Why wouldn't we start S6 search right now?

Ben Owen
Ben Owen
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Folks, The short answer

Folks,

The short answer for why we're finishing S5 is: That was a condition of the big grant for LIGO construction. The 1994 proposal promised a year of triple coincidence data at the initial design goal sensitivity. We reached that sensitivity with S5 starting late 2005, and with 50% triple coincidence duty cycle that works out to about two calendar years, so we should end in October.

(Which reminds me, I need to look into getting tickets to run my last shifts at Hanford....)

But of course the next question is, why did we plan things that way before doing the upgrade to advanced LIGO? Part of the answer is, we were talking about an experiment on an unprecedented scale, and had to demonstrate we could run things well before the NSF would approve funding for the full upgrade. Part of it is, building the data analysis pipelines, working out new algorithms, etc is just as crucial as the physical commissioning of the instrument, and that takes a lot longer than we expected. It's not just a matter of plugging in some well-tested pieces. Notice how each run of Einstein@Home we have a new executable?

If we had full advanced LIGO instrumental sensitivity, that'd be great, but our data analysis setup wouldn't be ready to take full advantage of it. We're still building up the mathematical and software tools to do all the searches we want to do, with Einstein@Home and with smaller cluster-run searches. While the instruments are down for upgrades we are going to be very busy squeezing more out of older data so we're ready for the next batch.

Also, the upgrades to full advanced LIGO are going to take several years, even if the funding gets approved later this year as we hope. S6 will be a relatively small upgrade called "enhanced LIGO." The noise will be down about a factor of 2, and it should be searching early 2009 to late 2010. Then we'll be down a few years for the big upgrade, maybe running searches in 2014 or so.

And last but not least - it turns out we can do a little science even with our current sensitivity. In particular with periodic signals like Einstein@Home is looking for we can point to some objects, like the Crab pulsar, where we can say "It's theoretically possible we could have seen that, and therefore the fact that we didn't places an interesting upper limit on the emission." Of course if we get *really* lucky we'll see something, and we're hoping we do, but even without that we're at least putting experimental bounds that are on the same plot as the theoretical ones.

By the way, you might check arXiv:0708.3818, which is about searches of S4 data which are rather similar to what Einstein@Home is now doing in the sense of looking for signals over the whole sky. Check out the last plot and related discussion to get some idea that the sensitivity is reaching some milestones. We haven't finished post-processing yet, but we expect Einstein@Home's final numbers to be better than that (even for S4) thanks to all the computing power you've been donating.

Hope this helps,

Ben

P.S. See gr-qc/0702039 for our latest discussion of known pulsars, in particular the Crab.

rbpeake
rbpeake
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RE: ...Also, the upgrades

Message 71073 in response to message 71072

Quote:

...Also, the upgrades to full advanced LIGO are going to take several years, even if the funding gets approved later this year as we hope. S6 will be a relatively small upgrade called "enhanced LIGO." The noise will be down about a factor of 2, and it should be searching early 2009 to late 2010. Then we'll be down a few years for the big upgrade, maybe running searches in 2014 or so.

And last but not least - it turns out we can do a little science even with our current sensitivity. In particular with periodic signals like Einstein@Home is looking for we can point to some objects, like the Crab pulsar, where we can say "It's theoretically possible we could have seen that, and therefore the fact that we didn't places an interesting upper limit on the emission." Of course if we get *really* lucky we'll see something, and we're hoping we do, but even without that we're at least putting experimental bounds that are on the same plot as the theoretical ones....

Hope this helps,

Ben


Ben,

Thank you! Your posts are always so interesting and informative! :)

I hope you guys are first in a positive detection of gravity waves, because it seems the upcoming NASA LISA mission is hot on your heels! ;)

It is nice that the LISA web page notes that "LISA will make its observations in a low-frequency band that ground-based detectors can't achieve. Note that this difference in frequency bands makes LISA and ground detectors complementary rather than competitive. This range of frequencies is similar to the various types of wavelengths applied in astronomy, such as ultraviolet and infrared. Each provides different information."

