We review development of the TIMS beginning in the early part of the decade and up to preliminary results of work in progress. We describe a geostationary application (geoCARB) at near PDR maturity for mapping CO2, CH4 and CO column mixing ratios on continental scale areas (e.g., Australia and East Asia) several times per day on contiguous samples with spacing the order 3 km at the sub satellite point. Measurements per footprint are expected to be acquired with median mission SNRs >> 300, 300 and 240 in the traditional spectral regions (e.g., OCO and TANSO-FTS on GOSAT) for CO2, namely the O2 A-band, and the weak and strong bands of CO2 near 1.61 and 2.06 microns; and >> 200 in a region near 2.32 microns for CO and CH4.The resolving powers are 15000, 15000, 11000 and 11000 in the 4 regions, respectively. Given this performance the median mission retrieval for CO2, CH4 and CO column mixing ratio is expected to be considerably better than 0.7, 1.0 and 10.0%, respectively. These measurements over several years would provide a break through reduction in the uncertainty for the sources of CO2 and CH4 within the large geostationary field of regard of the geoCARB, and the CO measurement would assist in source attribution.

The tropospheric Infrared Mapping Spectrometers (TIMS) operating at 2.33 and 4.68 µm were developed to demonstrate retrieval of atmospheric CO in several layers. In this presentation we describe the architecture of the 2.33 TIMS spectrometer, recap its development, develop its noise model, and validate that against TIMS demonstration data. We briefly describe a multi-channel geostationary space application, called geoCARB, of the TIMS technology and use the model to predict its signal to noise ratio (SNR).

Geostationary mapping of carbon monoxide (CO) with multi-layer vertical resolution on 7 × 7 km footprints over the N and S American Continents and with 1 hour repeat time is a goal of the NRC Decadal Research Survey GEO-CAPE mission [1]. With support from the NASA ESTO Instrument Incubator Program (IIP) we have demonstrated Tropospheric Infrared Mapping Spectrometers (TIMS) operating at 2330 and 4680 nm that can achieve this goal. Here we show atmospheric data acquired by the 2330 TIMS in a deployment on an airship that reinforces the conclusion above. We discuss a concept for the GEO-CAPE application.

Geostationary mapping of carbon monoxide (CO) with multi-layer vertical resolution on 7 × 7 km footprints over South and North America from 45°S to 50°N and with 1 hour repeat time is a goal of the NRC Decadal Research Survey GEO-CAPE mission [1]. With support from the NASA ESTO Instrument Incubator Program (IIP) we have demonstrated Tropospheric Infrared Mapping Spectrometers operating at 2330 and 4680 nm that can address this goal. Here we show atmospheric data acquired simultaneously in these regions and the multi-layer retrieval of CO from these data. We show a space application that would satisfy the GEO-CAPE requirements.

The Earth Science Decadal Survey Report of the U.S. National Research Council (NRC) describes requirements for improved atmospheric measurements to gain crucial understanding for air quality, climate change, and weather [1]. Improved vertical and horizontal resolution, temporal resolution and coverage are required. Our NASA Earth Science Technology Office (ESTO) Instrument Incubator Program (IIP) project is responsive as it is focused on demonstrating a Tropospheric Infrared Mapping Spectrometers (TIMS) technology that would provide considerably improved vertical and horizontal resolution, temporal resolution and coverage for measurements of Carbon Monoxide CO. It uses the CO solar reflective band near 2.3 mum and thermal emissive near 4.65 mum. It would also facilitate improved measurements of CH4, and H2O partial columns (vertical information), including considerable improvement in the boundary layer. The technology readily extrapolates to spectral regions that provide for retrieval of other important species (e.g., 9.6 and 3.6 mum for ozone O3 and formaldehyde HCOH) [2,3]. We describe the TIMS hardware and demonstration measurements, and a concept for application by the NRC mission GEO-CAPE.

