Sensor Noise in LISA Pathfinder: In-Flight Performance of the Optical Test Mass Readout.

We report on the first subpicometer interferometer flown in space. It was part of ESA's Laser Interferometer Space Antenna (LISA) Pathfinder mission and performed the fundamental measurement of the positional and angular motion of two free-falling test masses. The interferometer worked immediately, stably, and reliably from switch on until the end of the mission with exceptionally low residual noise of 32.0_{-1.7}^{+2.4} fm/sqrt[Hz], significantly better than required. We present an upper limit for the sensor performance at millihertz frequencies and a model for the measured sensitivity above 200 mHz.

Analysis of the accuracy of actuation electronics in the laser interferometer space antenna pathfinder.

The Laser Interferometer Space Antenna Pathfinder (LPF) main observable, labeled Δg, is the differential force per unit mass acting on the two test masses under free fall conditions after the contribution of all non-gravitational forces has been compensated. At low frequencies, the differential force is compensated by an applied electrostatic actuation force, which then must be subtracted from the measured acceleration to obtain Δg. Any inaccuracy in the actuation force contaminates the residual acceleration. This study investigates the accuracy of the electrostatic actuation system and its impact on the LPF main observable. It is shown that the inaccuracy is mainly caused by the rounding errors in the waveform processing and also by the random error caused by the analog to digital converter random noise in the control loop. Both errors are one order of magnitude smaller than the resolution of the commanded voltages. We developed a simulator based on the LPF design to compute the close-to-reality actuation voltages and, consequently, the resulting actuation forces. The simulator is applied during post-processing the LPF data.

LISA Pathfinder Performance Confirmed in an Open-Loop Configuration: Results from the Free-Fall Actuation Mode.

We report on the results of the LISA Pathfinder (LPF) free-fall mode experiment, in which the control force needed to compensate the quasistatic differential force acting on two test masses is applied intermittently as a series of "impulse" forces lasting a few seconds and separated by roughly 350 s periods of true free fall. This represents an alternative to the normal LPF mode of operation in which this balancing force is applied continuously, with the advantage that the acceleration noise during free fall is measured in the absence of the actuation force, thus eliminating associated noise and force calibration errors. The differential acceleration noise measurement presented here with the free-fall mode agrees with noise measured with the continuous actuation scheme, representing an important and independent confirmation of the LPF result. An additional measurement with larger actuation forces also shows that the technique can be used to eliminate actuation noise when this is a dominant factor.

Beyond the Required LISA Free-Fall Performance: New LISA Pathfinder Results down to 20 µHz.

In the months since the publication of the first results, the noise performance of LISA Pathfinder has improved because of reduced Brownian noise due to the continued decrease in pressure around the test masses, from a better correction of noninertial effects, and from a better calibration of the electrostatic force actuation. In addition, the availability of numerous long noise measurement runs, during which no perturbation is purposely applied to the test masses, has allowed the measurement of noise with good statistics down to 20 µHz. The Letter presents the measured differential acceleration noise figure, which is at (1.74±0.05) fm s^{-2}/sqrt[Hz] above 2 mHz and (6±1)×10 fm s^{-2}/sqrt[Hz] at 20 µHz, and discusses the physical sources for the measured noise. This performance provides an experimental benchmark demonstrating the ability to realize the low-frequency science potential of the LISA mission, recently selected by the European Space Agency.

Charge-Induced Force Noise on Free-Falling Test Masses: Results from LISA Pathfinder.

We report on electrostatic measurements made on board the European Space Agency mission LISA Pathfinder. Detailed measurements of the charge-induced electrostatic forces exerted on free-falling test masses (TMs) inside the capacitive gravitational reference sensor are the first made in a relevant environment for a space-based gravitational wave detector. Employing a combination of charge control and electric-field compensation, we show that the level of charge-induced acceleration noise on a single TM can be maintained at a level close to 1.0 fm s^{-2} Hz^{-1/2} across the 0.1-100 mHz frequency band that is crucial to an observatory such as the Laser Interferometer Space Antenna (LISA). Using dedicated measurements that detect these effects in the differential acceleration between the two test masses, we resolve the stochastic nature of the TM charge buildup due to interplanetary cosmic rays and the TM charge-to-force coupling through stray electric fields in the sensor. All our measurements are in good agreement with predictions based on a relatively simple electrostatic model of the LISA Pathfinder instrument.

Sub-Femto-g Free Fall for Space-Based Gravitational Wave Observatories: LISA Pathfinder Results.

