20 research outputs found
Determination of Redshifts for Selected IVS Sources. I
From observations with the 6-m BTA telescope at SAO RAS, we have determined
spectroscopic redshifts of seven optical objects whose coordinates coincide
with those of radio sources from the list of IVS (International VLBI Service
for Geodesy and Astrometry). When compared to radio data, the obtained spectra
and redshifts provide evidence for reliable identification of four observed
objects; the other three require further study. The distances to the sources
derived from our measurements will make it possible to refine the current
estimates for parameters of cosmological models based on proper motions of
these objects, which are determined from geodetic VLBI observations.Comment: 8 pp., submitted to Astrophysic
The Pioneer Anomaly
Radio-metric Doppler tracking data received from the Pioneer 10 and 11
spacecraft from heliocentric distances of 20-70 AU has consistently indicated
the presence of a small, anomalous, blue-shifted frequency drift uniformly
changing with a rate of ~6 x 10^{-9} Hz/s. Ultimately, the drift was
interpreted as a constant sunward deceleration of each particular spacecraft at
the level of a_P = (8.74 +/- 1.33) x 10^{-10} m/s^2. This apparent violation of
the Newton's gravitational inverse-square law has become known as the Pioneer
anomaly; the nature of this anomaly remains unexplained. In this review, we
summarize the current knowledge of the physical properties of the anomaly and
the conditions that led to its detection and characterization. We review
various mechanisms proposed to explain the anomaly and discuss the current
state of efforts to determine its nature. A comprehensive new investigation of
the anomalous behavior of the two Pioneers has begun recently. The new efforts
rely on the much-extended set of radio-metric Doppler data for both spacecraft
in conjunction with the newly available complete record of their telemetry
files and a large archive of original project documentation. As the new study
is yet to report its findings, this review provides the necessary background
for the new results to appear in the near future. In particular, we provide a
significant amount of information on the design, operations and behavior of the
two Pioneers during their entire missions, including descriptions of various
data formats and techniques used for their navigation and radio-science data
analysis. As most of this information was recovered relatively recently, it was
not used in the previous studies of the Pioneer anomaly, but it is critical for
the new investigation.Comment: 165 pages, 40 figures, 16 tables; accepted for publication in Living
Reviews in Relativit
From Clock Synchronization to Dark Matter as a Relativistic Inertial Effect
Lecture at BOSS2011 on relativistic metrology, on clock synchronization,
relativistic dynamics and non-inertial frames in Minkowski spacetime, on
relativistic atomic physics, on ADM canonical tetrad gravity in asymptotically
Minkowskian spacetimes, on the York canonical basis identifying the inertial
(gauge) and tidal degrees of freedom of the gravitational field, on the
Post-Minkowskian linearization in 3-orthogonal gauges, on the Post-Newtonian
limit of matter Hamilton equations, on the possibility to interpret dark matter
as a relativistic inertial effect connected with relativistic metrology (i.e.
clock synchronization) in Einstein GR.Comment: 90 pages. Lecture at BOSS201