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SIM Status
by
copernicus
on 20 Oct, 2010 17:56
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There has been some recent developments in the Space Interferometry Mission, SIM. They are not good. This is summarized in the following article that I wrote for Space Review -
http://www.thespacereview.com/article/1711/1/ NASA is now in the process of shutting down the SIM project and reassigning personnel. For those of you who thought that NASA was planning a major effort to seek nearby Earth-like planets, think again. If NASA is not directed by Congress to proceed with SIM, then this marks the end of the agency's involvement in trying to find those warm, habitable planets located in nearby solar systems. If SIM is halted, then we face a 10 or 20 year hiatus in that search.
If any of you out there can suggest how this recent short-sighted decision can be reversed, let me know. Ross, do you have any ideas?
Phil Horzempa
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#1
by
Hungry4info3
on 20 Oct, 2010 18:06
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If SIM is halted, then we face a 10 or 20 year hiatus in that search.
While I would love to see SIM fly, this statement is simply untrue. Doppler spectroscopy and photometry are still powerful tools and the current exoplanet census attests to that. If SIM doesn't fly, it will have an impact on exoplanet science, but not a 10 or 20 year hiatus.
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#2
by
copernicus
on 21 Oct, 2010 05:55
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Doppler spectroscopy is only able to find planets that are larger, and usually much larger, than the Earth. Photometry (transit method) is useful when examining a large sample of stars since only a few percent of exoplanet orbits are aligned correctly. The transit method becomes especially problematic when one is looking for an Earth-sized planet that is located at about 1 A.U. from its parent star. The odds of a transit in that case drop dramatically. It is more common to find transits of planets that are Hot Jupiters or Hot Super Earths because they are located only a fraction of an A.U. from their parent star (do the geometry). However, these Hot Exoplanets are not conducive to life.
SIM is an astrometry mission. It is able to find planets in all orbital inclinations. It is able to find planets with a mass of 1 Earth, or lighter. Because of this advanced capability SIM is the ONLY proposed mission that is able to find Earths orbiting nearby stars and located about 1 A.U. from those stars. That caveat is why I mentioned the 10 to 20 year gap. I am not kidding.
The Doppler and Transit methods will continue to discover Jupiter-class and Super-Earth class planets as far into the future as you please. But they will not be able to find Earth analogs orbiting nearby stars in the Habitable Zone of those stars. Locating these neighboring Earth-clones is crucial. SIM is the only effort that can locate those NEARBY Earths.
Once we can locate those nearby Earth twins, follow-up missions will know where to look. Those future missions will be able to utilize spectroscopy to analyze the surfaces and atmospheres of those Earth analogs. In the longer term, they will be able to produce crude images and crude maps.
So, I am not exaggerating when I state that if SIM is halted, then the whole sequence of Exo-Planet missions will be disrupted. I do not understand NASA's logic in ending this effort. All that I know are its actions. Without public announcement, it is ending, for 10 or 20 years, its program to find and characterize NEARBY Earths. And by nearby, I mean within 20 - 30 light years. Being nearby is crucial in that those planets will be bright enough to allow future space telescopes to collect enough photons to do serious work.
An Earth twin located at 20 light years' distance is 10,000 times brighter than an identical planet located 2,000 light years away. I picked the second distance of 2,000 Light Years because that is the distance of the stars that Kepler transit space telescope is now monitoring. It will be fantastic when Kepler discovers Earth-sized planets. However, what Kepler will provide are mainly statistics on the prevalence of Earth analogs. Those newly discovered Earth twins will be much too far away, and hence much too dim, for any detailed follow-up investigations.
A mission such as SIM is the ONLY way forward if we want to actually KNOW something about the nature of Earth analogs. We need nearby targets that only SIM can find.
So, the cancellation of SIM means that NASA is stepping away from this effort at least until 2020, and possibly longer.
Phil H.
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#3
by
Lampyridae
on 21 Oct, 2010 06:44
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[tinfoil_hat]
Are these politicians afraid of finding earthlike planets? Finding one nearby would probably mean a demand for an even bigger telescope to actually image the thing.
[/tinfoil_hat]
What about a star occulter for JWST? Would that not serve an equivalent, albeit somewhat handicapped, purpose? At least as far as spotting exoplanets goes?
