An application of a DIAL technique that accurately resolves the vertical distribution of tropospheric ozone up to at least 12 km altitude in one minute, during either the day or night, is described. The prototype instrument is located in the Colorado mountains and is to serve as the first NOAA ozone lidar within a planned tropospheric monitoring network. A schematic of the tropospheric ozone lidar, and a sequence of ozone profiles with an offset of 10 exp 12 between profiles are shown.

Ozone (O3) and aerosol distributions were remotely measured from an aircraft using a differential absorption lidar (DIAL) system as part of the 1988 NASA Global Tropospheric Experiment - Arctic Boundary Layer Experiment (ABLE-3A). The airborne DIAL system made simultaneous measurements of O3 and aerosols from the surface to above the tropopause. These measurements were made in a broad range of atmospheric conditions over the tundra, ice, and ocean regions near Barrow and Bethel, Alaska, during July and August 1988. The tropospheric composition over the Arctic was found to be strongly influenced by stratospheric intrusions. Regions of low aerosol scattering and enhanced O3 mixing ratios were usually correlated with descending air from the upper troposphere or lower stratosphere. Several cases of enhanced O3 were observed during ABLE-3A in conjunction with enhanced aerosol layers in the free troposphere resulting from biomass burning. As was found in the Amazon, the products of biomass burning can significantly alter O3 concentrations in the troposphere. This paper describes the NASA airborne DIAL system and discusses the large-scale variations of O3 and aerosols observed with the airborne DIAL system during ABLE-3A.

The measurement of tropospheric carbon monoxide with gas filter radiometers is examined on the basis of the MAPS experiment. The performance characteristics of an instrument that uses the MAPS detectors, broadband filters, and gas cells in a system similar to the GASCOFIL system described by Morrow and Nicholls (1985) is determined. The signal function for two carbon monoxide channels of the MAPS instrument as it was flown in 1981 is shown. The measurements of the lower pressure channel are weighted to a higher altitude. The signal function, when integrated over altitude and multiplied by the normalization constant, yields the value of the signal. Both signal functions approach zero at the top because the gas concentration approaches zero. The present data reduction technique assumes that there are no clouds in the field of view. If clouds are present, the inferred carbon monoxide mixing ratio is too high, and those points must be rejected from the data set.

Results are presented of an experiment employing a laser source and very high resolution ultraviolet absorption spectroscopy to measure the concentration of OH in a clean environment with a sensitivity limit of about 200,000/cu cm (0.01 pptv), with random noise near 50,000/cu cm. This is a factor of 10 lower than the peak values expected in winter and should easily show the seasonal rise to a summer peak 100 times larger than the sensitivity limit. The experiment is to be run under both (normally) clean tropospheric conditions and during the (occasionally) polluted upslope conditions.

The measurement of the important atmospheric molecules O3, NO2, CH2O, H2O, NO3, and HONO can be measured using long path differential absorption spectroscopy. The experiment is located at the Fritz Peak Observatory, 17 km west of Boulder, Colorado. This site permits both the measurement of clean continental air during times of westerly air flow, as well as polluted urban air during easterly up-slope episodes. The spectrograph used in this study is a low resolution double crossed Czerny-Turner, with a well matched receiving telescope. This spectrograph uses a 1 x 1024 element Reticon diode array detector to measure the molecular absorption spectra of these molecules in 40 nm bands in the near ultraviolet-visible region. The total optical path for this experiment is 20.6 km, and the path is folded by a 121 element retroreflector array thereby allowing the light source and spectrograph to be in the same location. Deduction of atmospheric concentrations these molecules over this path is accomplished by using a least squares procedure that employs the method of singular-value decomposition.

The spectroscopic method is used to examine anthropogenic change of atmospheric trace gases in the 1.0-3.5-micron region. During 1979-1990, CO2 is found to show an increase of 0.4 percent/yr; for CH4, the figure is 1.1 percent/yr, which is a slight decrease from the 1979-1985 interval. N2O exhibits no trend within an upper limit of 1 ppb/yr. The behavior of CO is dominated by a large seasonal variation, and no reliable trend can be concluded.

