by Pucacco, Giuseppe and Bassan, Massimo and Visco, Massimo
27pages, 20 figures

We investigate autonomous perturbations on the orbits of LISA, namely the effects produced by fields that can be expressed only in terms of the position, but not of time in the Hill frame. This first step in the study of the LISA orbits has been the subject of recent papers which implement analytical techniques based on a “post-epicyclic” approximation in the Hill frame to find optimal unperturbed orbits. The natural step forward is to analyze the perturbations to purely Keplerian orbits. In the present work a particular emphasis is put on the tidal field of the Earth assumed to be stationary in the Hill frame. An accurate interpretation of the global structure of the perturbed solution sheds light on possible implications on injection in orbit when the time base-line of the mission is longer than that assumed in previous papers. Other relevant classes of autonomous perturbations are those given by the corrections to the Solar field responsible for a slow precession and a global stationary field, associated to sources like the interplanetary dust or a local dark matter component. The inclusion of simple linear contributions in the expansion of these fields produces secular solutions that can be compared with the measurements and possibly used to evaluate some morphological property of the perturbing components.

by de Vine, Glenn and Ware, Brent and McKenzie, Kirk and Spero, Robert E. and Klipstein, William M. and Shaddock, Daniel A.
4 pages, 4 figures, to appear in Physical Review Letters end of May 2010

We report on the first demonstration of time-delay interferometry (TDI) for LISA, the Laser Interferometer Space Antenna. TDI was implemented in a laboratory experiment designed to mimic the noise couplings that will occur in LISA. TDI suppressed laser frequency noise by approximately 10^9 and clock phase noise by 6×10^4, recovering the intrinsic displacement noise floor of our laboratory test bed. This removal of laser frequency noise and clock phase noise in post-processing marks the first experimental validation of the LISA measurement scheme.

by Cerdonio, M. and De Marchi, F. and De Pietri, R. and Jetzer, P. and Marzari, F. and Mazzolo, G. and Ortolan, A. and Sereno, M.
15 pages, 5 figures

We calculate the effect of the Earth-Moon (EM) system on the free-fall motion of LISA test masses. We show that the periodic gravitational pulling of the EM system induces a resonance with fundamental frequency 1 yr^-1 and a series of periodic perturbations with frequencies equal to integer harmonics of the synodic month (9.92 10^-7 Hz). We then evaluate the effects of these perturbations (up to the 6th harmonics) on the relative motions between each test masses couple, finding that they range between 3mm and 10pm for the 2nd and 6th harmonic, respectively. If we take the LISA sensitivity curve, as extrapolated down to 10^-6 Hz, we obtain that a few harmonics of the EM system can be detected in the Doppler data collected by the LISA space mission. This suggests that the EM system gravitational near field could provide an absolute calibration for the LISA sensitivity at very low frequencies.

by Manca, Gian Mario and Vallisneri, Michele
RevTeX4, 21 pages, 9 PDF figures

The efficient placement of signal templates in source-parameter space is a crucial requisite for exhaustive matched-filtering searches of modeled gravitational-wave sources. Unfortunately, the current placement algorithms based on regular parameter-space meshes are difficult to generalize beyond simple signal models with few parameters. Various authors have suggested that a general, flexible, yet efficient alternative can be found in randomized placement strategies such as random placement and stochastic placement, which enhances random placement by selectively rejecting templates that are too close to others. In this article we explore several theoretical and practical issues in randomized placement: the size and performance of the resulting template banks; the effects of parameter-space boundaries; the use of quasi-random (self avoiding) number sequences; most important, the implementation of these algorithms in curved signal manifolds with and without the use of a Riemannian signal metric, which may be difficult to obtain. Specifically, we show how the metric can be replaced with a discrete triangulation-based representation of local geometry. We argue that the broad class of randomized placement algorithms offers a promising answer to many search problems, but that the specific choice of a scheme and its implementation details will still need to be fine-tuned separately for each problem.

by Cerdonio, Massimo and De Marchi, Fabrizio and De Pietri, Roberto and Jetzer, Philippe and Marzari, Francesco and Mazzolo, Giulio and Ortolan, Antonello and Sereno, Mauro
11 pages, 6 figures, to be published on the special issue of “Celestial Mechanics and Dynamical Astronomy” on the CELMEC V conference

The analysis of non-radiative sources of static or time-dependent gravitational fields in the Solar System is crucial to accurately estimate the free-fall orbits of the LISA space mission. In particular, we take into account the gravitational effects of Interplanetary Dust (ID) on the spacecraft trajectories. The perturbing gravitational field has been calculated for some ID density distributions that fit the observed zodiacal light. Then we integrated the Gauss planetary equations to get the deviations from the LISA keplerian orbits around the Sun. This analysis can be eventually extended to Local Dark Matter (LDM), as gravitational fields are expected to be similar for ID and LDM distributions. Under some strong assumptions on the displacement noise at very low frequency, the Doppler data collected during the whole LISA mission could provide upper limits on ID and LDM densities.

by Gair, Jonathan R and Mandel, Ilya and Sesana, Alberto and Vecchio, Alberto
14 pages, 6 figures, 2 tables, accepted for proceedings of 13th GWDAW meeting

