| Chandrayaan-1 X-ray
Spectrometer (C1XS) |
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| When a primary X-ray beam strikes a sample the x-ray
can either be absorbed or scattered by the atoms in the
sample. The X-ray when absorbed by an atom transfers all
its energy to an innermost electron. If the primary X-ray
has sufficient energy, this electron gets ejected from
the inner shell creating vacancies causing an unstable
condition for the atom. The atom returns to its stable
condition when electrons from an outer shell is transferred
to the inner shell and in this process a characteristic
x-ray is released. Because electrons in atom of a given
element has a unique set of energy levels, each element
produces x-rays with a unique set of energies. Thus one
can non-destructively measure the elemental composition
of a sample. The process of emission of characteristic
x-rays is called ‘X-ray Fluorescence’ or XRF. The Sun
provides a natural source of X-rays and strikes the lunar
surface and it is possible to infer elemental composition
of lunar surface through detection of characteristics
X-rays. |
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| Scientific Objective: |
| The primary goal of the C1XS instrument is to carry
out high quality X-ray spectroscopic mapping of the Moon,
in order to constrain key questions on the origin and
evolution of the Moon. C1XS would use X-ray fluorescence technique (1.0-10 keV)
for measuring elemental abundance of Mg, Al, Si, Ca, Fe, Ti
distributed over the surface of the Moon. |
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| Payload Configuration Details: |
| C1XS has been designed as a thin, low profile detector.
The instrument uses the recently developed technology
of the Swept Charge Device (SCD) X-ray sensors mounted
behind low profile gold/copper collimators and aluminium
/polycarbonate thin film filters. The system has the virtue
of providing superior X-ray detection, spectroscopic and
spatial measurement capabilities, while also operating
at near room temperature. A deployable shield protects
the SCDs during passages through the Earth’ s radiation
belts, and from major particle events when at the Moon.
In order to record the incident solar X-ray flux at the
Moon, which is needed to derive absolute lunar elemental
surface abundances, C1XS carries an X-ray Solar Monitor. |
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| In normal solar conditions, C1XS will be able to detect
elemental Mg, Al and Si on the lunar surface. During
solar flare events, it would be possible to detect other
elements such as Ca, Ti and Fe. |
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| Heritage: |
| The primary C1XS instrument is based on the successful
D-C1XS instrument on the ESA SMART-1 mission. In comparison
to D-C1XS instrument on SMART-1 the C1XS experiment onboard
Chandrayaan-1 would be carrying out further observations
by exploiting the following situations |
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Observe the Moon during the rising phase of the
solar cycle when X-ray signals are expected to be
significantly enhanced |
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Reach the lunar orbit in much less time and hence
would be subjected to significantly less damaging
radiation enroute |
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Would observe the Moon from a much closer (100
km) circular, polar orbit |
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Will have increase in collection area from the
redesigned collimator and facet geometry |
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| Chandrayaan-1 X-ray Spectrometer (C1XS) is realized through ESA with collaboration between Rutherford Appleton Laboratory, UK and ISRO Satellite Centre, ISRO. Part of this payload is redesigned by ISRO to suit Chandrayaan-1 scientific objectives. |
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| Rutherford Appleton Laboratory D-C1XS websites: |
| http://www.ssd.rl.ac.uk/SMART-1/index.htm |
| Aberystwyth D-C1XS website: |
| http://www.aber.ac.uk/physics/missions.shtml |
| A major success of the instrument on board
Smart-1 has been the first unambiguous remote sensing
of Calcium on the Moon |
| http://smart.esa.int/science-e/www/object/index.cfm?fobjectid=37455 |
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