Characteristics of tropospheric methane distribution and behavior relevant to an investigation of global climate change are discussed. Of several observational objectives, source characterization is identified as being particularly well suited to space-based measurement. Simple dispersion models are used to relate emission rates due to point sources and distributed sources to field of view and sensitivity of nadir-viewing instruments. Using these models in conjunction with instrument specifications, the contributions of the Tropospheric Radiometer for Atmospheric Chemistry and Environmental Research (TRACER) and the Tropospheric Emission Spectrometer (TES) are evaluated. General points related to methane observation are discussed, and future work is described.

Measurements of gaseous air pollutants over three separate open paths in Atlanta, Georgia, conducted with a differential optical absorption spectrometer (DOAS) during July and August 1990 are reported. Over path 1 (1099 m) and path 2 (1824 m), O3, SO2, NO2, HNO2, HCHO, benzene, toluene, and o-xylene were measured. NO and NH3 were monitored over path 3 (143 m). Federal reference method (FRM) instruments were located near the DOAS light receivers, and measurements of O3, NO2, and NO were made concurrently with the DOAS. Correlation coefficients between the two measurement paths ranged from 0.87 for toluene to 0.99 for ozone. Comparisons between FRM and DOAS for O3, NO2, and NO showed good correlations but some differences in average concentrations, most notably for NO, whose FRM concentrations averaged less than 40 percent of the DOAS concentrations. The advantages of the DOAS system over traditional FRM systems are discussed.

Attention is given to an airborne UV-DIAL being developed in response to major unresolved issues concerning ozone nonattainment, the single most important air quality problem in the U.S. The system itself, its testing and characterization, and some of the principal applications of the system as an environmental monitoring tool are described. UV-DIAL will allow for the concurrent measurement of range-resolved concentrations of ozone and sulfur dioxide gases in the lower three to four kilometers of the troposphere. Achievable cell resolution will be between 50 and 200 m in the vertical and 500 and 1000 m in the horizontal; the required averaging of 'off-line' and 'on-line' signal pairs prior to the DIAL calculations to achieve acceptable SNRs will largely determine the size of these cells. Simulations conducted to examine the consequences of statistical and systematic errors on the derived gaseous pollutant concentrations and to select suitable algorithms for the detailed data processing showed that the precision of the calculated concentrations for both ozone and sulfur dioxide was generally acceptable with regard to statistical errors.

Results of ground-based remote sensing of atmospheric species conducted in Beijing from October 1989 to December 1990 for several periods of time on clear days are presented. Total columns of O3, NO2, NO3, and the slant column of O3 and NO2 were obtained by solar and skylight spectrophotometer (SSS) through direct sun/moon and zenith sky measurements, respectively. Results of aerosol measurements performed by SSS in Beijing are also reported. Beginning on October 25, 1990, total columns of O3, SO2, and UVB radiations were measured by Brewer spectrophotometer. It is found from the wintertime measurements that total O3 increases with time while UVB radiation decreases. There is a 14-d period for the variation of O3 amounts. The amount of SO2 increases during the hot season in Beijing.

UARS is designed to provide the most extensive data base ever obtained on the coupled energy input, chemistry, and dynamics of the earth's upper atmosphere to increase enormously the current understanding of the upper atmosphere and to improve assessments of the depletion of stratospheric ozone caused by human activities. The UARS mission, observatory, and investigations are described. The UARS experimental investigations consist of energy input experiments, chemical species and temperature experiments, and dynamics experiments. Two instruments measure solar UV energy input while another measures energetic particle energy input and associated X-radiation emission from the atmosphere. Four instruments address chemical concentrations, and two make direct measurements of upper atmosphere winds.

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.

Microwave limb sounding can provide important measurements for understanding global change and processes in Earth's stratosphere, mesosphere, and lower thermosphere. An experiment for this purpose, operating at millimeter wavelengths, is now ready for launch on the NASA Upper Atmosphere Research Satellite (UARS). An enhanced experiment at submillimeter wavelengths is also in study for the future NASA Earth Observing System (EOS).

