Slide 1

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 NASAs 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 Slide 2 Spatial Resolution 130m/km flight alt. (2.6 km from 20km) Swath Width 2 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 Slide 3 NAST Flight History 1998-2004: 17 Missions 152 Mission sorties 850 Flight hours ER-2 Proteus NAST-M NAST-I S-HIS MAS S-HIS NAST-I NAST-M MissionLocationPlatformYear Wallops 98VirginiaER-21998 Camex-3FloridaER-21998 WINTEXWisconsinER-21999 Wallops 99VirginiaER-21999 C-IOPOklahomaProteus2000 WV-IOPOklahomaProteus2000 AFWEXOklahomaProteus2000 A-PCA/HI/Japan/AKProteus2001 CLAMSVirginiaProteus2001 IHOPOklahomaProteus2002 CRYSTAL-FACEFloridaProteus2002 TX2002TexasER-22002 THORPEXHawaiiER-22003 ATOSTMaineER-22003 INTEXVirginiaProteus2004 EAQUATE-1ItalyProteus2004 EAQUATE-2United KingdomProteus2004 Slide 4 NAST-I Major Characteristics LW band7.8 16.1 m PC HgCdTe cooled to 77K MW band4.8 7.8 m PC HgCdTe cooled to 77K SW band3.7 4.8 m PV InSb cooled to 77K detector size1 mm entrance pupil diameter0.28in scan angle+/- 48.4 maximum IFOV7.45 collimated beam diam. in interferometer1.5in beamsplitter/compensator 1.9in clear aperture KBr alignment technique dynamic based on HeNe laser OPD +/- 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 Slide 5 NAST-I Schematic Slide 6 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 Slide 7 NAST-I System Diagram Input Optics Micheleson Interferometer Aft Optics Detectors and Preamplifiers PCI bus 1.2Gbyte disk 133MHz Triton Pentium Single Board Computer SCSI bus A/D DSP Card Anti-aliasing filter IR Light spatial (cm -1 ) temporal f (sec -1 ) electrical signal (V) optical signal (photons) flight computer cm sec Slide 8 NAST Layout In ER-2 SuperPod Scanning Interferometer Sounder 4 16 m Electronics, Control & Navigation MIT/RLE Microwave Sounder NASA ER-2 NADIR 2.6km IFOV 20km Altitude +/- 23km Ground Swath Processing & Recording ER-2 at Patrick AFB Slide 9 NAST-M (54, 118 GHz) NAST-I 3.5 16 micron @ 0.25 cm-1 Proteus Configuration Slide 10 WB-57 Pallet Rack designed by SED/MSB and fabricated by SED fab NAST-I WB-57 Pallet Configuration Slide 11 Compare Model and Measurements: Flight 98-117 Data Slide 12 Background Brightness Temperature Background estimate is obtained from: Background is 180 o 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 T simulated =>[R anodize * BB(285 K)]+BB(240 K) Background Flux Brightness Temp Hot, Amb cal target measurement Theoretical Hot, Amb cal target flux Calibrated Responsivity Simulate Background using Black Anodize Reflectivity Estimated R anodize Measured R anodize ** R anodize measurements were performed on Black Anodize Al similar to that found on NAST-I Slide 13 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 detector MW detector SW detector Slide 14 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