*************************************************************************** Gazette IERS Gazette IERS Gazette IERS Gazette IERS Gazette ________________________________________ No 44, 20 September, 1999 / _________________________________/ Contact: iers@obspm.fr ftp: hpiers.obspm.fr (145.238.100.28) WWW: http://hpiers.obspm.fr *************************************************************************** FIRST ANNOUNCEMENT International Astronomical Union International Earth Rotation Service U.S. Naval Observatory TOWARDS MODELS AND CONSTANTS FOR SUB-MICROARCSECOND ASTROMETRY IAU Colloquium 180 27-31 March 2000 U.S. Naval Observatory, Washington, DC, USA http://aa.usno.navy.mil/colloq180/ ANNOUNCEMENT The adoption of the International Celestial Reference System (ICRS) by the XXIII General Assembly of the IAU provides an improved reference system for positional astronomy. However, the specifications of the ICRS remain incomple- te for Earth-based observing systems because the system cannot be accurately propagated to arbitrary epochs using currently adopted algorithms for Earth orientation. Current models for precession and nutation, specified by the IAU in the early 1980s, are now known to have deficiencies that are significant for many modern applications, such as ground-based interferometry. Moreover, a new set of values of fundamental astronomical constants (parameters) is needed consistent with ICRS accuracy and expressed in units that are properly specified, in a relativistic sense, in the barycentric and geocentric refe- rence systems defined by previous IAU resolutions. Procedures for dealing with the small offsets of the ICRS from the system defined by the kinematics of Earth rotation must also be specified for those observations sensitive to it. Furthermore, the needed change in the precession/nutation model will require reconsideration of the definition of Universal Time. The reports of the IAU Working Groups addressing these issues will be presen- ted and discussed. The major purpose of the colloquium is to prepare resolu- tions for consideration by a Joint Discussion at the XXIV IAU General Assembly that will complete the specification of the ICRS. These resolutions will, in effect, specify definitions, standard algorithms, and parameters that link observable quantities with reference coordinates within the ICRS system. Specifically to be recommended are definitions of the celestial ephemeris pole and celestial ephemeris origin, an improved precession/nutation theory, and a new set of standard values for astronomical constants. This colloquium will also discuss future requirements of the celestial refe- rence system that are necessary to support present and planned high-precision astrometric programs. These programs include ground-based observations currently made in the optical, IR, and radio regimes using both single- aperture telescopes and interferometers. Future proposed space missions using or providing accurate astrometry include DIVA, FAME, SIM, Darwin, NGST, Terrestrial Planet Finder, and GAIA. The microarcsecond-level of precision anticipated for future observational systems demands improved models at all levels of analysis. These improved models are likely to require increased attention to the definitions of the various reference frames involved and the transformations between them, within the relativistic framework previously established by the IAU. The specification of new models and constants will also contribute to many other aspects of astronomy, astrophysics, geodesy, geophysics, space navigation, and timing. In order to accomplish its goals, the colloquium will be organized in a work- shop format, with both formal presentations and discussion sessions. Arrange- ments will be made for meetings of the relevant IAU Working Groups if needed. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ORGANIZATION This meeting is sponsored by the International Astronomical Union (IAU) and the International Earth Orientation Service (IERS). Supporting IAU Commissions include 4, 8, 19, 24, 31, and 40. SCIENTIFIC ORGANIZING COMMITTEE: Kenneth Johnston (chair), Victor A. Brumberg, Nicole Capitaine, Veronique Dehant, Toshio Fukushima, Wenjing Jin, Jean Kovalevsky, Dennis McCarthy, Francois Mignard, Gerard Petit, P. Kenneth Seidelmann, Michael Soffel, E. Myles Standish, Jan Vondrak. LOCAL ORGANIZING COMMITTEE: George Kaplan (chair), F. Stephen Gauss, Brian Luzum, Chopo Ma, Nancy Oliversen, Lynn Treadway, Sean Urban. PROCEEDINGS EDITORS: Kenneth Johnston, Dennis McCarthy, George Kaplan. WEB SITE: http://aa.usno.navy.mil/colloq180/ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - PRELIMINARY PROGRAM Celestial Reference Systems and Frames Celestial Reference Systems - Overview Report of the IAU Working Group on the International Celestial Reference System Celestial Reference Frame Realizations at Various Wavelengths - Present Status and Future Possibilities: Radio, Optical, Infrared, UV, X-Ray, etc. Limitations on the Accuracy of Celestial Reference Frames - Source Structure, Binary Stars, Microlensing, Interstellar/Intergalactic/Interplanetary Medium Effects, Earth's Atmosphere, Terrestrial Reference Frame Dynamical Reference Frame - Current Relevance and Future Prospects Definition of the Celestial Ephemeris Pole and the Celestial Ephemeris Origin