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Advanced LIGO: Context and Overview
The LIGO Mission
LIGO was approved by the National Science Foundation to directly observe gravitational waves
from cosmic sources, and to open the field of gravitational wave astronomy. The program and
mission of the LIGO Laboratory is to:
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observe gravitational wave sources;
develop advanced detectors that approach and exploit the facility limits on interferometer
performance;
operate the LIGO facilities to support the national and international scientific community;
and support scientific education and public outreach related to gravitational wave astronomy.
LIGO is envisioned as a new capability contained in a set of facilities and not as a single
experiment. The LIGO construction project has provided the facilities that support the scientific
instrumentation, and the initial set of laser interferometers to be used in the first LIGO scientific
observation periods.
The facilities include the buildings and vacuum systems at the two observatory sites. The two
observatories are located at Hanford, Washington and Livingston, Louisiana. The performance
requirements on the LIGO facilities were intended to accommodate the initial interferometers and
future interferometer upgrades and replacements, and possible additional interferometers with
complementary capabilities. The requirements on the LIGO facilities were intended to permit
future interferometers to reach levels of sensitivity approaching the ultimate limits of groundbased interferometers, limited by reasonable practical constraints on a large facility at a specific
site.
This proposal is for the second generation of instruments to be installed in the LIGO
infrastructure, and is expected to bring the science of gravitational radiation from a discovery
mode to a mode of astrophysical observation.
Detector Design Fundamentals
The effect of a propagating gravitational wave is to deform space in a quadrupolar form. The
effect alternately elongates space in one direction while compressing space in an orthogonal
direction and vice versa, with the frequency of the gravitational wave. A Michelson interferometer
operating between freely suspended masses is ideally suited to detect these antisymmetric
distortions of space induced by the gravitational waves; the strains are converted into changes in
light intensity and consequently to electrical signals via photodetectors.
Limitations to the sensitivity come from two sources: extraneous forces on the test masses, and
from a limited ability to sense the response of the masses to the gravitational wave strain.
Seismic motion causes forces on the mirrors due to the direct coupling through the isolation and
suspension system, which is minimized through design; and due to the time-varying mass
distribution near the mass (the Newtonian background). The thermal motion of the test mass and
the suspension also plays a role; this influence is managed through the selection of lowmechanical-loss materials and designs which capitalize on them.
Sensing limitations arise most fundamentally due to the statistical nature of the laser light used in
the interferometry, and the momentum transferred to the test masses by the photons (linking the
sensing and stochastic noise limitations to sensitivity). Frequency noise and intensity fluctuations
in the laser light, and scattered light which adds random phase fluctuations to the light, can also
mask gravitational signals.
In the limit, valid for LIGO, that the instrument is short compared with the gravitational strain
wavelength, longer arms give larger signals. In contrast, most competing noise sources remain
constant with length; this motivates the 4km baseline of the Observatories. More generally, the
scientific capability of LIGO is defined within the limits imposed by the physical settings of the
interferometers and by the facility design, by the design of the initial detectors and ultimately by
future interferometers designed to progressively exploit the facility capabilities.
Although the rates for gravitational wave sources have large uncertainty, a linear improvement in
sensitivity linearly improves the distance searched for detectable sources. This increases the
detection rate by the cube of the sensitivity improvement.
LIGO Initial Detector Scientific Goals
The scientific program for LIGO is to test relativistic gravitation and to open the field of
gravitational wave astrophysics. The program for the initial detectors is designed to understand
the detector and to execute searches for astrophysical sources of all types. The program is
designed to make detections as well as to set upper limits.
There are no known gravitational wave sources whose “best-guess” rates and strengths are
sufficiently large that detections are assured during the initial LIGO Science Run. There are great
uncertainties associated with either or both the rates and strengths of all of the conjectured
sources. However, the initial LIGO Science Run, with the initial detectors, will extend the
sensitivity to gravitational wave sources in a new frequency regime by two to three decades in
amplitude and bandwidth from all previous searches
Although the existence of gravitational radiation is not a unique property of General Relativity,
that theory makes a number of unambiguous predictions about the character of gravitational
radiation. These can be verified by observations with LIGO providing there are sufficiently high
signal to noise detections. These include probes of strong-field gravity associated with black
holes, the spin character of the radiation field, and the wave propagation speed.
