Engineering topics

McNamara, Paul

Publications and source records attributed to McNamara, Paul.

6 records

NASA NTRS2012

NASA's Gravitational - Wave Mission Concept Study

With the conclusion of the NASA/ESA partnership on the Laser Interferometer Space Antenna (LISA) Project, NASA initiated a study to explore mission concepts that will accomplish some or all of the LISA science objectives at lower cost. The Gravitational-Wave Mission Concept Study consisted of a public Request for Information (RFI), a Core Team of NASA engineers and scientists, a Community Science Team, a Science Task Force, and an open workshop. The RFI yielded were 12 mission concepts, 3 instrument concepts and 2 technologies. The responses ranged from concepts that eliminated the drag-free test mass of LISA to concepts that replace the test mass with an atom interferometer. The Core Team reviewed the noise budgets and sensitivity curves, the payload and spacecraft designs and requirements, orbits and trajectories and technical readiness and risk. The Science Task Force assessed the science performance by calculating the horizons. the detection rates and the accuracy of astrophysical parameter estimation for massive black hole mergers, stellar-mass compact objects inspiraling into central engines. and close compact binary systems. Three mission concepts have been studied by Team-X, JPL's concurrent design facility. to define a conceptual design evaluate kt,y performance parameters. assess risk and estimate cost and schedule. The Study results are summarized.

Stebbins, Robin↗

NASA NTRS2012

Space-Based Gravitational-Wave Observatory (SGO) Mission Concept Study

The LISA Mission Concept has been under study for over two decades as a space-based gravitational-wave detector capable of observing astrophysical sources in the 0.0001 to 1 Hz band. The concept has consistently received strong recommendations from various review panels based on the expected science, most recently from the US Astr02010 Decadal Review. Budget constraints have led both the US and European Space agencies to search for lower cost options. We report results from the US effort to explore the tradeoffs between mission cost and science return.

Livas, Jeffrey↗

NASA NTRS2005

Laser frequency stabilization for LISA

The requirement on laser frequency noise in the Laser Interferometer Space Antenna (LISA) depends on the velocity and our knowledge of the position of each spacecraft of the interferometer. Currently it is assumed that the lasers must have a pre-stabilized frequency stability of 30Hz/square root of Hz over LISA'S most sensitive frequency band (3 mHz - 30 mHz). The intrinsic frequency stability of even the most stable com- mercial lasers is several orders of magnitude above this level. Therefore it is necessary to stabilize the laser frequency to an ultra-stable frequency reference which meets the LISA requirements. The baseline frequency reference for the LISA lasers are high finesse optical cavities based on ULE spacers. We measured the stability of two ULE spacer cavities with respect to each other. Our current best results show a noise floor at, or below, 30 Hz/square root of Hz above 3 mHz. In this report we describe the experimental layout of the entire experiment and discuss the limiting noise sources.

Mueller, Guido↗

NASA NTRS2005

Polarization Considerations for the Laser Interferometer Space Antenna (LISA)

A polarization ray trace model of the Laser Interferometer Space Antenna's (LISA) optical path is being created. The model will be able to assess the effects of various polarizing elements and the optical coatings on the required picometer level interferometry. All of the computational steps are described in detail. This should eliminate any ambiguities associated with polarization ray trace modeling of interferometers and provide a basis for determining its limitations and serve as a clearly defined starting point for future improvements.

Waluschka, Eugene↗

NASA NTRS2005

Modeling the Laser Interferometer Space Antenna Optics

Creating an optical model of the Laser Interferometer Space antenna which can be used to predict optical sensitivities and set tolerances sufficiently well such that picometer level displacements can be reliably seen poses certain challenges. In part, because the distances between key optical elements, the proof masses, are constantly changing, at speeds of meters/second, the separation between them is about 5 million kilometers and a contributing factor to optical jitter is the self-gravity of the spacecraft. A discussion of the current state and future approach(s) to the creation of such an optical model will be presented.

Waluschka, Eugene↗

NASA NTRS2005

Polarization Considerations for the Laser Interferometer Space Antenna

A polarization ray trace model of the Laser Interferometer Space Antenna s (LISA) optical path is being created. The model will be able to assess the effects of various polarizing elements and the optical coatings on the required, very long path length, picometer level dynamic interferometry. The computational steps are described. This should eliminate any ambiguities associated with polarization ray tracing of interferometers and provide a basis for determining the computer model s limitations and serve as a clearly defined starting point for future work.

Waluschka, Eugene↗