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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Calibration Results for J-ERS-1 SAR Data Produced by the Alaska SAR Facility

The Alaska SAR Facility has been receiving and processing SAR data from the J-ERS-1 satellite since Spring 1992. Corner reflectors have been set up for J-ERS-1 SAR calibration at a site near Delta Junction, in central Alaska. Image quality and calibration analysis results from the Delta Junction site and others will be presented in this paper. The impact of the 3-bit Analog-to-Digital Converter and the automatic stepping of the gain as a function of range in the J-ERS-1 radar receiver on calibration performance has been assessed. Preliminary observations on J-ERS-1 SAR data are that the average Signal-to-Noise ratio is generally fairly low, in the range 5-6 dB. Azimuth ambiguity levels are higher than preflight analysis indicated. Over land, the dynamic range in the backscatter at L-band for approximately 36 degree incidence angle is often fairly high...

Freeman, A.↗
NASA NTRS1986

Present statue of Japanese ERS-1 Project

Earth Resources Satellite 1 (ERS-1) will be launched in the FY 1990 with the H-1 rocket from Tanegashima Space Center. ERS-1 will seek to firmly establish remote sensing technologies from space by using synthetic aperture radar and optical sensors, as well as primarily exploring for non-renewable resources and also monitoring for land use, agriculture, forestry, fishery, conservation of environment, prevention of disasters, and surveillance of coastal regions. ERS-1 is a joint project in which the main responsibility for the development of the mission equipment is assumed by the Agency of Industrial Science and Technology, MITI, and the Technology Research Association of Resources Remote Sensing System, while that for the satellite itself and launching rocket is assumed by the Science and Technology Agency (STA) and the National Space Development Agency (NASDA). In relation to this project, users have maintained a close working relationship with the manufacturers after submitting their requirements in 1984 on the specifications of the mission equipments. This missions parameters are outlined.

Ishiwada, Yasufumi↗
NASA NTRS1986

Off-line processing of ERS-1 synthetic aperture radar data with high precision and high throughput

The first European remote sensing satellite ERS-1 will be launched by the European Space Agency (ESA) in 1989. The expected lifetime is two to three years. The spacecraft sensors will primarily support ocean investigations and to a limited extent also land applications. Prime sensor is the Active Microwave Instrumentation (AMI) operating in C-Band either as Synthetic Aperture Radar (SAR) or as Wave-Scatterometer and simultaneously as Wind-Scatterometer. In Europe there will be two distinct types of processing for ERS-1 SAR data, Fast Delivery Processing and Precision Processing. Fast Delivery Proceessing will be carried out at the ground stations and up to three Fast Delivery products per pass will be delivered to end users via satellite within three hours after data acquisition. Precision Processing will be carried out in delayed time and products will not be generated until several days or weeks after data acquisition. However, a wide range of products will be generated by several Processing and Archiving Facilities (PAF) in a joint effort coordinated by ESA. The German Remote Sensing Data Center (Deutsches Fernerkundungsdatenzentrum DFD) will develop and operate one of these facilities. The related activities include the acquisition, processing and evaluation of such data for scientific, public and commercial users. Based on this experience the German Remote Sensing Data Center is presently performing a Phase-B study regarding the development of a SAR processor for ERS-1. The conceptual design of this processing facility is briefly outlined.

Gredel, J.↗
NASA NTRS1987

A study of the feasibility of using sea and wind information from the ERS-1 satellite. Part 1: Wind scatterometer data

The use of scatterometer and altimeter data in wind and wave assimilation, and the benefits this offers for quality assurance and validation of ERS-1 data were examined. Real time use of ERS-1 data was simulated through assimilation of Seasat scatterometer data. The potential for quality assurance and validation is demonstrated by documenting a series of substantial problems with the scatterometer data, which are known but took years to establish, or are new. A data impact study, and an analysis of the performance of ambiguity removal algorithms on real and simulated data were conducted. The impact of the data on analyses and forecasts is large in the Southern Hemisphere, generally small in the Northern Hemisphere, and occasionally large in the Tropics. Tests with simulated data give more optimistic results than tests with real data. Errors in ambiguity removal results occur in clusters. The probabilities which can be calculated for the ambiguous wind directions on ERS-1 contain more information than is given by a simple ranking of the directions.

