scholarly journals Independent analysis of γδ data of ILS and INDLS catalogs to obtain the spin of the bright Gaia DR2 reference frame

2021 ◽  
pp. 2-2
Author(s):  
G. Damljanovic ◽  
M. Stojanovic ◽  
J. Aleksic
Keyword(s):  
Reference Frame ◽  
Least Squares Method ◽  
Relative Rotation ◽  
V Band ◽  
Independent Analysis ◽  
Standard Distribution ◽  
Long Time ◽  
Celestial Reference System ◽  
G 13 ◽  
Gaia Dr2

The Gaia DR2 reference frame should be without relative rotation to the quasars (QSOs) and consistent with the International Celestial Reference System (ICRS). For the faint part of DR2 (stars with Gaia magnitude G ? 16) that task was done via Gaia's observations of QSOs (G ? 17 mag), but the bright DR2 (G ? 13 mag) is difficult to validate and it rotates relative to the faint DR2 at rate of the order of 0.1 mas/yr. Very bright DR2 stars (G ? 6 mag) mostly have inferior astrometry. Here, the aim is to determine two spin components (?X and ?Y) of the bright DR2 using International Latitude Service (ILS, for 387 stars) and independent latitude stations (INDLS, for 682 stars) catalogs of proper motion in declination ??; both are referred to the Hipparcos reference frame and their stars are mostly from 4 to 8 mag in the V-band (critical part of DR2). Also, using the new Hipparcos (NHIP) values ?? for ILS and INDLS stars, we can see that the merit of the ILS and INDLS is the long time baseline (?t ? 90 years) important for ?? because the standard deviation of ?? is opposite to ?t. Applying the least squares method (LSM) to the differences of ?? between two catalogs (ILS-DR2, INDLS-DR2, etc.), our results support the mentioned spin. The 3? criterion and Tukey's fences method were used to reject some stars, the Abbe criterion to explain the variability in ILS-DR2 and other ?? differences, and the Shapiro-Wilk test to check the standard distribution of differences. The obtained ?Y is significant at the 2 ? level, and the ILS and INDLS catalogs could be useful for validation of the bright reference frame of Gaia DR2.

scholarly journals The Celestial Reference System in Relativistic Framework

1990 ◽  
Vol 141 ◽  
pp. 99-110
Author(s):  
Han Chun-Hao ◽  
Huang Tian-Yi ◽  
Xu Bang-Xin
Keyword(s):  
Coordinate System ◽  
Reference Frame ◽  
Reference System ◽  
Light Deflection ◽  
Coordinate Systems ◽  
Definition Of ◽  
Celestial Sphere ◽  
Celestial Reference System ◽  
Relativistic Framework

The concept of reference system, reference frame, coordinate system and celestial sphere in a relativistic framework are given. The problems on the choice of celestial coordinate systems and the definition of the light deflection are discussed. Our suggestions are listed in Sec. 5.

scholarly journals Relativistic Effects in the Rotation of Jupiter’s Inner Satellites

2020 ◽  
Vol 55 (3) ◽  
pp. 118-129
Author(s):  
Vladimir V. Pashkevich ◽  
Andrey N. Vershkov
Keyword(s):  
Solar System ◽  
Reference Frame ◽  
Central Body ◽  
Relativistic Effects ◽  
Euler Angles ◽  
Coordinate Systems ◽  
Geodetic Precession ◽  
Long Time ◽  
Celestial Reference Frame ◽  
Jupiter’S Satellites

AbstractThe most significant relativistic effects (the geodetic precession and the geodetic nutation, which consist of the effect of the geodetic rotation) in the rotation of Jupiter’s inner satellites were investigated in this research. The calculations of the most essential secular and periodic terms of the geodetic rotation were carried out by the method for studying any bodies of the solar system with long-time ephemeris. As a result, for these Jupiter’s satellites, these terms of their geodetic rotation were first determined in the rotational elements with respect to the International Celestial Reference Frame (ICRF) equator and the equinox of the J2000.0 and in the Euler angles relative to their proper coordinate systems. The study shows that in the solar system there are objects with significant geodetic rotation, due primarily to their proximity to the central body, and not to its mass.