We report the first results of the LISA Pathfinder in-flight experiment. The results demonstrate that two free-falling reference test masses, such as those needed for a space-based gravitational wave observatory like LISA, can be put in free fall with a relative acceleration noise with a square root of the power spectral density of 5.2±0.1 fm s^{-2}/sqrt[Hz], or (0.54±0.01)×10^{-15} g/sqrt[Hz], with g the standard gravity, for frequencies between 0.7 and 20 mHz. This value is lower than the LISA Pathfinder requirement by more than a factor 5 and within a factor 1.25 of the requirement for the LISA mission, and is compatible with Brownian noise from viscous damping due to the residual gas surrounding the test masses. Above 60 mHz the acceleration noise is dominated by interferometer displacement readout noise at a level of (34.8±0.3) fm/sqrt[Hz], about 2 orders of magnitude better than requirements. At f≤0.5 mHz we observe a low-frequency tail that stays below 12 fm s^{-2}/sqrt[Hz] down to 0.1 mHz. This performance would allow for a space-based gravitational wave observatory with a sensitivity close to what was originally foreseen for LISA.

2-µm Ho emitter-based coherent DIAL for CO(2) profiling in the atmosphere.

We report on the use of a thulium-fiber-pumped holmium-based emitter in a coherent differential absorption lidar (CDIAL) experiment for high time and space resolution of CO(2) absorption field in the atmosphere. The 2-µm high-power dual-wavelength single-mode Q-switched Ho:YLF oscillator delivers 10-mJ pulses with a duration of 40 ns at 2 kHz. Both short pulse duration and high repetition rate were chosen to increase the DIAL precision and time and space resolution in coherent detection. The CDIAL provides 150-m range and 15-min time-resolved CO(2) absorption coefficient with a calculated instrumental error of 0.5% at 500 m and less than 2% at 1 km. Dry-air CO(2) mixing ratio estimates from the DIAL system are compared with simultaneous in situ gas analyzer measurements during a 20-h-long experiment.

[Pulsatile administration of LH-RH: diagnostic and therapeutic applications]. / Administration pulsatile de la LH-RH: applications diagnostiques et thérapeutiques.

Hypothalamic hypogonadotropic hypogonadism (HHH), a disorder occurring in both sexes, is characterized by a partial or complete inability to synthesize and/or release LH-RH from the hypothalamus which result in absence or defects of amplitude and frequency of gonadotropin secretion. Long term substitution by pulsatile exogenous LH-RH usually result in complete normalization of both pituitary and gonadic hormones. Such a treatment allows differentiation between hypothalamic and pituitary causes of hypogonadotrophic hypogonadism. Ovulation and fertility can be achieved in most of women with hypothalamic amenorrhea treated with pulsatile LH-RH using i.v. bolus doses of 25-100 ng/kg at 1-2 h intervals. In opposite LH-RH therapy yields inferior results to human menopausal gonadotropin (hMG) in chronic anovulatory patients with persistent LH secretion or polycystic ovary syndrome (PCOS) as shown by one randomized and several non-controlled studies. Successful pulsatile LH-RH treatment following a 2 months LH-RH analog suppression in PCOS previously refractory to LH-RH alone represents a new promising approach. The majority of men with complete HHH begin to produce sperm only after 1 year of therapy. Both the testicular volume and the mean sperm concentrations were below the normal values after 2 years of treatment in spite of normalization of testosterone, LH and FSH levels. Pulsatile LH-RH does not seem significantly improve the treatment of infertile HHH men compared to hMH/hCG.

[Stimulation of ovulation by pure FSH for in vitro fertilization. Study of the route of administration]. / Stimulation de l'ovulation par la FSH pure en vue de fécondation in vitro. Etude de la voie d'administration.

Pulsatile injection of FSH to stimulate ovulation for in vitro fertilization was undertaken in order to compare the intramuscular route with the pulsatile subcutaneous route in two groups of 6 patients each selected at random. The patients were selected in such a way as to reduce as far as possible the parameters that would make it difficult to interpret the results. Both from the point of view of the numbers of patients who responded to stimulation of ovulation as well as the numbers of pregnancies that were obtained, the intramuscular route seems to be preferable.

Influence of the frequency of gonadotropin-releasing hormone (GnRH) administration on ovulatory responses in women with anovulation.

In attempt to optimize gonadotropin-releasing hormone (GnRH) treatment of anovulation, we compared the effect of intravenous GnRH administration at three pulse intervals (PI) during 63 cycles in 30 anovulatory patients who had: (1) amenorrhea secondary to anorexia nervosa (group I: 10 patients, 21 cycles); (2) unexplained anovulation with normal to high luteinizing hormone plasma levels (group II: 12 patients, 24 cycles); and (3) polycystic ovarian disease (PCOD) (group III: 8 patients, 18 cycles). Ovulation was achieved more frequently in group I (85%) than in group II (41%) or in group III (50%). In both groups I and II, the frequency of ovulatory responses was not different with the PI used, and 6 of the 17 women treated for infertility conceived; 3 with 90-minute PIs, 2 with 64-minute PIs, and 1 with 128-minute PIs. In women with PCOD, seven of the nine ovulatory responses and three pregnancies were obtained with 128-minute PIs. The overweight women with PCOD did not respond reliably to GnRH at the doses used, i.e., 4 to 15 micrograms per pulse. In all groups, the urinary estrone and estradiol preovulatory peak, duration of luteal phase, progesterone levels, and preovulatory follicle diameter were unrelated to the frequency of GnRH administration.