The gravitational wave “sky” is entirely unexplored. Since many prospective gravitational wave
sources have no corresponding electromagnetic signature (e.g., black hole interactions), there
are good reasons to believe that the gravitational-wave sky will be substantially different from the
electromagnetic one. Mapping the gravitational-wave sky will provide an understanding of the
universe in a way that electromagnetic observations cannot. As a new field of astrophysics it is
quite likely that gravitational wave observations will uncover new classes of sources not
anticipated in our current thinking.
The initial LIGO detectors can measure:
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Compact binary inspirals of two 1.4 MO
• neutron stars to a distance of 20 Mpc;
Gravitational waves from gamma-ray bursts if the broadband RMS strain is ~10-18 m;
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Black hole formation and ringdown of two 20 MO
• black holes to a distance of ~100 Mpc;
Nonaxisymmetric supernovae to ~15 Mpc if centrifugal hangup forces the object into a
triaxial shape which then emits a substantial fraction of its rotational energy as gravitational
waves;
Nascent neutron stars to a distance of ~1 Mpc;
General gravitational wave bursts whose source or detailed character (i.e., waveform) is
not known in advance for strains greater than ~10-18;
Pulsars and rapidly rotating neutron stars as distant as 10 kpc for mass asymmetry
parameters >10-5 and for stellar rotation rates > 150 Hz (i.e., 300 Hz gravitational wave
signals);
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Stochastic gravitational wave background if GW ~10-5.
Advanced LIGO Scientific Goals
The Advanced LIGO interferometers proposed here promise an improvement over initial LIGO in
the limiting sensitivity by more than a factor of 10 in the frequency band 100 Hz < f < 200 Hz. This
translates into an enhanced physics reach that, during its first several hours of operation will
exceed the integrated observations of the 1 year LIGO Science Run. These Advanced LIGO
interferometers will also have a considerably greater sensitive frequency range. These
improvements will enable the next generation of interferometers to study sources not accessible
to initial LIGO. The Advanced LIGO detectors will also be able to perform all observations
described earlier at greater sensitivity and higher event rate:
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Inspiraling neutron star (NS) and black hole (BH) binaries: two 1.4 MO• neutron stars will
be detectable at a distance of 300 Mpc; NS+BH binaries will be visible to 650 Mpc;
coalescing BH+BH systems are visible to cosmological distance, to z=0.4.
Tidal disruption of a NS by a BH: the coalescence of a NS+BH binary may be accompanied
by the tidal disruption of the lighter star. Detection by Advanced LIGO would be able to
provide observational data on the NS radius that may be compared with nuclear equation of
state predictions.
BH+BH mergers and ringdowns: gravitational radiation in the LIGO band from BH+BH
interactions comes primarily from the final merger and ringdown phases of these
coalescences. Advanced LIGO will be able to detect radiation from BH binaries having total
mass as great as 2000 MO
• to distances corresponding to z=1.
Supernovae: empirical evidence suggests that neutron stars in type II supernovae receive
kicks of magnitude as large as ~1000 km/s. These violent recoils imply that the supernova
event may be strongly asymmetric. Further, numerical models suggest that the proto-neutron
star will be unstable to convective overturn, and that gravitational radiation produced in the
first second or so of its life may be detectable anywhere throughout our Galaxy and its
orbiting companions (i.e., the Magellanic Clouds).
Nascent neutron stars: the narrowband tunability of Advanced LIGO interferometers will be
exploited to search with high sensitivity at higher frequencies for gravitational radiation arising
from rotating compact stars, especially from Low-Mass X-Ray Binaries (LMXB). Neutron star
rotation rates of ~100 revolutions per second may be detectable to distances encompassing
the Virgo Cluster.
General gravitational wave bursts: the Advanced LIGO reach will enable observational
searches for gravitational wave bursts correlated with Gamma-Ray Bursts (GRBs) to much
greater distances than will be possible with initial LIGO. The next generation of orbiting
gamma-ray telescopes will be operational in the time frame of Advanced LIGO operations;
thereby providing astrophysical triggers for GRBs. Independently verified triggers enable onsource/off-source observations of gravitational waves to be made.
Stochastic Signals: the sensitivity improvement of Advanced LIGO, coupled with the
decrease in lower frequency cutoff, means that an observational measurement of the
stochastic gravitational wave background can be performed with limiting sensitivity after 1
year of observation of GW~5x10-9.