Resolution of important outstanding questions in air quality, climate change and ozone layer stability demands global observations of multiple chemical species with high horizontal and vertical resolution from the boundary layer to the stratopause. We present a mission concept that delivers the needed atmospheric composition observations, along with cloud ice and water vapor data needed for improvements in climate and weather forecasting models. The mission comprises ultraviolet and infrared nadir and microwave limb viewing instruments observing wide swaths each orbit.We review the scientific goals of the mission and the measurement capabilities this concept will deliver. We describe how precessing orbits offer significant improvements in temporal resolution and diurnal coverage compared to sun-synchronous orbits. Such improvements are needed to quantify the impact of critical "fast processes" such as deep convection on the composition and radiative properties of the upper troposphere, a region where water vapor and ozone are strong but poorly understood greenhouse gases.This concept can serve as the "Global Atmospheric Composition Mission" (GACM) recently recommended by the National Academy of Sciences decadal survey as one of 17 priority earth science missions for the coming decade.

Spectrometers, in which a grating is coupled with a two dimensional detector array to provide high resolution spectra without the need for spectral scan mechanisms can be designed in compact, rugged, configurations, making them well suited for spaceborne spectral mapping applications. We are pursuing the use of this technology for spaceborne tropospheric air quality monitoring, targeting high spectral resolution solar reflective and thermal emission spectroscopy in the wavelength range 2 to 5 μm. In this region key tropospheric pollutant and greenhouse gases such as O3, CO, CO2, CH4, HCHO, and H2O, have strong spectral features. The relatively short wavelengths allow for the use of well-developed detector technology and passive cooling. With sufficient resolving power, sensitivity, and judicious combination of spectra, good information on tropospheric vertical distributions, including boundary layer data, can be obtained. This paper describes the performance characteristics of a laboratory prototype of such a spectrometer, focused on the measurement of CO spectra in the range 4.56 to 4.73 μm. The design uses a cooled grating and optical train, coupled with a cooled 1024 x 1024 pixel HgCdTe array. It achieves a spectral resolution of ~0.32 cm-1 and NESR of 5.8x10-9 w/cm2/sr/cm-1. Both laboratory absorption spectra and zenith-looking air emission spectra of CO are presented. The spectrometer is the pre-cursor to a combined 4.6/2.33 μm instrument being developed under NASA funding and designed to demonstrate the unique vertical information capability of such a combination for tropospheric CO measurement. We give a brief discussion of a spaceborne concept focused on this technique.

We are currently developing grating mapping spectrometers (GMS) with very high spectral resolution, very low noise, and very wide field of view. These also would be very compact facilitating deployment in either a leo or geo application. The measurement set could be very comprehensive, addressing air quality, climate change and meteorology, or subsets of these. For this presentation we'll focus on potential applications of these GMS for air quality measurements of the species ozone O3, formaldehyde HCHO and carbon monoxide CO. We will discuss these applications at various levels of complexity and the commensurate value for application to understanding and forecasting air quality. At lowest complexity we would utilize a single GMS operating in the solar reflective infrared region for column measurements of O3 and HCHO. A more complex approach would utilize a second and/or third GMS for thermal emissive O3 measurements that provide improved vertical resolution, and for CO profile. Our major emphasis is the lowest tropospheric air layer 0-2 km. For realistic models of these GMS we'll present retrieval performance as predicted by a linear error analysis. In a polar leo orbit the most complex approach could provide twice daily global mapping with some footprints as small as 1.6 km at nadir. We'll present results from an in house lab demonstration GMS. This demo is a predecessor to an advanced design that we are currently developing with support of the NASA ESTO Instrument Incubator Program (IIP).

