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Space-geodetic measurement systems are capable of determining: (1) a terrestrial, body-fixed reference frame defined in practice by the stated positions and secular motions of a set of observing stations, (2) a celestial, space-fixed reference frame defined in practice by the stated locations of celestial objects, and (3) the rotation parameters linking these two frames together.
The expected motion characteristics of the real earth are systematically analysed based on available dynamical theories for the rigid model, the elastic earth model and the earth model with liquid core. The various axes which are implicit in the dynamical theories are investigated regarding observability on the basis of astronomical observations and suitability for defining reference directions. The observational insignificance of the ''diurnal polar motion'' is demonstrated. A special effort is made to clarify customarily used terminology.
The International VLBI Service for Geodesy & Astrometry (IVS) regularly provides high-quality data to produce Earth Orientation Parameters (EOP), and for the maintenance and realization of the International Terrestrial and Celestial Reference Frames, ITRF and ICRF. The first iteration of the celestial reference frame (CRF) at radio wavelengths, the ICRF1, was adopted by the International Astronomical Union (IAU) in 1997 to replace the FK5 optical frame. Soon after, the IVS began official operations and in 2009 there was a significant increase in data sufficient to warrant a second iteration of the CRF, ICRF2. The most recent ICRF3, was adopted by the IAU in 2018. However, due to the geographic distribution of observing stations being concentrated in the Northern hemisphere, CRFs are generally weaker in the South due to there being fewer Southern Hemisphere observations. To increase the Southern Hemisphere observations, and the density, precision of the sources, a series of deep South observing sessions was initiated in 1995. This initiative in 2004 became the IVS Celestial Reference Frame Deep South (IVS-CRDS) observing program. This paper covers the evolution of the CRDS observing program for the period 1995 to 2021, details the data products and results, and concludes with a summary of upcoming improvements to this ongoing project.
Venus rotation, discussing radar and optical and UV photography observations
The telescope system was designed as a multi-user facility for observations of celestial objects at infrared wavelengths, where ground-based observations are difficult or impossible due to the effects of telluric atmospheric absorption. The telescope is mounted in a Lear jet model 24B which typically permits 70 min. of observing per flight at altitudes in excess of 45,000 ft (13 km). Telescope system installation is discussed, along with appropriate setup and adjustment procedures. Operation of the guidance system is also explained, and checklists are provided which pertain to the recommended safe operating and in-flight trouble-shooting procedures for the equipment.
Aircraft stabilization for solar eclipse observation, emphasizing use of autopilot for maximum control
Analytical methods and observational requirements for interpretation of asteroid distributions
Variable polarization of magnetic star HD 71866 studied by observational program between January and April 1966
Optical polarimetric observations of quasi-stellar objects
Cosmological model for universe based on astronomical observations and validity of einstein theory and existing laws of physics
A clearly established diffuse celestial gamma-ray component was seen by SAS-2 above 35 MeV, after examining several regions of the sky at different latitudes, including the north celestial pole. For energies above 100 MeV the gamma ray results are consistent with an equation of the form I(b)=C1+C2/sin b with the second term being dominant, suggesting that the radiation above 100 MeV comes largely from the local regions of the galactic disk. Between 35 and 100 MeV, a similar equation is also a reasonable representation of the data, but here the two terms are comparable, with the first, or isotropic term, actually being the larger one. In addition to indicating that the diffuse radiation is partially galactic, these results imply a steepness for the energy spectrum of the diffuse isotropic component which places significant constraints on possible theoretical models of this radiation.
Relation between theoretical and observational models of atmospheric properties and changes during decreasing solar activity
Three distinct coordinate systems are required in the interpretation of the lunar range observations: a celestial frame and two-body-fixed frames. However, there is no coordinate system that is uniquely, or even preferentially, related to the observations themselves. Effectively, one specifies the coordinate systems by the procedures used in data reduction and parameter improvement. Each of the three systems affects the others in some way, and internal inconsistencies are quite possible. The discussion examines some of the more important aspects of this problem.
Surface properties, temperature effects, cooling behavior, and observability of neutron stars
Photoelectric observations of 27 long period variable stars on UBV photometric system
Observational study of lunar visible emission according to study of line depths
Red shifts of radio galaxies observed spectroscopically with 120-inch telescope, using prime focus and image tube