Improvement of BepiColombo's radio science experiment through an innovative Doppler noise reduction technique

The Mercury Orbiter Radio science Experiment (MORE), onboard the ESA/JAXA BepiColombo mission to Mercury, is designed to estimate Mercury’s gravity field, its rotational state, and to perform tests of relativistic gravity. The state-of-the-art onboard and ground instrumentations involved in the MORE experiment will enable to establish simultaneous X/X, X/Ka and Ka/Ka-band links, providing a range rate accuracy of 3 µm/s (at 1000 s integration time) and a range accuracy of 20 cm. The purpose of this work is to show the improvement achievable on MORE’s performance by means of the Time-Delay Mechanical Noise Cancellation (TDMC) technique. The TDMC consists in a combination of Doppler measurements collected (at different times) at the two-way antenna and at an additional, smaller and stiffer, receive-only antenna that should be located in a site with favorable tropospheric conditions. This configuration could reduce the leading noises in a Ka-band two-way link, such as those caused by troposphere and ground antenna mechanical vibrations. We present the results of end-to-end simulations and estimation of Mercury’s gravity field and rotational state considering the TDMC technique. We compare results for a two-way link from NASA’s DSS-25 (in Goldstone, CA) or from ESA’s DSA-3 (in Malargue, Argentina), while we assume APEX as the receive-only antenna. We show that in best-case noise conditions, the TDMC technique allows to obtain a factor-of-two accuracy gain on both global and local parameters, considering DSA-3 as two-way antenna. Such improvement in the scientific objectives of MORE is of geophysical interest as it could provide a constraint on the interior structure of Mercury

El origen del sistema de relaciones laborales en el Uruguay

The purpose of this paper is the identification of issues that help to explain the origin of a Labor Relations Systems in this country. It includes the analysis of the different components and their links with the social, economic and political context.Labor relations, collective bargaining

Report on first inflight data of bepicolombo’s mercury orbiter radio-science experiment

BepiColombo’s Mercury Orbiter Radio-science Experiment (MORE) was conceived to enable extremely accurate radio tracking measurements of the Mercury Planetary Orbiter to precisely determine the gravity field and rotational state of Mercury, and to test theories of gravitation (e. g. Einstein’s Theory of General Relativity). The design accuracy of the radio tracking data was 0.004 mm/sec (at 1000 s integration time) for range-rate measurements and 20 cm for range (at a few seconds of integration time). These accuracies are attained due to a combination of simultaneous two-way microwave links at X (7.2-8.4 GHz) and Kaband (32-34 GHz) to calibrate the dispersive plasma noise component. In this letter, we present the first analysis of range and range-rate data collected by ESA’s deep space antenna (DSA) during the initial cruise phase of BepiColombo. The novel 24 Mcps pseudo-noise (PN) modulation of the Ka-band carrier, enabled by MORE’s Ka-band Transponder (KaT), built by Thales Alenia Space Italy, provided two-way range measurements to centimeterlevel accuracy, with an integration time of 4.2 s at 0.29 astronomical units. In tracking passes with favorable weather conditions, range-rate measurements attained an average accuracy of 0.01 mm/s at 60 s integration time. Data from 20 to 24 May 2019 were combined in a multi-pass analysis to test the link stability on a longer timescale. The results confirm the noise level observed with the single-pass analysis and provide a preliminary indication that the MORE PN ranging system at 24 Mcps is compatible with the realization of an absolute measurement, where the need to introduce range biases in the orbital fit is much more limited than in the past. We show that in the initial cruise test the BepiColombo radio link provided range measurements of unprecedented accuracy for a planetary mission, and that, in general, all target accuracies for radio-metric measurements were exceeded

Determination of Jupiter’s mass from Juno radio tracking data

Juno has been in a highly elliptical (average eccentricity e=0.95), nearly polar, 53-day orbit around Jupiter since July 2016. The solar-powered, spin-stabilized spacecraft hosts a complete suite of scientific investigations (gravity science, magnetospheric science, particles and fields analysis) aimed at shedding light into the planet’s interior and formation [1]. The gravity science investigation relies on Doppler tracking of Juno at Ka-band (32–34 GHz) as it flies by close to Jupiter’s top clouds (∼4000  km altitude on average). Measurements of the spacecraft’s radial velocity (Doppler) with respect to NASA Deep Space Station (DSS) 25 are fitted in the least-square sense to accurate dynamic models of the Juno’s motion to reconstruct its trajectory and estimate Jupiter’s gravity field coefficients [2]. After the first two pericenter passages dedicated to the gravity investigation, Juno had already revealed a north–south asymmetry of the gravity field, which has been tied to the presence of zonal winds at ∼3000  km depth [3,4]. The most recent analysis of the gravity science dataset (hereafter called GRAV), after 11 dedicated perijoves at the midpoint of Juno’s mission, has decreased the uncertainties on the gravity field coefficients, while providing also a determination of the gas giant’s tidal response and pole dynamics [5]. Before the end of the mission scheduled in July 2021, Juno might also unveil fine features of Jupiter’s gravity, such as its frequency-dependent tidal response, the presence of normal modes within the planet, and the depth of the Great Red Spot [6–8]. The GRAV data are sensitive to Jupiter’s gravity field; however, due to the limited timespan of the observations (6–8 h) compared with the 53-day orbital period, it is not possible to decorrelate the monopole component of Jupiter’s gravity field (proportional to the planet’s mass times the gravitational constant GMJ) from the low-degree components [9]. An improvement over the current estimate of GMJ, based on observations of the motion of Jupiter’s satellites from the latest ephemeris reconstruction (GMJ=126,686,534.196±2.7  km3/s2, where the quoted uncertainty is 1-σ) [10], would be relevant for spacecraft navigation, planetary ephemerides generation, and general relativity experiments in the solar system [11]. Before the arrival of the JUICE and Europa Clipper missions to the Jovian system in the 2030s, Juno will be the only spacecraft capable of such a determination

El origen del sistema de relaciones laborales en el Uruguay

The purpose of this paper is the identification of issues that help to explain the origin of a Labor Relations Systems in this country. It includes the analysis of the different components and their links with the social, economic and political context. El objetivo de este documento es identificar las condicionantes que contribuyen a explicar el surgimiento de un Sistema de Relaciones Laborales en el país. Incluye el análisis de las características de los componentes sistema y sus interrelaciones con el contexto social, económico y político.Labor relations, collective bargaining