Measurements of the column CH4, CO and CO2 are high priorities of the NPOESS Pre-Planned Product Improvement (P3I) data sets. Risk reduction for existing NPOESS instruments, including mitigation of daytime CO2 SWIR non-LTE effects, is also a high priority. We have proposed an NPOESS Instrument Of Opportunity (IOO) to address these priorities. It consists of two grating mapping spectrometers (GMSs). One that would acquire measurements with high spectral resolution Δv < 0.13 cm-1 of CH4, CO and H2O absorption lines in reflected sunlight in the VSWIR region 4281 to 4301 cm-1, and another for measurements with Δv < 0.30 cm-1 in the SWIR region 2355 to 2430 cm-1. The IOO will acquire spectra on a crosstrack swath from nadir to 55 degrees (about 1400 km on the ground) on footprints that are about 1.55 and 3.1 km on a side at nadir for the two GMS, respectively. The small footprint facilitates cloud screening, and identification of pollution hotspots. We use linear error analysis (LEA, based on the Rodgers [1] paper) to estimate the proposed IOO's performance. The LEA indicates that the IOO should be able to provide CH4 and CO column retrieval over sunlit land (and from ocean glitter when it is viewed) that satisfies or exceeds NPOESS P3I Environmental Data Records (EDRs) requirements in all aspects except refresh where the IOO would provide every two days vs the once per day requirement. Further, it shows the VSWIR IOO data when used in combination with the NPOESS Cross Track Infrared Sounder (CrIS) [2] data should provide: (a) CO profile data with sensitivity to CO in near surface air that is enhanced compared to that in the current TERRA-MOPITT, ACQUA-AIRS and AURA-TES data sets because these are limited to thermal infrared measurements that lack sensitivity to CO in near surface air layer where there is little contrast between the air temperature and the ground surface temperature, (b) CH4 profile with sensitivity in the near surface air layer that is crucial for identifying CH4 sources/sinks (c) and significant improvement in the CrIS retrieved humidity in the near surface layer of air. We show the SWIR IOO data can be used for CO2 column retrieval with near surface air layer sensitivity in the daytime. And also that in combination with CrIS SWIR data facilitates CO2 SWIR non-LTE mitigation that is required for advanced sounding quality temperature profile (TP) retrieval from CO2 SWIR data in daytime conditions. This provides risk reduction in case of degradation in the CrIS LWIR region data.

Precise measurements of CH 4 in a column of near surface air, and in partial columns above this, would be very valuable in identifying sources/sinks of atmospheric CH 4 , and its transport. For this purpose we have proposed a grating mapping spectrometer (GMS) for deployment as an Instrument of Opportunity (IOO) on the NPOESS that acquires data in the 2990 to 3050 cm -1 spectral region. It will provide measurements of CH 4 absorption of sunlight in the weaker CH 4 features in the region, and of thermal emission in the stronger CH 4 features in the region. It is the combination of the two that provides the vertical information. The IOO will acquire spectra on a crosstrack swath centered on nadir, and with 1/2 width of 55 degrees on each side of nadir (about 2800 km full width swath on the ground for a nominal 828 km satellite altitude). This with footprints that are about 3.1 km on a side at nadir. The small footprint facilitates cloud screening, and identification of CH 4 source hotspots. A capability to project the slit to nadir along the direction from satellite to sun will be utilized for over the ocean viewing in order to facilitate measurements in solar glitter. It will obtain spectra with resolution n -1 and sample spacing -1 . Based on the spectral characteristics and currently achievable very low-noise we do a linear error analysis (Rodgers, [1]) for the simultaneous retrieval of multi-column CH 4 , humidity, and surface parameters and 13 CH 4 total column. We show that useful multi-column CH 4 retrievals can be obtained, with good near surface sensitivity in sunlit conditions. We also show the 13 CH 4 column can be retrieved with precision better than 3%. Retrieval of 13 CH 4 column in the earth's atmosphere is analogous in difficulty to retrieval of the major CH 4 isotope column in the Martian atmosphere by a similar GMS deployed on a Mars orbiter. We show that H 2 O vertical information can be retrieved from these measurements and discuss the potential for ethane column retrieval.

