NAST-I Development History• Developed by MIT Lincoln Laboratory in 18 months for
NPOESS using a COTS BOMEM (now ABB) interferometer, detectors, and optics
• Flown aboard NASA's high-altitude ER-2, Northrop Grumman Proteus aircraft, and NASA’s WB-57
• Produces high spatial and spectral resolution data suitable for synthesizing data products of candidate NPOESS sounders
• NAST-I has achieved excellent performance logging over 850 operational hours to date
Spatial Resolution130m/km flight alt.(2.6 km from 20km)
Swath Width2 km /km flight alt.(40 km from 20 km)
Water Vapor Mixing Ratio( Uncorrected)
NAST-I Overview
Temperature (K)
Relative humidity (%)
• Instrument Characteristics – infrared Michelson interferometer (9000 spectral channels) 3.5 – 16 microns @ 0.25 cm-1
• Aircraft Accommodation – ER-2 Super pod & Proteus Underbelly pod
• Radiative Measurement Capability– calibrated radiances with 0.5 K absolute accuracy, 0.1 K precision
NAST Flight History• 1998-2004: 17 Missions
• 152 Mission sorties
• 850 Flight hours
NAST-I
NAST-M
SHIS
MAS
ER-2
Proteus
NAST-M
NAST-I
S-HIS
MAS
S-HIS
NAST-I
NAST-M
Mission Location Platform Year
Wallops 98 Virginia ER-2 1998
Camex-3 Florida ER-2 1998
WINTEX Wisconsin ER-2 1999
Wallops 99 Virginia ER-2 1999
C-IOP Oklahoma Proteus 2000
WV-IOP Oklahoma Proteus 2000
AFWEX Oklahoma Proteus 2000
A-P CA/HI/Japan/AK Proteus 2001
CLAMS Virginia Proteus 2001
IHOP Oklahoma Proteus 2002
CRYSTAL-FACE Florida Proteus 2002
TX2002 Texas ER-2 2002
THORPEX Hawaii ER-2 2003
ATOST Maine ER-2 2003
INTEX Virginia Proteus 2004
EAQUATE-1 Italy Proteus 2004
EAQUATE-2 United Kingdom Proteus 2004
NAST-I Major Characteristics
LW band 7.8 – 16.1m PC HgCdTe cooled to 77KMW band 4.8 – 7.8m PC HgCdTe cooled to 77KSW band 3.7 – 4.8m PV InSb cooled to 77Kdetector size 1 mm
entrance pupil diameter 0.28inscan angle +/- 48.4maximumIFOV 7.45collimated beam diam. in interferometer 1.5in
beamsplitter/compensator 1.9in clear aperture KBralignment technique dynamic based on HeNe laserOPD +/- 2.0cm (high resolution mode)OPD velocity 5.2cm/sec, RMS variation under 1%sweep time 0.77sec turnaround time 0.044sec
Input Optics
Detector Characteristics
Micheleson Interferometer
NAST-I Schematic
Background Radiance in NAST-I• NAST-I operates at room temperature (ground and flight)• Cold field stop and baffles within detector package significantly
reduce background radiation from surrounding structures• Some flux is modulated by the interferometer and detected
Optical Bench NAST Detector Assembly
NAST-I System Diagram
InputOptics
MichelesonInterferometer
AftOptics
Detectors andPreamplifiers
PCI bus
1.2Gbyte disk
133MHz Triton Pentium Single Board Computer
SCSI bus
A/D DSP CardAnti-aliasing
filter
IR Light spatial (cm-1) temporal f (sec-1)
electrical signal (V)
optical signal (photons)
flight computer
cm sec
NAST Layout In ER-2 SuperPod
Scanning InterferometerSounder4 – 16 m
Electronics, Control & Navigation
MIT/RLEMicrowave Sounder
NASA ER-2
NADIR 2.6km IFOV20km Altitude+/- 23km Ground Swath
Processing & Recording
ER-2 at Patrick AFB
NAST-M (54, 118 GHz)
NAST-I3.5 – 16 micron @ 0.25 cm-1
Proteus Configuration
WB-57 Pallet
Rack designed by SED/MSB and
fabricated by SED fab
NAST-I
WB-57 Pallet Configuration
Flight AMB BB (258 K)
0.01
0.1
1
600 900 1200 1500 1800 2100 2400 2700 3000Wavenumber (cm-1)
NE
dN
(m
W/m
2 -sr-
cm-1
)
SW Measured
MW Measured
LW Measured
Model
Compare Model and Measurements: Flight 98-117 Data
Flight HOTBB (333 K)
0.01
0.1
1
10
600 900 1200 1500 1800 2100 2400 2700 3000Wavenumber (cm-1)
NE
dN
(m
W/m
2-s
r-cm
-1)
SW Measured
MW Measured
LW Measured
Model
Flight T = 258 K
0.01
0.1
1
600 900 1200 1500 1800 2100 2400 2700 3000Wavenumber (cm-1)
NE
dN
(m
W/m
2 -sr-
cm
-1)
Total NEdN
Detector
Amplifier
Aliasing
Quantization
Mirror Velocity
WF Tilt Jitter
Flight T = 333 K
0.01
0.1
1
10
600 900 1200 1500 1800 2100 2400 2700 3000Wavenumber (cm-1)
NE
dN
(m
W/m
2 -sr-
cm
-1)
Total NEdN
Detector
Amplifier
Aliasing
Quantization
Mirror Velocity
WF Tilt Jitter
150
170
190
210
230
250
270
290
310
600 1000 1400 1800 2200 2600 3000Wavenumber (cm-1)
Te
mp
era
ture
(K
)
Flight
Ground
240
250
260
270
280
290
300
600 900 1200 1500 1800 2100 2400 2700 3000Wavenumber (cm-1)
Bri
gh
tne
ss
Te
mp
(K
)
T_measured
T_simulated
Background Brightness Temperature
• Background estimate is obtained from:
• Background is 180o out-of-phase with scene radiation
• Spectral signature indicates it is reflected off of Black Anodized Al
• Mounts, and most structures on the bench are Black Anodized Al
• Bkgd differs from ground to flight
• Including background in alignment NEdN calculation is essential for obtaining accurate results
Tsimulated =>[Ranodize * BB(285 K)]+BB(240 K)
Background Flux Brightness Temp
))()((/)()(21)( BambBhotambXhotXrealBkgd
Hot, Amb cal target measurement
Theoretical Hot, Amb cal target fluxCalibrated
Responsivity
Simulate Background using Black Anodize Reflectivity
Estimated Ranodize
Measured Ranodize
** Ranodize measurements were performed on Black Anodize Al similar to that found on NAST-I
Modification History• Beamsplitter replacement• Improved shock
mounts/isolation• PID thermal control of canister• Circuit added to DA servo
control to insert static offset in both sweep directions (UW)
• Gain tuning of DA servo gains• Component replacement in
DA servo and metrology laser electronics
• LW detector, cooler, and optics
LW detectorMW detector
SW detector
NAST-I Lessons Learned• Worked well
– Integrated Dewar Cooler Assembly (IDCA)– Stirling cycle cooler– Reflective optical design– Coregistration– Bomem interferometer– MIT LL Porch swing– Simple design: reliability
• What could be better– LW detector performance– Data collection– Data quicklook analysis– Vibration isolation– BS/CS wedge– More metrology signals – Improved GPS