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SIM illustration
The future of the Space Interferometry Mission (SIM) may be in jeopardy after it failed to make the cut in the latest astronomy decadal survey. (credit: NASA)

SIM and the “ready, aim, aim” syndrome


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While the space community’s attention has been diverted by the continuing debate over the fate of the Constellation human spaceflight program, an equally momentous controversy has been brewing in NASA’s Astronomy division. It may sound absurd, but NASA is on the verge of pulling the plug on the search for other Earths orbiting nearby stars. While it will continue with a low-level effort to detect giant “unearthly” planets, those are not the worlds that hold out much hope to be life-supporting.

The end of SIM means the end of looking for nearby Earths.

Right now, we humans are on the threshold of being able to find twins of our Earth. This would be the fulfillment of years of effort to answer one of the “Big Questions” of civilization: “Are we alone in the universe?” Instead of charging ahead, with gusto, to address this issue, the space agency is reluctant. It appears about to turn aside from this grand challenge. This momentous change in NASA’s vision is taking place under the radar of public attention.

The catalyst for this stunning change at NASA is the release of a report in August by the Astro2010 committee of the National Academies known as the Astronomy and Astrophysics Decadal Survey. The Astro2010 team was charged by the National Academy of Sciences to review NASA’s astronomy program and to inform the agency of the priorities that should be given to various projects. This is the latest in a series of such reviews conducted every ten years, collectively known as the decadal surveys.

Buried in the nooks and crannies of the report is a momentous directive: “Shut It Down!” The “it” in this case is NASA’s search for twins of our Earth in our corner of the galaxy. For the most part, this is happening in stealth mode. Most of the science community, as well as the American public, have no idea that NASA’s science program is in danger of being radically altered.

Let’s examine the details of the Astro2010 report and see how those details spell the end of this grand venture.

The most immediate fallout is NASA’s probable cancellation of the Space Interferometry Mission, or SIM. This cancellation will end the keystone project in the search for “new” Earths. It is no exaggeration to say that if NASA goes ahead with de-funding SIM, then the whole roadmap that earlier NASA teams had painstakingly defined for detecting Earth-like worlds will come to a crashing halt. The end of SIM means the end of looking for nearby Earths.

The SIM space observatory is a wonderfully capable discovery machine, unlike anything that has preceded it. It utilizes an elegant device called an interferometer, which combines the light from two separate telescopes. By adjusting the spacing between those telescopes one obtains ultra-high-resolution data on the positions of stars. This will allow us to detect, with exquisite precision, the paths that those stars weave through the heavens, which, in turn, will indicate the presence of planets that orbit those stars through the “wobble” in the star’s motion created by the influence of those planets. SIM will be able to detect not only the giant Jupiter-like planets that observers on the ground have found, but (and this is the key to its significance) it can detect the presence of small, lightweight planets such as twins of the Earth. And it will find the ultimate prize, i.e., nearby Earths that circle Sun-like stars in our stellar neighborhood. SIM is the only project that can do that.

SIM is important not only for its own mission, but for the essential groundwork that it will lay for future missions. Those follow-on missions will be able to analyze the atmospheres that blanket those worlds, as well as producing the first crude images of those Pale Blue Dots. In turn, those missions will be followed by space telescopes that can produce improved images of those Earth analogs and perhaps detect the byproducts of life, such as chlorophyll, oxygen, and even smog.

Those revolutionary spacecraft will need a roadmap of the heavens. They will need to know which of the nearby solar systems to examine. The stars are numerous, and having a guide to promising locales is essential to those future missions.

The Astro2010 report has a list of recommended missions for the next decade, and SIM and its successors are notable by their absence.

The key will be finding the “exoEarths” that are close to us, meaning within 30 light-years. Only those Earths that are close enough to our solar system will reflect sufficient light from their parent Sun to allow telescopes, of any design, to examine them in detail. SIM is the only mission capable of detecting those nearby Earths. SIM will be a guide, a “GPS” for those who seek other Earths. Without SIM, all future endeavors to examine and chart those nearby Earths will stall.

In addition, SIM will be a pathfinder for the use of interferometers in space. This is a vital technology for future projects such as the planned Life Finder and Planet Imager missions, which will use arrays of space telescopes. Those arrays will use the technique of interferometry to combine their light and produce exquisite data, and maps, of those nearby Earths. Without SIM’s pioneering effort, those projects will be delayed for decades.

So far, NASA has launched one planet-hunting space telescope, Kepler, whose mission is still in progress. That spacecraft is designed to stare at a sector of stars located about 2,000 light years away and is looking for mini-eclipses of those stars. This transit method will reveal the presence and size of planets that may orbit the stars. It will be exciting news when Kepler detects Earth-sized planets for the first time. However, those small, rocky worlds will be immensely distant, much too far away for any detailed follow-up investigations. In order to determine if there are other Earths that could, or do, support life, we need to look at solar systems that are in our vicinity.

The SIM project has had a long, tortured history. It began its career 20 years ago, at first referred to as AIM or OSI. Two previous decadal surveys, in 1990 and 2000, approved of the mission and recommended that NASA build and launch SIM. It gained new start approval in 1997, entering Phase A, the initial planning stage of any NASA mission. SIM then entered Phase B in 2003. It progressed rapidly in this detailed design stage and successfully completed its engineering development by 2005. All technology challenges have been completed and peer reviewed. These two phases completed SIM’s formulation stage. However, just as it was about to enter Phase C, the beginning of the implementation stage, budget machinations at NASA served to stall the project.