Anderson, D.↗
NASA NTRS1991

Update on the NASA ER-2 Doppler radar system (EDOP)

An update on the development status of EDOP, a dual-beam Doppler weather radar to be flown on the NASA ER-2 aircraft, is presented. The EDOP system is an X-band Doppler radar with a dual-beam configuration in the ER-2 nose, such that one beam is nadir pointing and the other at an angle of 35 deg forward of the nadir. The dual beams, as used on ELDORA, directed at, e.g., 20 deg fore and aft of the normal to the fuselage, require only a linear rather than L-shaped flight pattern to compute air motions. On the ER-2, EDOP will essentially map out high-resolution time-height sections of reflectivity and vertical hydrometeor velocity from the nadir beam. Flying EDOP with other ground-based and airborne radars will also provide a more complete picture of the overall 3D precipitation and hydrometeor structure of storms.

Heymsfield, Gerald M.↗
NASA NTRS1993

On the accuracy of ERS-1 orbit predictions

Since the launch of ERS-1, the D-PAF (German Processing and Archiving Facility) provides regularly orbit predictions for the worldwide SLR (Satellite Laser Ranging) tracking network. The weekly distributed orbital elements are so called tuned IRV's and tuned SAO-elements. The tuning procedure, designed to improve the accuracy of the recovery of the orbit at the stations, is discussed based on numerical results. This shows that tuning of elements is essential for ERS-1 with the currently applied tracking procedures. The orbital elements are updated by daily distributed time bias functions. The generation of the time bias function is explained. Problems and numerical results are presented. The time bias function increases the prediction accuracy considerably. Finally, the quality assessment of ERS-1 orbit predictions is described. The accuracy is compiled for about 250 days since launch. The average accuracy lies in the range of 50-100 ms and has considerably improved.

Koenig, Rolf↗
NASA NTRS1994

Harvard ER-2 OH laser-induced fluorescence instrument

The Harvard ER-2 OH instrument is scheduled to be integrated into the NASA ER-2 high altitude aircraft ozone payload in August 1992. Design and fabrication is presently underway. This experiment is a descendant of a balloon borne instrument designed and built in the mid-1980s. The ER-2 instrument is being designed to measure OH and HO2 as part of the NASA ozone payload for the investigation of processes controlling the concentration of stratospheric ozone. Although not specifically designed to do so, it is hoped that valid measurements of OH and HO2 can be made in the remote free troposphere with this instrument.

Wennberg, Paul O.↗
NASA NTRS1994

Arctic geodynamics: Arctic science and ERS-1 satellite altimetry

A detailed gravity field map of the mid Arctic Ocean, spreading ridge system was produced on the basis of ERS-1 satellite altimetry data. Areas of special concern, the Barents and Kara Seas, and areas surrounding the islands of Svalbard, Frans Josef Land and Novoya Zemlya are reviewed. ERS-1 altimetry covers unique Arctic and Antarctic latitudes above 72 degrees. Before ERS-1 it was not possible to study these areas with satellite altimetry. Gravity field solutions for the Barents Sea, portions of the Arctic Ocean and the Norwegian sea are shown. The largest gravity anomalies occur along the Greenland fracture zone as well as along transform faults near Svalbard.

