEAR was able to narrow things down. Eros appears to be a type L or type LL chondrite. Bear in mind, no one had examined an asteriod from this close a range before, and it was inevitable that a lot of lessons were going to be learned on how asteroid missions should be conducted in the future.

Persons close to the Hayabusa team have reported in here before, and I would love to hear what they think in regards to how NEAR influenced the planning for their mission. In the meantime, here is what I can note ostensively -

Some of the most interesting and intriguing images from Eros were the very last ones at closest range. It's obvious the Hayabusa team wanted very close and very detailed images from several points on Itokawa, hence Minerva.

The X-ray spectrometer on NEAR performed brilliantly. A similar device was included on Hayabusa.

The gamma ray spectrometer on NEAR was a real problem child. It never got the data it was designed for until after they pulled off that unlikely landing on Eros, and it had sat there for a week. Hayabusa didn't carry any similar instrument.

The magnetometer on NEAR never detected any intrinsic magnetic signature at EROS. When it failed to do so even after the landing, it was quickly and unceremoniously turned off. Hayabusa carried no magnetometer.

The NIS performed well according to it's design. As you have pointed out so well, edstrick, the reality of Eros was that more resolution, even from it's planned 35 km orbital results, would have been highly desirable. Hayabusa carried an instrument with improved resolution.

After all was said and done, the comparison of Eros with meterorite samples was not definitive. Hayabusa bringing back two samples from Itokawa would absolutely NAIL the comparisons, along with much else.

Part of what I was trying to allude to with my "scraping NEAR and Deep Space 1" remarks was to point out that Hayabusa would have been a very differently designed, and undoubtedly more costly, mission had it not had previous experience to draw on. Part of what was learned this time around was that Eros and Itokawa were more different than expected, which created some problems for Hayabusa's landing attempts. This points to a need for a CONTOUR type mission to visit several different NEAs.