44 research outputs found
Space-time localization of inner heliospheric plasma turbulence using multiple spacecraft radio links
Radio remote sensing of the heliosphere using spacecraft radio signals has
been used to study the near-sun plasma in and out of the ecliptic, close to the
sun, and on spatial and temporal scales not accessible with other techniques.
Studies of space-time variations in the inner solar wind are particularly
timely because of the desire to understand and predict space weather, which can
disturb satellites and systems at 1AU and affect human space exploration. Here
we demonstrate proof-of-concept of a new radio science application for
spacecraft radio science links. The differing transfer functions of plasma
irregularities to spacecraft radio up- and downlinks can be exploited to
localize plasma scattering along the line of sight. We demonstrate the utility
of this idea using Cassini radio data taken in 2001-2002. Under favorable
circumstances we demonstrate how this technique, unlike other remote sensing
methods, can determine center-of-scattering position to within a few
thousandths of an AU and thickness of scattering region to less than about 0.02
AU. This method, applied to large data sets and used in conjunction with other
solar remote sensing data such as white light data, has space weather
application in studies of inhomogeneity and nonstationarity in the near-sun
solar wind.Comment: 28 Pages including 14 Figures (7 unique figures in both inline format
and full-page format)
The future of planetary atmospheric, surface, and interior science using radio and laser links
Studies of planetary systems using spacecraft radio links constitute the field of Radio Science (RS). Experiments have been conducted on almost every planetary mission in the past five decades and have led to numerous discoveries. With substantial technical advancements in recent years, the following significant accomplishments are noted: • Elucidated the thermal history of the Moon from the GRAIL high precision gravitational field • Unveiled the interiors of Titan, Enceladus, Mercury, Phobos, Vesta, Ceres, and cometary nuclei from gravity fields, contributing to understanding their origins (Figure 1) • Sounded Titan, Saturn, and Pluto's atmospheres • Explored the surface properties of Pluto and 67P/Churyumov-Gerasimenko • Refined models for the atmospheres, surfaces, and interior structure of Mars and Venus • Juno and Cassini are currently measuring the gravity fields of Jupiter and Saturn to reveal their interior structures • Provided evidence for subsurface oceans on icy moons to expand understanding of potentially habitable bodies • Investigated the solar corona and the interaction of the solar wind with planetary atmospheres, and • Profiled the structure of Saturn's rings, which interact with moonlets
Orbital effects of a monochromatic plane gravitational wave with ultra-low frequency incident on a gravitationally bound two-body system
We analytically compute the long-term orbital variations of a test particle
orbiting a central body acted upon by an incident monochromatic plane
gravitational wave. We assume that the characteristic size of the perturbed
two-body system is much smaller than the wavelength of the wave. Moreover, we
also suppose that the wave's frequency is much smaller than the particle's
orbital one. We make neither a priori assumptions about the direction of the
wavevector nor on the orbital geometry of the planet. We find that, while the
semi-major axis is left unaffected, the eccentricity, the inclination, the
longitude of the ascending node, the longitude of pericenter and the mean
anomaly undergo non-vanishing long-term changes. They are not secular trends
because of the slow modulation introduced by the tidal matrix coefficients and
by the orbital elements themselves. They could be useful to indepenedently
constrain the ultra-low frequency waves which may have been indirectly detected
in the BICEP2 experiment. Our calculation holds, in general, for any
gravitationally bound two-body system whose characteristic frequency is much
larger than the frequency of the external wave. It is also valid for a generic
perturbation of tidal type with constant coefficients over timescales of the
order of the orbital period of the perturbed particle.Comment: LaTex2e, 24 pages, no figures, no tables. Changes suggested by the
referees include
Gravity, Geodesy and Fundamental Physics with BepiColombo’s MORE Investigation
