Future remote sensing instruments for the National Aeronautic and Space Administration (NASA) Earth Science Enterprise (ESE) will depend heavily upon lidars as active sources. Applications will include measurement of the chemical composition of the atmosphere, including global atmospheric CO2, tropospheric wind velocity and surface altimetry. In many cases, the technology requirements for these measurements exceed the state of the art in commercially available laser systems. Consequently, considerable research will be necessary in laser technologies in order to enable the future measurement needs of the ESE. In this paper we will describe the strategy that NASA's ESE will use to develop the necessary laser and supporting technologies. We will illustrate roadmaps of the various measurement needs detailing specific technology investments. In particular we will review the findings from workshops recently conducted by NASA to determine the technology drivers for these measurements. The Earth Science Technology Office is responsible for developing advanced technologies for the ESE, as such, this information is presented in order to communicate the relevancy of, and the need for investments in these technologies to the broadest technical audience.

ITTs Advanced Engineering and Sciences Division and the Hampton University Center for Lidar and Atmospheric Sciences Students (CLASS) team have worked closely to design, fabricate and test an eye-safe, scanning aerosol-lidar system that can be safely deployed and used by students form a variety of disciplines. CLASS is a 5-year undergraduate- research training program funded by NASA to provide hands-on atmospheric-science and lidar-technology education. The system is based on a 1.5 micron, 125 mJ, 20 Hz eye-safe optical parametric oscillator (OPO) and will be used by the HU researchers and students to evaluate the biological impact of aerosols, clouds, and pollution a variety of systems issues. The system design tasks we addressed include the development of software to calculate eye-safety levels and to model lidar performance, implementation of eye-safety features in the lidar transmitter, optimization of the receiver using optical ray tracing software, evaluation of detectors and amplifiers in the near RI, test of OPO and receiver technology, development of hardware and software for laser and scanner control and video display of the scan region.

We report on a diode pumped Tm: YLF laser generating 1.9 micrometers output. Recently, research is being pursued to produce laser wavelength around 2 micrometers by separating the Ho and Tm ions in different laser hosts. Compared to co-doped laser hosts; a higher efficiency performance can be achieved by directly pumping the Holmium with a 1.9 micrometers Tm laser due to the elimination of energy sharing between Tm and Ho as well as deleterious upconversion effects in co-doped systems. A 300-mJ Tm:YLF laser at room temperature has been demonstrated. The laser design and laser performance is described. To our knowledge, this is the highest energy ever reported for this laser material.

This paper addresses current design improvement issues of aerosol sensing Micro-Pulse Lidars (MPL). MPLs are designed to adhere to eye-safety restrictions while achieving acceptable signal to noise ratios (SNR). This method is realized by reducing the per pulse energy of the laser and employing a narrow receiver field-of-view (FOV). Due to the narrow FOV requirement, only a partial return signal is measured until the laser beam propagates a distance where the receiver FOV fully overlaps the laser beam. This is called the full overlap distance and is usually 4 km or more for reasonable MPL parameters. Accurate MPL measurements are typically only possible beyond this distance. The fraction of laser beam energy that is within the receiver FOV versus range is called the overlap function. The causes of the overlap function are discussed. An overlap related problem with current MPL designs is that the majority of the atmospheric aerosols are located below an altitude of 4 km to 5 km, within the partial overlap region. Another problem is that the overlap function is not thermally constant. This introduces errors in the experimentally derived overlap function and system constant factor, ultimately leading to errors in the retrieved lidar signal.

The GroundWinds New Hampshire instrument is a direct detection Doppler LIDAR system that utilizes backscatter signal from both Rayleigh and Mie scattering to measure Doppler shifts in the atmosphere from the ground. This system is the first of two planned systems that will be used to validate the technology and improve the design for other potential implementations. As a means to that end, a validation campaign was conducted in September 2000 to compare the GroundWinds measurements to that from four other systems. These were the GLOW instrument, the NOAA Mini MOPA system, and a Microwave sounder from the National Weather Service. This paper will review the design of the GroundWinds instrument, as well as summarize some of the preliminary GroundWinds results from the field experiment.

