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ToSeek
2006-Oct-31, 06:14 PM
NASA Announces Discovery Program Selections (http://www.nasa.gov/home/hqnews/2006/oct/HQ_06342_Discovery_AO.html)


NASA Monday selected concept studies for missions that would return a sample of an enigmatic asteroid, probe the chemistry of Venus' atmosphere and reveal the interior structure and history of the Earth's moon.

Also selected for further study are three missions of opportunity that would make new use of two NASA spacecraft that have completed their primary objectives.

"The science community astounded us with the creativity of their proposals," said NASA's Science Mission Directorate Associate Administrator Mary Cleave. "We look forward to the new knowledge of our solar system that these concepts may provide."

Swift
2006-Oct-31, 06:25 PM
I really like this Mission of Opportunity, though I'm kind of surprised they think it could work

-- The Extrasolar Planet Observations and Characterization (EPOCh) mission would use the high-resolution camera on the Deep Impact spacecraft to search for the first Earth-sized planets detected around other stars. L. Drake Deming of Goddard is EPOCh's principal investigator.

Ilya
2006-Nov-10, 02:46 PM
I really like this Mission of Opportunity, though I'm kind of surprised they think it could work
Apparently this is a case of making lemonade out of lemons. Deep Impact's camera is defocused, which is bad for its original purpose (observing comets), but is a good thing if you are watching for tiny dips in a star's brightness (transiting planets). You don't want sharp images of the stars as the physical structure of the CCD pixels has discontinuities. If you had a very sharp, point-like star image, small attitude disturbances will project the image on different parts of the pixel region, possibly on the boundary between two pixels. This would make the brightness appear to oscillate and give false positives. With an out-of-focus image, you sum up the smudged area which is less prone to such artifacts.

Ilya
2006-Nov-10, 02:58 PM
In 2005 not one Discovery mission proposal was accepted. From what I read, the evaluating committee (or whatever it is called) judged every proposal either to have too low scientific return, or to be unrealistic to fit in Discovery budget. IOW, all "low-hanging fruit" had been picked, and remaining proposals are either too ambitious or so unambitious as not to be worth bothering. Since laws of nature did not change between 2005 and 2006, either Discovery budget must have increased, or the committee must have lowered the bar of "scientific return."

Larry Jacks
2006-Nov-10, 03:41 PM
In 2005 not one Discovery mission proposal was accepted. From what I read, the evaluating committee (or whatever it is called) judged every proposal either to have too low scientific return, or to be unrealistic to fit in Discovery budget. IOW, all "low-hanging fruit" had been picked, and remaining proposals are either too ambitious or so unambitious as not to be worth bothering. Since laws of nature did not change between 2005 and 2006, either Discovery budget must have increased, or the committee must have lowered the bar of "scientific return."

Not necessarily. The 3 opportunity missions are using spacecraft that hadn't completed their primary missions in 2005. As to the others, maybe they weren't ready for evaluation or sufficiently developed in 2005 but were able to make the cut this time. Or, perhaps they were able to better demonstrate their ability to perform the mission within the budget constraints. It doesn't necessarily infer at all that the standard was lowered this year.

Ilya
2006-Nov-10, 06:39 PM
"Lowered the bar" was kind of a joke -- I did not seriously believe that happened. I can, however, believe that the price cap was raised.

Swift
2006-Nov-10, 07:50 PM
Apparently this is a case of making lemonade out of lemons. Deep Impact's camera is defocused, which is bad for its original purpose (observing comets), but is a good thing if you are watching for tiny dips in a star's brightness (transiting planets). You don't want sharp images of the stars as the physical structure of the CCD pixels has discontinuities. If you had a very sharp, point-like star image, small attitude disturbances will project the image on different parts of the pixel region, possibly on the boundary between two pixels. This would make the brightness appear to oscillate and give false positives. With an out-of-focus image, you sum up the smudged area which is less prone to such artifacts.
Thanks for the explanation. I thought that they were going to try to directly image the exo-planet, rather than look for light dips from transits. That makes a lot more sense.