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