11 May 2010



Chandrayaan-1 was the Indian Space Research Organisation (ISRO's) first mission to the Moon, launched in October 2008 on board a Polar Satellite launch vehicle from the Satish Dhawan Space Centre (SDSC) launch site in India.

Image of the Earth's Moon, with its dark basaltic mare.

​​​​​​​The Moon

Credit: Lick Observatory/ESA/Hubble
On board were 11 instruments, five of which were developed in India with the remaining six experiments provided by international partners from the UK, Sweden, Germany, Bulgaria and America. These instruments included several remote sensing instruments; an infrared spectrometer, a multi-spectral imaging camera, a high-energy X-ray Spectrometer and the Compact Imaging X-ray Spectrometer (C1XS), a low-energy X-ray Spectrometer. Together these instruments were designed to give a comprehensive view of the Moon in infrared, optical and X-ray wavelengths.

C1XS: Science and Imaging Goals

The C1XS instrument was constructed at RAL Space, in collaboration with ISRO. The polar orbit of Chandrayaan-1 meant that C1XS could have mapped the entire lunar surface, including all the Apollo landing sites and areas previously seen by D-CIXS on SMART-1. The Apollo sites are very important because we have moon rock and soil samples from these sites which we can compare with our remote sensing observations.

The X-rays that C1XS (and D-CIXS) were designed to detect originally come from the Sun. Unfortunately, solar X-ray emission is highly variable and during the SMART-1 and Chandrayaan-1 mission they have been very intermittent. C1XS only saw 30 bursts of X-rays from the Sun which greatly limited the mapping coverage possible. When a solar X-ray hits the surface of the Moon it will only penetrate a few microns into the surface. If we are lucky, the solar X-ray will interact with an atom in the lunar surface and remove one of the innermost electrons from the atom. This will force the atom to rearrange its electrons with the result that the atom will emit a NEW X-ray! This new X-ray is what C1XS was designed to measure.

C1XS can determine the energy ("colour") of the X-ray very precisely and therefore work out exactly which element on the lunar surface emitted the X-ray and therefore provides information on the elemental composition of the lunar surface. If the Sun had behaved as we expected it to, C1XS would have been able to detect the major rock-forming elements magnesium, aluminium and silicon, all across the Moon. Additionally, when the Sun provided more energetic X-rays, C1XS would have been able to add calcium, titanium and even iron to this list. As well as detecting these important elements, C1XS could also provide us with information on the abundances of these elements. This is vital for geochemists to be able to work out which minerals we are seeing on the lunar surface.

The C1XS instrument on a cleanroom table.  
Image: C1XS

Credit: STFC RAL Space

In order to correctly determine the abundance of the elements on the lunar surface, we also need to know exactly how many X-rays and their energy (colour). To do this, C1XS carries an X-ray Solar Monitor (XSM) which was designed to measure the Sun's X-ray output simultaneously with the C1XS X-ray measurements from the lunar surface.

Unfortunately, the Chandrayaan-1 mission ceased operating in late August 2009 due to a major failure on the spacecraft. However, despite being hampered by an incredibly quiet Sun, C1XS was able to build on the initial work of D-CIXS and has collected data from around 30 solar flares, including the Apollo 14 landing site!

For more information

For more information please contact: RAL Space Enquiries