ELISA: a cryocooled 10 GHz oscillator with 10-15 frequency stability

This article reports the design, the breadboarding and the validation of an ultra-stable Cryogenic Sapphire Oscillator operated in an autonomous cryocooler. The objective of this project was to demonstrate the feasibility of a frequency stability of 3x10-15 between 1 s and 1,000 s for the European Space Agency deep space stations. This represents the lowest fractional frequency instability ever achieved with cryocoolers. The preliminary results presented in this paper validate the design we adopted for the sapphire resonator, the cold source and the oscillator loop.Comment: 13 pages, 10 figure

Frequency Synthesis Chain For The ESA Deep Space Network

International audienceA report is presented on the measurement of a frequency synthesiser that provides round frequencies (10 GHz, 5 MHz, 100 MHz) with high spectral purity from a cryocooled sapphire oscillator in the vicinity of 10 GHz. The synthesiser and sapphire oscillator are a part of Elisa, a frequency reference that exhibits a stability of parts in 10(-15) from 1 s to 1000 s integration time, designed and implemented for the European Space Agency. The synthesiser features low 1/f phase noise, -96 dBc/Hz at 1 Hz off the carrier at the 10 GHz output, and -133 dBc/Hz at 1 Hz offset at the 100 MHz output

ULISS project: First comparison of cryocooled sapphire oscillators at the 10-15 level

International audienceWe already demonstrated a state-of-the-art Cryogenic Sapphire Oscillator (CSO), which incorporates a pulse-tube cooler instead of a bath cryostat - thus eliminating the need for regular supplies and manual transferring of liquid helium. The advent of reliable and cryocooled (CSO) open the possibility to implement such an ultra-stable reference not only in metrological laboratories with liquid helium facilities but also in remote sites like base stations for space navigation, VBLI antenna sites, ... The first prototype, i.e. ELISA, has been implemented in the ESA ground station in Malargüe (Ar) in April 2012. A second CSO was recently achieved using the same technology but specially designed to be transportable. After its complete assembly the CSO was coold down for the first time, and a preliminary frequency stability evaluation was done by direct comparison between the two CSOs. The Allan deviation was derived from data collected during more than 3 days. A short term frequency stability better than 2×10-15 at 1s was obtained. In spite of bad environemental conditions (infrastructure works in the building: implementation of an air conditioning in our laboratory which is not still effective) the frequency stability stays better than 4×10-15 for τ <; 1,000s and 1×10-14 over one day

Single-breath method for assessing the viscoelastic properties of the respiratory system.

In order to explain the time dependency of resistance and elastance of the respiratory system, a linear viscoelastic model (Maxwell body) has been proposed. In this model the maximal viscoelastic pressure (Pvisc.max) developed within the tissues of the lung and chest wall at the end of a constant-flow (V') inflation of a given time (tI) is given by: Pvisc,max = R2V'(1-e(-tI/tau2), where R2 and tau2 are, respectively, the resistance and time constant of the Maxwell body. After rapid airway occlusion at t1, tracheal pressure (Ptr) decays according to the following function: Ptr(t) = Pvisc(t) + Prs,st = Pvisc,max(etocc/tau2)+ Prs,st, where tocc/is time after occlusion and Prs,st is static re-coil pressure of the respiratory system. By fitting Ptr after occlusion to this equation, tau2 and Pvisc,max are obtained. Using these values, together with the V' and tI pertaining to the constant-flow inflation preceding the occlusion, R2 can be calculated from the former equation. Thus, from a single breath, the constants tau2, R2 and E2 (R2/tau2) can be obtained. This method was used in 10 normal anaesthetized, paralysed, mechanically ventilated subjects and six patients with acute lung injury. The results were reproducible in repeated tests and similar to those obtained from the same subjects and patients with the time-consuming isoflow, multiple-breath method described previously

High Stability Cryocooled 10 GHz Oscillator For The European Space Agency

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