Thursday, April 19, 2012

The Likely End to a Space-Based GW Detector

LISA...

(The video below is large [~44 MB] and dated, but gives good background on the motivation and specifics of a space-based gravitational-wave detector:)



About this time last year, I wrote a blog post about the NASA withdrawal from being a full partner in the LISA (Laser Interferometer Space Antenna) with the ESA (European Space Agency).  At that time, it meant that US scientists would still be able to receive funding to develop research programs and contribute to the LISA effort but the ESA would be responsible for the bulk of the work.  This withdrawal by NASA was caused by the poor state of the agency's funding and the cost of the James Webb Space Telescope.  For all of us in doing research in gravitational waves, it was a horrible setback; LISA was once a flagship mission of NASA's Physics of the Cosmos program and the best hope we had of detecting low frequency gravitational waves (< 10 Hz). 

This then led the ESA to redevelop their plans for a new version of LISA (that is referred to as eLISA but is officially known as NGO [New Gravitational-wave Observatory]) in order to lower the cost of the mission by at least 20% and preserve as much of the science as possible.  This new design was published in their "Yellow Book" at the beginning of the year which included, among other things, only 2 arms in a triangular formation (previously there were 3 arms and each corner pair of arms could function as an independent detector), reduced distance between satellites (1 million kilometers instead of 5 million), and a new orbit which is similar to the LISA orbit (in orbit around the Sun about 20o behind Earth in its orbit) but will allow the detector to drift away into the solar system over time.  Below is a short movie illustrating a few orbits - the "drift away" is not noticeable:




The newly designed eLISA/NGO received the highest science ratings of the projects up for funding at the ESA.  However, the ESA Science Programme Committee has concerns about the technological readiness of eLISA/NGO to fly in the 2020 time frame and has passed it over to recommend the JUICE (JUpiter ICy moons Explorer)This is likely the last nail in the coffin for a space-based gravitational-wave detector in the foreseeable future.  (Note:  NGO can be considered for future launch opportunities but that is way down the road.)  There is a slight chance that the recommendation could be rejected in favor of gravitational waves when the 19 member states of the ESA make the final decision on May 2.  However, I heard the news of this recommendation from a friend who specializes in LISA science and he didn't seem hopeful for the 11th hour pardon.

I wonder what will happen to the LISA Symposium that is supposed to take place in Paris at the end of May...  Or for that matter, the LISA Pathfinder mission (which will demonstrate the basic abilities that LISA would have needed to have) which is scheduled to launch on June 30.

UPDATE:  I've heard from a LISA colleague that LISA Pathfinder is still a go!  Thanks!

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On a more uplifting front, I had the wonderful opportunity to speak at Ole Miss (this link will take you to their gravity research group - they do great work!) about the importance of outreach, useful skills for it, and different ways to do outreach (and this blog was featured!).  That night, I also got to demonstrate my points by giving one of their monthly public science cafes.  This experience gave me the chance to really consider what it is that I have been doing professionally for the last 5 years...  What have I learned?  What mistakes did I make?  What surprised me?  What ideas can I pass along on how to do outreach to those who are expected to do it but aren't afforded the extra time like I am?  I'm thinking about posting a summary of my thoughts and speaking points in next week's post (unless something else newsworthy happens in the mean time)!

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