Summary/Resolution Relativistic Considerations for High Precision Dynamical Astronomy Relativity and Astronomy - Overview Report of the Working Group on General Relativity for Space-Time Reference Systems and Metrology Report of the Working Group on Relativity for Celestial Mechanics and Astrometry Summary/Resolution Precession and Nutation Report of the IAU Working Group on Non-Rigid Earth Nutation Theory VLBI Observations Rigid-Earth Nutation Models Improved Models for Precession and Nutation Sub-Diurnal Effects Summary/Resolution Time and Constants Time and Standards - Overview Report of the Working Group on Astronomical Standards Report of IAG Special Commission 3 on Parameters Report on SOFA Future Coordinated Universal Time Summary/Resolution Discussion of Resolutions for the IAU General Assembly Definition of the Celestial Ephemeris Pole and Celestial Ephemeris Origin, Relativity, Constants (Parameters), Time, Precession/Nutation, Others as Needed Discussion of Resolutions Requirements for Improved Accuracy in Celestial Reference Systems Ground-Based Observations Optical Interferometry Radio IR Space Missions FAME SIM GAIA Relativistic Timescales for Sub-Microarcsecond Astrometry Distance Scales, Stellar and Galactic Dynamics Searches for Planetary Systems IERS, Geophysics, Geodesy Adoption of Resolutions for the IAU General Assembly Summary - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - CALL FOR PAPERS Because of the workshop nature of this colloquium, only invited papers will be oral. Papers directly relevant to the topics of the colloquium are solicited from attendees. All contributed papers will be poster papers. It is hoped that multiple poster sessions will not be needed, and that poster papers can remain in place the entire week of the colloquium. Paper abstracts should be submitted online via the colloquium web site. The deadline for abstract submissions is 15 Jan (15 Nov for those requesting financial assistance; see below). At least one author of each paper must be a colloquium participant. A point of contact must be designated for each paper (one of the authors who will be attending the colloquium), who will be notified of paper acceptance within two weeks of submission. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - LOGISTICAL INFORMATION LOCATION OF COLLOQUIUM: Both oral and poster sessions will be held in building 56 of the U.S. Naval Observatory in Washington, DC. This is a recently renovated building with a new conference room, probably not familiar to most conference participants. Rooms for working group meetings will be made available if needed. REGISTRATION: Registration procedures for the colloquium itself have not yet been esta- blished. The registration fee will be approximately $200 US. We hope to be able to offer online or fax registration with credit card payment of the registration fee. For those unable to register this way, paper mail regis- tration will be accepted if accompanied by an international money order, traveler's check, or personal check drawn on a US bank (in US dollars only). We will not be able to accept institutional purchase orders. PLEASE DO NOT ATTEMPT TO REGISTER FOR THE COLLOQUIUM NOW. Registration procedures will be posted on the web site when available. HOTEL RESERVATIONS: Blocks of hotel rooms have been reserved for colloquium attendees at two hotels within walking distance of the Naval Observatory, the Holiday Inn and the Savoy Suites. Room rates in the reserved blocks range from $115 to $149 (plus tax). Hotel rooms can be reserved now -- see colloquium web site for details. Hotel reservations are separate from colloquium registration and are the responsibility of the individual participant. Rooms in the blocks reserved for the colloquium must be booked by 11 Feb for the Holiday Inn and 18 Feb for the Savoy Suites. Information on other nearby hotels is also given on the web pages. RECEPTION AND BANQUET: A reception at the Naval Observatory is being arranged for early in the week, and a banquet at one of the hotels for later in the week. Both events will be covered by the registration fee. Guests will be welcome at the reception, and guest tickets for the banquet will be available at cost (approximately $40). FINANCIAL ASSISTANCE: A limited amount of financial assistance will be available. Requests for such assistance should be sent to Dr. Kenneth Johnston, Chair of the Colloquium 180 Scientific Organizing Committee, at e-mail address johnston.kenneth@usno.navy.mil or at postal address Dr. Kenneth Johnston Chair, Colloquium 180 SOC U.S. Naval Observatory 3450 Massachusetts Avenue NW Washington, DC 20392-5420 USA The deadline for consideration for financial assistance is 15 Nov. Those requesting financial assistance must have submitted abstracts for any contri- buted papers by this date. FURTHER INFORMATION: Further information will be posted at the colloquium's web site, http://aa.usno.navy.mil/colloq180/, as it becomes available. We hope to see as many of our colleagues as possible at this important meeting. Kenneth J. Johnston Chair, IAU Colloquium 180 Scientific Organizing Committee johnston.kenneth@usno.navy.mil George H. Kaplan Chair, IAU Colloquium 180 Local Organizing Committee gkaplan@usno.navy.mil --------------------------------------------------------------------------------