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#4
by
copernicus
on 21 Oct, 2010 07:56
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An external occulter for JWST is a great proposal. It goes by the name New Worlds Probe. And it would be able to produce a crude image, as well as crude spectra, of nearby Earths. However, because the occulting starshade will need to be about 20,000 miles away from the JWST, it will take a lot of time to change targets. Therefore, this mission would benefit immensely from the data of SIM, as SIM will tell it where to look. In fact, such a mission, on its own, may not have enough time to perform a search for candidates before its consumables ran out.
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#5
by
GClark
on 22 Oct, 2010 05:41
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It's not NASA that's stepping away from this mission. The recently completed Astrophysics Decadal didn't recommend it. Congress puts great weight in the recommendations of the Decadal Surveys. Internal Astrophysics community politics killed SIM, not NASA.
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#6
by
simonbp
on 26 Oct, 2010 23:42
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And Astro2010 didn't recommend it because the SIM project has been working since the mid-1980s, without much result. Plus, as the years went on, the number detectable planets from SIM dropped as the budget projections just went up...
Kepler flew because it shot for much more modest goals, and looks like it will accomplish them. With limited exoplanet resources, you can't simultaneously be expensive, take forever to fly, and have no verification that it will actually work. But that's what JPL is notorious at: Funding projects driven by engineers that gradually become completely decoupled from the science.
Some form of TPF will fly, but it probably not look like SIM...
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#7
by
Archibald
on 14 Nov, 2010 17:22
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Can someone with more knowledge please enlight me.
What was general consensus ten years ago ? I mean, back in, say, 2002 was it considered possible to find very small exoplanets without the TPF or SIM ?
I mean that TPF was thrown to the dust bin in what, 2006, and well, this did not prevent amazing discoveries since then.
The Gliese 581 system revealed many interesting worlds to "old fashioned" instruments that the TPF was supposed to make laughable.
To caricature: are TPF and SIM dinosaurs made obsolete by the flur of recent discoveries ?
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#8
by
Hungry4info3
on 14 Nov, 2010 21:38
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Archibald,
A SIM-type mission would still be useful but it is not a necessity. Radial velocity techniques can find many of the worlds that, 10 years ago, would have been considered only detectable by SIM.
RV precision is pushing into the realm of Earth-mass planets. Additional technology is in the development phase to improve substantially on this.
See
this paper.
Searches for extrasolar planets using the periodic Doppler shift of stellar spectral lines have recently achieved a precision of 60 cm s-1, which is sufficient to find a 5-Earth-mass planet in a Mercury-like orbit around a Sun-like star. To find a 1-Earth-mass planet in an Earth-like orbit, a precision of approx 5 cm s-1 is necessary.
This wide-line-spacing comb, or 'astro-comb', is well matched to the resolving power of high-resolution astrophysical spectrographs. The astro-comb should allow a precision as high as 1 cm s-1 in astronomical radial velocity measurements.
Progress in research and development of the technology continues.
http://www.eso.org/public/news/eso0826/Essentially, the loss of SIM is not as devestating as is being made out to be.
To caricature: are TPF and SIM dinosaurs made obsolete by the flur of recent discoveries ?
Not quite yet. TPF especially.
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#9
by
Archibald
on 15 Nov, 2010 14:15
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thank you. I was intrigued, if not overwhelmed, by the large number of future telescopes to go to Sun-Earth L2 in the future. Way too much projects - this is suspect - show me the money !
So I downloaded past (2001) and recent (2010) astrophysic decadal surveys.
The difference is quite marked. Back in 2001 they endorsed a kind of gradual path, akin to Spitzer > Webb > SAFIR > SIM > TPF
Ten years later, well, not much remain of that. Not a word of SAFIR with SIM and TPF cancelled a long time ago - and the survey clearly not in a hurry about their eventual resurection.
I'd really like to see some criticism of (now cancelled) TPF and Darwin. Were ESA and NASA too ambitious ? Did these projects came too earlier ?
The next "realistic" step we can hope for looks like the Webb starshade or occulter. That something the survey seem to be positive about.
I'm curious to know if ESA ever thought of a Starshade for Hershell ?
That's a fair amount of questions ! But we have some fairly impressive experts down on this forum
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#10
by
Robotbeat
on 15 Nov, 2010 16:10
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A Webb starshade is ambitious, too. It'd need an advanced propulsion system (ion-propulsion is fine) unless you want to use it for just a very short time.
It's still a shame that SIM is being canceled.
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#11
by
copernicus
on 08 Dec, 2010 05:57
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#12
by
Hungry4info3
on 08 Dec, 2010 15:18
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An online petition site has been started urging NASA and the Congress to reverse the decision to cancel SIM. It can be found here.
Maybe you should also do a fund-raiser...