The HALOE experiment will fly on the Upper Atmosphere Research Satellite (UARS) in the last quarter of 1991. The experiment uses the solar occultation limb sounding approach, in combination with gas filter and broadband radiometry to provide measurements of temperature profiles and key gases in the ClO(y), NO(y), and HO(y) chemical families of the middle atmosphere. The instrument has been characterized in great detail to determine gains, spectral response, noise, crosstalk, field-of-view, and thermal drift characteristics. A final end-to-end test using a gas cell to simulate the atmosphere demonstrated measurement repeatability to about 1 percent and agreement between measured and calculated signals to within about 1 percent to 3 percent. This latter agreement provides confidence in knowledge of both the hardware as well as the software.

The Earth Observing System (EOS), the centerpiece of NASA's Mission to Planet Earth, is to study the interactions of the atmosphere, land, oceans, and living organisms, using the perspective of space to observe the earth as a global environmental system. To better understand the role of clouds in global change, EOS will measure incoming and emitted radiation at the top of the atmosphere. Then, to study characteristics of the atmosphere that influence radiation transfer between the top of the atmosphere and the surface, EOS wil observe clouds, water vapor and cloud water, aerosols, temperature and humidity, and directional effects. To elucidate the role of anthropogenic greenhouse gas and terrestrial and marine plants as a source or sink for carbon, EOS will observe the biological productivity of lands and oceans. EOS will also study surface properties that affect biological productivity at high resolution spatially and spectrally.

The SAGE III instrument, the latest in a series of satellite-based instruments employing the self-calibrating solar occultation technique to monitor aerosols and trace gases in the atmosphere, and potential contributions to monitoring global change and other EOS objectives are described. Uses of these data are illustrated with SAGE I and II long-term ozone, aerosol, and water vapor data. The SAGE III instrument will improve the SAM II and SAGE data products with greater overall accuracy, and will provide the ability to extend these measurements over a greater height range. SAGE III will provide long-term self-calibrating global data sets from the midtroposphere to mesosphere, which will contribute greatly to the quantification and understanding of global change.

The SAFIRE experiment was conceived to satisfy a long-standing need for simultaneous middle atmosphere observations of ozone and important O(y), HO(y), NO(y), ClO(y), and BrO(y) gases, coupled with dynamics data. This will be accomplished using interferometry and broadband radiometry to sound the Earth limb in the far IR and mid IR, respectively. The experiment will employ the latest developments in detector and cryogenic cooling technology in order to achieve the measurement objectives. Detailed instrument and simulated atmospheric retrieval studies show that important gases such as OH, HO2, H2O2, HDO, N2O5, and HOCl can be observed with good accuracy.

The Global Ozone Monitoring Experiment (GOME) and the Scanning Imaging Absorption spectroMeter for Atmospheric ChartographY (SCIAMACHY) are diode based spectrometers that will make atmospheric constituent and aerosol measurements from European satellite platforms beginning in the mid 1990's. GOME measures the atmosphere in the UV and visible in nadir scanning, while SCIAMACHY performs a combination of nadir, limb, and occultation measurements in the UV, visible, and infrared. A summary is presented of the sensitivity studies that were performed for SCIAMACHY measurements. As the GOME measurement capability is a subset of the SCIAMACHY measurement capability, the nadir, UV, and visible portion of the studies is shown to apply to GOME as well.

The notion of a ground-based long-term measuring network specifically designed to provide the earliest possible detection of changes in the composition and structure of the stratosphere and to understand the causes of those changes is examined. The network's short-term goals are: to study the temporal and spatial variability of atmospheric composition and structure; to provide the basis for ground truth and complementary measurements for satellite systems such as the NASA Upper Atmosphere Research Satellite; and to critically test multidimensional stratospheric models and provide the broad data base required for improved model development. Priorities, instrumentation, station considerations, and site requirements are also discussed.

Attention is given to a ground-based differential absorption lidar system developed and operated at the JPL Table Mountain Facility for measurements of stratospheric ozone concentration profiles from approximately 15 to 20 km altitude. The seasonal variations observed between February 1988 and late 1990 are presented as a function of altitude. For the summer 1989 Stratospheric Ozone Intercomparison Campaign, the lidar measurements were found to agree with the average of the results obtained from seven different instruments over a 14-d period to within 5 percent over the altitude range 18 to 49 km. The status of this instrument is discussed, with emphasis on areas of improvement over the present system.