A pulsed Doppler lidar for short range atmospheric backscatter measurements has been developed using fiber- optic components. The system employs a MOPA architecture and operates at a wavelength of 1.548 micrometers in a short pulse, low pulse energy, high repetition rate mode with a 30 mm diameter monostatic aperture. Details of the design and performance are given.

We have developed simplified conical scanning telescopes using Holographic Optical Elements (HOEs) to reduce the size, mass, angular momentum, and cost of scanning lidar systems. This technology enables wide-angle scanning and three-dimensional measurements of atmospheric backscatter when used in airborne instruments, and high temporal and spatial resolution observations of atmospheric dynamic structure, including wind profiles from ground-based facilities. We deployed the Holographic Airborne Rotating Lidar Instrument Experiment (HARLIE) on the ground at the Department Of Energy's (DOE) central site in northern Oklahoma during their most recent Atmospheric Radiation Measurement (ARM) program Water Vapor Intensive Operating Period (WVIOP) in September-October 2000, in order to take advantage of the many coincident atmospheric measurements taking place at that time while collecting data with which to develop data reduction algorithms. We are evaluating the HARLIE technology and scanning techniques with an eye toward their application into other types of lidar systems, including Raman and Doppler lidar systems.

We report the results of three campaigns in which the horizontal wind vector at cloud altitudes was measured using the holographic, conical-scan lidar HARLIE in its zenith-viewing mode. Measurements were made during the HOLO-1 and HOLO-2 tests in Utah and New Hampshire in March and June 1999, respectively, and at the DoE-ARM site in Oklahoma in September/October 2000. A novel algorithm facilitates the wind vector analysis of the HARLIE data. Observed wind velocity and direction were compared with radiosonde records and with other data obtained from video cloud imagery and independent lidar ranging. The results demonstrate good agreement between HARLIE data and the results of other methods. The conically scanning holographic lidar opens up new possibilities for obtaining the vertical profile of horizontal winds.

The Goddard Lidar Observatory for Winds (GLOW) is a mobile Doppler lidar system which uses direct detection Doppler lidar techniques to measure wind profiles from the surface into the lower stratosphere. GLOW is intended to be used as a field deployable system for studying atmospheric dynamics and transport and can also serve as a testbed to evaluate candidate technologies developed for use in future spaceborne systems. In September of 2000 GLOW particpated in a three week intercomparison experiment at the GroundWinds facility in North Glen, NH. More than 50 hours of line-of-sight wind profile data were obtained in a wide variety of conditions including both day and night operation. Typical clear air lidar wind profiles extended to altitudes of 20 km with a 1 km vertical resolution and 1 minute averaging. A description of the mobile system is presented along with the examples of lidar wind profiles obtained with the Goddard system during the New Hampshire experiment.

A variation of the direct detection Doppler Lidar method known as the edge technique is discussed. This new method uses a frequency-agile laser transmitter to alternate the outgoing laser pulse between the two edges of a high resolution Fabry-Perot etalon. The difference in sign of the two slopes of the edge allows the unwanted molecular return signal to be eliminated as a background error source. This technique is similar to that of the 'double-edge' technique, with the main advantage being reduced complexity and cost for the system. By eliminating the error in the wind velocity measurement due to the molecular return, transmitter powers, within the eye-safety range, may be utilized to measure winds within the planetary boundary layer (PBL) with reasonable accuracy for many applications.