Identifying the properties of the first generation of seeds of massive black holes is key to understanding the merger history and growth of galaxies. Mergers between ~100 solar mass seed black holes generate gravitational waves in the 0.1-10Hz band that lies between the sensitivity bands of existing ground-based detectors and the planned space-based gravitational wave detector, the Laser Interferometer Space Antenna (LISA). However, there are proposals for more advanced detectors that will bridge this gap, including the third generation ground-based Einstein Telescope and the space-based detector DECIGO. In this paper we demonstrate that such future detectors should be able to detect gravitational waves produced by the coalescence of the first generation of light seed black-hole binaries and provide information on the evolution of structure in that era. These observations will be complementary to those that LISA will make of subsequent mergers between more massive black holes. We compute the sensitivity of various future detectors to seed black-hole mergers, and use this to explore the number and properties of the events that each detector might see in three years of observation. For this calculation, we make use of galaxy merger trees and two different seed black hole mass distributions in order to construct the astrophysical population of events. We also consider the accuracy with which networks of future ground-based detectors will be able to measure the parameters of seed black hole mergers, in particular the luminosity distance to the source. We show that distance precisions of ~30% are achievable, which should be sufficient for us to say with confidence that the sources are at high redshift.

by Polnarev, A. G. and Roxburgh, I. W. and Baskaran, D.
16 pages, 6 figures, 1 table. A reworked and considerably improved version of ArXiv:astro-ph/0103472, Published in PRD

We investigate the possibility of observing very small amplitude low frequency solar oscillations with the proposed laser interferometer space antenna (LISA). For frequencies $latex \nu$ below $latex 3\times 10^{-4} {\rm Hz}$ the dominant contribution is from the near zone time dependent gravitational quadrupole moments associated with the normal modes of oscillation. For frequencies $latex \nu$ above $latex 3\times 10^{-4} {\rm Hz}$ the dominant contribution is from gravitational radiation generated by the quadrupole oscillations which is larger than the Newtonian signal by a factor of the order $latex (2 \pi r \nu/ c)^4$, where $latex r$ is the distance to the Sun, and $latex c$ is the velocity of light.

The low order solar quadrupole pressure and gravity oscillation modes have not yet been detected above the solar background by helioseismic velocity and intensity measurements. We show that for frequencies $latex \nu \lesssim 2\times 10^{-4} {\rm Hz}$, the signal due to solar oscillations will have a higher signal to noise ratio in a LISA type space interferometer than in helioseismology measurements. Our estimates of the amplitudes needed to give a detectable signal on a LISA type space laser interferometer imply surface velocity amplitudes on the sun of the order of 1-10 mm/sec in the frequency range $latex 1\times 10^{-4} -5\times 10^{-4} {\rm Hz}$. If such modes exist with frequencies and amplitudes in this range they could be detected with a LISA type laser interferometer.

by Polnarev, A. G. and Roxburgh, I. W. and Baskaran, D.
16 pages, 6 figures, 1 table. A reworked and considerably improved version of ArXiv:astro-ph/0103472, Published in PRD

We investigate the possibility of observing very small amplitude low frequency solar oscillations with the proposed laser interferometer space antenna (LISA). For frequencies $latex \nu$ below $latex 3\times 10^{-4} {\rm Hz}$ the dominant contribution is from the near zone time dependent gravitational quadrupole moments associated with the normal modes of oscillation. For frequencies $latex \nu$ above $latex 3\times 10^{-4} {\rm Hz}$ the dominant contribution is from gravitational radiation generated by the quadrupole oscillations which is larger than the Newtonian signal by a factor of the order $latex (2 \pi r \nu/ c)^4$, where $latex r$ is the distance to the Sun, and $latex c$ is the velocity of light.

The low order solar quadrupole pressure and gravity oscillation modes have not yet been detected above the solar background by helioseismic velocity and intensity measurements. We show that for frequencies $latex \nu \lesssim 2\times 10^{-4} {\rm Hz}$, the signal due to solar oscillations will have a higher signal to noise ratio in a LISA type space interferometer than in helioseismology measurements. Our estimates of the amplitudes needed to give a detectable signal on a LISA type space laser interferometer imply surface velocity amplitudes on the sun of the order of 1-10 mm/sec in the frequency range $latex 1\times 10^{-4} -5\times 10^{-4} {\rm Hz}$. If such modes exist with frequencies and amplitudes in this range they could be detected with a LISA type laser interferometer.

by Stebbins, R. T.
To be published in Classical and Quantum Gravity; Proceedings of the Seventh International LISA Symposium, Barcelona, Spain, 16-20 Jun. 2008; 10 pages, 1 figure, 3 tables

The LISA science requirements and conceptual design have been fairly stable for over a decade. In the interest of reducing costs, the LISA Project at NASA has looked for simplifications of the architecture, at downsizing of subsystems, and at descopes of the entire mission. This is a natural activity of the formulation phase, and one that is particularly timely in the current NASA budgetary context. There is, and will continue to be, enormous pressure for cost reduction from both ESA and NASA, reviewers and the broader research community. Here, the rationale for the baseline architecture is reviewed, and recent efforts to find simplifications and other reductions that might lead to savings are reported. A few possible simplifications have been found in the LISA baseline architecture. In the interest of exploring cost sensitivity, one moderate and one aggressive descope have been evaluated; the cost savings are modest and the loss of science is not.

by Lanting, T. and Dobbs, M. and Spieler, H. and Lee, A. T. and Yamamoto, Y.
6 pages, 5 figures

We have designed and demonstrated a Superconducting Quantum Interference Device (SQUID) array linearized with cryogenic feedback. To achieve the necessary loop gain a 300 element series array SQUID is constructed from three monolithic 100-element series arrays. A feedback resistor completes the loop from the SQUID output to the input coil. The short feedback path of this Linearized SQUID Array (LISA) allows for a substantially larger flux-locked loop bandwidth as compared to a SQUID flux-locked loop that includes a room temperature amplifier. The bandwidth, linearity, noise performance, and dynamic range of the LISA are sufficient for its use in our target application: the multiplexed readout of transition-edge sensor bolometers.