Precise positions of Triton in 2010–2014 based on Gaia-DR2

2021 ◽  
Author(s):  
Huiyan Zhang ◽  
Yong Yu ◽  
Dan Yan ◽  
Kai Tang ◽  
Rongchuan Qiao
Keyword(s):  
Solar System ◽  
Physical Properties ◽  
Orbital Evolution ◽  
Astronomical Observatory ◽  
Standard Errors ◽  
Origin And Evolution ◽  
Important Target ◽  
Long Time ◽  
Gaia Dr2

Abstract With unique orbital and physical characteristics, Triton is a very important target since it may contain information of the origin and evolution of the solar system. Besides space explorations, ground-based observations over long time also play key role on research of Triton. High-precision positions of Triton obtained from ground telescopes are of great significance for studying its orbital evolution and inverting the physical properties of Neptune. As a long-term observational target, Triton has been observed by the 1.56 m telescope of Shanghai Astronomical Observatory since 1996. In this paper, based on our AAPPDI software and with Gaia DR2 as the reference catalogue, 604 positions of Triton during 2010-2014 are calculated, with standard errors of $19mas-88mas$. A comparison between our results and the ephemeris (DE431+nep096) is also given.

scholarly journals Long-term trends of air pollutant concentrations in Poland

2019 ◽  
Vol 116 ◽  
pp. 00027
Author(s):  
Szymon Hoffman
Keyword(s):  
Least Squares Method ◽  
Monitoring Network ◽  
Air Pollutant ◽  
Pollutant Concentrations ◽  
Hourly Data ◽  
Long Time ◽  
Long Term Trends ◽  
Air Pollutant Concentrations ◽  
Term Data

The assessment of changes in air pollution quality for 4 selected sites in Southern and Central Poland was presented in this paper. The evaluation was based on the sets of long-term data, recorded by the state air monitoring network. Concentrations of O3, PM10, SO2, NOx, and CO, were considered. The basis for the calculations were 12-year time series of hourly concentrations. Using the hourly data, the monthly averages were calculated to illustrate seasonal changes of pollutant concentrations. Linear trends were adjusted to the concentration courses with the least squares method. Long-time trends were calculated for each pollutant separately. Based on the analysis of the trend lines slopes, risks those may arise in the future were identified.

scholarly journals Gaia Data Release 2

2018 ◽  
Vol 616 ◽  
pp. A14 ◽  
Author(s):  
◽  
F. Mignard ◽  
S. A. Klioner ◽  
L. Lindegren ◽  
J. Hernández ◽  
...  
Keyword(s):  
Reference Frame ◽  
Large Scale ◽  
Point Sources ◽  
Vector Spherical Harmonics ◽  
Homogeneous Set ◽  
Rotating Reference Frame ◽  
Optical Domain ◽  
Celestial Reference System ◽  
Celestial Reference Frame ◽  
Cross Match

Context. The second release of Gaia data (Gaia DR2) contains the astrometric parameters for more than half a million quasars. This set defines a kinematically non-rotating reference frame in the optical domain. A subset of these quasars have accurate VLBI positions that allow the axes of the reference frame to be aligned with the International Celestial Reference System (ICRF) radio frame. Aims. We describe the astrometric and photometric properties of the quasars that were selected to represent the celestial reference frame of Gaia DR2 (Gaia-CRF2), and to compare the optical and radio positions for sources with accurate VLBI positions. Methods. Descriptive statistics are used to characterise the overall properties of the quasar sample. Residual rotation and orientation errors and large-scale systematics are quantified by means of expansions in vector spherical harmonics. Positional differences are calculated relative to a prototype version of the forthcoming ICRF3. Results. Gaia-CRF2 consists of the positions of a sample of 556 869 sources in Gaia DR2, obtained from a positional cross-match with the ICRF3-prototype and AllWISE AGN catalogues. The sample constitutes a clean, dense, and homogeneous set of extragalactic point sources in the magnitude range G ≃ 16 to 21 mag with accurately known optical positions. The median positional uncertainty is 0.12 mas for G < 18 mag and 0.5 mas at G = mag. Large-scale systematics are estimated to be in the range 20 to 30 μas. The accuracy claims are supported by the parallaxes and proper motions of the quasars in Gaia DR2. The optical positions for a subset of 2820 sources in common with the ICRF3-prototype show very good overall agreement with the radio positions, but several tens of sources have significantly discrepant positions. Conclusions. Based on less than 40% of the data expected from the nominal Gaia mission, Gaia-CRF2 is the first realisation of a non-rotating global optical reference frame that meets the ICRS prescriptions, meaning that it is built only on extragalactic sources. Its accuracy matches the current radio frame of the ICRF, but the density of sources in all parts of the sky is much higher, except along the Galactic equator.

