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All sourcesNASA NTRSDOE OSTI
NASA NTRS2010

Laser Interferometry for Gravitational Wave Observation: LISA and LISA Pathfinder

The Laser Interferometer Space Antenna (LISA) is a planned NASA-ESA gravitational wave observatory in the frequency range of 0.1mHz-100mHz. This observation band is inaccessible to ground-based detectors due to the large ground motions of the Earth. Gravitational wave sources for LISA include galactic binaries, mergers of supermasive black-hole binaries, extreme-mass-ratio inspirals, and possibly from as yet unimagined sources. LISA is a constellation of three spacecraft separated by 5 million km in an equilateral triangle, whose center follows the Earth in a heliocentric orbit with an orbital phase offset oF 20 degrees. Challenging technology is required to ensure pure geodetic trajectories of the six onboard test masses, whose distance fluctuations will be measured by interspacecraft laser interferometers with picometer accuracy. LISA Pathfinder is an ESA-launched technology demonstration mission of key LISA subsystems such us spacecraft control with micro-newton thrusters, test mass drag-free control, and precision laser interferometry between free-flying test masses. Ground testing of flight hardware of the Gravitational Reference Sensor and Optical Metrology subsystems of LISA Pathfinder is currently ongoing. An introduction to laser interferometric gravitational wave detection, ground-based observatories, and a detailed description of the two missions together with an overview of current investigations conducted by the community will bc discussed. The current status in development and implementation of LISA Pathfinder pre-flight systems and latest results of the ongoing ground testing efforts will also be presented

Guzman, Felipe↗
NASA NTRS1984

High sensitivity laser interferometry for detection of boundary-layer transition

A high sensitivity laser interferometry for continuous monitoring of optical path changes is presented. The sensitivity to small changes in the optical path is achieved by means of a feedback system which keeps the interferometer at its maximum (and linear) position. Two experiments were designed to verify the interferometer's performance, both in direct and in scattering configurations. In each case, small temperature fluctuations were introduced as the signal source. Simultaneous measurement of temperature were compared with the results of the interferometer. Good correlation between the results were obtained. Finally, the application of the high sensitivity interferometer for detection of boundary-layer transition is examined. Optical signal strength and possible sources of noise are examined. Some methods of model surface preparation for enhancement of signal-to-noise ratio are discussed.

Modarress, D.↗
NASA NTRS2012

Comparing Laser Interferometry and Atom Interferometry Approaches to Space-Based Gravitational-Wave Measurement

Thoroughly studied classic space-based gravitational-wave missions concepts such as the Laser Interferometer Space Antenna (LISA) are based on laser-interferometry techniques. Ongoing developments in atom-interferometry techniques have spurred recently proposed alternative mission concepts. These different approaches can be understood on a common footing. We present an comparative analysis of how each type of instrument responds to some of the noise sources which may limiting gravitational-wave mission concepts. Sensitivity to laser frequency instability is essentially the same for either approach. Spacecraft acceleration reference stability sensitivities are different, allowing smaller spacecraft separations in the atom interferometry approach, but acceleration noise requirements are nonetheless similar. Each approach has distinct additional measurement noise issues.

Baker, John↗
NASA NTRS2003

Precision Pointing for the Laser Interferometry Space Antenna Mission

The Laser Interferometer Space Antenna (LISA) mission is a planned NASA-ESA gravitational wave detector consisting of three spacecraft in heliocentric orbit. Lasers are used to measure distance fluctuations between proof masses aboard each spacecraft to the picometer level over a 5 million kilometer separation. Each spacecraft and its two laser transmit/receive telescopes must be held stable in pointing to less than 8 nanoradians per root Hertz in the frequency band 0.1-100 mHz. The pointing error is sensed in the received beam and the spacecraft attitude is controlled with a set of micro-Newton thrusters. Requirements, sensors, actuators, control design, and simulations are described.

Hyde, T. Tupper↗
NASA NTRS2003

Precision Pointing for the Laser Interferometry Space Antenna Mission

The Laser Interferometer Space Antenna (LISA) mission is a planned NASA-ESA gravitational wave detector consisting of three spacecraft in heliocentric orbit. Lasers are used to measure distance fluctuations between proof masses aboard each spacecraft to the picometer level over a 5 million kilometer separation. Each spacecraft and its two laser transmit/receive telescopes must be held stable in pointing to less than 8 nanoradians per root Hertz in the frequency band 0.1-100 mHz. The pointing error is sensed in the received beam and the spacecraft attitude is controlled with a set of micro-Newton thrusters. Requirements, sensors, actuators, control design, and simulations are described.

