Kepler Channel Noise Problem

TheoA wrote:Hence it is all being mixed together.

Borucki wrote:will be corrected or the data flagged to avoid being mixed in with the
low noise data

(emphasis mine)

TheoA wrote:Keep in mind that the due to the quarterly roll the planet field affected is actually (4) times 3 or 12/84 ~ 15% once you cut through the spin.

I'm not sure I understand. Why would there be more noisy channels after the roll?
Edit: Okay I see what you're saying. What exactly are the channels? Surely, they aren't those observation rectangles that Kepler is looking at, I counted them recently, and there's far less than 84.

TheoA wrote:I remember the heart stopping moments with the explosive bolts on the mars rovers.

O_o what? I don't remember anything of the sort but then again, it's been a while.

I'm willing to bet that there has been disclosure of this issue, and that Nature just picked it up recently. But I don't know for sure.

Quite informative as to the nature of the data channels. Looks like TheoA's thing about the rotation of the spacecraft compromising more data fields was well-founded. The total data should still only be 3.5% noisier than usual though, as not every field is under the same channel all the time.
http://infox.ru/science/universe/2009/11/02/NoisyCCDamplifiersdelayKeplerplanetsearch.phtml (In Russian)

Sirius_Alpha wrote:
http://infox.ru/science/universe/2009/11/02/NoisyCCDamplifiersdelayKeplerplanetsearch.phtml (In Russian)

http://translate.google.ru/translate?u=http%3A%2F%2Finfox.ru%2Fscience%2Funiverse%2F2009%2F11%2F02%2FNoisyCCDamplifiersdelayKeplerplanetsearch.phtml&sl=ru&tl=en&hl=ru&ie=UTF-8

The sense comprehensible?
Everything is worse than previously thought

In general total - a loss 1-2 years in collection high precision data and 15% data after correction.

Sigh! Why does the only article with some accurate insight have to be Russian.

The present algorithm adjusts the photon count received by comparing the light from one star to all the others.
The essential concept behind differential photometry.

So its the light from all 100% of the data that is being compromised 3.84% before being sent to Earth.

Because the full data set is not sent to Earth this not a fixable with processing on Earth type issue.

Keep in mind that Kepler was designed to detect planets as small as Mars.
A Habitable zone Earth was originally a very easy catch.
The degradation is quite dramatic.

On the bright side this should not affect the ability to detect Jupiter.

Get ready for a tonnes of hot Jupiters and more spin on how valuable these are.

yaay. All together now. yaay.

TheoA wrote:yaay. All together now. yaay.

Agree. We hope to fix the problem next year. All is not lost.

I wonder how accurate uhudshililas already collected over 6 months of data? At 2, 5 or 10 times worse?

Also note the space craft has only enough consumables for a 5 year mission, esp. to de-spin the gyroscopes.

The loss of 3 years is likely to be fatal to finding Earths IMHO.

Thanx Borislav.

I think that 2.5 year extension was to work without propellant potentially. Still think it will be fatal.

The primary mission of Kepler was actually to perform a census of the planets and so give us a very good statistical understanding of whats out there.

Right now it looks like this is severely compromised.

(some parts of this post have been removed as I calmed down a bit after writing it )
Alright, let's break it down.

15% of the data may have noise in it, and in that 15% of the data, only 25% of it is noisier than usual. That means that 3.57% of the total data will be noisier than usual. Since it was made clear that the noisy data can be flagged out, or corrected, that means that while that data won't help the hunt for exo-Earths, it won't hinder it either.

Why is everyone assuming that all the exo-Earths occupy that 15% of the data? Is Kepler that cursed? Those who know me well enough on this forum (and elsewhere) know that I'm a chronic pessimist, and yet even I think that we're still good to go.

TheoA, three years of the mission have not been lost, just 15% of the data from those three years, at most. Not all of the target stars have this noise issue. Remember HAT-P-7 b's secondary light curve and the "We have the ability to detect exo-Earths" press release? With the issue known before launch, it's obvious that not all target stars are affected from this data. If HAT-P-7 b is in the other 85% of the data, then why can't some exo-Earths? Is there something I'm not seeing here? Some reason why the other 85% (at least) of the data that will be unusable?

Edit (upon re-reading):

How sure are you that 100% of the stars will be affected by the 3 channels? Do all the photons from each star pass through each channel? (edit again:) And how does this fit in with the detection of the HAT-P-7 b secondary transit, which was of similar depth to an Earth-radius planet?

edit again...
Recall from the power-point presented earlier.

All 84 channels are operating & producing useful data
Photometric precision is about 1.5 times design values

Note it doesn't say that the 84 channels are functioning perfectly, but rather, are producing useful data. Is there some reason to doubt this? Even with 15% of the data noisier than usual, with a photometric precision of 1.5 times the design value, wouldn't this help alleviate the worry?

Someone on UMSF posted this image.

It suggests that channels are used for specific areas of the sky, instead of each channel processing all the data.

Sirius,

You might have to read the Russian article again to see why all the data is being degraded.

There is nothing wrong with the photometers.

The problem is with the amplifiers. The article says that the signal is amplified 100 times and then de-amplified 100 times to remove noise. Kinda like Dolby processing.

This process has to be perfect as the next step is to compare the stars to each other and transmit the signal differences alone back to Earth. Can\'t stress this enough. The Signal itself is never sent back.

So the data from each photometer is compared with the others and the differences are transmitted back.

So if 3 amplifiers pump an anomalous 3% change into the matrix, any signal of less than roughly 1/8000 will simply not exist. There will be nothing sent back.

Also apparently this anomalous signal varies as well. So the only way to deal with it is to strike a line at say 1/5000 and drop everything below that. Simply too degraded to use.

This is what Borucki means when he says NO Earths in the habitable zone can be detect before the fix. Not just in that 15%, but in all 100%. We need a 1/10,000 signal to detect Earth. So there is an outside chance the dimmer stars might allow detection. But you see where I\'m going. All spin.

Remember Kepler was originally designed as a 1/100,000 machine. While COROT was a 1/10,000 machine.

Now the article could be wrong, but nothing Borucki says contradicts it.

As far as the HAT-P-7 b data, that was taken from the calibration data only and apparently used a manual over ride. More spin.

Alright, that makes sense. But I am still curious as to how they pulled off measuring that HAT-P-7 b secondary transit then?

Sirius_Alpha wrote:Alright, that makes sense. But I am still curious as to how they pulled off measuring that HAT-P-7 b secondary transit then?

http://infox.ru/science/universe/2009/11/02/NoisyCCDamplifiersdelayKeplerplanetsearch.phtml

Как признают создатели аппарата, о проблемах в нескольких усилителях было известно еще до запуска космического аппарата. «Все об этом знали, и все беспокоились», – признался Nature специалист по научному оборудованию Kepler Даг Калдуэлл. Во время летных испытаний даже удалось поймать фазовый эффект от одной известной экзопланеты: поскольку время и место появления эффекта были известны, можно было обойтись без дифференциальной фотометрии.

They write, during the calibration period (early May) mode differential photometry was not used.