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The Kepler space telescope was a marvelous instrument and performed great science however it has now failed due to the loss of 2 reaction wheels it requires 3 to function. As designed Kepler only had one backup wheel. It can no longer do the job it was intended to do. My question is why didn't the engineers that designed Kepler put in duel redundant reaction wheels for each axis? The reaction wheels are the weak link they only have a limited lifespan. putting 3 backup wheels for each axis would have extended Kepler's life for many many years to come. the cost compared to the overall cost of Kepler would have been negligible. It just seams to me the engineers would have taken lessons learned from hubble (gyroscopes and reaction wheels fail). in the past NASA has embraced the dual redundant theology why not now. — Preceding unsigned comment added by 126.96.36.199 (talk) 02:10, 7 March 2014 (UTC)
No, the full service lifetime for Kepler does not inherently demonstrate poor engineering.
However, at the base of what you ask is a good question. I do not have detailed knowledge of the design process which was used for Kepler. However, I can make some general comments. A large portion of engineering is making trade-offs based on various requirements. One of the huge limitations in building anything for space is the amount that it weighs. The weight of a satellite determines a large number of aspects of what and how something can be done, how much it costs, what lift capability is required, etc. It can even limit: can this be done at all with current technology? Weight, among many other limitations, usually means that such designs are not made with huge amounts of redundancy – particularly when lives are not at stake – which is not needed to reliably meet the service lifetime criteria which is a basic part of the specifications toward which the engineers are designing. The design of Kepler resulted in it being operational until 4.2 years after being launched. This exceeded the design criteria by 20%. [This percentage may be a bit off. The 3.5 year design lifetime may have been specified as the amount of time on-station, collecting data, not from launch. I would need to double check, but don't have the time at the moment.]
As to the engineers learning from Hubble: I expect that the engineers involved had access to, and learned from, the problems and failure analyses which were performed on the various issues that have occurred with Hubble.
For some things, there has come to be an expectation that items designed for space will exceed their designed lifespan. While there are cases like Spirit (rover) and Opportunity (rover) where the designed lifespan has been spectacularly exceeded, it is certainly not always the case. Of course, there are also some times where there are partial, or complete, failures. — Makyen (talk) 03:39, 7 March 2014 (UTC)
The story I heard is that there are $105 reactions wheels and there are $106 reaction wheels. The lower cost ones are known to be less reliable, but for a mission on a tight budget there may be no choice. This makes perfect sense, but it also seems that if they are known to be unreliable, maybe two spares would have been better than one. But this leads into all sorts of questions about where mass and dollars are best spent, how certain they were that previous reaction wheel failure modes had been addressed, and so on. LouScheffer (talk) 15:18, 7 March 2014 (UTC)
We should split the "objective and methods" section of this article into subsections as follow:
1. Kepler's field of view, the properties of observed stars and ways it observed them?
2. Automated data processing from observed stars to threshold crossing events.
3. Steps which turn good candidates from threshold crossing events to Kepler objects of interest and then in turn to Kepler candidates.
4. Ways Kepler candidates are confirmed through other exoplanet detection methods or validated by ruling out false positives. In addition, include ways planets are confirmed which do not go through standard Kepler pipeline process (such as circumbinary planets).
FWIW - Seems NASA will be announcing a "new discovery" made by the Kepler (spacecraft) on Thursday, April 17, 2014 at 2 p.m./et/usa - perhaps interestingly, Science (journal) has "embargoed the findings" until the time of the news conference - more =>
I have not looked at the above sources, but it appears that there should be at least mention of it. The article is not exclusive to any one specific type of research done with the data. If the data provides other benefit, then it should be mentioned, within reason. — Makyen (talk) 20:13, 21 April 2014 (UTC)