Hayabusa - The Return To Earth, The voyage home Options

[Holder of the Tw...]

Well, it did everything NEAR did on only about 2/3 of the money

Hayabusa had no gamma ray spectrometer, and no magnetometer. To my knowlege, Hayabusa did not return surface pictures of Itokawa as detailed as the final pictures of Eros from NEAR. And while touch-and-go landings are impressive, orbiting small irregular bodies - which Hayabusa never did - is pretty impressive, too.

[Guest_BruceMoomaw_*]

Let me amend: ALMOST everything. (Its best photos of Itokawa's surface were as high-resolution as NEAR's best photos of Eros' surface -- and its maneuvers around the asteroid were at least as intricate as NEAR's.)

[tedstryk]

Well, it did everything NEAR did on only about 2/3 of the money, which is not to be sneezed at -- especially since it gave us nice comparative data on another asteroid.  Unfortunately, it now looks as though everything it tried to do BEYOND what NEAR did will be a washout.

It also gave us closeup data on a class of world that, other than Galileo's glimpses of Dactyl, we had never seen close up. A very important mission. I must admit that I have no confidence now that it will return to earth. My hope is that it will regain orientation long enough to transmit the data (and possibly more images) from its last landing attempt.

[odave]

And also remember that this is primarily an engineering mission, and as such even the failures are valuable. I'm sure JAXA/ISAS is keeping a list of what went right and wrong. Hopefully backup reaction wheels are near the top under "what to do better next time"

[hugh]

To my knowlege, Hayabusa did not return surface pictures of Itokawa as detailed as the final pictures of Eros from NEAR. 

This 11-17 JAXA release claimed a resolution of 1.5 - 2.0 cm a pixel for the closest image obtained by Hayabusa. NEAR Shoemaker’s last image had a resolution of about 1.1cm, but covered a smaller area, and had about 1/8 the number of pixels that were in the Hayabusa image.

[edstrick]

Hayabusa returned a huge amount of infrared spectrometer data. The NEAR instrument failed early in the mission, and the high-orbit data (as I recall) didn't tell much about surface composition variation, as it was mostly unresolved. The X-Ray composition data may be significantly better than NEAR's, but published data in science result papers will tell.

[lyford]

Heathens! How dare you try to explain away Hayabusa's divine epicycles as a mere illusion of refrence point!! 

Well - I think Hayabusa's epicycles ARE part of a divine plan - from the JAXA home page, it appears no one less than The Pope himself is working on their Vision:


I mean, who else besides Elvis wears all white?

And while we're at it, does anyone else think Harrison Schmitt is slowly morphing into Von Braun?

As for Hayabusa being an engineering mission, JAXA itself only weighted science observations as 50 points out of 500 total for mission success. Though it does appear that some encounter data has been useful, that still leaves :

3. Touch-down and Sample
4. Capsule Recovered
5. Sample obtained for Analysis

as unfulfilled criteria. Without 4 and 5, we may never really know if 3 was accomplished it seems. Space science can't be done on the cheap, not even by the Japanese.

[The Messenger]

Does anyone have any insight into why reaction wheels have been such a bug-a-boo? I know, from my own work with inductive circuits in a vacuum, there are always serious overheating issues when radiation is the only way to disappate heat energy. Are the reaction wheels being driven to greater loads than expected?

[Holder of the Tw...]

Hayabusa returned a huge amount of infrared spectrometer data.  The NEAR instrument failed early in the mission, and the high-orbit data (as I recall) didn't tell much about surface composition variation, as it was mostly unresolved.  The X-Ray composition data may be significantly better than NEAR's, but published data in science result papers will tell.

The NIS instrument on NEAR returned three solid months worth of data from Eros before it failed. At the time, it was in a 50 km circular orbit, and able to resolve a spot 330x650 meters. This is 1 to 2 percent the length of Eros, so it was resolving the asteroid just fine. The reason it didn't show much surface variation is because, as this instrument discovered, there was no significate variation to report. The NIS also made significant contributions to studying the spectra of asteroid 253 Mathilde and comet Hyakutake.