We have developed a pulsed, narrow line Raman shifted alexandrite laser to produce tunable near-IR radiation in the 1140 nm absorption band of water vapor. With the first Stokes Raman conversion in hydrogen, the full tuning range of alexandrite, 730-790 nm, can potentially cover the wavelength range 1050 1200 nm. The application to differential absorption lidar, DIAL, is the vertical profiling of humidity and temperature in the atmosphere. This paper reports the application of Raman-shifted alexandrite radiation for new quantitative measurements of the strengths and widths of water vapor absorption lines between 8865 and 8915 cm^-1. Alexandrite wavelength determination was obtained with oxygen A-band rotational lines near 765 nm. Similar applications and studies of the water vapor band near 940 nm can be readily carried out by Raman-shifting in deuterium.

Vertical concentration profiles of O₃ and NO₂ in the lower troposphere were measured simultaneously using a multi wavelength differential absorption lidar (DIAL) system based on a pair of Nd:YAG pumped dye lasers each capable of emitting two wavelength on alternate pulses. A mixture of Rhodamine 590 and Rhodamine 610 dyes and second harmonic generation was used to generate wavelengths 288.2 nm and 293. 5 nm for O₃ measurement, and sum frequency mixing of LDS765 dye laser radiation with Nd:YAG fundamental was used to generate wavelengths 448.1 nm and 446.8 nm for NO₂ measurement. O₃ profiles of approximately 30-50 ppb and NO₂ profiles of 0-20 ppb were obtained for vertical range 1500-2500 m. The measurement error was estimated to be < 6 ppb for 150 m range resolution, or < 0.9 ppm-m, for both O₃ and NO₂.

Preliminary experiments toward the implementation of Doppler spectral scanning differential absorption lidar (DSS DIAL) are described. In separate tests, CO2 laser pulses were reflected from either a ground-based retroreflector (36-km round-trip distance) or a retroreflector on the GEOS-3 satellite (approximately 2000-km round-trip distance). The returns were split into a reference channel and an absorptive gas-cell channel. The light was coherently detected with heterodyne receivers and analyzed. Results from the ground-based system produced data that matched expected values in one case but its repeatability remains to be determined. We are currently investigating the satellite-based system to assess the DSS DIAL technique.

The CO₂ laser is well suited for detecting a number of chemicals in the 9.3 - 10.7 micrometers band. However, there are several important species that require emission at 8 - 8.5 micrometers , which is not available from this laser. This has led to the development of a CO₂ wavelength shifting technique that allows for interrogation of the 8 micrometers region. A two-stage process using the non-linear crystal AgGaSe₂ accomplishes the shifting. In the first stage, the 10.6 micrometers CO₂ laser pump is doubled to 5.3 micrometers by second harmonic generation which then pumps the second stage, shifting the wavelength to 8.3 micrometers by optical parametric oscillation. Energy conversion efficiencies of 40 percent have been obtained for the first stage shift and 10 percent in the second stage.

Raman lidar has been demonstrated to provide vertical profiles of several of the key parameters needed for investigations of air quality. The time sequence of atmospheric profiles is most valuable for understanding the meteorological processes controlling the evolution of events and exposure associated with air pollution. The vibrational and rotational Raman lidar signals provide simultaneous profiles of meteorological data, ozone and measurements of airborne particulate matter. An operational prototype Raman lidar instrument makes use of 2nd and 4th harmonic generated laser beams of a Nd:YAG laser to provide both daytime and nighttime measurements. The Raman scatter signals from vibrational states of water vapor and nitrogen provide robust profiles of the specific humidity in the lower atmosphere. The temperature profiles are measured using the ratio of rotational Raman signals at 530 and 528 nm from the 532 nm beam of the Nd:YAG laser. In addition, the optical extinction profiles can be determined from the measured gradients in each of several molecular species scattering profiles compared to the molecular scale height. Wavelengths at 284 nm, 530 nm and 607 nm have been used routinely to determine profiles of optical extinction. The ozone profiles in the lower troposphere are measured using a DIAL analysis of the ratio of the vibrational Raman signals for nitrogen (284 nm) and oxygen (278 nm), which are on the steep side of the Hartley band of ozone. Examples from several data sets are used to demonstrate the utility of Raman lidar to describe the evolution of air pollution events. The examples presented have been selected to show the new level of understanding of air pollution events that is being gained from applications of lidar techniques.

