Gamma Ray Spectrometer (GRS)
A germanium semiconductor crystal cooled to below -180 degrees centigrade by a Stirling cryocooler is employed as a main detector of GRS. GRS has an
excellent energy resolution 20 times superior to those used in past lunar missions. Thus, GRS can discriminate the incident gamma-ray energies with
high precision and can determine abundances of more than 10 elements in the lunar surface.
Neutrons are produced in the lunar subsurface by irradiation of Galactic Cosmic Ray. Gamma rays with the energy characteristic to each element on the
Moon are produced by interactions of those neutrons with surface elements. Natural radioisotopes also emit gamma rays. Elemental composition is
determined by measuring the gamma-ray energies from the lunar orbit.
GRS will observe chemical abundances of materials (K, U, Th, O, Mg, Al, Si, Ti, Fe, Ca, H, etc.) on lunar surface globally.
The results will be highly accurate and will provide clues leading to advancement in research of the origin and evolution of the moon.
The observations will contribute to lunar resource exploration, especially for water existence. Water is very essential for human activity in a lunar
platform in the future and local supply of water is necessary for the sake of cost performance. GRS can identify gamma rays from hydrogen and can map
hydrogen.
Measurement of elemental abundances
Evidence of water - A hydrogen peak is appeared if water exists on the moon.
Lunar Radar Sounder (LRS)
Specifications
Mass: 23.182kg
Power: 56.7W
Sounder obs.
SDR frequency: 5MHz(main freq.)
Radiation Power: 800W
Pulse width: 200 micro sec
Modulation: 10kHz/micro sec
Sounding depth: 5km
Natural plasma wave obs.
Frequency: 10Hz - 30MHz
Telemetry speed
High speed: 492kbps
Low speed: 176kbps
LRS is designed for sounding the surface and subsurface structures of the Moon by using HF radar technique with the frequency of 5 MHz. The low
frequency radar method makes it possible to realize the mapping of the subsurface structure within a depth of several km with a range resolution of
less than 100 m for a region with a horizontal scale of several tens of km. LRS will contribute to the study of the thermal history of the lunar
surface region relating to a time scale of several tens of millions of years.
The LRS system transmits RF pulses with frequency of 5 MHz which is able to penetrate deep into the Moon's subsurface region.
When the radio waves meet with the discontinuity of subsurface material, it makes a subsurface echo signal. Observation of subsurface signal makes it
possible to see subsurface structure of the Moon.
LRS uses two sets of 30m tip-to-tip long dipole antennas for the 5 MHz radar observation.
Example of the LRS observation over a synthesized moon's surface and subsurface structure is demonstrated in the below panel.
Lunar Magnetometer (LMAG)
LMAG magnetometer can measure a magnetic field weaker than 1/100,000 of the geomagnetic field. Its sensor is mounted on the
edge of a super-lightweight mast extended from the spacecraft at 12m length in order to avoid the magnetic interference.
Magnetic anomalies on the Moon
There are many magnetic anomalies on the Moon where the field intensity is stronger than ordinary regions. We shall perform the high-precision
observation to give more detailed map of anomalies in wider regions, enhancing the study of the magnetic anomaly bearing mechanism and of the
existence of the ancient lunar magnetic fields.
Example of the lunar magnetic anomaly
(Reiner Gamma region on the near side).
Plasma energy Angle and Composition Experiment (PACE)
LMAG and PACE enable us to study on the present and ancient (say, 3-4 billion years ago) environment of magnetic fields and plasma on and around the
Moon and also on the evolution of its deep interior.
PACE consists of 4 sensors: ESA (Electron Spectrum Analyzer)-S1, ESA-S2, IMA (Ion Mass Analyzer), and IEA (Ion Energy Analyzer). ESA-S1 and S2 measure
the three-dimensional distribution function of low energy electrons below 15 keV, while IMA and IEA measure the three-dimensional distribution
function of low energy ions below 28 keV/q.
Pictures of PACE sensors (top) Cross sections of PACE sensors (bottom)
PACE sensors are top hat type electrostatic analyzers with angular scanning deflectors at the entrance and toroidal electrodes inside. IEA-S and IMA-S
have additional electrodes that are used for controlling sensitivity electrically. In order to measure ion mass, LEF (Linear Electric Field) TOF (Time
Of Flight) ion mass analyzer is attached to IMA.
Sputtered ions from the lunar surface will be measured for the first time. Recently, ground-based observations have revealed the existence of tenuous
alkali-atmosphere around the moon. The rarefied atmosphere is thought to be produced mainly by solar photons and the solar wind.
Sputtering by the solar wind that is one of the source mechanisms of the tenuous atmosphere presumably produces the secondary ions reflecting the
composition of the lunar surface.
Upper-atmosphere and Plasma Imager (UPI)
From an orbit around the Moon the Upper-atmosphere and Plasma lmager (UPl) will look at the Earth using two telescopes : an extreme ultraviolet
telescope(TEX) to observe the plasmasphere and a visible telescope (TVIS) to observe global distribution of aurora and airglow.
TEX detects the resonance scattering emissions of oxygen ion and helium ion. The telescope employs a high-efficiency mirror and micro-channel plates
with a resistive anode producing 128x128pixel images. The corresponding spatial resolution is 500km.
TVIS is equipped with a fast catadioptric optics and a high-sensitivity CCD to image swift aurora and dark airglow. TVIS has a field-of-view
equivalent to the Earth disk seen from the Moon. Spatial resolution is about 30km on the Earth's surface.
Observation wavelengths can be changed by selecting filters.
UPI expanding its arm for function testing.
TEX and TVIS are mounted on a special two-axes gimbals mount.The primary and secondary axes cancel the orbital motions of the satellite and the Moon,
respectively. Thus, the telescopes can stay pointed to the Earth. UPl is operational only when the satellite is in the lunar shade and visible from
the Earth.
From TEX observations we will know the spatial plasma distribution around the Earth every 10 minutes. Especially, imaging of the entire globe by
oxygen ion emission will promote the space plasma physics. Using images of the auroral ovals teken by TVIS intensities and shapes of conjugate auroras
will be quantitatively compared.
Images Copyright: JAXA
[edit on 23/12/2007 by internos]
