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Akatsuki Venus Climate Orbiter
pandaneko
post Nov 9 2011, 01:19 PM
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QUOTE (rlorenz @ Nov 9 2011, 09:52 PM) *
Well, this is exactly the trade that any system design has to make.... and engineers do it when they can get away without a big engine, but missions typically demand the performance that only a biprop can give.


Thanks, Ralph

I have been frustrated a lot. I want to see lots and lots of different facets of our other planets. I probably have another 25 years and these satellites keep failing. I wish they launched at least one satellite every year. Yes, trade-offs..., yes, and thanks again for further thoughts.

Pandaneko
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Paolo
post Nov 10 2011, 10:46 AM
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actually, this has been done on the MRO, which used six monopropellant engines instead of a larger, bi-prop one to perform Mars orbit insertion


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djellison
post Nov 10 2011, 02:44 PM
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They were all significantly more powerful than a usual RCS thruster. They were, infact, the descent engines for the 2001 lander.
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pandaneko
post Jan 31 2012, 12:36 PM
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This news just in. (21:09 31 January 2012, The Yomiuri newspaper)

JAXA announced that they will try and re-insesrt Akatsuki into Venus orbit in December 2016, if the prove conditions remain good.

In this case, Akatsuki's orbit will be oval in shape and it will have to observe Venus from a distance. However, according to JAXA there will not be much of a problem in observing clouds and atmosphere of Venus.

Akatsuki used its smaller engines in November last year to correct its course and is programmed to have its closest encounter in November 2015. However, forcing Akatsuki into a circular orbit at this time will mean an orbit which is not really ideal for atmospheric observation. It is for this reason that they want to opt for June 2016, which is the next closest encounter.

However, missing the earliest opportunity means physical deterioration of the probe and JAXA are saying that they may try re-insertion in November 2015, if the conditions are found to be bad by then.

P
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stevesliva
post Jan 31 2012, 05:06 PM
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Cool! Thanks for the update.
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tolis
post Jan 31 2012, 11:05 PM
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QUOTE (pandaneko @ Jan 31 2012, 12:36 PM) *
This news just in. (21:09 31 January 2012, The Yomiuri newspaper)

JAXA announced that they will try and re-insesrt Akatsuki into Venus orbit in December 2016, if the prove conditions remain good.

In this case, Akatsuki's orbit will be oval in shape and it will have to observe Venus from a distance. However, according to JAXA there will not be much of a problem in observing clouds and atmosphere of Venus.

Akatsuki used its smaller engines in November last year to correct its course and is programmed to have its closest encounter in November 2015. However, forcing Akatsuki into a circular orbit at this time will mean an orbit which is not really ideal for atmospheric observation. It is for this reason that they want to opt for June 2016, which is the next closest encounter.

However, missing the earliest opportunity means physical deterioration of the probe and JAXA are saying that they may try re-insertion in November 2015, if the conditions are found to be bad by then.

P


December 2016 isn't too bad, less than 5 years from now. Past missions like Hayabusa showed that the Japanese design a lot of flexibility/versatility into their spacecraft and that helps getting them through tight spots like this one. If they're not too unlucky with solar activity, we might be seeing some first-rate Venus science come 2017..
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elakdawalla
post Jan 31 2012, 11:12 PM
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Some Japanese followers of mine on Twitter have said that it's actually not December 2016 they were discussing, but June 2016. Also, apparently the choice of 2016 for orbit entry isn't as set in stone as Yomiuri makes it seem. At the press briefing they seemed to have been discussing trade-offs between degradation of the orbiter's systems and the fact that with every Venus swingby they do, they can improve the scientifically useful characteristics of the orbit they can achieve on the next encounter.


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pandaneko
post Feb 1 2012, 12:54 PM
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The Sankei newspaper here carried an article about Akatsuki's failure as follows. Time stamp for this article is 19:24 31 January 2012. I believe that this will be the general public's understanding of this failure. It goes as follows.

"Failure cause is bad design. Venus probe Akatsuki, fuel did not reach its engine. 19:24 31 January 2012."

"Space Activities Comission (SAC) accepted a report submitted by JAXA on the causes of orbit insertion failure of Akatsuki that the failure was due to the valve mulfunctioning which prevented the flow of fuel to the engine.

According to this report a larger than assumed amount of salt was formed during the 6 months flight to Venus by the reaction of evaporated oxidiser and fuel. This adhered to the valve for the fuel tank, preventing opening of the valve for fuel supply.

The reaction between the oxidiser and fuel itself had been predicted at the desing stage. However, the design team failed to predict that the valve component problem would lead to more than 100 times the amount of oxidiser migrating into fuel than assumed. Adding to this, part of inspection and testing had also been skipped due to cost and time constraints.

Prof Y Inatani of JAXA commented that it was outside their expectation and that a well thought design should have prevented it during the design stage. Akatsuki is still flying, powered by smaller engines with a view to trying re-insertion in 2016."

P
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nprev
post Feb 1 2012, 03:24 PM
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Thank you, P.

And as usual there is never enough time, testing, or money.

