Possible Relativistic Definitions of Parallax, Proper Motion and Radial Velocity

Abstract

The accuracy of future space-based astrometric observations is expected to attain a level of 1 microarcsecond. In this paper, the authors briefly describe a relativistic model of space-based optical positional observations valid at a high level of accuracy, and suggest definitions of parallax, proper motion, and radial velocity compatible with general relativity at a level of 1 microarcsecond. Although the definitions are quite simple (see Klioner and Kopeikin, 1992), their interpretation at such a high level of accuracy is rather tricky. Parallax and proper motion are no longer two independent effects. Second-order effects due to parallax and proper motion as well as the effects resulting from interaction between the two effects are important. Moreover, parallax, proper motion, and other astrometric parameters are defined operationally and have some meaning only within the particular model of relativistic reductions chosen. That is why the whole relativistic model of observations must be considered. It also is clear that to convert observed proper motion and radial velocity into true tangential and radial velocities of the observed object, additional information is required. Since that information is not always available, the concepts of "apparent proper motion," "apparent tangential velocity," and "apparent radial velocity" are suggested. These concepts represent useful information about the observed object and should be distinguished from "true tangential velocity" and "true radial velocity." Definitions of all these concepts are discussed below. Throughout the paper the following constraints on the various parameters are used to decide if a particular effect should be retained to attain the accuracy of 1 microarcsecond: (1) barycentric position of the observer, and (2) barycentric velocity of the observer.

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Document Details

Document Type
Technical Report
Publication Date
Mar 01, 2000
Accession Number
ADA435884

Entities

People

  • S. Klioner

Tags

Communities of Interest

  • Space

DTIC Thesaurus Topics

  • Abstracts
  • Accuracy
  • Artificial Satellites
  • Binary Stars
  • Coordinate Systems
  • General Relativity
  • Information Operations
  • Observation
  • Observatories
  • Observers
  • Quadrupole Moment
  • Radial Velocity
  • Solar System
  • Space Based
  • Space Stations
  • Time Dependence
  • Time Intervals

Fields of Study

  • Physics

Readers

  • Astronomy and Astrophysics.
  • Control Systems Engineering.
  • Vision Science/Vision Psychology/Cognitive Neuroscience.

Technology Areas

  • Space