1. Chandrayaan-2 Large Area Soft X-ray Spectrometer (CLASS)
ISRO Satellite Centre, Bangalore
Open University, UK
Rutherford Appleton Laboratory, UK
S. Narendranath (ISRO) & the CLASS team

2. CLASS
Science
COSPAR 2012

3. Lunar surface chemistry from X-ray spectra
Global mapping of major rock forming elements
Na, Mg, Al, Si, Ca, Ti, Fe
Regional studies (25 km resolution)
Central peak composition
Ejecta material of large basins & craters
Search for pyroclastic deposits
Compare chemistry of small scale lava flows
Secondary objective
Explore chemical composition from particle induced X-ray emission (PIXE)
COSPAR 2012

4. Experiments in the past
Spectral reflectance in IR/VIS
Elemental abund from band ratios
X-rays
Direct measurement from line flux
Gamma rays
COSPAR 2012

5. A composition hitherto un sampled Na measured in C1XS
C1XS on Chandrayaan-1 : Major results A collaboration: RAL, UK & ISRO satellite centre funded by ESA & ISRO
A composition hitherto un sampled
Na measured in C1XS
Low Ca, high Al
Sodic plagioclase?
Narendranath et al, Icarus, 2012
Apollo 14 site measurement
Measurable PIXE
Mg Al Si Ca
11 Jan 2009
Weider et al, PSS, 2012
Credit: B. Kellett, RAL

6. CLASS
INSTRUMENT
COSPAR 2012

7. CLASS on Chandrayaan-2 Parameter C1XS CLASS! Remarks Spectral res
Geometric area
(single det )
24 cm2
( 1cm2 x 24)
64 cm2
(4 cm2 x 16)
Sensitivity
0.015 ph/cm2/s
0.009 ph/cm2/s
5σ at Si for 16s
Spatial resolution
50 km
25 km
At 200 km
Energy range
0.8 – 20 keV
0.8 – 15 keV
XRF lines from keV
Spectral res
keV , -150C
< keV, -200C
Targeted
X-ray detector
SCD (CCD-54)
SCD (CCD-236)
Swept charge devices from e2V
Operating temp
Targeted: -170C
Achieved:-100C
Targeted: -200C
Optimal temp range TBD
COSPAR 2012

8. Swept charge device (SCD)
Courtesy: A. Holland, Open university, UK
COSPAR 2012

9. CLASS package Quadrant package with four CCD-236
Four cards for processing electronics
Al door with 4 Fe-55 sources
Al filters (0.2µm) for blocking visible light
Cu collimator coated with gold
Temperature sensor on each detector
Passive cooling using heat pipes
Weight = 8.5 kg
Power = 26 W (raw)
COSPAR 2012

10. Current stage of development
Procurement of flight SCD (CCD-236) in progress
Optimization of device underway (jointly with OU)
Mechanical and thermal design analysis initiated
Change transport model – version 1 ready (presented at SPIE mtg, Amsterdam (Athiray et al) – July 2012
COSPAR 2012