Advanced X-ray Imaging
AXIOM (Advanced X-ray Imaging Of the Magnetosphere) is a space
mission concept which has been put forward in response to the European Space
Agency's (ESA's) Call for Medium size missions, due for launch in the timeframe
2020 - 2022. A consortium of institutes in the UK, Europe and the USA has
submitted a proposal for AXIOM to ESA in December 2010. You can find the
list of collaborating institutes and personnel
A paper presenting the scientific aims and the design concept of the AXIOM mission
has been published (July 2011) in Experimental Astronomy and
a pre-print can be found here.
AXIOM aims to investigate the response of the Earth's magnetosphere to the
impact of the solar wind in a unique manner that has never been attempted
before: AXIOM will carry out soft X-ray imaging and spectroscopy of the Earth's
bow shock, the cusps, magnetosheath and magnetopause.
You can read the AXIOM proposal's Executive Summary
Why X-ray imaging?
Only in the last decade or so we have come to realise
that the magnetosphere around the Earth, when buffeted by the solar wind,
shines in soft X-rays. Charge exchange interactions between high-charge-state
heavy ions (like C, N, O, Fe, ...) in the solar wind and atoms and molecules
in the Earth's exosphere are known to lead to the production of X-rays, in the
form of emisson lines at energies which are characteristic of the incoming ions.
This realisation, and the advanced optics and sensors now available for
focussing and detecting X-rays, are making it possible to take images of a
large part of the magnetosphere, thus providing global measurements that have
never been attempted so far. These measurements are intended to study in detail
the magnetosphere's conditions at 'quiet' times, when the solar wind flows past
the Earth at its average density and speed, and compare them with those during
'storm' conditions, following for example the occurrence of a Coronal Mass
Ejection (CME) from the Sun.
Where is AXIOM going to observe from?
In order to image a very large section of the Earth's
magnetosphere AXIOM has to travel far away from it. The orbit currently
considered takes AXIOM very close to the Moon, at some 50 - 55 Earth's radii
away from our planet; AXIOM will essentially orbit the Earth in ~28 days
together with the Moon, and will be kept oriented to look at the nose of the
magnetosphere as much as possible as it travels around the Earth.
What else is in the AXIOM payload?
In order to interpret the X-ray data in the most
accurate way, and to properly model the response of the Earth's magnetosphere
to different conditions of the solar wind (fast and slow, and during the passage
of CMEs) we need to monitor the solar wind conditions in-situ. As a consequence
AXIOM will carry proton, alpha particle and heavy ion analysers, and a
magnetometer, which will characterise the solar wind conditions, measure its
velocity, density, temperature and composition, and will establish the magnitude
and orientation of the magnetic field, simultaneously with the X-ray
ESA's Cosmic Vision 2015-2025
A proposal for AXIOM was submitted to
ESA'a 2010 M-class mission call in December 2010.
How is the Consortium made up?
The AXIOM proposal preparation has been led in the UK
by Graziella Branduardi-Raymont from the
Mullard Space Science
Laboratory, Department of Space and Climate Physics of
University College London, in collaboration with
staff of the
Department of Physics and
Astronomy of Leicester University,
and of Imperial College London.
In the USA, collaborators are from
Space Flight Center. Scientific support is also provided by
Pierre Simon Laplace in France. Overall, a large team of scientists and
engineers are working together to develop the AXIOM mission concept, with the
hope of turning it into reality.
We welcome all feedback, comments and suggestions from
the UK, European and world-wide scientific community. Please click
here if you
want to show your interest in this exciting mission.
5 July 2011
gbr [at] mssl.ucl.ac.uk