The Goddard mobile lidar was deployed at Cannon Air Force Base near Clovis, New Mexico during the Spring of 1990. Measurements of stratospheric ozone and temperature were made over a period of six weeks. Data from the lidar system is compared with data from a balloon-borne, ultraviolet instrument launched from nearby Ft. Sumner, New Mexico. Along with several improvements to this instrument which are now underway, a second lidar dedicated to temperature and aerosol measurements is now being developed.

Instrumentation under construction and testing at the NOAA Aeronomy Laboratory for conducting measurements of the zenith sky and the moon in order to measure molecular abundances of trace gases in the stratosphere at extremely low levels of absorption (less than 0.05 percent) is discussed. The instrumentation consists of a telescope (for lunar observation at night or direct sun during the day), a light feed, a spectrograph, an array detector, and a data analysis system. The telescope design is a dual off-axis parabolic feed with polarizers, depolarizers, image rotators, and other optical modifiers that can be inserted at the feed focus to test their effect on the residual spectrum. The spectrograph is a cast aluminum 3/8-m f/6 double crossed Czerny-Turner system.

Results of ongoing studies of high-resolution solar absorption spectra aimed at the identification and quantification of trace constituents of importance in the chemistry of the stratosphere and upper troposphere are presented. An analysis of balloon-borne and ground-based spectra obtained at 0.0025/cm covering the 700-2200/cm interval is presented. The 0.0025/cm spectra, along with corresponding laboratory spectra, improves the spectral line parameters, and thus the accuracy of quantifying trace constituents. Results for COF2, F22, SF6, and other species are presented. The retrieval methods used for total column density and altitude distribution for both ground-based and balloon-borne spectra are also discussed.

A ground-based solar spectrum at a spectral resolution of about 0.002/cm is used to determine the altitude of the HNO3 layer. The 870/cm spectral region, which is essentially free from absorptions from other species, is employed. The data were obtained with the University of Denver 2.5-m maximum path difference Fourier Transform interferometer spectrometer system. A set of 13 HNO3 vertical profiles were used in the analysis. The best fit obtained for the 'starting' profile (which is centered at 24 km), and the best fit for the profile centered at 26 km are shown. For displacements of greater than 2 km, the discrepancy between the synthetic and observed spectra becomes readily discernible by inspection of the spectra. It is shown that the 'best fit' rms residuals are quite sensitive to the assumed altitude of the HNO3 layer.

Millimeter-wave radiometers are being used in remote sensing of stratospheric trace gases. For constituents with relatively strong spectral lines (several K), for example, ozone and water vapor, a total power radiometer with a simple load-switch calibration technique may be sufficient. If the spectral lines are weaker, and the signal to noise ratio is smaller than 10-4, a balanced calibration technique should be applied. Unfortunately, this can not easily be realized in the millimeter-wave region. Therefore, a quasi-balanced noise source in the atmosphere itself is planned.

We present an assessment of the trend detection capabilities of ground-based microwave measurements of ozone, focusing on the 20-60 km region. Uncertainty due to variable forward model and calibration errors is 3-5 percent; due to temperature profile errors, 1-2 percent; and due to spectral measurement errors, 1-3 percent. The measurement resolution is 8-10 km below 40 km, and increases to 17 km at 60 km. The net error for trend detection is 4-6 percent. Comparison with other measurements suggests interannual variations can be measured to 3-5 percent. We conclude a trend of 0.5 percent per year would be detected in about 10 years.

For the high-altitude ER-2 observations of ClO, O3, H2O, N2O, NO(y), CFCl3, and CF2Cl2 during August 17-September 29, 1987 and January 3-February 20, 1989, condensation nuclei, wind, temperature, and pressure are presented as averages of all flights. The data are displayed as vertical profiles over the airfields Punta Arenas (53 deg S, 71 deg W) and Stavanger (59 deg N, 6 deg E) and within the vortices at about 72 deg S and 78 deg N, respectively. It is shown that the Antarctic ozone hole was caused by chlorine chemistry whose balance was altered by reactions on the surface in crystals in polar stratospheric clouds. Similar processes were observed in the Arctic, whose vortex is thus primed for ozone loss.

