We measured Newton's gravitational constant G using a new torsion balance method. Our technique greatly reduces several sources of uncertainty compared to previous measurements: (1) It is insensitive to anelastic torsion fiber properties; (2) a flat plate pendulum minimizes the sensitivity due to the pendulum density distribution; (3) continuous attractor rotation reduces background noise. We obtain G = (6.674215+/-0.000092) x 10(-11) m3 kg(-1) s(-2); the Earth's mass is, therefore, M = (5.972245+/-0.000082) x 10(24) kg and the Sun's mass is M = (1.988435+/-0.000027) x 10(30) kg.

We propose a new type of resonant-mass gravitational wave detector, a truncated icosahedral gravitational wave antenna. It will be omnidirectional, and able to measure the direction and polarization of a detected wave. We solve a model for this system, calculate the strain noise spectrum, and conclude that its angle-averaged energy sensitivity will be 56 times better than the equivalent bar-type antenna with the same noise temperature.PACS numbers: 04.80,+z, 06.70.Dn Confirmed detection of gravitational waves from astrophysical sources will found a new astronomy, and allow direct investigation of the gravitational force under extreme conditions. The best current antennas, such as the LSU detector [1], are sensitive enough to detect a gravitational collapse in our galaxy, but the conventional wisdom is that we need to look at least 10 3 farther in distance to have an "assured" event rate of several per year. This requires reducing the energy resolution by 10 6 . The best known methods for improving cryogenic resonantmass detectors will contribute by reducing the energy resolution in proportion to the reduction of the noise temperature T n from its current value of ~7 mK. However, it is commonly believed that quantum noise will present a formidable barrier for improvement by more than 10 5 , not quite enough for assured detection.However, there are other ways to improve resonantmass antennas that are independent of T". One way is to increase the cross section. Another is to make multiple antennas, aimed in different directions, so every source direction and polarization will be within at least one antenna pattern. This method adds the ability to determine source direction and polarization. A spherical antenna promises to provide all three improvements in a single instrument.The question becomes the actual magnitude of these improvements. We have invented a design for a nearly spherical antenna, which we call a truncated icosahedral gravitational wave antenna (TIGA), that provides an elegant solution to certain complications of a spherical antenna, and therefore lets us calculate the quantitative improvement. We conclude that a TIGA will be about 56 times more sensitive in energy than the equivalent bar-type antenna with the same noise temperature T n . Combined with a quantum limited T n , this is a sufficient factor to increase our range by more than the desired factor of 10 3 . If we assume construction of a set of detectors for different frequencies, or "xylophone," the sensitivity is further improved and wave form information can be obtained.It was recognized long ago [2] that a sphere is a very natural shape for a resonant detector of gravitational waves. A free sphere has 5 degenerate quadrupole modes of vibration that will interact strongly with a wave, a bar has only 1. Each free mode can act as a separate antenna, oriented towards a different polarization or direction. Wagoner and Paik [3] found a set of equations to determine the source direction from the free mode amplitudes. They also calculated the ang...

We discuss the data acquisition and analysis procedures used on the Allegro gravity wave detector, including a full description of the filtering used for bursts of gravity waves. The uncertainties introduced into timing and signal strength estimates due to stationary noise are measured, giving the windows for both quantities in coincidence searches. ͓S0556-2821͑96͒01414-2͔ PACS number͑s͒: 04.80.Nn

We report the results of a theoretical and experimental study of a spherical gravitational wave antenna. We show that it is possible to understand the data from a spherical antenna with 6 radial resonant transducers attached to the surface in the truncated icosahedral arrangement. We find that the errors associated with small deviations from the ideal case are small compared to other sources of error, such as a finite signal-to-noise ratio. An in situ measurement technique is developed along with a general algorithm that describes a procedure for determining the direction of an external force acting on the antenna, including the force from a gravitational wave, using a combination of the transducer responses. The practicality of these techniques was verified on a room-temperature prototype antenna.

A spherical gravitational wave detector can be equally sensitive to a wave from any direction, and also can be able to measure its direction and polarization. We derive a set of equations to describe the mechanics of a spherical antenna coupled to an arbitrary number of attached mechanical resonators. A special arrangement of six resonators is proposed, which we term a truncated icosahedral gravitational wave antenna. An analytic solution to the equations of motion is found for this case. We find that direct deconvolution of the gravitational tensor components can be accomplished with a specified set of linear combinations of the resonator outputs, which we call the mode channels. We develop one simple noise model for this system and calculate the resulting strain noise spectrum. We conclude that the angle-averaged energy sensitivity will be 56 times better than for the typical equivalent bar-type antenna with the same noise temperature.