scholarly journals DIVISION I / COMMISSION 8 / WORKING GROUP DENSIFICATION OF THE OPTICAL REFERENCE FRAME

2008 ◽  
Vol 4 (T27A) ◽  
pp. 34-36
Author(s):  
Norbert Zacharias ◽  
Imants Platais ◽  
William F. van Altena ◽  
Beatrice Bucciarelli ◽  
Thomas E. Corbin ◽  
...  
Keyword(s):  
Reference Frame ◽  
San Francisco ◽  
Working Group ◽  
Web Site ◽  
Division I ◽  
General Assembly ◽  
Optical Reference ◽  
Celestial Reference Frame ◽  
The Web

A continuation of this WG was voted for at the IAU GA 2006 in Prague. The International Celestial Reference Frame (ICRF) is defined by the positions of 212 distant quasars at radio wavelengths. The primary, optical reference frame is the Hipparcos Celestial Reference Frame (HCRF), which is the Hipparcos Catalog without astrometric ‘problem’ stars (in: H. Rickman (ed.) 2001, Proceedings IAU XXIV General Assembly, Transactions IAU XXIVB (San Francisco: ASP), Resolution B1.2). The Tycho-2 catalog with its 2.5 million brightest stars forms the first step in the densification of the optical reference frame. However, the limiting magnitude of about V = 12 of the Tycho-2 catalog is not sufficient for most applications in astronomy and the goal of this IAU Working Group is to further extend the grid of highly accurate positions and motions toward more and fainter stars. The web site of this WG is at <ad.usno.navy.mil/dens_wg/>.

scholarly journals Extension of the Optical Reference Frame:Space Based

1998 ◽  
Vol 11 (1) ◽  
pp. 304-306
Author(s):  
S. Röser
Keyword(s):  
Reference Frame ◽  
General Assembly ◽  
Radio Sources ◽  
Practical Realization ◽  
The Earth ◽  
Optical Reference ◽  
Hipparcos Catalogue ◽  
Optical Wavelengths ◽  
Celestial Reference Frame ◽  
23Rd General

At its 23rd General Assembly, Kyoto 1997, the IAU decided that the International Celestial Reference Frame (ICRF) should be defined by the positions of 608 compact extragalactic radio sources (Ma & Feissel 1997), with the Hipparcos Catalogue (ESA 1997) being its practical realization at optical wavelengths. Although the Hipparcos instrument was unable to observe the defining sources of the ICRF directly in the optical regime, it is linked to the ICRF via a number of auxiliary observations (Kovalevsky et al. 1997). The Hipparcos Catalogue is the first celestial reference frame which is constructed from observations not made from the surface of the Earth.

scholarly journals Contributions of the USNO to the Optical Reference Frame

1997 ◽  
Vol 165 ◽  
pp. 453-462
Author(s):  
Thomas Corbin
Keyword(s):  
Reference Frame ◽  
Reverse Order ◽  
Good Working ◽  
Working Definition ◽  
Optical Reference ◽  
Definition Of ◽  
Celestial Sphere ◽  
Celestial Reference Frame ◽  
Frame Rigidity ◽  
Zero Points

A good, working definition of what is required in a celestial reference frame is that it must provide observable fiducial points on the Celestial Sphere with internally consistent positions that are referred to coordinate axes of known direction. In reality, this statement gives the goals in the reverse order from that in which each must be achieved, the definition of the axes, or zero points of the system give orientation to the observationally defined set of primary objects whose coordinate relation to each other must give the frame rigidity. Finally, the primary objects are generally too sparse to define the frame within areas of less than tens of square degrees, and so additional objects must be related to the frame to increase the density. This last step is required to make the frame useful for most observational applications.

scholarly journals Towards the Definition of a Unified Celestial Optical/Radio Reference Frame

1988 ◽  
Vol 129 ◽  
pp. 317-318
Author(s):  
K. J. Johnston ◽  
J. Russell ◽  
Ch. de Vegt ◽  
J. Hughes ◽  
D. Jauncey ◽  
...  
Keyword(s):  
Reference Frame ◽  
Reference Frames ◽  
Radio Observations ◽  
Minimum Density ◽  
Optical Reference ◽  
Definition Of ◽  
Celestial Reference Frame

