D-CIXS Presentation

Picture

D-CIXS Team

D-CIXS Experiment

Swept Charge Device

D-CIXS Collimator

D-CIXS Mechanical Design

D-CIXS Observations

High Throughput Spectroscopy

Lunar Science

Lunar Origin

South Polar Atkin Basin

Lunar Ice

Lunar Plasma Science

Mercury

Demonstration of a

Compact Imaging X-ray Spectrometer

PRINCIPAL INVESTIGATOR

Manuel Grande
Rutherford Appleton Laboratory
Chilton, Didcot, Oxfordshire, OX11 0QX
Phone: +44 1235 44 6501
Fax: +44 1235 44 5848
E-mail: m.grande@rl.ac.uk

CO-Principal INVESTIGATOR:

J Huovenin

University of Helsinki Observatory (UHO)

CO-INVESTIGATORS:

D-CIXS Lunar Scientific Objectives

High Throughput Science

• The D-CIXS instrument is designed for high throughput spectroscopy,

• Its large aperture means that high quality spectra and good spatial resolution can be obtained even from a spacecraft moving with orbital velocity over the weakly emitting surface .

Global Coverage

• It will provide the first high-resolution global map of surface geochemistry and the relative abundances of the major lunar rock types.

Petrological Survey

• Observations can distinguish between theories of crustal accretion and establish whether past planetary convection existed.

• Of fundamental importance is to understand the reasons for the differences between crust and maria. Mg/(Mg + Fe) ratios constrain models of Lunar evolution.

Impact Sites and Lava Flows

• Probe the geochemistry of the central regions of the larger impact basins which may contain exposed mantle material, and which exhibited unusual spectral signatures within the Clementine data.

• Vertical variations in crustal composition can be revealed by examination of impact crater ejecta and central peaks (as demonstrated by Clementine), which represent exhumed or exposed crustal material, and by placing these measurements within the reference frame of Clementine topography.

• The time series of lava flows can reveal petrological evolution, as it does on Earth.

Lunar Resource Evaluation

• Direct relevance to lunar resource evaluation, as a precursor to future exploitation of the Moon as a base for space exploration, for which the abundance of metals such as Al, Fe, Mg, Mn and Ti within the regolith must be known.

Plasma Wake and X-rays from the Dark Side.

• Recent Japanese X-ray observations (Kamata et al 1998) of the Moon suggest that X-ray production on the night side due to energetic particle impact is an important effect. These particles are presumably enhanced as a result of acceleration in the Moon's plasma wake.

Cometary X-rays

• In the event that a suitable target becomes available, D-CIXS will, due to its very high effective area be able to resolve the conflicting theories of X-ray generation at comets. To do this an extremely high resolution spectrum is required to compare against the predictions of different models. The D-CIXS team contains proponents of the two leading theories. Comet Enke may well provide a suitable target.

Pictures from The New Solar System, ed Beatty, Petersen and Chaitkin, Cambridge University Press.

The Origin of the Earth-Moon System

• The current "best" theory is the impact of a Mars sized planet on the proto-Earth. But it has problems in terms of detailed composition.
• Following Clementine it is now clear that all Apollo samples came from the Procellarum basin, a single, anomalous region which was reprocessed by a massive impact.
• X-ray florescence is the measurement which provides the elemental abundances, essential for geochemical identification.
• This is the measurement needed over the "typical" 85% of the Moon's surface. Only the nearside equator was mapped by Apollo.
• The Ratio of Mg/Fe enables us to constrain origin theories
• The Moon is a witness to Inner Solar System history. It is the test of our understanding of the formation of Earth-like planets.

The D-CIXS instrument is designed for high throughput spectroscopy, and hence can make this critical measurement

The Swept Charge Device is a new technology arising out of the IMPACT program. Samples in the lab show excellent performance. We have worked with EEV to produce a new specification and layout, well suited to a planetary X-ray target.

Swept Charge Device Characteristics:

Sensitive area: 10 x 10 mm

Energy Resolution: <200eV

Operating temperature: Near Room Temperature (-5^oC)

Radiation Tolerance : Very high compared to a standard X-ray CCD

Polar Ice and SMART-1

• Clementine flew over the pole every five hours. These images are composites, showing the addition of alternate orbit polar images over the course of one lunar day (one Earth month).