The design and the performance of the new Raman lidar of the Radio Science Center for Space and Atmosphere (RASC) at Kyoto University are presented. The system is located at near Shigaraki, Japan, where also one of the world largest atmospheric radars, the MU radar, is operated. Measurement parameters of the lidar are atmospheric temperature (with rotational Raman and with Rayleigh integration technique), water vapor mixing ratio, and optical particle properties. Common Raman lidar takes vibrational-rotational Raman backscatter of nitrogen as a reference signal. In contrast to this, our system makes use of the approximately 10-times stronger pure-rotational Raman signals for deriving both atmospheric temperature and a temperature independent Raman reference signal. This modification leads to a significant reduction of measurement uncertainties. With the RASC lidar, rotational Raman signals with, to our best knowledge, unprecedented intensity can be taken by means of a high-throughput receiver. This allows not only nighttime temperature measurements with a resolution of, e.g., a few minutes near the tropopause, but made also, to our knowledge, the first daytime measurements possible.

In the present work, an IR lidar-dial technique was used to monitor ozone concentration in Madrid urban atmosphere. Interestingly, it was found an unusual increase of ozone concentration due to heavy traffic conditions accompanying the holiday rush despite the prevailing low photochemical activity. Consequently, the usual daily ozone profile shifts towards late hours. A direct and quantitative correlation between ozone pollution and human activity such as the excess of vehicle traffic accompanying summer holidays departures from Mdrid City was observed. This new type of information can stimulate the development of local models to understand the dynamic underlying urban pollution.

A XeF (351 nm) Raman lidar has been used to monitor tropospheric aerosols over the Sallentum peninsula of Italy and the vertical profile measurements of the aerosol extinction and backscatter coefficient and of the lidar ratio are presented in the paper. The measurements have been performed on a fixed schedule along one year and reveal that the aerosols are confined to lower altitudes and are characterized by larger lidar ratio values during autumn and winter months.

A general-purpose remote sensing lidar system model has been developed for use with aerosol targets as well as hard targets in various atmospheric conditions and battlefield aerosol smoke conditions to model the actual analogue return waveform. A description of the model with equations and some of the aerosol parameters are presented. An empirically determined impulse response function from a commercially developed short-range system that operates at 0.905 micrometers is used in the prediction of the analogue output waveform for this particular system. The computed waveforms show the effects of backscatter for aerosol smoke conditions. Some experimental validation of the model for a hard target in military fog oil smoke is shown. This model will be used to predict performance of the current lidar sensor as well as other senors under various other atmospheric and battlefield smoke conditions.

Characteristics of cirrus clouds forming just below the tropical tropopause and associated atmospheric turbulence in this region are studied using a monostatic lidar and Mesosphere Stratosphere Troposphere (MST) radar. The lidar data shows quite frequent occurrence of cirrus clouds near the tropical tropopause. The vertical extent is confined to the region just below the tropopause with a width of about 1-2 km. Based on cloud optical depth these cirrus clouds can be classified as; the subvisual cirrus with optical depth (tau) _c < 0.05 and thick or opaque cirrus with optical depth (tau) _c < 0.05. Frequency of occurrence of subvisual clouds is larger than that of the thick clouds. While the subvisual cirrus occurs more frequently at an altitude approximately 16 km, the optically thick clouds occur more frequently around approximately 14 km. The lidar signal scattered by these clouds shows significant depolarization, indicating the presence of abundant amount of non-spherical particles. The MST radar observations of vertical wind during the lidar observation revealed that the region between 10 km to 16 km, where these clouds are observed, is highly turbulent. A study of the Turbulent Kinetic Energy profile has shown high er values during the period of cloud occurrence. altitude profile of the vertical gradient eddy diffusion coefficient in the latitude region 10 to 16 km shows a sharp positive peak followed by a sharp negative peak above, when the cloud is strong and continuous. On other periods when the cloud is weak and discontinuous in this region is relatively low and the peaks are rather broad. This means that a region of divergence followed by a region of convergence above is favorable for the cirrus cloud formation.

