IN23B-01 INVITED
NASA Earth Science Technology
Many promising remote sensing technologies and systems of space-based observations will be bringing scientific data and observations to Earth scientists in the next 5 to 10 years. These include instruments such as passive and active microwave and optical sensors for measuring geophysical parameters of the atmosphere, the seas and the land masses. Also, advanced information systems will be storing, processing and transmitting data collected from spaced based sensors so that massive amounts of data will be available for scientists to analyze and include in their models. This talk will describe the direction NASA is taking in instrument and information system technology through its investments.
IN23B-02 INVITED
NASA ESTO: Preparing the Future of Earth Science Observation Technology
NASA's Earth-Sun System Technology Office (ESTO) is investing in passive remote sensing technologies that will provide revolutionary advances in our knowledge of the Earth system. We will focus specifically on two Instrument Incubator Program (IIP) projects, the Far-Infrared Spectroscopy of the Troposphere (FIRST) instrument already developed and the In-situ Net Flux within the Atmosphere of the Earth (INFLAME) instruments presently in development. Both of these sensors provide measurements of the Earth's radiation balance presently not available in any other sensors. ESTO is also investing in detector technologies for future Earth science missions through the Far-Infrared Detector Technology Advancement Partnership (FIDTAP), a joint effort concurrently supported by NASA Langley and DRS Technologies, Inc. These sensors and technologies will position NASA to implement missions spelled out in the recent National Research Council's Decadal Survey for Earth Sciences.
IN23B-03
The Glacier and Ice Sheet Topography Interferometer: An Update on a Unique Sensor for High Accuracy Swath Mapping of Land Ice
We discuss the innovative concept and technology development of a Ka-band (35 GHz) radar for mapping the surface topography of glaciers and ice sheets. The "Glacier and Land Ice Surface Topography Interferometer" (GLISTIN) is a single-pass, single platform interferometric synthetic aperture radar (InSAR) with an 8mm wavelength, which minimizes snow penetration yet remains relatively impervious to atmospheric attenuation. Such a system has the potential for delivering topographic maps at high spatial resolution, high vertical accuracy, independent of cloud cover, with a subseasonal update and would greatly enhance current observational and modeling capabilities of ice mass-balance and glacial retreat. To enable such measurements, a digitally beamformed antenna array is utilized to provide a wide measurement swath at a technologically feasible transmit power. To prove this concept and advance the technology readiness of this design we are currently funded by the NASA Earth Science Technology Office (ESTO) Instrument Incubator Program (IIP) to build and test a 1m x 1m digitally-beamformed (DBF) Ka-band slotted waveguide antenna with integrated digital receivers. This antenna provides 16 simultaneous receive beams, effectively broadening the swath without reducing receive antenna gain. The implementation of such a large aperture at Ka-band presents many design, manufacturing and calibration challenges which are addressed as part of this IIP. The integrated DBF array will be fielded at the Jet Propulsion Laboratory's antenna range to demonstrate the overall calibration, beamforming and interferometric performance through creation of topographic imagery of the local Arroyo Seco. Currently entering the third year of the program, we will overview the system concept, array implementation and status of the technology. While the IIP addresses the development of the major technology challenges, an additional effort will demonstrate the phenomenology of the measurement by adapting the NASA ESTO-funded Uninhabited Aerial Vehicle - Synthetic Aperture Radar (UAVSAR) system for Ka-band single-pass interferometry. The conversion to Ka-Band will utilize the modular UAVSAR system originally designed for L-Band operation, retaining the radar control, data acquisition and processing infrastructure and requiring only minor pod and RF modifications. We will fly the Ka-Band interferometer aboard the UAVSAR platform over regions of Greenland, flying a grid over Jakobshavn glacier, then a transect from the coast to Swiss Camp ending at Greenland's Summit. Over a period of 4-5 weeks at the beginning of the melt season, these flight missions will be repeated in different snow/ice conditions. The flight data will be compared with airborne laser altimetry (Airborne Topographic Mapper lidar instrument, NASA GSFC/Wallops), field observations (GPS data at Swiss Camp, Summit), and climate data from the Automatic Weather Station (Colorado University) network (snowfall, corrected for densification) to estimate penetration and produce topographic surface maps. Topography is an essential piece of information for glaciology and a high-quality topographic map (tens of cm height accuracy over 10m pixels) will be produced. The experiment will pave the way to making more topographic products available to glaciologists and aid in the design a spaceborne mission capable of delivering similar products at the continental scale.
