AIRS is a key facility instrument on the first post meridian (PM) platform as part of NASA's Earth Observing System (EOS) program. The Atmospheric Infrared Sounder measurement technique is based on passive JR remote sensing using a high spectral resolution grating spectrometer. The structure of the infrared focal plane for the AIRS instrument has been defined and is presented in this paper.The optical footprint of 8. 1 mm by 36.3 mm along with the necessary support and interface components leads to a ftcal plane assembly of 53 mm by 66 mm. the largest ever built at LIRIS. With 4208 diodes and 274 photoconductois in the same frcal plane to achieve the wide spectral coverage from 3.7 to 15.4 tim, a modular approach is required. Ten PV modules utilize silicon Readout Integrated Circuits (ROICs)joined to the detector arrays as either direct or indirect hybrids while two PC modules coyer the I 3.7 to 1 5.4 mm range, optically chopped and led out to uncooled preamplifiers. The simultaneous operation of PV and PC devices in the same focal plane has required unique approaches to shielding, ROTC output design and lead routing.High Dfs of 7El4 and 3E1 1 cm-Hzl/2/W are needed to meet the sensitivity requirements of the 4.2 and 15.0 .tm regions respectively. The 35 .tm by 800 jim PC detectors on a 50 im pitch have necessitated modifications to standard delineation techniques. while the MW performance is nearly D BLIP for PV devices. Dispersed energy is presented to the modules through 1 7 narrow band filters packaged into a single precision assembly mounted within 0. 1 8 -0.25 mm of the focal plane surface. The more thaii 50 componelits comprising the focal plane in conjunction with the tightly spaced optical pattern preseited by the grating add a high degree of complexity to the assembly process. This paper focuses on the architectural constraints derived from performance, interface and reliability requirements. Key aspects of these requirements are presented and their impact on the partitioning of the I 2 modules is discussed. The rationale for the spectral range assigned to each module is reviewed relative to PV and PC performance capabilities, ROIC design guidelines and physical constraints due to manufacturahility and assembly. Results of structural and thermal analyses for the various module configurations and assembled focal plane to determine compliance with the stringent stability and positional requirements are presented. Specific features of the module carrier/interface boards and the multilayered focal plane carrier/interface board are included as well as a review of the overall assembly sequence of the focal plane as influenced by repairability and reliability considerations.The comprehensive redundance strategy applied to the design of the FPA/dewar assembly will be reviewed, and the approach for operation/survival in the radiation environment is discussed. Key features of the ROIC. PV and PC array designs will he presented, along with results of analyses performed. This work is being funded by NASA Goddard Spa...

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AIRS is a key instnnnent in NASA's Earth Observing System (EOS) Program. Passive IR remote sensing is performed using a high resolution grating spectrometer design with a wide spectral coverage focal plane assembly (FPA). The hybrid HgCdTe focal plane consists of twelve modules, ten photovoltaic (1W) and two photoconductive (PC), providing spectral response from 3.7 to 15.4 jtm. The PV modules use silicon readout integrated circuits (ROICs)joined to the detector arrays as either direct or indirect hybrids. The PC modules are optically chopped and led out to warm electronics. Operating at 58K, the sensitivity requirements approach BLIP in the critical 4.2 and 15.0 n bands. The optical fooqxint coupled with the support and interface components of the focal plane make it a very large assembly, 53mm x 66mm. Dispersed energy from the grating is presented to the modules through 17 narrowband filters mounted 0.2 mm above the focal plane in a single, removable precision assembly.With PV and PC devices on the same focal plane operating simultaneously, shielding and lead muting as well as ROIC design have been optimized to minimize any interactions between them. Multilayer carriers have been designed to lead out the closely spaced PC arrays and the entire focal plane itselL Multilayer shielded flex cables are used to interconnect the focal plane to a very unique dewar. The tightly spaced optical pattern, along with more than 50 components in the focal plane, make this a highly complex assembly. The vacuum dewar while providing approximately 600 leadouts, is directly coupled to the cold spectrometer and operates at 155 K while cooling the focal plane to 58 K via a sapphire rod interfaced to a pulse tube cooler.This paper discusses the key features of the FPA/dewar assembly, modeling/analyses done in support of the design, and results of design validation activities to date.

Traditionally, photoconductive (PC) HgCdTe detectors have been used in interferometers for detection in the 14-15 .tm range. In this paper we present recent quantum efficiency and junction impedance data which demonstrate that P-on-n HgCdTe photovoltaic (PV) detectors with 16-17 m cutoff wavelengths at 70 K are suitable for use in spaceborne remote sensing interferometrjc instruments such as IMG-2, ATRAS, TES and CCOSM. The performance of these large-area detectors is of particular importance for interferometers because they have higher linearity at higher fluxes than PC HgCdTe arrays. The linearity requirement of 1% for the IMG-2 instrument, with background fluxes in excess of 1016 ph/cm2-s, is only marginally met by PC HgCdTe detectors. We present, for the first time, data showing better than 1% linearity at fluxes of l.3x10'7 phlcm2-s for PV HgCdTe detectors with 60 K cutoff wavelengths of 15.5 pm.

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