But afterwards, there always is learning. It's a truly ancient, perhaps inevitable, pattern.


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hendric
post Feb 1 2012, 03:44 PM
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Yes, I imagine somewhere on a stone tablet or cave wall is something to this effect:

FINDING ON MAMMOTH HUNT

We fail to to kill mammoth today

We check with spear design team

We find spear design team did not attach spearpoint to spear

Also, spear throwing team not properly trained due to time constraints, and was throwing wrong end of spear to mammoth

We will miss ZOG greatly


Ha, maybe that's what cave paintings really are, instruction manuals! smile.gif


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Paolo
post Jun 11 2012, 11:24 AM
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some rare scientific results from Akatsuki's Venus flyby
Characteristic features in Venus’ nightside cloud-top temperature obtained by Akatsuki/LIR
JAXA has a summary (in Japanese only) on the mission webpage


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James Van Allen
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pandaneko
post Jun 28 2012, 08:25 AM
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QUOTE (Paolo @ Jun 11 2012, 08:24 PM) *
some rare scientific results from Akatsuki's Venus flyby
Characteristic features in Venus’ nightside cloud-top temperature obtained by Akatsuki/LIR
JAXA has a summary (in Japanese only) on the mission webpage



Thanks, Paolo

What follows is the first of my translation which may last for a few more days. This actually comes from ISAS (now part of JAXA) web pages.

[11 May 2012]

It is almost 2 full years since the launch on 21 May 2010. Thank you for your continuing interest in Akatsuki.

2011 for our Akatsuki operation team was filled up with new challenges, such as the firing test of the damaged main engine, reduction of the probe mass by releasing the oxidiser, orbit changes by the smaller attitude control engines.

We are still preparing ourselves for the 2015 re-union, but at the same time we have been making the best use of this period and conducted a few observations such as "Looking at Venus from 1300X 10,000 km", "Solar uki has corona observation by shatting up radio waves (My translation can be very wrong, P)", and these have been reported at various international meetings.

Akatsuki is very fortunately flying without any hithces. Here, now, we offer our sincere apologies for the lack of information over the past 12 months. What follows is , albeit very brief, our account of the orbital control operation since the autumun of last year.


"Akatsuki's new orbital plan"

Akatsuki started its new orbital journey in November 2011. By firing 4 small attitude control engines for a long time indeed, 3 times over the period and it managed a delta V approx. 240 m/s and entered into an orbit which ensures an encounter in November 2015.

(end of translation of this particular session)

After this there are a few more remarks which we already know from my past translations. The point of this article is (I think) that Akatsuki is still flying healthy and we may even get scientiffic results in 2015.

P
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pandaneko
post Jun 29 2012, 08:06 AM
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QUOTE (Paolo @ Jun 11 2012, 08:24 PM) *
some rare scientific results from Akatsuki's Venus flyby
Characteristic features in Venus’ nightside cloud-top temperature obtained by Akatsuki/LIR
JAXA has a summary (in Japanese only) on the mission webpage



[8 June 2012]

Venus night side temperature distribution seen by the LIR camera

(actually, there two more reports in between, but they relate to Venus going across the Sun. So, I am not translating them. P)

An attempt was made to capture the image of Venus by the onboard camera on the night of 9 December 2010 while Aklatsuki was limping away from Venus, being very much mindfull of the scar on its bottom. At this time Akatsuki was already 600,000 km away from Venus, but the LIR camera managed to capture the whole surface.

There had been a few sporadic spectrographic observations made both from the ground stations and space probes this was the first ever snap shot of this kind.

During the two minutes period in which 32 cumulative images were to be made the attitude of Akatsuki was somewhat disturbed. To combat this issue we position -corrected these cumulative images and layed them over one another and actually came up with a slightly better image in terms of resolution.

If you take a look at this image and analyse the so called peripheral temperature reduction by which the surface temperature of Venus seems to go lower as you look away from the centre of the disk towards the peripheral area. By analysing it carefully we concluded that the reason is due to the reduction in number of cloud particles in the upper atmosphere of Venus.

Observed absolute temperatures are staying relatively higher compared with past observations. This is thought to be due to the fact that the temperatures are actually rising, or alternatively we are looking at the lower layers with higher temperaturers seen through thinning upper layer clouds.

In addition, we can observe at the poles low temperature band zones (Polar clour) and similar band structures in mid to lower attitude areas with even finer temp. distributions on a much smaller scale. At the polar regions we may even be seeing polar dipole regions with high temperatures.

Akatsuiki is in good shape except for the main engine. The next earliest opportunity for re-insertion is end 2015. Once placed in its final circular orbit we expect to be able to obtain far superier resolution on a continuous basis.

(end of translation, P)
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Paolo
post Oct 29 2012, 05:36 PM
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an interesting paper on orbit strategies for the return of Akatsuki to Venus
THE TRAJECTORY CONTROL STRATEGIES FOR AKATSUKI RE-INSERTION INTO THE VENUS ORBIT


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I'm one of the most durable and fervent advocates of space exploration, but my take is that we could do it robotically at far less cost and far greater quantity and quality of results.

James Van Allen
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