LIGO Facility Scientific Capability
The LIGO facility design envisaged a progression of increasingly sensitive interferometers
capable of extending the physics reach of the observatories. In the design of the observatories,
LIGO incorporated critical design features into its facilities in order to optimize LIGO’s ultimate
performance capabilities. These features include the following:
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A thick monolithic and rigid foundation slab for the vacuum chambers housing the
interferometers that is mechanically isolated from the exterior structure of the large
experimental halls. This design provides a protected instrument foundation that is weakly
coupled to the building frame.
A specially designed and constructed beam tube system that would guarantee the ability to
reach limiting strain sensitivities of order 10-25 /Hz above 10 Hz. Construction of this
subsystem required great care in the control of air leaks, residual hydrocarbon contamination,
and scattered light control. Scattered light control required a specially designed and
fabricated system of internal baffles. These baffles control scattered light so that the phase
noise contribution will be no greater than 1/10 the Standard Quantum Limit for a 1-tonne
mass.
A specially designed and constructed system of large vacuum chambers and pumping
subsystems capable of providing a vacuum quality that complements the beam tube
subsystem.
The system design for LIGO facilities provides an environment for future interferometers that is
ultimately limited by two sources of noise:
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Time-dependent gravity gradients at frequencies below 20 Hz. This ‘Newtonian background’
is due to the changes in density of the ground due to seismic motion leading to changes in
the mass distribution near the test masses, and thus to motions of the mass. This noise
source may limit the proposed Advanced LIGO sensitivity in the 10-20 Hz range for some
operational configurations; in later upgrades to Advanced LIGO, it may be suppressed
through e.g., monitoring with seismic arrays.
Phase variations induced in the light by residual gas in the beam tubes for frequencies above
200 Hz. This noise source lies well below the envelope of other limitations of performance of
the Advanced LIGO instrument
The Observatories
LIGO Hanford Observatory
LIGO Hanford Observatory (LHO), located on the U.S. Department of Energy Hanford site in
eastern Washington, comprises 5 major experimental halls for the interferometer spread over 5
miles. 1.2-m diameter ultrahigh vacuum tubing connects these halls. Three support buildings
house laboratories, offices, and an amphitheater, and two additional buildings are associated with
maintenance and operations. Approximately 90,000 square feet of this space is under tight
environmental control to minimize contamination of sensitive equipment. The physical plant has
been designed to provide a low vibration environment similar to the surrounding undeveloped
shrub-steppe environment.
LHO houses two interferometers with arm lengths of 4 km and 2 km. The 4-km equipment is
installed in vacuum chambers in the corner station and the two end stations on each arm. The 2km equipment uses vacuum chambers in the corner station and the two midstations situated
halfway down each arm. The two interferometers share 2 km of beam tube along each arm. The
beam tube can eventually accommodate up to 5 interferometer beams and the current station
buildings can accommodate up to 3 interferometers to accommodate future growth.
Figure 1 The LIGO Hanford Observatory (LHO) in aerial view. The 4-km interferometer arms are shown with the 5
main buildings shown along the orthogonal arm layout.
LIGO Livingston Observatory
Figure 2 The LIGO Livingston Observatory (LLO) corner region in aerial view.
The LIGO Livingston Observatory, located in pine forests between Baton Rouge and New
Orleans, Louisiana, is the site of a single 4-km laser interferometer gravitational wave detector.
Construction of its physical facilities, nearly identical to those at LHO, is complete. Differences
from the LHO site are:
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the absence of mid-stations, since only a single 4-km interferometer is installed;
the corner station, which houses the vertex of the single interferometer, is smaller than at
LHO. It can accommodate one additional interferometer without requiring additional civil
construction, while the LHO corner station houses two interferometers and accommodates a
third interferometer within the existing space.
The beam tube dimensions are identical to those at LHO.
Initial LIGO
Status of the LIGO Construction Project
The NSF Cooperative Agreement of May 1992 initiated LIGO Construction and Construction
Related Research and Development. The Project schedule and cost estimates were reviewed by
the NSF during September 1994 and presented to the National Science Board in November
1994. The total funding established by the Board for Construction and Construction Related R&D
were $272.1 million and $20.0 million, respectively. In addition, the NSF provided $68.7 million for
Operations through September 30, 2001 covering the period of Installation and Commissioning.
A performance measurement baseline was established in April 1995. This baseline was used for
tracking and reporting construction performance and actual costs. The LIGO construction effort is
effectively complete, on cost and close to schedule. The effort remaining is related to detector
installation and commissioning and the hardware for the LIGO Data Analysis System (LDAS).
