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IERS Message No. 509                                    October 30, 2024
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IAU Symposium 401: Advancing Reference Systems, Ephemeris, and Standards


Dear Colleagues,

It is our pleasure to announce that the International Astronomical Union
(IAU) Symposium "Advancing Reference Systems, Ephemeris, and Standards:
from the Earth and the Moon to Solar System Bodies" (IAUS 401) will be
held from August 4 to 9, 2025 at the National University of La Plata
(UNLP), La Plata (Argentina).

Reference systems and their standardization are of paramount importance
to many fields of astronomy. Some examples are the reduction of ground-
based observations, space astrometry, astrophysics missions, and space
missions to solar system planetary bodies and beyond. The concept of a
reference system and its realization requires the convergence of
reference frames, ephemeris, and time scales to be developed respecting
associated standards, thus fulfilling one of the IAU strategic goals as
the provider of astronomical standards and their use.

The IAUS 401 will provide a forum to discuss the latest results and
prospects in these fields, and thus facilitate the coordination of 
common standards across agencies and organizations.

The IAUS 401 is structured in six key topics:

1.- Earth rotation models and Earth Orientation Parameters (EOP)

2.- Celestial and terrestrial reference systems/frames

3.- Reference systems/frames for the Moon and other solar system bodies

4.- Time scales and time metrology

5.- Ephemerides of solar system objects

6.- Astronomical standards

The IAUS 401 registration, abstracts submission, and IAU travel grant
applications will start at the beginning of November. The symposium will
be in a hybrid format, to welcome both in-person and online
participation.

For additional information and contact details please refer to IAUS 401
website:

https://iaus401.fcaglp.unlp.edu.ar/

We are looking forward to seeing you in La Plata.

Sincerely,

Alberto Escapa,
on behalf of the SOC and the LOC


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