The Vaisala ceilometer LD-40 'Tropopauser' is a compact eye-safe lidar measuring continuously under all possible climatic conditions and scanning the atmosphere up to a height of 13000 m. It uses laser diodes with 855 nm wavelength that are pulsed at an average frequency of 4000 Hz. The distance of the system's range bins is 7.5 m. Its main purpose is reporting cloud base heights and vertical visibility for aviation safety purposes. This paper focuses on the additional parameters this affordable lidar is able to report due to its advanced technical properties. These parameters include kind of precipitation detected, presence and distance of cirrus, extinction coefficients within clouds, vertical profiles of planetary boundary layer backscatter power, and a comparison of cloud coverage detected by a ceilometer with values obtained with a total cloud coverage scanner. Comparison instruments include regular radiosonde soundings performed at the Meteorological Observatory Lindenberg of the German Weather Service.

This work presents the aerosol vertical profiles obtained by means of an elastic backscatter ground-based LIDAR, using the 532-nm radiation from a Nd:YAG laser. Simultaneously, the aerosol size distribution in the ambient air was continuously monitored at ground level using an aerosol spectrometer that performs particulate measurements by laser light scattering. Additional information about aerosol index was obtained from TOMS data. The vertical profiles have been useful to relate satellite observations with ground level measurements. In our experiment, deployed on the Iberian Peninsula, an estimation of the provenance of aerosols was made by analyzing the results provided by these instruments, jointly with synoptic meteorological information available.

We propose and analyze a new modulation sequence for Random- Modulation Continuous-Wave (RM-CW) lidar. It is compared to known sequences, and shown to have significantly better, and nearly-ideal, signal properties. Namely, the cross- correlation function of this new sequence - named the AA1- sequence - consists of single peaks separated by zeros. Consequently, unlike the A1- and A2-sequence, it is immune to interference caused by backscattering from different ranges. Also, since the demodulation sequence is balanced, the new sequence, unlike the M-sequence, does not require the low laser output power to be zero to maintain desired cross-correlation properties; in lidar using a semiconductor laser as a transmitter, this would eliminate coupling between the demodulated signal amplitude and the emission wavelength, and thus facilitate wavelength-dependent measurements. Furthermore, we have calculated the post- demodulation signal-to-noise ratio in the presence of an additive noise of arbitrary power spectra density - it is applicable in all cases where the noise does not depend on the signal, which is typical in direct-detection mid-IR lidar. The results show that in baseband transmission all these sequences have similar noise properties, except that the M-sequence - due to its imbalance property - has a much stronger near-zero-frequency noise pickup, which results in significantly worse noise performance in practical systems. Therefore, we claim that the new modulation sequence would yield superior performance in RM-CW lidar.

Rayleigh lidar observations of temperature in the stratosphere and mesosphere are carried out an Gadanki from February 29 to March 31, 2000, which provided a powerful means of studying the gravity wave characteristics over the tropical atmosphere during winter. The potential energy per unit mass associated with the gravity wave activity in the upper stratosphere and mesosphere is found to undergo periodic fluctuations, which are closely correlated with the zonal wind fluctuations in the stratosphere produced by the equatorial waves. This provides the first observational evidence for the modulation of the gravity wave activity by the long period equatorial waves over the tropical middle atmosphere. The vertical wave number spectra of gravity waves shows that power spectral density decease with increasing wave number with a slope less than that expected for the saturated gravity wave spectrum in the stratosphere and mesosphere. PSD decreases for vertical wavelengths smaller than about 10 km in the stratosphere while the decrease is observed for the complete range of observed gravity wave spectrum in the mesosphere. A monochromatic upward propagating gravity wave with periodicity of 6 hour, amplitude of about 1 K to 3 K and vertical wavelength of 11 km was observed on 22 March, 2000.