The procedures used in making the lidar measurements of O3 and aerosols are discussed, and selected data samples of O3 and aerosol distributions observed during flights between Stavanger (59 deg N, 3 deg E) and the North Pole between about 40 deg W and 20 deg E meridians are presented. The 'on' and 'off'; laser wavelengths used for the DIAL measurements during the Airborne Arctic Stratospheric Expedition (AASE) were 301.5 and 311 nm, respectively. An intercomparison between airborne DIAL and ozonesonde measurements of O3 in the vicinity of Bear Island is shown. The DIAL profiles were obtained by averaging the lidar returns over a 5-min period and then calculating the DIAL O3 profile. Lidar measurements at 603 and 1064 nm are used to infer physical characteristics of the different types of aerosols observed during the AASE.

Atmospheric emission spectra obtained with two different spectrometer systems are presented. The first system (the BOMEM Michelson interferometer) is designed for emission work. Spectra were obtained under adverse conditions in the Antarctic, and are still of good absolute accuracy. The second system (a modified Bruker Instruments IFS120 very high spectral resolution interferometer) demonstrates the sensitivity that can be achieved even at higher spectral resolution. This system shows that mid-IR atmospheric emission spectra can be obtained with a good SNR in a reasonable length of time at a relatively high resolution. A properly designed high resolution system should achieve high accuracy, sensitivity, and resolution, thereby permitting measurements of many atmospheric constituents when solar spectra cannot be obtained.

A Grille Spectrometer was operated on board Spacelab-1, launched on 28 November 1983 for a nine-day mission. Solar occultation absorption spectra that show ozone-specific absorption features have been taken in the infrared range between 1039.6 and 1081.3 cm-1, with a spectral resolution of about 0.055 cm-1. Northern as well as southern hemisphere locations have been covered. The determination of ozone vertical-concentration profiles from these spectra has required the development of an improved inversion program based on Mill's algorithm. The most important ameliorations are the more accurate treatment of the molecular-line parameters and the introduction of Fourier-filter techniques for minimizing the influence of noise that severely affects the ozone spectra. The resulting ozone vertical profiles, between about 25 and 65 km altitude, are discussed and compared with data taken at the same time and location by other instruments (e.g., SME). In the future, these results will be compared with data taken with the same instrument during the ATLAS-1 mission and with a slightly adapted version of the spectrometer onboard the Soviet space station MIR is order to detect global changes.

The Smithsonian Astrophysical Observatory's program of balloon-borne stratospheric spectroscopic measurements is described, including instrumentation, recent scientific results, and future plans. The design and operation of the FIRS-2 far-infrared spectrometer is discussed. The current status of our efforts to recover mixing-ratio profiles with about 1 percent precision is presented. Representative recent results are shown giving mixing-ratio profiles from 20 to 50 km, selected from the suite HOCl, HCl, HF, NO2, N2O, HNO3, OH, HO2, H2O2, H2O (and isotopes), O2 (and isotopes), O3 (and isotopes), and CO2 (and isotopes). The utility of O2 and CO2 spectral lines for information on view angle or temperature and pressure is discussed. Future plans are mentioned, including the use of FIRS-2 on a balloon platform for UARS correlative measurements, the use of FIRS-2 on the NASA DC-8 platform for polar measurements, and the potential benefits of a FIRS instrument on a Shuttle platform.

The Far Infrared Limb Observing Spectrometer (FILOS) is an instrument designed to measure chemical species in the upper atmosphere using limb emission in the far infrared region of the spectrum. FILOS uses three Fabry-Perot etalons in series to obtain a resolution of 0.0017/cm near 101/cm (99 microns). The instrumental concept and atmospheric measurements are discussed.

Measurements of the 142 GHz rotational line of O3 are performed with a cooled total power radiometer. The spectral data obtained with this instrument are inverted with the Chahine algorithm in order to obtain an altitude profile of O3 in the range of 20 km to 70 km. Such profiles are compared with ozone measurements from other techniques available in the alpine region, such as Umkehr and balloon sonde data. For the correction of tropospheric effects mainly originating from water vapor, data from a dual channel radiometer at 21 GHz/31 GHz are used.