Initial LIGO Detector Commissioning
Installation is complete for the three interferometers. The commissioning of the instruments
continues, with most subsystems completely operational and in use in the first science running.
Several subsystems are coming on-line in preparation for the next science run. The instruments
have shown a steady improvement in sensitivity, at all frequencies in the planned observation
band, during the commissioning process. An example of progress is seen in Figure 3.
Figure 3 This figure shows the progression in the strain sensitivity as a function of frequency for the Hanford 4-km
interferometer over the year from December 2001 to December 2002. The most recent noise level is a factor 10 to 300
above the final specification; many of the sources of excess noise have been identified and are being addressed.
Future improvements to reach the design sensitivity will involve some modifications to the
electronics and to the mechanical infrastructure, and optimization of control systems and filters.
Substitute recycling mirrors (with an optimized transmission for the observed mirror optical
properties) will be installed during favorable opportunities. It is anticipated that this series of
improvements in performance will largely take place between the upcoming second science run,
and the third science run, planned for the fall of 2003.
The LIGO Science Runs
Since the completion of LIGO construction an extensive commissioning program has been
undertaken. The observatories are now interleaving continued commissioning with science runs.
The timing of the runs is designed to balance the competing demands for improvements to the
performance of the machines (in sensitivity and duty cycle) with the desire to observe.
The first science run, S1, took place from 23 August through 8 September 2002, and involved the
three LIGO interferometers, the UK-German GEO-600 interferometer, with some overlap in
observing with the Japanese TAMA detector. The LIGO instruments operated in their design
configuration, and accumulated roughly 100 hours of observation in triple coincidence between
the two sites during the S1 run. The data for this run are currently being analyzed.
The second science run, S2, is planned to take place from 14 February 2003 until 14 April 2003.
The objective for this run is to improve the upper limits on gravitational wave flux by at least an
order of magnitude compared to the S1 run. The present sensitivity of the instruments (January
2003) enables this goal. The third science run, S3, is planned for late 2003, following a significant
commissioning interval, and will represent a transition to a mode where observation dominates
over commissioning at the Observatories. We plan to intersperse science runs with periods
dedicated to detector improvements that will be coordinated with the LSC. The overall goal is to
obtain at least one year of integrated data with an RMS strain sensitivity of h ~ 10-21 (integrated
noise level in a 1 kHz band) within the first three years of running (ending in 2006). Once that
goal is achieved and the physics results have been obtained, installation of improved
interferometers can commence.
Astrophysics data analysis uses calibrated reduced data sets, but access to the raw data will be
possible using the LIGO data archive. For initial LIGO, data analysis is conducted using the LIGO
Data Analysis Systems (LDAS) and Detector Monitor Tool (DMT) systems that operate at the
LIGO sites and campuses, These are employed both by the LSC and Laboratory scientists. In
addition, we hope that the university LSC collaborators will carry out some distributed data
analysis in the first GryPhyN Tier 2 centers1. The computing architectures, software
infrastructure, diagnostics and calibration systems, and search algorithms are being prepared and
will be tested during the engineering data runs.
LIGO Scientific Collaboration (LSC, please see below) “upper limit” groups are undertaking the
search for chirp signals from binary inspirals, periodic signals from neutron stars and burst signals
from supernovae and gamma ray bursts. Data are also being correlated with relevant optical data
and, in the case of supernovae, with neutrino signals. Results from the analysis of S1 data,
providing new upper limits to the gravitational wave flux, are being prepared for publication.
LIGO Scientific Collaboration
A fundamental goal of LIGO has been to become a true national facility available to the scientific
community. In order to accomplish this, LIGO has broadened the participation to include the
community of scientists interested in participating in the LIGO research program. In order to
achieve this goal, the LIGO Scientific Collaboration (LSC) 2 was formed and has now been
functional for several years.
LIGO has been organized such that science programs will be performed through the LSC. The
LSC consists of both LIGO Laboratory scientists and those from collaborating groups. The
collaboration members committed to "LIGO I", the initial LIGO detector science runs, will be
responsible for the science in this beginning phase of observation. This group in LIGO is well
defined and presently consists of 111 LIGO Laboratory scientists and 134 scientists from
collaborating institutions. The LSC is organized so as to provide “equal scientific opportunity” to
all members whether they are from within LIGO Laboratory or the broader LSC. It is growing
steadily and will remain open to new members over the coming years. It is worth noting that the
LSC has significant international participation, including collaborating groups from India, Russia,
Germany, U.K, Japan and Australia. The international partners are involved in all aspects of the
LIGO research program.