Hyde, T. Tupper↗
NASA NTRS1988

Skin friction measurements by laser interferometry in swept shock wave/turbulent boundary-layer interactions

The laser interferometric skin friction meter was used to measure wall shear stress distributions in two interactions of fin-generated swept shock waves with turbulent boundary layers. The basic research configuration was an unswept sharp-leading-edge fin of variable angle mounted on a flatplate. The results indicate that such measurements are practical in high-speed interacting flows, and that a repeatability of + or - 6 percent or better is possible. Marked increases in wall shear were observed in both swept interactions tested.

Kim, Kwang-Soo↗
NASA NTRS1989

Skin-friction measurements by laser interferometry

The measurement of skin friction in rapidly distorted compressible flows is difficult, and very few reliable techniques are available. A recent development, the laser interferometer skin friction (LISF) meter, promises to be useful for this purpose. This technique interferometrically measures the time rate of thinning of an oil film applied to an aerodynamic surface. Under the proper conditions the wall shear stress may thus be found directly, without reference to flow properties. The applicability of the LISF meter to supersonic boundary layers is examined experimentally. Its accuracy and repeatability are assessed, and conditions required for its successful application are considered.

Kim, K.-S.↗
NASA NTRS2003

Precision Pointing for the Laser Interferometry Space Antenna Mission

This viewgraph presentation discusses requirements for control systems in the design and production of space-based telescopes. Specific topics covered include: pointing control methods, wavefront control methods, vibration control methods and thermal control methods. Control systems on the Hubble Space Telescope and the James Webb Space Telescope are reviewed. Control system requirements for future space telescopes are also mentioned.

Hyde, T. Tupper↗
NASA NTRS2004

Modeling of proof mass self-gravity field for the Laser Interferometry Space Antenna (LISA)

This paper describes the development of the self-gravity modeling tool used to predict and control the motion of one of the proof masses of the orbiting LISA gravitational wave detector. LISA is a space-borne gravitational wave detector, which is formed by three spacecraft orbiting the Sun and forming the vertices of an equilateral triangle with a side of 5 million km in length. Requirements on the forces and moments, and the force gradients and moment gradients, applied to the proof mass exist. This paper computes these quantities analytically, so that gravitational balancing considerations can now be done effectively.

Quadrelli, Marco B.↗
NASA NTRS1999

Phase-Shifted Laser Feedback Interferometry

Phase-shifted, laser feedback interferometry is a new diagnostic tool developed at the NASA Lewis Research Center under the Advanced Technology Development (ATD) Program directed by NASA Headquarters Microgravity Research Division. It combines the principles of phase-shifting interferometry (PSI) and laser-feedback interferometry (LFI) to produce an instrument that can quantify both optical path length changes and sample reflectivity variations. In a homogenous medium, the optical path length between two points is the product of the index of refraction and the geometric distance between the two points. LFI differs from other forms of interferometry by using the laser as both the source and the phase detector. In LFI, coherent feedback of the incident light either reflected directly from a surface or reflected after transmission through a region of interest will modulate the output intensity of the laser. The combination of PSI and LFI has produced a robust instrument, based on a low-power helium-neon (HeNe) gas laser, with a high dynamic range that can be used to measure either static or oscillatory changes of the optical path length. Small changes in optical path length are limited by the fraction of a fringe that can be measured; we can measure nonoscillatory changes with a root mean square (rms) error of the wavelength/1000 without averaging.

Ovryn, Benjie↗
NASA NTRS1996

Application of Phase Shifted, Laser Feedback Interferometry to Fluid Physics

We have combined the principles of phase-shifting interferometry (PSI) and laser-feedback interferometry (LFI) to produce a new instrument that can measure both optical path length (OPL) changes and discern sample reflectivity variations. In LFI, coherent feedback of the incident light either reflected directly from a surface or reflected after transmission through a region of interest will modulate the output intensity of the laser. LFI can yield a high signal-to-noise ratio even for low reflectivity samples. By combining PSI and LFI, we have produced a robust instrument, based upon a HeNe laser, with high dynamic range that can be used to measure either static (dc) or oscillatory changes along the optical path. As with other forms of interferometry, large changes in OPL require phase unwrapping. Conversely, small phase changes are limited by the fraction of a fringe that can be measured. We introduce the phase shifts with an electro-optic modulator (EOM) and use either the Carre or Hariharan algorithms to determine the phase and visibility. We have determined the accuracy and precision of our technique by measuring both the bending of a cantilevered piezoelectric bimorph and linear ramps to the EOM. Using PSI, sub-nanometer displacements can be measured. We have combined our interferometer with a commercial microscope and scanning piezoelectric stage and have measured the variation in OPL and visibility for drops of PDMS (silicone oil) on coated single crystal silicon. Our measurement of the static contact angle agrees with the value of 68 deg stated in the literature.

Ovryn, Ben↗