A ground-based, portable microwave radiometer that will be used to measure water vapor in the 30-80-km altitude region, and is to operate 24 hr a day, is described. The thermally excited 22.235-GHz rotational-transition line of water vapor is employed. The emission from this region produces a signal with an apparent brightness temperature of the order 0.1 to 0.5 K. A steerable reflector is used to provide optimal viewing angles, depending on the geographic location and season. Periodic tipping curve scans by this reflector permit determination of the amount of tropospheric correction that is applied to the data. All local oscillators in the receiver are crystal-controlled so that narrow-band spectral analysis of the received line shape can be performed.

A novel mm-wave radiometer system specifically designed for measuring water vapor in the stratosphere is presented. The instrument, which is based on an HEMT front-end amplifier, is described in detail. The data retrieval scheme and the results of an extensive instrument data simulation study are also presented. The device's principal features are its capability to conduct measurements of the water vapor profile simultaneously from 25-75-km altitude, with excellent long-term relative precision, and semiautomatically at a remote site.

The calibration plan for the SAGE III instruments for maintaining instrument performance during the Earth Observing System (EOS) mission lifetime is described. The SAGE III calibration plan consists of detailed preflight and inflight calibration on the instrument performance together with the correlative measurement program to validate the data products from the inverted satellite measurements. Since the measurement technique is primarily solar/lunar occultation, the instrument will be self-calibrating by using the sun as the calibration source during the routine operation of the instrument in flight. The instrument is designed to perform radiometric calibration of throughput, spectral, and spatial response in flight during routine operation. Spectral calibration can be performed in-flight from observation of the solar Fraunhofer lines within the spectral region from 290 to 1030 nm wavelength.

Measurements from two independent satellite data sets have been used to derive the climatology of the integrated amount of ozone in the troposphere. These data have led to the finding that large amounts of ozone pollution are generated by anthropogenic activity originating from both the industrialized regions of the Northern Hemisphere, and from the southern tropical regions of Africa. To verify the existence of this ozone anomaly at low latitudes, an ozonesonde capability has been established at Ascension Island (8 degree(s)S, 15 degree(s)W), since July, 1990. According to the satellite analyses, Ascension Island is located downwind of the primary source region of this ozone pollution, which likely results from the photochemical oxidation of emissions emanating from the widespread burning of savannas and other biomass. These in situ measurements confirm the existence of large amounts of ozone in the lower atmosphere. A summary of these ozonesonde data to date is presented. In addition, some ozone profile measurements are presented from SAGE II which can be used to provide upper tropospheric ozone measurements directly in the tropical troposphere. A preliminary comparison between the satellite observations and the ozonesonde profiles in the upper troposphere and lower stratosphere also are presented.

Regional scale, Eulerian framework air quality simulation models are currently being evaluated using pollutant and meteorological measurements from special surface networks and airborne p1atforms. An evaluation protocol for such models using this data base has been developed and adopted by the National Acid Precipitation Assessment Program; it includes "Operational" and "Diagnostic" components. This paper focuses on the diagnostic evaluation of the Regional Acid Deposition Model (RADM) , using aircraft measurements from the Acid Model Operational Diagnostic Evaluation Study (AcidMODES) program under sponsorship of the United States Environmental Protection Agency (USEPA) . RADM's ability to resolve horizontal patterns and gradients as well as the vertical structure of primary and secondary acidic pollutant species in the mixed layer over the major source region for sulfur and nitrogen emissions is an essential diagnostic test and is demonstrated. The potential roles of remote sensing in the evaluation of regional models are suggested.

Following its first flight on board the Space Shuttle 'Challenger' as part of the Spacelab 3 payload, the Atmospheric Trace Molecule Spectroscopy (ATMOS) instrument has been operated at the Jet Propulsion Laboratory's Table Mountain Observatory (TMO; 34.4 deg N, 117.7 deg W, 2.23 km altitude) in the San Gabriel Mountains of Southern California. With the delay in the resumption of regular Shuttle flights, ATMOS has acquired a large number of high-quality, high-resolution infrared solar absorption spectra, spanning a period between late-1985 and mid-1990. These spectra are being analyzed to derive the column abundances of several atmospheric species including O3, HCl, HF, and HNO3. Although limited in temporal coverage, the preliminary results for these gases are discussed here in the context of the requirement and contribution to be made by similar instruments in detecting long term changes in stratospheric composition.