Gaia DR2: orbit improvement based on new debiasing of asteroid astrometry

2020 ◽  
Author(s):  
Paolo Tanga ◽  
Federica Spoto ◽  
Ferreira Joao ◽  
Machado Pedro
Keyword(s):  
Reference Frame ◽  
Spatial Scales ◽  
Field Of View ◽  
Systematic Bias ◽  
Proper Motions ◽  
Imaging Device ◽  
Celestial Sphere ◽  
Orbit Improvement ◽  
Gaia Dr2 ◽  
Very High

&lt;p&gt;&lt;strong&gt;Gaia DR2, validating the debiasing of asteroid astrometry by orbit improvement&lt;/strong&gt;&lt;/p&gt; &lt;p&gt;The optimal exploitation of asteroid astrometry is seminal at many tasks such as the monitoring of impact risks by potentially hazardous asteroids, and the measurement of subtle dynamical effects. These can include, most notably, the Yarkovsky thermal recoil force or perturbations due to other asteroids.&lt;/p&gt; &lt;p&gt;The Gaia mission has published astrometry with very high accuracy for 14.099 asteroids in the Data Release 2 (DR2), and about 10 times more are coming in DR3 (end 2021). The level of accuracy of Gaia is unprecedented, reaching 1 mas or better for each epoch, but it deserves unprecedented care to be exploited.&lt;br /&gt;&amp;#160;&lt;br /&gt;In particular, most archival data (astrometry available at the Minor Planet Center) are the result of a calibration with respect to pre-Gaia catalogues, that are often affected by local systematic errors. Such errors have different possible sources. They can be the result of the tiling of the celestial sphere by a imaging device, whose field of view presents some residual distortion in its astrometric reduction. There can also be effects related to the coupling of two different catalogs, distant in time, used to derive proper motions. Eventually, the adopted reference frame can also introduce other effects.&lt;/p&gt; &lt;p&gt;As it has been documented several times in literature such systematic bias, that can vary on spatial scales of a few degrees or less, can also be function of other parameters, such as the magnitude range considered (different bias affect stars of different brightness).&amp;#160;&lt;/p&gt; &lt;p&gt;To take into account these effects and apply the required corrections, we developed a completely new bias correction computation around on the position of single asteroid observations, instead of the classical approach of computing corrections on fixed grid for each catalogue. Despite being much more time-consuming, our approach allows us to reach a full flexibility on effects related to the field of view size of single surveys, magnitude limit and also epoch-dependent variations. We also implement corrections to the reference frame rotation detected for bright stars (V&lt;12) in Gaia DR2 (Lindegren 2020) necessary to obtain a full consistency.&lt;/p&gt; &lt;p&gt;After having completed the debiasing of astrometry archived at MPC for all asteroids in Gaia DR2, we have run an orbit improvement procedure for all of them, that also exploits a refined error model.&amp;#160;We illustrate here the results of our processing, in particular investigating the improvement in the ephemeris uncertainty, and the perfomance of the debiasing.&lt;br /&gt;&amp;#160;&lt;/p&gt;

scholarly journals Common Pedagogical Issues with De Broglie Waves: Moving Double Slits, Composite Mass, and Clock Synchronization

2015 ◽  
Vol 2015 ◽  
pp. 1-8
Author(s):  
Robert L. Shuler
Keyword(s):  
Special Relativity ◽  
Reference Frame ◽  
Kinematic Analysis ◽  
Clock Synchronization ◽  
Pedagogical Issues ◽  
De Broglie Waves ◽  
Independent Analysis ◽  
Electron Interference ◽  
Similarity And Difference ◽  
Double Slit

