Abbas, M.

Bly, V.

Brasunas, John

Edgerton, M.

Hagopian, J.

Mamakos, W.

Morell, A.

Pasquale, B.

NASA Technical Reports Server

G O D D A R D   S P A C E   F L I G H T   C E N T E R 
Limb sounding of the lunar limb with a 
Fourier transform spectrometer 
J. Brasunas1, M. Abbas2, V. Bly1, M. Edgerton1, J. Hagopian1,  
W. Mamakos3, A. Morell1, B. Pasquale1 
1  NASA Goddard, Greenbelt, MD  
2  NASA Marshall, Huntsville, AL 
3  Design Interface, Finksburg, MD 
 
 
Houston, TX – March 15-16, 2012 
 
https://ntrs.nasa.gov/search.jsp?R=20120011586 2019-08-30T20:52:12+00:00Z
G O D D A R D   S P A C E   F L I G H T   C E N T E R 
Planetary FTS at  
NASA GSFC 
•NASA Goddard has launched a series of Fourier transform 
spectrometers (FTS) to the solar system – including the IRIS 
on two Voyagers, and Cassini CIRS at Saturn 
 
• Passive IR remote sensing in emission (limb & nadir) is a 
power tool for characterization of 
- Surface and atmosphere temperatures 
- Composition 
- Dynamics via the thermal wind equation 
 
• Increased in size, culminating in 43 kg for CIRS, so develop 
CIRS-lite at 15-20 kg for future planetary missions 
 
 
LSA2_2012 - Brasunas    2 
G O D D A R D   S P A C E   F L I G H T   C E N T E R 
Developing  
CIRS-lite 
• Technology advances include: 
- high Tc superconductor bolometers (YBCO @ 87K, MgB2 
@ 37K) 
- Carbon nano-tube (CNT) layer for IR absorption 
- a COTS-based moving mirror mechanism compatible 
with near 77K operation 
- Synthetic (CVD) diamond beam-splitter  
- Single crystal silicon (SCS) telescope primary 
 
•Very broad spectral coverage, ~ 7 to 300 microns, monitors 
a rich set of molecular lines 
 
 
 
LSA2_2012 - Brasunas    3 
G O D D A R D   S P A C E   F L I G H T   C E N T E R 
CIRS-lite and other 
FTS instruments 
 
LSA2_2012 - Brasunas    4 
Parameter CIRS CIRS-lite IRIS Mars TES PFS 
band-pass (µm) 7 to 1000 7 to 333 5 to 50 6 to 50 0.9 to 45 
resolution (cm-1 )  apodized 0.5 0.125 2.4 5 1.5 
telescope diameter (cm) 50 15 4 15 5 /4 
detectors HgCdTe 
thermopile 
HgCdTe 
high Tc 
thermistor 
bolometer 
DTGS 
pyroelec. 
PbSe, PbS 
LiTaO3 
detector temperature (K) 
optics temperature (K) 
75 and 170 
170 
75 and 89 
~150 
250 
250 
Uncooled 
uncooled 
210 and 290 
290 
point-able mirror no TBD 1 kg no yes yes 
footprint (km @ 250 km) 1 & 0.05 1 & 0.4 16 2 7 & 14 
mass (kg) 43 15 to 20 14 14 31 
 
G O D D A R D   S P A C E   F L I G H T   C E N T E R 
CIRS to CIRS-lite 
LSA2_2012 - Brasunas    6 
-CVD diamond has very broad  
transmission  --> drop one FTS 
 
- more sensitive FIR detectors (HTS  
bolometers vs. thermopiles) for smaller 
optics 
 
- double-passed moving cube-corner 
enables higher spectral resolution 
G O D D A R D   S P A C E   F L I G H T   C E N T E R 
Moving mirror  
mechanism 
LSA2_2012 - Brasunas    7 
Red: speed 
Blue: drive force 
bread
board 
G O D D A R D   S P A C E   F L I G H T   C E N T E R 
CIRS-lite optical 
layout 
 