An almost inertial celestial reference frame based upon extragalactic sources is in the process of being established. This reference frame is to be global with a minimum density of one source/100 square degrees. The source positions will be based upon radio observations and will allow optical reference frames to be related to this frame at the 0.03 arc second level.

scholarly journals Division I Working Group on Future Development of Ground-Based Astrometry

2005 ◽  
Vol 1 (T26A) ◽  
pp. 55-58
Author(s):  
Magda Stavinschi
Keyword(s):  
Future Development ◽  
Working Group ◽  
Web Site ◽  
Division I ◽  
Division 1 ◽  
The Future

AbstractThe working group “The Future Development of Ground-Based Astrometry” of the IAU Division 1, founded in 2000, continued its activity for the last triennium. Part of its results—meetings or programs—are presented here. The FDGBA web site is http://www.astro.ro/wg

scholarly journals DIVISION I-III / WORKING GROUP CARTOGRAPHIC COORDINATES AND ROTATIONAL ELEMENTS

2008 ◽  
Vol 4 (T27A) ◽  
pp. 68-68 ◽  
Author(s):  
Brent A. Archinal ◽  
P. Kenneth Seidelmann ◽  
Michael F. A'Hearn ◽  
Edward L. Bowell ◽  
Albert R. Conrad ◽  
...  
Keyword(s):  
Solar System ◽  
Working Group ◽  
Business Meeting ◽  
Division I ◽  
General Assembly ◽  
Cartographic Coordinates ◽  
Solar System Bodies

The IAU/IAG Working Group on Cartographic Coordinates & Rotational Elements published its (2006) triennial report containing current recommendations for models for solar system bodies (Seidelmann et al. 2007). P. Kenneth Seidelmann stepped down as chairperson and B. A. Archinal was elected chairperson at the Working Group business meeting that took place at the IAU XXVI General Assembly in Prague in 2006.

scholarly journals DIVISION I / WORKING GROUP ASTROMETRY BY SMALL GROUND-BASED TELESCOPES

2008 ◽  
Vol 4 (T27A) ◽  
pp. 63-67
Author(s):  
William Thuillot ◽  
Magdalena Stavinschi ◽  
Alexander H. Andrei ◽  
Jean-Eudes Arlot ◽  
Marcelo Assafin ◽  
...  
Keyword(s):  
Working Group ◽  
Present Report ◽  
Division I ◽  
General Assembly ◽  
Binary Asteroids ◽  
Small Bodies ◽  
Observation Network ◽  
Set Up ◽  
Natural Satellites

At the IAU XXVI General Assembly in 2006, the Division I decided to create the Working Group on Astrometry by Small Ground-Based Telescopes (WG-ASGBT). Its scientic goals are to foster the follow-up of small bodies detected by the large surveys including the NEOs; to set-up a dedicated observation network for the follow-up of objects which will be detected by Gaia; to contribute to the observation campaigns of the mutual events of natural satellites, stellar occultations, and binary asteroids; and to encourage teaching astrometry for the next generation. The present report gives the main activities carried out in these areas with small telescopes (diameter less than 2m).

scholarly journals Dense optical reference frames: UCAC and URAT

2007 ◽  
Vol 3 (S248) ◽  
pp. 310-315
Author(s):  
N. Zacharias
Keyword(s):  
Reference Frame ◽  
Focal Plane ◽  
Reference Frames ◽  
Field Of View ◽  
Radio Sources ◽  
Proper Motions ◽  
Naval Observatory ◽  
Optical Reference ◽  
Celestial Reference Frame ◽  
The U.S

