LIGO, High Gear Science Run Options

[The Messenger]

http://www.spaceref.com/news/viewpr.html?pid=19142

ST. LOUIS, Mo. -- The quest to detect and study gravitational waves with the NSF-funded Laser Interferometer Gravitational-Wave Observatory (LIGO) is now in the fourth month of its first sustained science run since achieving its promised design sensitivity, project personnel announced at the annual meeting of the American Association for the Advancement of Science (AAAS). ...

Now that the LIGO is sensitive enough to detect changes in distance a mere thousandth the diameter of a proton, Marx adds, the science return should be even greater. Recent results from the Swift satellite pinpointing the location of short gamma-ray bursts (GRBs) have also heightened astronomers' interest in the results from LIGO's current observational run.

That level of sensitivity is, in my opinion, the most incredible technical achievement since the VLA.

The very long gamma ray associated with supernova/hypernova 1996aj should also be of great interest.

[Guest_Richard Trigaux_*]

So we shall soon know if gravity waves really exist.



Is it necessary for this to wait for the end of the run? Isn't it possible to check the data on the fly, so that an event may be seen as soon as it happens? (Not true if the expected event probability is of one per year, as I heard once).

Also it may be possible to have a background noise spectrum before the end of the run, even if not so accurate.


After reading the article, they expect a direct detection only if "nature is very kind". So perhaps they will announce one... or we still have some years to wait. Otherwise they will get only upper limits on various phenomena.

The LIGO site

[The Messenger]

So we shall soon know if gravity waves really exist.
Is it necessary for this to wait for the end of the run? Isn't it possible to check the data on the fly, so that an event may be seen as soon as it happens? (Not true if the expected event probability is of one per year, as I heard once).

Also it may be possible to have a background noise spectrum before the end of the run, even if not so accurate.
After reading the article, they expect a direct detection only if "nature is very kind". So perhaps they will announce one... or we still have some years to wait. Otherwise they will get only upper limits on various phenomena.

The LIGO site

The data reduction on LIGO takes months, and that is with a lot of number-chrunching on the Einstein at home network. Basically, they have to scrutinize every single bump and grind, and filtering out every Earth vibration is a daunting task. I would assume they will be crunching this eighteen month run on the fly, and if anything definitive happens, we will know as soon as they are certain.

The current constraints on gravity waves are lower than most theorists anticipated, but not lower than pessimistic estimates of what the gravity parameters should be for neutron star, black hole mergers and such. The "if nature is kind" clause is pessimistic, and some (most) theorists involved in the project expect positive results if the current sensitivities can be maintained for the full 18 month run.

[Guest_Richard Trigaux_*]

The data reduction on LIGO takes months, and that is with a lot of number-chrunching on the Einstein at home network. Basically, they have to scrutinize every single bump and grind, and filtering out every Earth vibration is a daunting task. I would assume they will be crunching this eighteen month run on the fly, and if anything definitive happens, we will know as soon as they are certain.

The current constraints on gravity waves are lower than most theorists anticipated, but not lower than pessimistic estimates of what the gravity parameters should be for neutron star, black hole mergers and such. The "if nature is kind" clause is pessimistic, and some (most) theorists involved in the project expect positive results if the current sensitivities can be maintained for the full 18 month run.

Yes, if they don't need things such as large windows or long-term averaging, they can do on the fly, the only delay being the calculation time.

Only if they were interested in very low frequencies they would need averaging on the whole run. If there is for instance something like a cosmological background oscillating at periods of days or more, we can know it only at the end of the run. But if there is something like a supernova or a black hole spiraling, they would recognize it immediately, or at least after the calculation time.

I can imagine the task -recognizing predictable patterns into an overwheelming noise- as I was somewhat involved in this when I was workig. This is also the way SETI works. (a spin-off of SETI!). But what if an UNEXPECTED signal comes? Will them just cull as noise all what is unexpected?