IN23B-04
Nexrad-In-Space - A Geostationary Satellite Doppler Weather Radar for Hurricane Studies
The Nexrad-In-Space (NIS) is a revolutionary atmospheric radar observation concept from the geostationary orbiting platform. It was developed over the last 4 years under the auspices of NASA's Earth Science Instrument Incubator Program (IIP). The NIS radar would provide Ka-band (35 GHz) reflectivity and line-of-sight Doppler velocity profiles over a circular Earth region of approximately 5200 km in diameter with a 12-km horizontal resolution, and a minimum detectable signal of 5 dBZ. The NIS radar achieves its superb sampling capabilities by use of a 35-m diameter, deployable antenna made from lightweight membrane material. The antenna has two transmit-receive array pairs that create a dual-beam, spiral-feed combined profile image of both reflectivity and Doppler velocity approximately every 60 minutes. This sampling time can be shortened even further by increasing the number of transmit-receive array pairs. It is generally recognized that the processes important in governing hurricane intensity and structure span a wide range of spatial and temporal scales. The environmental forcing considerations require a large domain. The vortex response to the environmental forcing ultimately involves convection on small horizontal scales in the eyewall and rainband regions. Resolving this environment-vortex-convection feedback in a numerical model requires observations on the space and time scales necessary to unambiguously define these structures within and surrounding the tropical cyclone. Because the time and space scales of these processes are small, continuous 3-dimensional independent observations of the 3-dimensional wind and precipitation structures will be needed to initialize numerical models critical for this purpose. The proposed NIS Doppler radar would be the first instrument capable of accomplishing this feat at time scales less than hours, and would create the opportunity for hurricane science to enter a new era of understanding and improved prediction. This talk will give a brief summary of the NIS instrument concept, the current technology status, the anticipated impacts on hurricane monitoring and model prediction, and the future science and technology roadmap.
IN23B-05
Recent Applications of Unmanned Autonomous Vehicles Supporting Earth Science Research
Advances in miniaturized sensors increase the capabilities of small unmanned aerial systems (UASs) to assist in measurement and monitoring of Earth processes and satellite ground-truthing. Two examples showing the versatility and capabilities of UASs serving as airborne platforms for Earth Science research are discussed. A recent application of includes the use UASs to study the supra-glacial melt pools on the Greenland Ice Sheet in August 2007. Three models of UASs were tested and employed: Manta, Silver Fox, and the electric Silver Fox (Advanced Ceramics Research, Inc.). Imagery from the campaign included a survey of the glacier terminus near Kangerlassuaq and collected imagery which included digital photos (7.2 mp) at a height of 800-1000 ft AGL and were combined in a mosaic and geo-referenced. A hyperspectral imager, designed for the Manta UAS, did collect data to develop algorithms for melt pool depth measurements on future UAS missions. The second example is the application of the Manta UAS in atmospheric research during the Maldives campaign in 2006. Researchers from Scripps Institute of Oceanography (Ramanathan et al., 2006) developed payloads for the effort while the manufacturer developed formation capabilities for their UASs. Up to six (three were needed for the mission) UASs could autonomously fly in a stacked formation. Mission requirements often flew the top UAS above 10,000 ft with the lowest UAS near 1,500ft and the middle UAS varied its altitude to correspond with cloud height. Current developments such as shipboard recovery systems and additional sensor capabilities to support upcoming research projects will also be discussed. http://www.acrtucson.com
IN23B-06
System Design and Technology Development for an Azimuth Scanning Microwave Limb Sounder
The NRC's Earth Science and Applications from Space decadal survey calls for a mission (GACM) to study global atmospheric composition, "with sufficient vertical resolution to detect the presence, transport, and chemical transformation of atmospheric layers from the surface to the lower stratosphere." Microwave limb sounding is particularly well suited for providing this information for the upper troposphere and above. The Microwave Limb Sounders on Aura and UARS have provided global measurements that have: quantified the evolution of the ozone layer; characterized the water vapor and cloud ice feedback mechanisms affecting climate change; documented the long range transport of pollution through tracers like CO; and improved the accuracy of global circulation models used for weather and climate forecasts. The Scanning Microwave Limb Sounder (SMLS) concept builds on the success of these instruments by adding an azimuth scan and increasing the antenna height to greatly improve horizontal and vertical resolution. The measurement swath is wide enough to provide, depending on orbit inclination, six or more daily measurements over midlatitudes. SMLS will incorporate a novel antenna design that enables rapid horizontal scanning, 4 Kelvin receiver front ends, advanced digital receiver back ends, and several lessons learned from previous missions. We will discuss the instrument design, technology development and readiness, and our approach to on-orbit calibration. We will also discuss plans and goals for a demonstration instrument that takes advantage of technologies developed through ESTO and other NASA and non-NASA programs. http://mls.jpl.nasa.gov/index- cameo.php
IN23B-07
Sensitive Broadband Receivers for Microwave Limb Sounding