• Areas in permanent darkness are black, while areas of permanent illumination are white; areas of mixed lighting condition are represented in various shades of grey.

• The south polar area has the largest area of permanent darkness, measuring more than 15,000 square kilometres. The north pole shows only about 500 square kilometres of darkness, although in practice the real area may be much greater.

• Several areas are evident that have near-constant Solar illumination. Such zones would have great value as sites for a permanent lunar outpost.

• Clementine did not cover both Summer and Winter, however, so the actual areas of perpetual light and dark are still unknown.

• Smart-1 will be able to provide illumination maps throughout a year, at a higher resolution than the Clementine survey, and hence accuately map candidate areas for water ice.

Collimator

The new resist is a negative resist that mainly consists of an epoxy resin which can be exposed using Ultra Violet (UV) radiation. This resist has been designed for very thick layers and has very good mechanical properties but more importantly can be used to produce features that have very good sidewall angles approaching 90 degrees and high aspect ratios.

• The current limit of the technology will give us 0.5 degree collimation, although this is unsuitable for the moon, which is a weak X-ray source.

The photograph shows a simple double step exposure (resist film exposed at different stages in a process to give steps in height). The height of the tallest structure is ~1mm and the important features to note are to near vertical wall angle and optically smooth sidewalls.

• The technology is used as part of an integrated dual collimator/filter structure which also rejects particle backgrounds and radiated heat from the Lunar surface

High Throughput Science

• The D-CIXS instrument images fluorescence X-rays from the Moon, as a means to carry out spatially resolved material analysis of the Lunar surface.

• Its large collecting area and angular acceptance makes it especially suitable for the Moon, a very weak source of fluorescence X-rays, where due to the orbital speed it is necessary to accumulate images quickly to avoid blurring due to the spacecraft motion over the surface, as well as to map the whole surface in a given time.

• D-CIXS has an effective area of 20 cm². Above are shown calculated spectra for 10 second observations in quiet and active periods using the CIXS area of 100 cm² .

X-Ray Image of the Moon from Y.Kamata et al 1998. The images show contours of X-ray emission (obtained by the Japanese ASCA satellite) superimposed on an optical image. In the broadband (left-hand) image the X-ray emission comes sunlit areas, in the Al-K fluorescence lines (right hand), the emission is uniform, including the night side, suggesting a contribution from energetic particles, perhaps modulated in the lunar wake. D-CIXS with its large effective are will provide the high-quality spectroscopy necessary to identify the processes. Its high time resolution spatial imaging will also be vital in this regard.

Measurements by GGS/Wind (Ogilvie et al 1994) and Lunar Prospector (Lin et al 1998) show that the energetic electrons of the solar wind are not shielded by the shadow, and that 1keV energy electrons are on occasion accelerated towards the surface.

• The South Pole-Aitken (SPA) Basin is the least known lunar terrain. Clementine laser altimeter measurements showed it to be 12 km deep.

• At 2500 km diameter it is the largest impact feature in the Solar System.

• The albedo map (top left) shows that the floor of the basin is markedly darker than the highlands surrounding it.

• Both iron (bottom left) and titanium (bottom right) concentration maps show enhanced values associated with the basin floor materials.

• These results suggest that the floor of the SPA is made up of relatively mafic rocks, but elemental mapping is needed.

• Explanation is controversial. Either a consequence of volcanic resurfacing or

• The major impact may have stripped off the feldspathic crust, exposing the mafic upper mantle of the Moon.

• D-CIXS will provide the first elemental mapping of the SPA, enabling us to choose between these possibilities. Viewing the Mantle would be a major step forward in constraining formation theories.

Mariner 10 measurements at Mercury suggest that the magnetosphere displays substorm like behaviour

The energetic electrons observed to precipitate would be a copious source of bremmstrahlung X-ray emission

So fluorescent (line) emission would tell us about the surface elemental composition, while bremmstrahlung (continuum) emission would tell us about the global magnetosphere.

It seems likely that Colombo will be chosen as the next ESA Cornerstone mission

The D-CIXS Instrument on SMART-1 is seen as an ideal precursor to a Mercury mission