Thinking out loud, at some point E@H might consider publicizing a "contest" between LISA and Einstein@home to encourage more crunchers to contribute to E@H so that this project comes out "first" with a gravity wave discovery! Just a thought! :)

Thanks again for your post!

Bikeman (Heinz-Bernd Eggenstein)
Bikeman (Heinz-...
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RE: Ben, Thank you! Your

Message 71074 in response to message 71073

Quote:



Ben,

Thank you! Your posts are always so interesting and informative! :)

I hope you guys are first in a positive detection of gravity waves, because it seems the upcoming NASA LISA mission is hot on your heels! ;)

It is nice that the LISA web page notes that "LISA will make its observations in a low-frequency band that ground-based detectors can't achieve. Note that this difference in frequency bands makes LISA and ground detectors complementary rather than competitive. This range of frequencies is similar to the various types of wavelengths applied in astronomy, such as ultraviolet and infrared. Each provides different information."

Thinking out loud, at some point E@H might consider publicizing a "contest" between LISA and Einstein@home to encourage more crunchers to contribute to E@H so that this project comes out "first" with a gravity wave discovery! Just a thought! :)

Thanks again for your post!

I think LISA is scheduled for 2017 or later, so there's a fair chance for LIGO to and other ground based interferometers to be the first to directly detect a GW.
CU
H-B

Stranger7777
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I've read the links you

I've read the links you posted. Thanks a lot. It's very informative. So, now we can try to detect GW using current sensitivity of detectors and computing power or we can wait for LISA to be started and then we can directly detect GW.
May be it's time to wait while our matematicians will improve algorithms that will effectively work on detection of GW on that level of sensitivity, that we will reach in 2017 and we (participants) will change our computer to more powerful, than can effectively serve to this observation?

P.S. I just looked at our history and found that humankind everytime try to "run faster than steam locomotive" (old saying :)
I think that it may be useless (just until we start work with LISA), but I prefer to run right now than wait to start later...

rbpeake
rbpeake
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RE: I think LISA is

Message 71076 in response to message 71074

Quote:
I think LISA is scheduled for 2017 or later, so there's a fair chance for LIGO to and other ground based interferometers to be the first to directly detect a GW.
CU
H-B


It is so ironic, I did some more research and a report is due out later today with a press conference tomorrow from the National Research Council's Beyond Einstein Program Assessment Committee regarding an evaluation of which "Beyond Einstein" mission should proceed forward! One of the Beyond Einstein missions under consideration is LISA, so we shall soon see! How coincidental is that! ;)

rbpeake
rbpeake
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RE: RE: I think LISA is

Message 71077 in response to message 71076

Quote:
Quote:
I think LISA is scheduled for 2017 or later, so there's a fair chance for LIGO to and other ground based interferometers to be the first to directly detect a GW.
CU
H-B

It is so ironic, I did some more research and a report is due out later today with a press conference tomorrow from the National Research Council's Beyond Einstein Program Assessment Committee regarding an evaluation of which "Beyond Einstein" mission should proceed forward! One of the Beyond Einstein missions under consideration is LISA, so we shall soon see! How coincidental is that! ;)


*Drumroll* Here are a few key highlights from the prepublication study:

Finding 4. LISA is an extraordinarily original and technically bold mission concept. LISA will open
up an entirely new way of observing the universe, with immense potential to enlarge our
understanding of physics and astronomy in unforeseen ways. LISA, in the committee’s view,
should be the flagship mission of a long-term program addressing Beyond Einstein goals.

Finding 5. The ESA-NASA LISA Pathfinder mission that is scheduled for launch in late 2009 will
assess the operation of several critical LISA technologies in space. The committee believes it is more
responsible technically and financially to propose a LISA new start after the Pathfinder results are
taken into account. In addition, Pathfinder will not test all technologies critical to LISA. Thus, it
would be prudent for NASA to invest further in LISA technology development and risk reduction,
to help ensure that NASA is in a position to proceed with ESA to a formal new start as soon as
possible after the LISA Pathfinder results are understood.