open40siThe Mercury Orbiter Radio Science Experiment (MORE) of the ESA mission BepiColombo will provide an accurate estimation of Mercury’s gravity field and rotational state, improved tests of general relativity, and a novel deep space navigation system. The key experimental setup entails a highly stable, multi-frequency radio link in X and Ka band, enabling two-way range rate measurements of 3 micron/s at nearly all solar elongation angles. In addition, a high chip rate, pseudo-noise ranging system has already been tested at 1-2 cm accuracy. The tracking data will be used together with the measurements of the Italian Spring Accelerometer to provide a pseudo drag free environment for the data analysis. We summarize the existing literature published over the past years and report on the overall configuration of the experiment, its operations in cruise and at Mercury, and the expected scientific results.openIess L.; Asmar S.W.; Cappuccio P.; Cascioli G.; De Marchi F.; di Stefano I.; Genova A.; Ashby N.; Barriot J.P.; Bender P.; Benedetto C.; Border J.S.; Budnik F.; Ciarcia S.; Damour T.; Dehant V.; Di Achille G.; Di Ruscio A.; Fienga A.; Formaro R.; Klioner S.; Konopliv A.; Lemaitre A.; Longo F.; Mercolino M.; Mitri G.; Notaro V.; Olivieri A.; Paik M.; Palli A.; Schettino G.; Serra D.; Simone L.; Tommei G.; Tortora P.; Van Hoolst T.; Vokrouhlicky D.; Watkins M.; Wu X.; Zannoni M.Iess L.; Asmar S.W.; Cappuccio P.; Cascioli G.; De Marchi F.; di Stefano I.; Genova A.; Ashby N.; Barriot J.P.; Bender P.; Benedetto C.; Border J.S.; Budnik F.; Ciarcia S.; Damour T.; Dehant V.; Di Achille G.; Di Ruscio A.; Fienga A.; Formaro R.; Klioner S.; Konopliv A.; Lemaitre A.; Longo F.; Mercolino M.; Mitri G.; Notaro V.; Olivieri A.; Paik M.; Palli A.; Schettino G.; Serra D.; Simone L.; Tommei G.; Tortora P.; Van Hoolst T.; Vokrouhlicky D.; Watkins M.; Wu X.; Zannoni M
OSS (Outer Solar System): A fundamental and planetary physics mission to Neptune, Triton and the Kuiper Belt
The present OSS mission continues a long and bright tradition by associating
the communities of fundamental physics and planetary sciences in a single
mission with ambitious goals in both domains. OSS is an M-class mission to
explore the Neptune system almost half a century after flyby of the Voyager 2
spacecraft. Several discoveries were made by Voyager 2, including the Great
Dark Spot (which has now disappeared) and Triton's geysers. Voyager 2 revealed
the dynamics of Neptune's atmosphere and found four rings and evidence of ring
arcs above Neptune. Benefiting from a greatly improved instrumentation, it will
result in a striking advance in the study of the farthest planet of the Solar
System. Furthermore, OSS will provide a unique opportunity to visit a selected
Kuiper Belt object subsequent to the passage of the Neptunian system. It will
consolidate the hypothesis of the origin of Triton as a KBO captured by
Neptune, and improve our knowledge on the formation of the Solar system. The
probe will embark instruments allowing precise tracking of the probe during
cruise. It allows to perform the best controlled experiment for testing, in
deep space, the General Relativity, on which is based all the models of Solar
system formation. OSS is proposed as an international cooperation between ESA
and NASA, giving the capability for ESA to launch an M-class mission towards
the farthest planet of the Solar system, and to a Kuiper Belt object. The
proposed mission profile would allow to deliver a 500 kg class spacecraft. The
design of the probe is mainly constrained by the deep space gravity test in
order to minimise the perturbation of the accelerometer measurement.Comment: 43 pages, 10 figures, Accepted to Experimental Astronomy, Special
Issue Cosmic Vision. Revision according to reviewers comment
Cassini Radio Science
Cassini radio science investigations will be conducted both during the cruise (gravitational wave and conjunction experiments) and the Saturnian tour of the mission (atmospheric and ionospheric occultations, ring occultations, determinations of masses and gravity fields). New technologies in the construction of the instrument, which consists of a portion on-board the spacecraft and another portion on the ground, including the use of the Ka-band signal in addition to that of the S- and X-bands, open opportunities for important discoveries in each of the above scientific areas, due to increased accuracy, resolution, sensitivity, and dynamic range.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43765/1/11214_2004_Article_1436.pd
MORE: An advanced tracking experiment for the exploration of Mercury with the mission BepiColombo
Precise microwave tracking of interplanetary spacecraft has been a crucial tool in solar system exploration. Range and range
rate measurements, the main observable quantities in spacecraft orbit determination and navigation, have been widely used to
refine the dynamical model of the solar system and to probe planetary interiors. Thanks to the use of Ka-band and multifrequency
radio links, a significant improvement in microwave tracking systems has been demonstrated by the radio science experiments