Preparation tasks for the runs are organized within the LSC, LSC members participate in the data
taking runs, and the analysis of the data is coordinated through the LSC proposal driven process.
The full LSC collaboration meets twice yearly in an extended meeting, and various working
groups meet more frequently. The LSC has produced White Papers that outline the plans for
technical development of LIGO and for science data analysis. A publication policy and a
conference committee are active, as well as the other functions necessary to make it a ‘full
service’ organization.
LIGO is available to all interested researchers through participation in the LSC, an open
organization. To join, a research group defines a research program with the LIGO Laboratory
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through the creation of a Memorandum of Understanding (MOU) and relevant attachments 3. The
group then presents its program to the LSC. When the group is accepted into the LSC it becomes
a full scientific partner in LIGO.
Fully Exploiting the LIGO Capability
As noted above, LIGO is designed to evolve and to support improvements in gravitational wave
detectors. A natural time for an upgrade to the instruments can be foreseen once the initial LIGO
goal of one year of integrated observation has been met. The initial LIGO infrastructure is well
designed to deliver its planned performance, and small advances in sensitivity at higher
frequencies may be possible with e.g., modest increases in the input laser power. However, a
large improvement will require an upgrade of the entire detector in a coordinated fashion. The
Advanced LIGO instrument fulfills our requirements of a significant step forward in sensitivity, and
can be delivered on a time scale that meshes with the end of the Initial LIGO observation plan.
Overview of the Next Generation LIGO Detector Concept
The sensitivity goals for the next generation LIGO detector systems are chosen to enable the
advance from plausible detection to likely detection. These sensitivity goals require an instrument
limited only by fundamental noise sources over a very wide frequency range. To achieve this
sensitivity, almost every aspect of the interferometer must be revised from the initial LIGO design.
The system described below is the reference concept that is the basis for structuring the R&D
program and the detailed studies of system tradeoffs performed as R&D results define the
feasible parameters.
The basic optical configuration is a power-recycled and signal-recycled Michelson interferometer
with Fabry-Perot “transducers” in the arms. Using the initial LIGO design as a point of departure,
this requires the addition of a signal-recycling mirror at the output “dark” port, and changes in the
RF modulation and control systems. This additional mirror allows the gravitational wave induced
sidebands to be stored or extracted (depending upon the state of “resonance” of the signal
recycling cavity), and leads to a tailoring of the interferometer response according to the
character of a source (or specific frequency in the case of a fixed-frequency source).
To improve the quantum-limited sensitivity, the laser power is increased from the initial LIGO
value of 10 W to ~200 W. The conditioning of the laser light follows initial LIGO closely, with a
ring-cavity mode cleaner and reflective mode-matching telescope.
Whereas initial LIGO uses 25-cm, 11-kg, fused-silica test masses, the test mass optics for
Advanced LIGO are larger in diameter (~30 cm) to reduce thermal noise contributions and more
massive (~40 kg) to keep the radiation reaction noise to a level comparable to the suspension
thermal noise; sapphire is the baseline material for the test masses. Compensation of the thermal
lensing in the test mass optics (due to absorption in the substrate and coatings) is added to
handle the much-increased power – of the order of 1 MW in the arm cavities.
The test mass is suspended by fused silica fibers, in contrast to the steel wire sling suspensions
used in initial LIGO. The resulting suspension thermal noise is anticipated to be less than the
radiation pressure noise (in broad-band observation mode) and to be comparable to the
Newtonian background (“gravity gradient”) at 10 Hz. The complete suspension has four pendulum
stages, contributing to the seismic isolation and providing multiple points for actuation.
The seismic isolation system is built on the initial LIGO piers and support tubes but otherwise is a
complete replacement, required to bring the seismic cutoff frequency from 40 Hz (initial LIGO) to
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10 Hz. RMS motions (frequencies less than 10 Hz) are reduced by active servo techniques. The
objective is to make the seismic noise negligible at all observing frequencies
The Advanced LIGO design permits full exploitation of the sensitivity and performance of any
terrestrial, recombined Fabry-Perot Michelson interferometer with room temperature optics and
suspensions, and transmissive optics. The actual overall performance is dominated at most
frequencies by the quantum noise of sensing the position of the test masses, with a contribution
at mid-frequencies from the internal thermal noise of the test mass. Advanced LIGO, with modest
enhancements after it enters scientific use, should take this interferometer architecture to its
technical endpoint. Further advances in sensitivity are anticipated to require major excursions to
techniques such as cryogenic optics and suspensions, purely reflective optics, and changes in
the readout to one which fully exploit our nascent understanding of the quantum nature of the
measurement (e.g., ’speed meters’). These later developments will be timely for instruments to be
developed in the second decade of this century.
