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Register a new userPulsar Navigation in the Solar System
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Jiang Dong
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The X-ray Navigation and Autonomous position Verification (XNAV) is tested which use the Crab pulsar under the Space Test Program that use starlight refraction. It provide the way that the spacecraft could autonomously determine its position with respect to an inertial origin. Now we analysis the sensitivity of the exist instrument and the signal process that use radio pulsar navigation and discuss the integrated navigation which use radio pulsar, then give the different navigation mission analysis and design process basically which include the space, the airborne, the ship and the land of the planet or the lunar. Our analysis show that we will have the stability profile (signal-to-noise is 5) that use a 2 meters antenna observe some strong sources of radio pulsar in 36 minutes which based on the todays technology. So the pulsar navigation can give the continuous position in deep space, hat means we can freedom fly successfully in the solar system use celestial navigation that include pulsar and traditional star sensor. It also can less or abolish the dependence to Global Navigation Satellite System (GNSS) which include GPS, GRONSS, Galileo and BeiDou et al.
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In-spiraling supermassive black holes should emit gravitational waves, which would produce characteristic distortions in the time of arrival residuals from millisecond pulsars. Multiple national and regional consortia have constructed pulsar timing arrays by precise timing of different sets of millisecond pulsars. An essential aspect of precision timing is the transfer of the times of arrival to a (quasi-)inertial frame, conventionally the solar system barycenter. The barycenter is determined from the knowledge of the planetary masses and orbits, which has been refined over the past 50 years by multiple spacecraft. Within the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), uncertainties on the solar system barycenter are emerging as an important element of the NANOGrav noise budget. We describe what is known about the solar system barycenter, touch upon how uncertainties in it affect gravitational wave studies with pulsar timing arrays, and consider future trends in spacecraft navigation.
The regularity of pulsar emissions becomes apparent once we reference the pulses times of arrivals to the inertial rest frame of the solar system. It follows that errors in the determination of Earths position with respect to the solar-system barycenter can appear as a time-correlated bias in pulsar-timing residual time series, affecting the searches for low-frequency gravitational waves performed with pulsar timing arrays. Indeed, recent array datasets yield different gravitational-wave background upper limits and detection statistics when analyzed with different solar-system ephemerides. Crucially, the ephemerides do not generally provide usable error representations. In this article we describe the motivation, construction, and application of a physical model of solar-system ephemeris uncertainties, which focuses on the degrees of freedom (Jupiters orbital elements) most relevant to gravitational-wave searches with pulsar timing arrays. This model, BayesEphem, was used to derive ephemeris-robust results in NANOGravs 11-yr stochastic-background search, and it provides a foundation for future searches by NANOGrav and other consortia. The analysis and simulations reported here suggest that ephemeris modeling reduces the gravitational-wave sensitivity of the 11-yr dataset; and that this degeneracy will vanish with improved ephemerides and with the longer pulsar timing datasets that will become available in the near future.
The laws of gravitation have been tested for a long time with steadily improving precision, leading at some moment of time to paradigmatic evolutions. Pursuing this continual effort is of great importance for science. In this communication, we focus on Solar System tests of gravity and more precisely on possible tests that can be performed with radio science observations (Range and Doppler). After briefly reviewing the current tests of gravitation at Solar System scales, we give motivations to continue such experiments. In order to obtain signature and estimate the amplitude of anomalous signals that could show up in radio science observables because of modified gravitational laws, we developed a new software that simulates Range/Doppler signals. We present this new tool that simulates radio science observables directly from the space-time metric. We apply this tool to the Cassini mission during its cruise from Jupiter to Saturn and derive constraints on the parameters entering alternative theories of gravity beyond the standard Parametrized Post Newtonian theory.
There is a vibrant and effective planetary science community in Canada. We do research in the areas of meteoritics, asteroid and trans-Neptunian object orbits and compositions, and space weather, and are involved in space probe missions to study planetary surfaces and interiors. For Canadian planetary scientists to deliver the highest scientific impact possible, we have several recommendations. Our top recommendation is to join LSST and gain access to the full data releases by hosting a data centre, which could be done by adding to the CADC, which is already highly involved in hosting planetary data and supporting computational modelling for orbital studies. We also support MSE, which can provide spectroscopy and thus compositional information for thousands of small bodies. We support a Canadian-led microsatellite, POEP, which will provide small body sizes by measuring occultations. We support the idea of piggybacking space weather instruments on other astronomical space probes to provide data for the space weather community. Many Canadian planetary scientists are involved in space probe missions, but through haphazard and temporary arrangements like co-appointments at US institutions, so we would like the community to support Canadian researchers to participate in these large, international missions.
The error in the Solar system ephemeris will lead to dipolar correlations in the residuals of pulsar timing array for widely separated pulsars. In this paper, we utilize such correlated signals, and construct a Bayesian data-analysis framework to detect the unknown mass in the Solar system and to measure the orbital parameters. The algorithm is designed to calculate the waveform of the induced pulsar-timing residuals due to the unmodelled objects following the Keplerian orbits in the Solar system. The algorithm incorporates a Bayesian-analysis suit used to simultaneously analyse the pulsar-timing data of multiple pulsars to search for coherent waveforms, evaluate the detection significance of unknown objects, and to measure their parameters. When the object is not detectable, our algorithm can be used to place upper limits on the mass. The algorithm is verified using simulated data sets, and cross-checked with analytical calculations. We also investigate the capability of future pulsar-timing-array experiments in detecting the unknown objects. We expect that the future pulsar timing data can limit the unknown massive objects in the Solar system to be lighter than $10^{-11}$ to $10^{-12}$ $M_{odot}$, or measure the mass of Jovian system to fractional precision of $10^{-8}$ to $10^{-9}$.
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