I'll concede the point made by Hugh on the picture resolution.

[Phil Stooke]

Even if Hayabusa only returned a quarter of NEAR's data volume (and I'm not suggesting I know what the fraction would be) - it's still important because it's a different world. We now have a very nice new data set for Itokawa which we didn't have before, so that's good. I absolutely agree JAXA's efforts are underfunded, but that's a political issue for Japan to resolve itself.

Actually, I think JAXA hurt itself a bit in its list of mission objectives. They assigned points to each mission phase, but they were too much weighted towards the final stages. I would have weighted them more heavily for the work done up to now, so that a more substantial degree of success would be shown today. The remote sensing was very valuable. Then the sample return would be 'icing on the cake' if it could be pulled off.

Ahh... I can almost hear the sound of the milk of human kindness sloshing around in me today. 'tis the season... I guess.

Phil

[edstrick]

Holder of the Two Leashes:
"The reason it didn't show much surface variation is because, as this instrument discovered, there was no significate variation to report. "

I remain unconvinced of that. The areas of greatest color and albedo variation, or features where composition variations might be expected, were generally well below 1/2 km in size. I'm specifically referring to the high albedo steep slopes inside the freshest craters and the small, slightly darker than general regolith smooth "ponds" in crater bottoms.

I note that the camera, which had a TINY CCD detector with non-square pixels and high noise levels (obvious in low-contrast stretched images of a high contrast target) had real trouble seeing color variations, but they were there once enough pixels on a target were averaged.

Global color variations are near zero, but weak local ones, mostly on 100 or 50 meter scales and smaller are present. I expect/suspect similar ones were present in infrared wavelengths but were undetected due to resolution and possible signal/noise factors.

[ljk4-1]

Would it have been easier to have Hayabusa touch down on several different places on Itokawa to take images and data, rather than have brought Minerva along to do that job?

Or even just one stationary lander to leave on the planetoid?

[RNeuhaus]

Minerva would do much better the job with imaging and temperature than Hayabusa but due to a bad luck it has gone away forewer. Hayabusa ANC wide camera is not designed to take close pictures but unless up to 50 meters from Itokawa.

Hence, Hayabusa has no legs to sit on Hayabusa.

The initial mission, JAXA took this as an engineering mission with much greater points (see the Lyford's previous comments) than the scientific mission.

Rodolfo

[Holder of the Tw...]

I note that the camera, which had a TINY CCD detector with non-square pixels and high noise levels (obvious in low-contrast stretched images of a high contrast target) had real trouble seeing color variations, but they were there once enough pixels on a target were averaged.

Global color variations are near zero, but weak local ones, mostly on 100 or 50 meter scales and smaller are present.  I expect/suspect similar ones were present in infrared wavelengths but were undetected due to resolution and possible signal/noise factors.

I misunderstood you completely. I thought you were saying that the NIS could not resolve any part of Eros. One theory about part of the variation you're talking about is that the color differences are due to the fresh material being "unweathered".

One other thing I don't understand, though, is what your whole point is. Are you saying NEAR should have been put off for five years in order to get more advanced infrared detector technology? Or perhaps you are saying the United States should have scuttled the NEAR and Deep Space 1 programs, waited for some other nation (perhaps Japan) to fly both a dedicated asteroid mission and ion engine driven spacecraft first, and then build our own programs on their experience more cheaply?

[Joffan]

One other thing I don't understand, though, is what your whole point is.  Are you saying NEAR should have been put off for five years in order to get more advanced infrared detector technology?  Or perhaps you are saying the United States should have scuttled the NEAR and Deep Space 1 programs, waited for some other nation (perhaps Japan) to fly both a dedicated asteroid mission and ion engine driven spacecraft first, and then build our own programs on their experience more cheaply?

I thought that the general mood of the board, the spirit of this thread, was that Hayabusa is a success of comparable magnitude to NEAR even without the sample return. It seemed to me that it is you that has a point to make, Holder, to whit that NEAR was hugely better than Hayabusa. Your brinkmanship in suggesting that the participants here would like to see any exploration programs whatsoever scuttled, no matter the host nation, is political posturing.