A new LISA simulator (LISACode) is presented. Its ambition is to achieve a new degree of sophistication allowing to map, as closely as possible, the impact of the different subsystems on the measurements. LISACode is not a detailed simulator at the engineering level but rather a tool whose purpose is to bridge the gap between the basic principles of LISA and a future, sophisticated end-to-end simulator. This is achieved by introducing, in a realistic manner, most of the ingredients that will influence LISA's sensitivity as well as the application of TDI combinations. Many user-defined parameters allow the code to study different configurations of LISA thus helping to finalize the definition of the detector. Another important use of LISACode is in generating time series for data analysis developments.

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Light deflection offers an unbiased test of Weyl's gravity since no assumption on the conformal factor needs to be made. In this second paper of our series "Light deflection in Weyl gravity", we analyze the constraints imposed by light deflection experiments on the linear parameter of Weyl's theory. Regarding solar system experiments, the recent CASSINI Doppler measurements are used to infer an upper bound, ∼ 10 −19 m −1 , on the absolute value of the above Weyl parameter. In non-solar system experiments, a condition for unbound orbits together with gravitational mirage observations enable us to further constrain the allowed negative range of the Weyl parameter to ∼ −10 −31 m −1 . We show that the characteristics of the light curve in microlensing or gravitational mirages, deduced from the lens equation, cannot be recast into the General Relativistic predictions by a simple rescaling of the deflector mass or of the ring radius. However, the corrective factor, which depends on the Weyl parameter value and on the lensing configuration, is small, even perhaps negligible, owing to the upper bound inferred on the absolute value of a negative Weyl parameter. A statistical study on observed lensing systems is required to settle the question.Our Weyl parameter range is more reliable than the single value derived by Mannheim and Kazanas from fits to galactic rotation curves, ∼ +10 −26 m −1 . Indeed, the latter, although consistent with our bounds, is biased by the choice of a specific conformal factor.

Abstract.The Weyl gravity appears to be a very peculiar theory. The contribution of the Weyl linear parameter to the effective geodesic potential is opposite for massive and nonmassive geodesics. However, photon geodesics do not depend on the unknown conformal factor, unlike massive geodesics. Hence light deflection offers an interesting test of the Weyl theory. In order to investigate light deflection in the setting of Weyl gravity, we first distinguish between a weak field and a strong field approximation. Indeed, the Weyl gravity does not turn off asymptotically and becomes even stronger at larger distances. We then take full advantage of the conformal invariance of the photon effective potential to provide the key radial distances in Weyl gravity. According to those, we analyze the weak and strong field regime for light deflection. We further show some amazing features of the Weyl theory in the strong regime.PACS numbers: 04., 04.50.+h,04.80.Cc,04.90.+e,95.30Sf,95.35.+d,96.40.Cd,98.80.Es

The joint ESA/NASA LISA mission consists in three spacecraft on heliocentric orbits, flying in a triangular formation of 5 Mkm each side, linked by infrared optical beams. The aim of the mission is to detect gravitational waves in a low frequency band. For properly processing the science data, the propagation delays between spacecraft must be accurately known. We thus analyse the propagation of light between spacecraft in order to systematically derive the relativistic effects due to the static curvature of the Schwarzschild spacetime in which the spacecraft are orbiting with time-varying light-distances. In particular, our analysis allows to evaluate rigorously the Sagnac effect, and the gravitational (Einstein) redshift.Comment: 6 figures; accepted for publication in PR

Using dual-frequency data from 36 GPS stations from the EUREF Permanent Network (EPN), the influence of the October 30, 2003 Halloween geomagnetic storm on kinematic GPS positioning is investigated. The Halloween storm induced ionospheric disturbances above the northern part of Europe and Scandinavia. It is shown that kinematic position repeatabilities for this period are mainly affected for stations in northern Europe with outliers reaching 12 cm in the horizontal, and 26 cm in the vertical. These magnitudes are shown to be possibly due to the second-order ionospheric delays on GPS signals, not accounted for in the kinematic GPS positioning analysis performed. In parallel, we generate hourly TEC (Total Electron Content) maps on a 1°9 1°grid using the dense EPN network. These TEC maps do not use any interpolation but provide a high resolution in the time and space and therefore allow to better evidence small structures in the ionosphere than the classical 2-hourly 2.5°9 5°grid Global Ionospheric TEC Maps (GIM). Using the hourly 1°9 1°TEC maps, we reconstruct and refine exactly the zones of intense ionosphere activity during the storm, and we show the correlation between the ionospheric activity and assess the quality of GPS-based kinematic positioning performed in the European region.

In high-precision geodetic time and frequency transfer, which requires precise modeling of code and carrier phase GPS data, the ionosphere-free combinations P 3 and L 3 of the codes and carrier phases, made on the two GPS frequencies, are used to remove the first-order ionospheric effect. We quantify the impact of the residual second-and third-order ionospheric effects on geodetic time and frequency transfer solutions for continental and intercontinental baselines. All time transfer computations are done using the ATOMIUM software, developed at the Royal Observatory of Belgium. In order to avoid contamination by some imperfect modeling of the second-and third-order ionospheric effects in the satellite clock products, only single-difference, common-view processing is used, based on code and carrier phase measurements. The results are shown for weak and strong solar activity, as well as for particular epochs of ionospheric storms. Secondorder ionospheric delays can lead to corrections up to about 10 ps in the common-view clock solution of intercontinental baselines with very different longitudes. However, realistic values of the geomagnetic field in the ionosphere are required to assess the amplitude of second-order ionospheric effects in time and frequency transfer during an ionospheric storm.

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