Microwave limb sounding is a proven remote-sensing technique that resolves the spectra of microwave thermal emission along a limb view of the earth's atmosphere with a cold space background. The temperature and composition of the atmosphere as a function of altitude is retrieved by analyzing the spectra returned from a vertical scan of the limb. The Microwave Limb Sounder (MLS) instrument on the NASA Upper Atmosphere Research Satellite (UARS) was the first experiment to study the microwave limb from space, and was followed by the current EOS MLS instrument on the Aura spacecraft. We are developing a new class of highly-sensitive broadband receivers for a next-generation microwave limb sounder that scans the limb in elevation and azimuth to generate a 3-D map of atmospheric composition. Sensitive receivers are needed to reduce integration times to allow the addition of rapid horizontal scanning while maintaining high measurement precision. The Scanning Microwave Limb Sounder (SMLS) will sample a 6000 km cross track swath with 50 km resolution while doubling the vertical resolution of its predecessor, Aura MLS. The wide swath allows for six or more daily samples for most of the mid latitudes. These frequent measurements, combined with the good horizontal and high vertical resolution of SMLS are key to enabling the study of fast processes in the upper troposphere affecting chemistry, climate, and air quality. Two receivers are being developed for SMLS: a 230 GHz channel will be used to study the upper troposphere and a 640 GHz channel will focus on measurements of the stratosphere. Both receivers feature broad tunable bandwidth (100 GHz each) to enable measurements of many important species including water, ozone, CO, HCN, NO, SO2, and acetone. Each receiver will downconvert the signal using a superconductor-insulator- superconductor (SIS) heterodyne mixer to achieve sensitivities of 100 K and 200 K for the 230 GHz and 640 GHz channels, respectively. The high spectral resolution achieved with heterodyne detection enables precision measurement of the profiles of pressure-broadened lines. Broad instantaneous bandwidth (up to 24 GHz for each channel) will enable multiple species to be measured simultaneously. The receiver for the lower-frequency channel features a 180-280 GHz sideband-separating SIS mixer. The input signal is split into two paths with a 90° relative phase shift using a waveguide branch-line quadrature hybrid coupler. Each path is separately downconverted using niobium / aluminum nitride / niobium SIS mixers. The downconverted outputs of the two mixers are recombined with a 6-18 GHz stripline 90° hybrid coupler to separate the two sidebands, with the final output in two 12 GHz wide sub-bands. Separating the sidebands increases the effective instantaneous bandwidth of the receiver, rejects unwanted flux from the image sideband, and improves calibration accuracy by eliminating the sideband imbalance uncertainty inherent to double-sideband mixers. The research described herein was carried out at the Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA, under contract with the National Aeronautics and Space Administration. http://mls.jpl.nasa.gov/index- cameo.php
IN23B-08
Space Borne Swath Mapping Laser Altimeters - Comparison of Measurement Approaches
Laser altimetry is an important technique for studying the surface topography of the planets and the Earth from orbit. Presently orbital laser altimeters profile surface height along a single ground track, such as the Geoscience Laser Altimeter System (GLAS) on Ice, Cloud, and land Elevation Satellite (ICESat). NASA is developing new technologies for an orbiting swath mapping laser altimeter with faster pulse rate and smaller footprint size to provide an instantaneous 3-dimentional measurement of the of icesheets, land topography and vegetation structure. The goal is to provide a greater than 200 m wide swath with 5 to 10 m diameter laser footprint from a 400 km altitude orbit. To achieve these goals, we have to use more efficient laser transmitters and more sensitive detectors to allow simultaneous multi-channel measurement with a reasonable instrument size and electrical power requirement. The measurement efficiency in terms of electrical energy needed per laser ranging measurement needs to be improved by more than an order of magnitude. Several different approaches were considered, including the use of fiber lasers, shorter laser pulse widths, lower noise analog detectors and photon counting detectors. The receiver sensitivity was further improved by averaging the results from a number of laser pulse measurements. Different laser pulse modulation formats, such as the pseudo random noise code modulation used in the Global Position System (GPS), were investigated to give more flexibility in laser selection and to further improve the ranging performance. We have analyzed and compared measurement performance for several different approaches using the receiver models that was validated with GLAS in orbit measurement data. We compared measurement performance with the traditional high-power low-pulse-rate laser transmitters to those with low-energy high-pulse-rate laser transmitters. For this work we considered laser characteristics representative of Microchip lasers at 1064 and 532 nm, and for pulsed Ytterbium fiber lasers at about 1?m wavelength. We considered Si APDs for analog detection, InGaAsP photocathode hybrid photomultiplier tubes for photon counting at 1?m, and Si APD single photon counting modules at 532 nm. For all cases we evaluated the probability of detection and the standard deviation of the ranging error as a function of the apparent surface reflectance defined as the product of the surface reflectance times the two-way atmosphere transmission. We also conducted several photon counting laser ranging experiments in the lab and in the field to validate our model and measurement techniques with various photon counting detectors. The results of the analysis and the experiments will be summarized and compared for parameters representative of future missions recommended by the National Research Council (NRC), such as ICESat II, LIST, and DESDynl.