In the mid 2000s big-ticket items such as Constellation and the James Webb Space Telescope were eating everyone’s lunch at NASA. As a result, SIM has been stuck in “Phase B limbo” since 2005. However, using a trickle of funding, the SIM team has worked on interferometer engineering risk reduction in the last few years. One result has been the construction of actual hardware. This hardware is being used for ground testing, but it is of high fidelity and could, in some cases, be upgraded to flight status. This is where things stand as of 2010.

NASA had charged several studies of how to proceed with finding other nearby Earths, and all of them concluded that SIM was the essential first step. It was implied that once funding was freed up in the coming decade that SIM and the other missions would proceed. We were ready, at last, to find worlds that would remind us of our home. Then, with little warning, the Astro2010 report came out with their implied directive to shut it down.

The search for extrasolar Earths is compelling. It is one aspect of NASA’s work that Americans implicitly understand.

As mentioned earlier, the Astro2010 report does not state this explicitly. In fact, they only mention the SIM project in footnotes. However, the report has a list of recommended missions for the next decade, and SIM and its successors are notable by their absence. This is especially remarkable. This Decadal Survey suggests that NASA ignore the recommendations of the two previous surveys that gave their blessings to SIM!

Instead, the Astro2010 committee designed its own physics mission, and gave it the name WFIRST. This would be a “Flagship-class” mission to look for dark energy. In a budget chart for the next decade, the Astro2010 team shows how the WFIRST mission will consume essentially all future funds for new missions. There is a sliver of funding for technology development for an exoplanet mission, but it is insignificant.

The decision of Astro2010 to eliminate nearly all traces of funding for planet-hunting space telescopes is breathtaking. They did offer a token to those studying exoplanets by adding a microlensing capability to the WFIRST infrared telescope. Microlensing can detect exoplanets by detecting subtle brightening of stars. However, microlensing will only find exoplanets that orbit stars located 20,000 light-years away. Distance, as noted above, is crucial to any follow-up missions. Microlensing, like the Kepler mission, can detect Earth-sized planets, but they will be so far away that it will be almost impossible to locate the stars around which they orbit. Like Kepler, microlensing will return data on the statistics of planet sizes, but will lead us no closer to finding a warm, water-bearing Earth twin.

Another aspect of this controversy is that WFIRST, along with its microlensing experiment, exists only on paper. By contrast SIM has achieved all technical milestones, has built hardware, and is ready to proceed. About 10 years ago, former NASA Administrator Dan Goldin complained about NASA’s “Ready, Aim, Aim” syndrome. This describes SIM’s situation exactly. It is a waste of effort and time and people’s careers to make a major investment in a space project, and then walk away after substantial progress has been made. It doesn’t make sense. It is demoralizing for those talented people who gave of themselves to make the project a reality.

If NASA accepted the Astro2010 recommendations and cancels SIM, then it will need to explain this to Congress and to the American public. The search for extrasolar Earths is compelling. It is one aspect of NASA’s work that Americans implicitly understand. It excites their imagination. Ask any of your friends, ask a stranger, for their thoughts about finding other life-supporting planets. You will get an earful. There is an innate urge in us to explore.

After successfully completing an arduous technical development and after having invested over a decade of time, money, and effort, SIM is ready to fly.

We, as a spacefaring nation, face a decision as to how to spend NASA’s precious dollars. We cannot afford everything. One option is to proceed with WFIRST, as recommended by Astro2010, at a cost of $2 billion. There are those in the astronomy community that feel that a mega-mission to study dark energy is premature. At this stage of our understanding of this phenomenon, it may be better to launch a small, cheaper mission to obtain some preliminary data.

The other option would be to save money that could be used for other astronomy missions. This could be done by proceeding with SIM. It has progressed far enough in Phases A and B,that it will need only about $1 billion to get to the launch pad. This option leaves enough cash for an Explorer-class or larger mission to study dark energy.

In addition to its primary mission of seeking new, nearby worlds, SIM’s ability to locate objects in the sky with mind-blowing precision will revolutionize other fields of astronomy. This capability is not to be taken lightly. There is much we need to learn about how stellar objects behave. Those targets include neutron stars, black holes, behemoth O and B stars, and Cepheid variable stars. Also, SIM will probe the role of dark matter by monitoring the motions of streams of stars in our galaxy. It will even be able to tell us something about the supermassive black hole in our galaxy’s center by studying recently-discovered hypervelocity stars that were probably flung out of the galaxy by that object.

So after successfully completing an arduous technical development and after having invested over a decade of time, money, and effort, SIM is ready to fly. Its mission to seek and to find other Earths is the first step in an effort that will take generations. SIM will be our generation’s contribution to this grand adventure of our species. As the popularity of the movie Avatar has demonstrated, we are driven to find those other Earths, those nearby worlds that will be studied and visited by our descendants. A Native American proverb states, “We will be known forever by the footprints we leave.” Now is not the time to step away from this challenge. We have set our goal and must go about the business of achieving it.


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