LSA2_2012 - Brasunas    8 
• 
G O D D A R D   S P A C E   F L I G H T   C E N T E R 
Nominal design 
LSA2_2012 - Brasunas    9 
Fig. 7 
telescope primary 
SCS D 
This image shows the optk;a{ sl.JJfaGS' a( a singl'e--
c;rysral ,r,;,,,,,, mim>" ","'""ting the liglt weighted. 
hJneyccmbed baa:::; ~ide . 
• 
CIRS-lite nominal design (planetary) 
• ~resoluti on 0_125 cm-1 apodized (FrS is double-passed; physical travel is I inch) 
• ~ coverage is 7 to 333 /111l, one FrS with 60 mm diamond beam spliner, no compensator 
. ~arrays 
TYPE WAVELENGTH ( !-1m ) 
hlgQ Tc 
PC HgCdTe 
PV HgCdTe 
16+ to 333 
9+ to 16+ 
7 to 9+ 
• ~ primary diameter is 15 em 
P~(mradJ!-Im) 
4 _3 x 4 _3 / 300 x 300 
1_5 x 1_5 / 200x200 
same as PC 
EXTENT 
I x 4 
I x 30 
same as PC 
• !hmmay be a point-able mirror in front of the telescope; similar to the TES design 
• ~ temperature is 140K (same as Voyager MIRIS) 
• all detectors near 70 to 90K, with passive cooler 
• ~FrS beam - 3_5 em -- need - 5 em clear aperture for beam splitter at 4 5 degrees _ 
G O D D A R D   S P A C E   F L I G H T   C E N T E R 
Lunar dust, 
volatiles 
 
LSA2_2012 - Brasunas    10 
Mission Science Goal Optics 
temperature 
Beam-
splitter 
detectors 
Planetary deep space atmospheres: composition, 
dynamics (remote sensing 
in emission) 
~150K diamond HgCdTe 
high Tc bolometers 
Lunar dust Dust, gas 
(remote sensing via solar 
absorption) 
~150K KBr or 
diamond 
HgCdTe 
thermal 
Lunar surface ices Near surface ice (in-situ) 
Reflection (NIR) 
Emission (FIR) 
 
100K/ambient 
100K/ambient 
 
ZnSe (NIR)  
diamond (FIR) 
 
HgCdTe (NIR) 
high Tc bolometer  (FIR) 
MgB2 (near 40K) 
 
Solar occultation measurements: from surface, from orbit (limb view) 
-lunar surface covered with dust grains levitated by charging mechanisms 
- charging via solar wind and UV photons 
- particular dust activity near the terminator (vacuum, little/no water) 
- dust has implications for lunar exploration (adhesive, mechanisms, …) 
- need to measure dust density, size distribution,  
-measure vertical distribution from orbit via onion-peeling technique 
- also measure H20 and CH4 from orbit  
G O D D A R D   S P A C E   F L I G H T   C E N T E R 
Lunar surface ices 
NIR 
• Clementine radar, Lunar Prospector neutron spectrometer, 
and LRO/LEND indicate water ice or hydrogen deposits in 
permanently shadowed regions (PSR)  
• LRO/LCROSS plume demonstrates hydroxyl group 
• LRO/DIVINER temperatures consistent with ice 
• Can distinguish hydrates from water ice via spectroscopy 
 
LSA2_2012 - Brasunas    11 
- combine CIRS-lite with an NIR source 
(laser, LED or thermal) to measure NIR 
reflectance of surface deposits 
 
- map concentration of water ice 
 
- use laser source or ultrasonic generator 
to drive off volatiles and get indication of 
distribution with depth 
 
 
. 
G O D D A R D   S P A C E   F L I G H T   C E N T E R 
Lunar surface ices 
FIR 
LSA2_2012 - Brasunas    12 
Water ice FIR emission 
features observed in  
interstellar dust, with 
40 and 60 micron peaks 
-FIR measurements (40 to 100 microns) can 
measure PSR temperatures (< 100K) and 
characterize two water ice features in the FIR 
 
- in amorphous ice, longer peak is suppressed 
 
- detection of these FIR emission features in an  
optically thick source such as the lunar surface 
requires a vertical temperature gradient 
 
- thermal conductivity of slowly deposited 
amorphous ice is 104 times less than crystalline 
 
- recent NASA GSFC results show MgB2 
bolometers (37K transition) are much faster 
than YBCO bolometers (consistent with PSR 
operation) 
 
 
G O D D A R D   S P A C E   F L I G H T   C E N T E R 
 
 
 
 
 
THAT’s All, FOLKS! 
LSA2_2012 - Brasunas    13 


Limb Sounding of the Lunar Limb with a Fourier Transform Spectrometer

Limb Sounding of the Lunar Limb with a Fourier Transform Spectrometer

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