Advanced LIGO R&D 2002-2006
During 2002 through 2006, most LIGO Laboratory detector R&D will be directed at the challenges
posed by the Advanced LIGO design. This R&D program is a significant part of the larger R&D
program of the LIGO Scientific Collaboration. The LSC program has been developed in a
collaborative manner and is coordinated through the LSC Working Groups and by the LIGO
Laboratory.
The R&D program currently underway, supported by the NSF under cooperative agreement PHY0107417, is designed to support this construction proposal. This proposal requests that
construction funding commence at a time when the major R&D issues are satisfactorily resolved,
and the subsystems ready for fabrication.
The activities carried out prior to construction funding include small-scale fundamental research
motivated by Advanced LIGO. Examples of this are studies of core optic substrate absorption,
measurement of mechanical losses in suspension fibers, and studies of candidate photodetectors
for the gravitational wave readout. The R&D program also includes large-scale prototypes of
subsystems such as full-scale seismic isolation systems, full-scale suspensions, and full-scale
core optics. In order to carry out this research, in most cases these components must be fully
engineered to the realistic requirements and configuration of Advanced LIGO. In order to study
the performance and control of a suspension subsystem, the prototype studied must represent
the Advanced LIGO design down to details such as suspension fiber material, bonding technique,
and control electronics design and component selection and physical layout. This kind of rigorous
full-scale development program is needed to reduce risks prior to defining and committing to a
construction project.
Advanced LIGO Schedule and Cost
The Advanced LIGO fabrication and construction schedule grows out of the tightly coordinated
R&D program currently underway. The objectives in establishing the schedule are to
 Allow the initial LIGO instruments to be fully exploited, and in particular to ensure the
commitment to a full integrated year of observation with in initial LIGO instruments
 Allow a complete R&D cycle, with extensive testing of final designs, before committing to
fabrication
 Bring the Advanced LIGO instruments on-line as quickly as possible to meet the
demands of the community for the observing capability of the Advanced LIGO detector.
The schedule is based on our extensive experience with the design, fabrication, construction, and
commissioning of the Initial LIGO detectors.
The highlights of the schedule are
 Receipt of funding for the fabrication and construction project in early 2005, with some
advance funding for critical long-lead items in early 2004
 Delivery of first interferometer hardware to the observatory staging facilities in mid-2006
 Decommissioning of initial LIGO at the LIGO Livingston Observatory in early 2007, and
simultaneous start of installation of Advanced LIGO there
 Decommissioning of initial LIGO at the LIGO Hanford Observatory in late 2007, and
simultaneous start of installation of Advanced LIGO there
 Both observatories in commissioning by mid-2008
 Both observatories in operation by late 2009
The cost estimate developed for this proposal was performed at the lowest feasible level, given
the present level of development in the WBS, in a bottom-up manner. Most subsystems have
been costed at a level of detail comparable to initial LIGO; several have not achieved the maturity
in R&D to allow this level of detail, but carry contingency appropriate to the basis. The techniques
used were the same methods used to estimate initial LIGO construction costs, though our cost
experience in initial LIGO substantially improved the input knowledge base for the new estimate.
Contingency was estimated using the formal graded approach to assessing technical, cost and
schedule risk that was used in initial LIGO.
The joint United Kingdom/German GEO Project4 has proposed to provide a capital investment in
this construction project. The UK proposal is for approximately $11.5 million. They propose to
apply these resources to providing the suspension subsystem, including suspension assemblies,
their controls, and installation and commissioning. The German proposal is for the design and
fabrication of the pre-stabilized laser subsystem, and the value of the contribution is planned to
be valued at XXXX.
With the GEO capital contribution, the required US Advanced LIGO costs are $ XXXXX K in FY
2002 $. Escalating this sum to the approximate mid-point of Advanced LIGO construction (2006),
using the average inflation rate quoted by the US Department of Labor for the last 6 years (2.4%),
yields a total request to the NSF for constructing Advanced LIGO of $ XXXXX K.
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