Astronomical research on asteroids, i.e. minor planets, is also
benefiting from the large-scale Gaia mission of the European Space
Agency (ESA). Even though the astrometry satellite's main purpose is to
precisely measure nearly one billion stars in the Milky Way, it has
tracked down a multitude of minor dwarf planets in our solar system.To
determine its current position in space and thus ensure Gaia's extremely
high measurement accuracy, images are taken every day of the regions of
the sky where the very faint satellite is located.
The Gaia astrometry satellite, which has been fully operational since
August 2014, measures with pinpoint accuracy the positions, movements
and distances of stars in the Milky Way, thereby furnishing the basis
for a three-dimensional map of our home galaxy. According to Dr.
Altmann, it became clear during preparation for the Gaia mission that
the ambitious accuracy goals required novel methods to determine the
position and velocity of the satellite itself. For this purpose an
observation campaign was launched to determine Gaia's position and
velocity from Earth. As early as 2009, Dr. Altmann of the ARI and his
colleague Dr. Sebastien Bouquillon of the Observatoire de Paris (France)
began planning the programme together with an international team. Among
the partners for the implementation, they attracted observatories in
Chile and Spain. The Institute for Astronomical Computing is responsible
for coordinating the daily observations. Since the launch of Gaia in
December 2013, Gaia's ground-based position measurements are transmitted
regularly to mission control, the European Space Operations Centre in
Darmstadt.
Dr. Altmann explains that the astrometry satellite is at a distance
of approximately 1.5 million kilometres and is always located in the
region of space away from the Sun as viewed from the Earth. "For this
reason Gaia's positioning images are also perfect for observing minor
planets. This so-called oppositional position brings these celestial
bodies closer to Earth, making them appear brighter than at other
times," continues the Heidelberg researcher. More than 2,000 small
planets have been found this way since the beginning of this year,
mainly on images from the VST telescope of the European Southern
Observatory (ESO) in Chile. Dr. Altmann indicates that nearly 40 per
cent of them are new discoveries. Moreover, these current measurements
are especially interesting for already known minor planets as well,
precisely because Gaia and the minor planets located in the same part of
space are always opposite the sun at the time of observation. Just like
with the full moon, the planets' entire earthward side is completely
illuminated only at that location. This allows the researchers to
measure the asteroid's reflectivity very accurately and draw conclusions
as to their chemical composition. Up to now only approximately 30
asteroids have their reflectivity sufficiently well-determined,
according to Dr. Altmann.
The Gaia astrometry satellite itself will also discover and
accurately measure many asteroids in its survey of the sky, but in
totally different regions. "In this respect, the observations from the
Gaia mission and the ground-based measurements complement each other
extremely well," says Dr. Altmann. "We hope not only to acquire new
insight into the origins of our home galaxy through the Gaia satellite
mission. We will certainly learn more about the origins of our solar
system," stresses Prof. Dr. Stefan Jordan of the Institute for
Astronomical Computing
This story is taken from Science Daily
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