of the Cassini mission to Saturn. The Cassini radio system has been used to carry out the most accurate test of general relativity
to date. Further developments in the radio instrumentation have been recently started for the Mercury Orbiter Radio Experiment
(MORE), selected for the ESA mission to Mercury, BepiColombo. MORE addresses the mission\u2019s scientific goals in geodesy,
geophysics and fundamental physics. In addition, MORE will carry out a navigation experiment, aiming to a precise assessment
of the orbit determination accuracies attainable with the use of the novel instrumentation. The key instrument is a Ka/Ka band
digital transponder enabling a high phase coherence between uplink and downlink carriers and supporting a wideband ranging
tone. The onboard instrumentation is complemented by a ground system based upon the simultaneous transmission and reception
of multiple frequencies at X- and Ka-band. The new wideband ranging system is designed for an end-to-end accuracy of 20cm
using integration times of a few seconds. Two-way range rate measurements are expected to be accurate to 3m/s, thanks to
nearly complete cancellation or calibration of the propagation noise from interplanetary plasma and troposphere. We review the
experimental configuration of the experiment and outline its scientific goals and expected results
Reducing Doppler noise with multi-station tracking: The Cassini test case
Doppler tracking of Solar System probes is used for spacecraft navigation, planetary geodesy, and tests of the theory of General Relativity. The spacecraft radial velocity is measured by observing the Doppler shift of a radio signal transmitted from an Earth station to the spacecraft and then re-transmitted back, while preserving phase coherence, to the same station (two-way link) or to a different station (three-way link). Specialized orbit determination software is then used to reconstruct the spacecraft trajectory and estimate planetary gravity field coefficients or relativistic parameters. The measurement noise is a crucial element for the accuracy of the final estimates, thus considerable effort has been devoted to improve the range rate accuracy by adopting higher frequency links to reduce the dispersive noise from interplanetary and ionospheric plasmas, and by calibrating the tropospheric path delays with microwave radiometers. While Ka-band radio links (32–34 GHz) allowed a successful suppression of plasma noise, reducing tropospheric noise and ground antenna mechanical noise has been more challenging. The Time-Delay Mechanical noise Cancellation (TDMC) technique is a promising method to reduce mechanical and tropospheric noises and to improve further the accuracy of Doppler measurements. The TDMC is a linear combination of simultaneous Doppler data from a main antenna providing the two-way link and a three-way antenna (generally smaller and stiffer). If the listen-only, three-way antenna is also located in a particularly dry site, the TDMC can considerably reduce both tropospheric and antenna mechanical noises, which are the leading disturbances in two-way Ka-band radio links. For an operational test of this method, we applied the TDMC to Doppler data at X-band (7.2–8.4 GHz) from the Cassini spacecraft acquired during the Saturn tour phase of the mission. Although X-band links are generally dominated by the highly-variable interplanetary plasma noise and are not suitable for the TDMC, we found that, when local noises are particularly large at the two-way antenna, this technique may still lead to up to a factor-of-three noise reduction (at 60-s integration time) with respect to the two-way link. The TDMC can maximize the data quality during unique events, mainly planetary or satellite flybys (such as those considered in the Europa Clipper and JUICE missions), where the scientific results could be severely hampered by adverse conditions at the tracking station
Precision of Radio Science Instrumentation for Planetary Exploration
Radio Science techniques have been used for planetary exploration, space physics, and experiments addressing aspects of relativity on many deep space missions. Various Radio Science experiments are also planned for many future missions. This paper presents the noise processes in the Radio Science data acquired by the Deep Space Network and provides a detailed noise model for Doppler radio science experiments. The most sensitive instrumentation and experiments to date achieve fractional frequency fluctuation noise of 3E-15 at an integration time of 1000 seconds, corresponding to better than 1 micron per second velocity noise. Our noise model focuses on the Fourier range in the millihertz to 1 Hz, but we briefly discuss noise in lower frequency observations. We identify phenomena limiting current Doppler sensitivity and discuss prospects for significant sensitivity improvements