AbstractA series of ground-based, dedicated astrometric, observational programs have been performed or are in preparation which provide a dense and accurate optical reference frame. Integral to all these programs are new observations to link the Hipparcos Celestial Reference Frame (HCRF) to the International Celestial Reference Frame (ICRF), based on compact, extragalactic radio sources.The U.S. Naval Observatory CCD Astrograph Catalog (UCAC) 3rd release is in preparation. A pixel re-reduction is in progress to improve astrometric and photometric accuracy as well as completeness of this all-sky reference catalog to 16th magnitude. Optical counterparts of ICRF radio sources have been observed with 0.9-meter telescopes contemporaneously. Scanning of over 5000 early-epoch astrograph plates on StarScan has been completed. These data will improve the proper motions of stars in the 10 to 14 mag range for the UCAC3 release.A 111 million-pixel CCD was successfully fabricated in 2006 and test observations at the USNO astrograph are underway. Four of such detectors will be used for the USNO Robotic Astrometric Telescope (URAT) focal plane assembly. Phase I of URAT will use the astrograph to reach 18th magnitude, while the new 0.85-meter telescope with a 4.5 deg diameter field of view will reach 21st magnitude. The URAT primary mirror has been fabricated.

scholarly journals Extension of The Optical Reference Frame: Ground Based

1998 ◽  
Vol 11 (1) ◽  
pp. 300-303
Author(s):  
N. Zacharias
Keyword(s):  
Reference Frame ◽  
Radio Sources ◽  
Proper Motions ◽  
Magnitude Range ◽  
Optical Reference ◽  
Hipparcos Catalogue ◽  
Optical Wavelengths ◽  
The Mean ◽  
Celestial Reference System ◽  
Celestial Reference Frame

The International Celestial Reference Frame (ICRF) is realized by the positions of 608 compact extragalactic radio sources (Ma & Feissel 1997) with milliarcsecond (mas) and sub-mas accuracy, all being on the same system, the International Celestial Reference System (ICRS). The Hipparcos Catalogue (ESA 1997) is the practical realization of the ICRF at optical wavelengths, giving accurate positions (≈ 1 mas) at the mean epoch of 1991.25 and proper motions (≈ 1 mas/yr) for 117995 stars. This is about 2.5 stars per square degree, most being in the 7 to 9 magnitude range and a few as faint as 12. However, for many astronomical applications the Hipparcos Catalogue is not dense enough and does not reach faint enough magnitudes. The Tycho Catalogue (ESA 1997) provides accurate positions (≈ 25 mas) for about one million stars to magnitude 11, but lacks precise proper motions. Ground-based observations are an efficient way to complement the Hipparcos mission and to extend the optical reference frame to fainter magnitudes and yield a denser grid of astrometric standard stars. New reductions of early epoch photographic data will be used to provide highly accurate proper motions for stars to about magnitude 12. Current and new observational projects will extend the optical reference frame to even fainter magnitudes.

scholarly journals DIVISION I / WORKING GROUP NOMENCLATURE FOR FUNDAMENTAL ASTRONOMY

2007 ◽  
Vol 3 (T26B) ◽  
pp. 74-78
Author(s):  
Nicole Capitaine ◽  
Alexandre H. Andrei ◽  
Mark R. Calabretta ◽  
Véronique Dehant ◽  
Toshio Fukushima ◽  
...  
Keyword(s):  
Working Group ◽  
Division I ◽  
General Assembly ◽  
Fundamental Astronomy

The IAU Division I Working Group onNomenclature for Fundamental Astronomy(NFA) was established by the IAU XXV General Assembly with the task of providing proposals for new nomenclature associated with the implementation of the IAU XXIV GA resolutions (2000) and to make related educational efforts for bringing the issue to the notice of scientists in the community.

Evaluating the Web-Site & Digital Environment of Airbnb

2019 ◽  
Vol 9 (3) ◽  
pp. 49-69
Author(s):  
Sidhhant Kapai
Keyword(s):  
San Francisco ◽  
Web Site ◽  
Lodging Industry ◽  
Digital Environment ◽  
Brand Recognition ◽  
A Company ◽  
The Web ◽  
New Framework ◽  
Current Practices

What began as a company in San Francisco to aid unemployed Brian Chesky and Joe Gebbia pay their housing rent and earn some extra cash, Airbnb today has disrupted and revolutionized the entire lodging industry by making provisions for additional rooms at the country's contemporaneous travel locations/destinations during peak seasons when hotel rooms are sold out and the remaining ones are available at skyrocketing prices In the following report, the current practices which have been implemented by Airbnb within the digital domain to enhance their brand recognition are discussed. The predominant sway of Airbnb's digital environment in a conventional, as well as new framework, have been previewed pertaining to focus on guest association and measurement of outcomes in digital interfaces.

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