.......Recommendation 1. NASA and DOE should proceed immediately with a competition to select a Joint
Dark Energy Mission for a 2009 new start. The broad mission goals in the Request for Proposal
should be (1) to determine the properties of dark energy with high precision and (2) to enable a broad
range of astronomical investigations. The committee encourages the Agencies to seek as wide a variety
of mission concepts and partnerships as possible.

Recommendation 2. NASA should invest additional Beyond Einstein funds in LISA technology
development and risk reduction, to help ensure that the Agency is in a position to proceed in
partnership with ESA to a new start after the LISA Pathfinder results are understood.

......................................................

So it looks like LISA will not fly for awhile!

jowr
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Hold on now. We are not

Hold on now.

We are not even done with S5 - for reasons explained in this thread - and the S4 data analysis is not even done yet. One thing at a time.

Where *is* the complete S4 analysis anyway? I'm sure it is still being worked on but since I haven't heard anything about it all I can do is guess. I'm especially interested to hear what was [or not] found because S4 was a marked improvement over S3...

Stranger7777
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I Agree. We want to see at

I Agree. We want to see at least partial results for S4 ASAP. And may be some information about S5. It is more pleasant for us to read this right on the E@H site, but to search throughout entire web for sands of this report. So, please.

AgnosticPope
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Quoting Dan: RE: S5 will

Message 71080 in response to message 71060

Quoting Dan:

Quote:
S5 will end on Sept. 1, or Oct. 1, or Nov. 1. It depends on the readiness of Enhanced LIGO. It goes like this: S5 ends, then there is one month freeze while they make calibration/postrun measurements on the IFO, then they commission Enhanced LIGO ~ 18 months (factor of about 2 improvement in sensitivity, or 8 in volume and hence rate), then they run S6 out to the start of 2011. At ~2011, shutdown for Advanced LIGO installation, ~3 years, come back online 2014, commission X number of years, gain of factor of 10-15 in sensitivity, the cube of that in rate, and then ... some 40 events per year of binary neutron star inspirals ... is the belief.


And quoting Ben:

Quote:
The short answer for why we're finishing S5 is: That was a condition of the big grant for LIGO construction. The 1994 proposal promised a year of triple coincidence data at the initial design goal sensitivity. We reached that sensitivity with S5 starting late 2005, and with 50% triple coincidence duty cycle that works out to about two calendar years, so we should end in October.


Somewhat unspoken in all this discussion is the real reason we need to gather and analyze years worth of data: we must integrate months worth of data scans to even hope to find a very small needle buried somewhere within a very huge haystack. The software to do the searches isn't by any means "off the shelf."

As Ben says:

Quote:
If we had full advanced LIGO instrumental sensitivity, that'd be great, but our data analysis setup wouldn't be ready to take full advantage of it. We're still building up the mathematical and software tools to do all the searches we want to do, with Einstein@Home and with smaller cluster-run searches.


Realize that the detector itself is on the surface of the Earth, spinning around the axis of the Earth at a speed of several hundred miles per hour, and that the axis of the Earth is spinning around the Sun at the rate of one revolution per year, and both of these will greatly impact the decision as to what data can be legitimately integrated with what other data to obtain a verifiable scientific result. Add to this the 50% duty factor, which results from the Earth-based detector being knocked out of lock (for one reason or another), somewhat at random, and a picture begins to form of just why you need to gather data for a couple of years before you have a legitimate shot at spotting that little old needle buried in that very huge haystack.

Not having a decent known extra-solar source of gravity waves to use for calibrating the instrument adds to the huge difficulty of developing the math and software routines as the developers have to guess at what they are doing without having any live data to test against. If they goof in the routine which compensates for the motion of the Earth then good data gets integrated with bad data and disappears from view.

The amazing thing to me is that they have any hope at all of discovering anything given that the whole idea has yet to produce any real results. I sure hope that the folks who developed all this software really do know what they are doing....

== Bill

Stranger7777
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So, the new S5R3 run will

So, the new S5R3 run will cover a wider range of frequency band. But, will it cover the same band as S5R1 and S5R2 with the new sensitivity (or, as you wish, a new number of parameters) or a new band besides previous searches?

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