This paper addresses gaps identified in pedagogical studies of how misunderstanding of De Broglie waves affects later coursework and presents a heuristic for understanding the De Broglie frequency of composite. De Broglie’s little known derivation is reviewed with a new illustration based on his description. Simple techniques for reference frame independent analysis of a moving double slit electron interference experiment are not previously found in any literature and cement the concepts. Points of similarity and difference between De Broglie and Schrödinger waves are explained. The necessity of momentum, energy, and wavelength changes in the electrons in order for them to be vertically displaced in their own reference frame is shown to be required to make the double slit analysis work. A relativistic kinematic analysis of De Broglie frequency is provided showing how the higher De Broglie frequency of moving particles is consistent with Special Relativity and time dilation and that it demonstrates a natural system which obeys Einstein’s clock synchronization convention of simultaneity and no other. Students will be better prepared to identify practical approaches to solving problems and to think about fundamental questions.

scholarly journals Comparison of proper motions in declination for 387 Gaia DR2 and HIPPARCOS stars from ILS observations over many decades

2019 ◽  
Vol 631 ◽  
pp. A145 ◽  
Author(s):  
G. Damljanović ◽  
F. Taris
Keyword(s):  
Reference Frame ◽  
Least Squares Method ◽  
Accurate Determination ◽  
European Space Agency ◽  
Original Method ◽  
Special Focus ◽  
Random Errors ◽  
Proper Motions ◽  
Single Star ◽  
Comparison Results

Context. The second solution of the Gaia catalog, which has been available since April 2018, plays an important role in the realization of the future Gaia reference frame. Since 1997, the reference frame has been materialized by the optical HIPPARCOS positions of about 120 000 stars. The HIPPARCOS has been compared with and linked to the International Celestial Reference Frame (ICRF). The ICRF is materialized by means of the radio positions of extragalactic sources using very large baseline interferometry observations. Both, the HIPPARCOS and Gaia missions belong to the European Space Agency, and it is important to note that the Gaia catalog is going to replace the HIPPARCOS catalog. Aims. It has been shown that the International Latitude Service zenith telescope data pertaining to ground-based surveys that span a time baseline of about 80 yr, and which are also key when measuring proper motions, could be useful for the accurate determination of μδ for 387 ILS stars. Therefore, in this study we aim first to reduce these stars to the HIPPARCOS reference system; second, to made our original catalog of μδ, which we refer to as the ILS catalog, for these 387 bright stars; third, to present comparison results of the four catalogs by pairs (the ILS, HIPPARCOS or HIP, new HIPPARCOS or NHIP, and Gaia DR2); and fourth, to analyze the differences in μδ between pairs of catalogs to characterize the μδ errors for these catalogs with a special focus on the Gaia DR2 and ILS catalogs. Methods. At seven ILS sites around the world at latitude 39.°1, a set of seven telescopes was used to monitor the latitude variation via observations of the same stars for about 80 yr. Here, the inverse task was applied to improve μδ values of the 387 HIPPARCOS stars using the previously mentioned observations. Due to the specific Horrebow-Talcott method of the measured star pair, it is difficult to determine μδ for each single star. However, we achieved this by developing the original method and in combination with the HIPPARCOS data. We used the previously developed least squares method and formula to determine the coefficients, which describe the systematic part of differences in μδ between the pairs of catalogs. Results. We calculated the coefficients with the aforementioned formula (in line with the coordinates, stellar magnitude, and color index of every star) to compare ILS, HIP, NHIP, and Gaia DR2 data of μδ against each other by using the set of 387 stars. The presented differences of μδ show that the systematic errors in the four catalogs are nearly at the same level of 0.1 mas yr−1. This means that the DR2 and ILS μδ values are in good agreement with each other, and with values from the HIPPARCOS and new HIPPARCOS catalogs. Also, the random errors of differences are small ones; they are near 1 mas yr−1 for ILS-HIP and ILS-NHIP, and about 2 mas yr−1 for ILS-DR2, HIP-DR2, and NHIP-DR2. It is important to note that there is a similar level of proper motion formal errors in HIPPARCOS and new HIPPARCOS catalogs.

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