Limitation of a received elastic scattering flux in the image plane of a scattering volume by spatial filters is a means of analyzing the spatial and power characteristics of a lidar signal. This analysis is of particular use with a lidar for studying optically dense aerosol objects. Special features of incoherent spatial filters and the association of the filter parameters with the performance of a lidar transceiver system are considered. Factors limiting the spatial filter operation, including the sounding beam divergence and spatial and frequency spectrum limitation by an optical receiving system, are examined. The latter two are most essential.

This paper presents the new concept in the field of imaging radar system, the concept of digital receiver. The paper presents not only the digital receiver model, also every function is describe in detail. The necessity of digitizing for the laser imaging radar reception is discussed, and the feasibility of digital reception is demonstrated by research results and laboratorial data.

A compact IR transmitter for the 8-12 micrometers atmospheric window is presented. The transmitter consists of two optical parametric oscillators (OPOs) in series, pumped by a 1.064 micrometers Nd:YAG laser. The first conversion stage is a double-pass non-critically phase-matched KTP OPO. A singly resonant configuration is used - the signal at 1.574 micrometers is resonated and coupled out with a 73 percent reflectivity output mirror. The first OPO's signal serves as a pump for a double-pass type I phase-matched AgGaSe2 OPO. This second OPO resonates the signal and couples out the idler at 8-11 micrometers . We eliminate high oscillating intensities inside the cavity by means of a low feedback. The low feedback causes a high threshold level, but have a minor influence on the total efficiency. Pumped by 6.5mJ at 1.574 micrometers , the AgGaSe2 OPO produced up to 0.5mJ at 8.5 micrometers , with beam quality of M² equals 4-5 and spectral width of 4-5cm^-1. Small physical dimensions, simplicity, and fairly good stability, makes this tandem OPO system usable for remote sensing applications. The described system is currently used for laboratory aerosol backscatter measurements.

The performance of a space-borne incoherent Doppler lidar system has been discussed by using modeled atmosphere and analytical calculations. With using the modeled atmosphere, the analytical calculations, and reasonable instrumental parameters, we estimated the error on the line-of-sight (LOS) wind under the assumptions that the horizontal and temporal variation of tropospheric aerosol and atmospheric molecule is negligible in no cloud condition. We used the solar radiance value measured in the troposphere to discuss the LOS wind error on the effect of the solar radiance during daytime. Although the LOS wind error depends on the system parameters, the comparison between the various analytical calculations suggested that the LOS wind errors for those the analytical methods were almost the same values. The simulations showed that the LOS wind error during daytime was almost the same as that during nighttime, suggesting that the wind velocity can be made measurement under the same LOS wind error condition if the integrated solar bandwidth of the filter is narrow enough.

Through the use of observation operators, modern data assimilation systems can ingest observations of quantities that are not themselves model variables, but are mathematically related to those variables. An example of this are the LOS (line of sight) winds that Doppler wind lidars provide. The model - or data assimilation system - needs information about both components of the horizontal wind vectors, whereas the individual observations in this case only provide the projection of the wind vector onto a given direction. In order to assess the expected impact of such an observing system, it is important to examine the extent to which a meteorological analysis can be constrained by the LOS winds. A single-level wind analysis system designed to explore these issues has been built at the NASA Data Assimilation Office. In this system, simulated wind observations can be evaluated in terms of their impact on the analysis quality under various assumptions about their spatial and angular distributions as well as the observation error characteristics. The basic design of the system will be presented along with experimental results obtained with it. In particular, the value of measuring LOS winds along two different directions for a given location will be discussed.

In order to get accurate survey and careful studied for some special places, such as ocean, earthquake area and flooded area, it is convenient to use the airborne surveying system. In this paper, the Real Time Image Capture Technology will be discussed first. Then the Real Time Image Receiving and Processing technology will be discussed. Finally the PASGI system will be introduced and the some simulating results will be given.