Trace gases measured by the Atmospheric Trace Molecule Spectroscopy (ATMOS) instrument during the Mar/Apr 1992(AT-1), Apr 1993(AT-2), and Nov 1994(AT-3) space-shuttle missions have been mapped into equivalent latitude/potential temperature (EqL/0) coordinates.

We present a short overview of applications of estimation theory in atmospheric chemistry and discuss some common methods of gridding and mapping of irregular satellite observations of chemical constituents. It is shown that these methods are unable to produce truly synoptic maps of short-lived photochemically active species due to insufficient temporal and spatial density of satellite observations. The only way to overcome this limitation is to supplement observations with prior independent information given, for instance, by atmospheric numerical models and/or climatologies. Objective approaches to combining such prior information with observations are commonly referred to as data assimilation. Mathematical basis of data assimilation known as optimal estimation equations is presented following Lorenc [1986]. Two particular techniques of data assimilation, the variational method and the extended Kalman filter, are briefly described, and their applications to time-dependent numerical photochemical models are discussed. We investigate validity of the linear approximation which is utilized in both methods, present time evolution of the linearization and covariance matrices, and discuss some of their properties. On the basis of ideas of Fisher and Lary [1995] we then employ a trajectory model and a photochemical box model for assimilation and mapping of the Upper Atmosphere Research Satellite (UARS) measurements of chemical species. The assimilation is performed using the variational technique and the extended Kalman filter, and results of bo th methods are presented and discussed.

The distribution and optical characteristics of Antarctic polar stratospheric clouds (PSCs) during the winter of 1992 as seen from the cryogenic limb array etalon spectrometer (CLAES) on the NASA Upper Atmosphere Research Satellite (UARS) are presented. The CLAES measurements are the first extensive stratospheric aerosol observations through much of the Antarctic polar night. An analysis of the vertical and areal distribution using the aerosol absorption coefficient measured at 780 cm−1 is presented, including a polar map showing the frequency of PSC occurrence during the two CLAES Antarctic viewing periods June 11 to July 10 and August 16 to September 18. The PSC seasonal evolution from CLAES is compared with a climatology based on the Stratospheric Aerosol Measurements II (SAM II) system. The frequency of PSC occurrence in the CLAES data sampled at latitudes similar to those observed with SAM II shows general agreement with the climatology. Some obvious differences between details of the PSC evolution seen by CLAES and the climatology are investigated with 1992 SAM II aerosol extinction data and shown to be due to intra‐annual variations specific to 1992, which appear in both data sets.

The CLAES measurement concept, instrument design, and performance are presented, and the scientific capabilities and measurement modes are discussed. The CLAES experiment involves remote measurement of earth-limb emission spectra. Characteristic vibration-rotation line spectral radiances are obtained between 3.5 and 13 microns and inverted through an iterative relaxation process to yield pressure, temperature, and species mixing ratio. The UARS limb-viewing instruments, including CLAES, combined with the 57-deg orbit inclination, allow for measurements to 80-deg latitudes. CLAES requires high spectral resolution and high radiometric sensitivity to isolate and accurately measure weak emissions from trace species such as HCl and NO against intense backgrounds from abundant emitters such as CO2, H2O, and O3. Accuracy and precision of retrieved quantities, observational modes, and calibration modes are also discussed.

Significant attention is focused on the study of the upper atmosphere and the potential effects of changes in the climate, weather, and protection provided by the ozone layer. The NASA Upper Atmospheric Research Satellite (UARS) (figure 1) , will provide a global, continuous, and comprehensive look at the upper atmosphere over an 18 month period with scheduled launch in the fall of 1991. The Cryogenic Limb Array Etalon Spectrometer (CLAES) will derive Stratospheric temperatures and constituent number densities from the measurement of infrared spectral emissions. Overviews of the CLAES experiment and hardware are given by Roche et al (Ref 1) and Burriesci et al. (Ref 2).