[X] My Assistant

[odave]

To be fair, the person who writes the Hayabusa website does not have the best English skills in the world. He/she may not mean exactly what they seem to be saying here.

True. The parent company of my company is Japanese, and my division works very closely with our counterparts across the Pacific. The language barrier is formidable and there is often need for clarification on e-mail or other documents we exchange. But over the years we've gotten pretty good at getting the core meaning from the context of each other's messages.

I don't think the passage on the website was intentionally written in a paternalistic manner. Basically, I think what they're saying is that instead of spitting out raw data, they'd rather release calibrated images with their own interpretations. They want to do this in a timely manner, and hope that all the Hayabusa fans will understand. I liken this to what we're seeing on the MER website's official status updates. We don't get them as often as raw image downloads (i.e. the last Oppy update was 9/22), but they do happen fairly often.

With that understanding, however, I am still bummed that they don't have a raw image mechanism like MER or Cassini - look at the level of excitement it generates (around here at least) even though the images are not calibrated and interpreted. But if that's what they want to do, I'm OK with it, and will stay tuned for more cool stuff.

Or, like others have suggested, I've just gotten spoiled

[tedstryk]

My hope is that this is an indication that they have come across something particularly surprising and interesting, and they are preparing some sort of major press release.

[helvick]

My hope is that this is an indication that they have come across something particularly surprising and interesting, and they are preparing some sort of major press release.

And my hope is that this is a good sign that everyone involved is totally focussed on hitting their mission objectives. JAXA have had more than their fair share of failures in the past for whatever reason, but now they look like having a genuine success. If nothing else their primary focus should be on the mission's objectives. If part of the price of succeeding is that we have to wait a couple of weeks or months for updates then lets not begrudge them that, to be fair they have been very open during the less critical parts of the cruise.

Hopefully we wont have to wait too long but let's not be critical.

[dilo]

Last update give a more reach dataset for estimating Hayabusa acceleration toward Itokawa. A fit of the Sept 19-26 parabolic arc give a=1.28E-7 m/s2, slightly smaller than previous one (-3.5%). However, expected gravitational effect should be about 10% stronger, due to lower average height above asteroid (15.9 instead of 16.7 Km)!
This confirm the non-gravitational nature of major acceleration components (probably, gravitation contribution is only 5-10% of total and its expected increase is masked by measure errors or other major effects).
As already highlighted, major component is probably solar pressure (radiation+wind).

[Toma B]

There is a new mission update here:

Hayabusa update

Few new images ( quite small)

[Toma B]

"On October 3rd, another Y-axis reaction wheel was found not functioning...."

Auch!!!....only one still left!!!

Then it's up to good old chemical rockets....but how much fuel is left there???

[Toma B]

"Hayabusa project has refrained from releasing high resolution images in order to retain the scientific output inside the science team."

So much for the raw images...

"REFRAINED FROM RELEASING" that's the way to atract new astronomers!!!
Thank you JAXA for REFRAINING!!!

[ugordan]

"On October 3rd, another Y-axis reaction wheel was found not functioning...."

Auch!!!....only one still left!!!

Then it's up to good old chemical rockets....but how much fuel is left there???      

Darn it. There seems to be a fundamental problem with the way the reaction wheels were carried out, this is just one too many failed wheels.
Just goes to show that in space, you need to have as few moving parts as possible (Galileo HGA/tape recorder anyone?)

I suspect the craft'll have enough RCS propellant to carry out the mission, but it's a setback nonetheless. The spacecraft needed RCS thrusters anyway to periodically desaturate the wheels' momentum, now they'll just take up the primary role of attitude control...

[dilo]

"Hayabusa project has refrained from releasing high resolution images in order to retain the scientific output inside the science team."

Very bad new!... JAXA policy is like ESA!
Thanks, NASA (from an European taxpayer!!!)

[tedstryk]

Very bad new!... JAXA policy is like ESA! 
Thanks, NASA (from an European taxpayer!!!)

I wouldn't go that far yet....they are still releasing information, including the images in today's release, every few days, which beats ESA. Also, it depends what they mean by refrain....are we going to wait a week or two or months....To be honest, I am wondering if there is a connection to the reaction wheel problem (seeing if this new mode works well before smeared images pop up and people start speculating).

[RNeuhaus]

I would like to understand better about the Hayabusa problem. After seeing the picture of the spacecraft. (I have not found any good and detailed Hayabusa description), it has 8 tiny chemical propulsors (4 above and 4 below) The ones propulsors above of the base has some inclination toward outside and the others from below are pointing to the land.

However, I am not sure what the below is referring:

As already reported, Hayabusa lost one reaction wheel (X-axis) on July 31st and has taken an alternative flight mode using two wheels for the attitude stabilization.

So far, the Hayabusa has two kind of propulsions: Ion Electirc (now works 2 of 3) and 8? chemical propulsors.


The question is what kind of propulsion is referring to the above report. What is RCS? Is that something related to chemical propulsion?

What is the impact with the losing of one "reaction wheel (X-axis)".

Rodolfo

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[ljk4-1]

I would like to understand better about the Hayabusa problem. After seeing the picture of the spacecraft. (I have not found any good and detailed Hayabusa description), it has 8 tiny chemical propulsors (4 above and 4 below) The ones propulsors above of the base has some inclination toward outside and the others from below are pointing to the land.

Rodolfo

Are the Japanese asking for help from space experts outside their country? I hope they can put any national pride aside and keep this mission from failing.

Have any space probe experts from other countries offered to help the Japanese on their own?

Space exploration should be considered a global effort these days. We're still all from the same space rock.

[tfisher]

The question is what kind of propulsion is referring to the above report.  What is RCS? Is that something related to chemical propulsion?

What is the impact with the losing of one "reaction wheel (X-axis)".

RCS is a fairly standard acronym for "Reaction Control System" (see the wikipedia entry). That system can include both reaction wheels (little gyros, with some way of spinning them faster to provide a torque) and thrusters. On Hayabusa there were originally three such wheels, controlling the orientation of the probe around three different spin axes (x,y, and z; or yaw, pitch, and roll), and as you observed 8 bipropellent chemical thrusters. It looks like in the report they use RCS to refer only to the chemical rocket thrusters, though.

From the sounds of it, the loss of another reaction wheel (they lost one already some time ago) will make spacecraft control a lot harder and probably require reprogramming of the craft's computers. But it probably isn't fatal to the mission goals. To quote a column from the Planetary Society - Japan, where the issue was considered back at the time of the first reaction wheel failing:

Then, what will happen if another wheel goes wrong, leaving only one operating normally? “HAYABUSA” is installed with equipment to control the attitude by injecting gas, so that in the case of only one normal wheel, it will be used as an alternate method. From now on there will be required of prompt resolution of problems. This is the way satellite or exploration probes are actually operated.

[RNeuhaus]

RCS is a fairly standard acronym for "Reaction Control System" ...

Tfisher, Thank you for the good comments.

I am wondering about why such a simple electric wheel motor have failed. It is strange since an electric motor only fails due to the overhaul or over voltage...

Rodolfo

[djellison]

Well - these things have to spin at thousands, tens of thousands, perhaps hundreds of thousands of RPM - (I've seen numbers between 6,000 and 60,000 rpm) and have their speed adjusted to impart forces onto the spacecraft...for day after day after day after day......

They just fail...they've failed on Hubble, they've failed on the ISS, it's just one of those components that dies eventually.

Doug