Elastic Light Scattering is a powerful technique to probe the optical properties of particulate systems. In particular, multi-spectral extinction and multi-angular scattering based on Fraunhofer diffraction have been used with varying degrees of success to probe particulate polydispersions. However, multi-angle scattering methods require complex detector geometries while extinction methods suffer from errors due to forward scattering. In this paper, we examine the use of an in-situ multimode fiber optic backscatter probe to collect multi-spectral backscatter data supplemented by multi-spectral extinction data. To perform particle sizing, efficiency kernels must be constructed that determines the absolute backscatter signal as a function of the particle size parameter (q) for unit concentration. These efficiency kernels can then be used to invert calibrated multi-spectral data. Within this scheme, the extinction measurements act as an empirical correction factor to the backscatter measurement kernels.

The aims of remote sensing techniques are to explore and monitor earth resources: soil, sub soil, water, vegetation and minerals. Moreover, the aim of remote sensing can be extended to monitor and record and changes that might occur to these resources, either because of human activities or natural processes. This study aims to use remotely sensed data to study the state of vegetation cover in Al-Hassa oasis during the past ten years and to assess the impact of the environmental changes resulted from the operation of the irrigation and Drainage Project.

On June 21st, 2000 the Multispectral IR and Visible Imaging Spectrometer (MIVIS) and the Visible IR Spectrometer have been mounted on a Casa 212 aircraft in order to compare the two sensors for environmental monitoring.

A hybrid approach of the generalized forward-backward method with spectral accelerate algorithm and Monte Carlo method is developed. It is applied to numerical simulation of bistatic scattering from 1D conducting sea surface with a ship presence under the TE and TM tapered wave incidence at low grazing angle (LGA). Numerical simulations of bistatic scattering at LGA show the functional dependence upon polarization, frequency, observation angle, sea surface wind speeds, ship location and other parameters.

Vast amounts of energy and chemical constituents are moved about within ocean and river currents. IN the case of deep ocean currents, some reasonable estimates of this transport can be derived from models and sea surface altimetry data. River flows can be estimated form river channel models and indirectly form stage/discharge relationships. However, much of what we know with some measure of accuracy about river and ocean current si derived form in situ measurements. Current meters are the usual choice for obtaining direct observations of the current profiles with depth. Obtaining such profiles using some form of remote sensing is a technological challenge. Surface currents, on the other hand, are more attractive targets for non-contact monitoring. However, useful relationships between the surface motion and the deeper motions are problematic with confounders including wind stress and/or density stratification. In spite of these impediments, there may indeed be some useful information derivable from observations limited to the surface motions of the oceans or rivers, particularly if observations can be obtained with high spatial and temporal density. This paper looks at the possibility of measuring surface currents using airborne and space-based Doppler lidars.

Traditional particle sizing techniques employing forward scattering angles to separate detection channels. These techniques require 2D detector geometry as well as collimating optics. Under certain approximations, forward scattering may be analyzed as a diffraction process that greatly simplifies data inversion. However, in that process, much of the particle size sensitivity in the sub-micron regime is lost due to the severe limits imposed by the diffraction approximation. To both improve the size range of operation and to develop a practical in-situ probe, we investigate another geometry that utilizes a simple single fiber-optic spectro radiometric detector in combination with a mechanism providing multiple field of view of the sample. This is obtained by using an expanding aperture that opens to a set of discrete radii. Different regions of the angular scattering spectrum are obtained by calculating the scattered signal difference between neighboring radii. For sizing applications, the system scattering kernels within Mie Scattering theory are calculated for unit concentration and variable size parameter 1 for each aperture using a simplified far-field plane wave approximation. The resulting multi angular/multispectral kernels provide a superset of scattering information that can lead to improved inversion capabilities to those obtained from multiangle measurements alone.