Anderson, Allen Joel↗
NASA NTRS1994

Design and performance/measurement simulation studies for a ER-2 sunphotometer

Work and results, including developed software, obtained under this grant (NAG 2-620) have been reported in various progress reports, an M.S. Thesis, and software programs. The purpose of this final report is simply to provide a documented listing of what has already been reported. This includes the following: (1) Conceptual Design and Simulation of a Spectral Sunphotometer for the ER-2 Aircraft; (2) Continued Simulation and Design Studies for an ER-2 Sunphotometer; and (3) Simulation and Performance Studies of a Spectra Sunphotometer for the ER-2 Aircraft. Also, software and computational results for modeling airmass and diffuse light effects due to aerosols were provided in support of NASA ARC research on the effects of aerosols resulting from the Pinatubo volcanic eruptions. The references for these articles are as follows: (1) Post Pinatubo Optical Depth Spectra vs. Latitude and Vortex Structure; and (2) Pinatubo and Pre-Pinatubo Optical-Depth Spectra -- Mauna Loa Measurements, Comparisons, Inferred Particle Size Distributions, Radiative Effects, and Relationships to Lidar Data.

Reagan, J. A.↗
NASA NTRS1994

Observation of melt onset on multiyear Arctic sea ice using the ERS 1 synthetic aperture radar

We present nearly coincident observations of backscattering from the Earth Remote-Sensing Satellite (ERS) 1 synthetic aperture radar (SAR) and of near-surface temperature from six drifting buoys in the Beaufort Sea, showing that the onset of melting in snow on multiyear sea ice is clearly detectable in the SAR data. Melt onset is marked by a clean, steep decrease in the backscattering cross section of multiyear ice at 5.3 GHz and VV polarization. We investigate the scattering physics responsible for the signature change and find that the cross section decrease is due solely to the appearance of liquid water in the snow cover overlying the ice. A thin layer of moist snow is sufficient to cause the observed decrease. We present a prototype algorithm to estimate the date of melt onset using the ERS 1 SAR and apply the algorithm first to the SAR data for which we have corresponding buoy temperatures. The melt onset dates estimated by the SAR algorithm agree with those obtained independently from the temperature data to within 4 days or less, with the exception of one case in which temperatures oscillated about 0 C for several weeks. Lastly, we apply the algorithm to the entire ERS 1 SAR data record acquired by the Alaska SAR Facility for the Beaufort Sea north of 73 deg N during the spring of 1992, to produce a map of the dates of melt onset over an area roughly 1000 km on a side. The progression of melt onset is primarily poleward but shows a weak meridional dependence at latitudes of approximately 76 deg-77 deg N. Melting begins in the southern part of the study region on June 13 and by June 20 has progressed to the northermost part of the region.

Winebrenner, D. P.↗
NASA NTRS1997

Ice velocity at the ice front of the Filchner-Ronne Ice Shelf, Antarctica, as observed with ERS interferometry

ERS images of the two ends of the ice front of the Filchner-Ronne ice shelf (Antarctica) were utilized interferometrically to study the deformation rate of the ice shelf in response to viscous creep. On the western bank of Berkner Island (BI), near Hemmen Ice Rise (HIR), a time series of ERS data acquired in February 1992, in both ascending and descending mode, and with a three-day time interval, were utilized to map the ice velocity in two dimensions. Finite-element ice-shelf flow simulations are compared with the ERS interferograms to interpret the ice motion in terms of the physical constraints on ice-shelf flow. The efforts to fit artificial interferograms generated with model velocity output suggest that the flow regime is strongly influenced by three processes. First, a void-creation process responsible for rifts at coastal margins tends to uncouple the ice shelf from the ice rise and neighboring coast of BI. Secondly, sea ice within the void space appears to act as a binding agent between discrete ice-shelf fragments, allowing rigid-body rotations of these fragments. Third, strain rates appear to be enhanced in a narrow zone adjacent to HIR, implying significant strain softening along the boundary. It is believed that synthetic aperture radar (SAR) interferogram/model intercomparison represents a powerful impetus towards the development of better, more physically realistic ice-shelf flow models.

Rignot, Eric↗
NASA NTRS1996

A Comparison of Measurements from ATMOS and Instruments Aboard the ER-2 Aircraft: Halogenated Gases

We compare volume mixing ratio profiles of N2O, CFC-11, CFC-12, CCl4, SF6, and HCl in the mid-latitude lower stratosphere measured by the ATMOS Fourier transform spectrometer on the ATLAS-3 Space Shuttle Mission with in situ measurements acquired from the NASA ER-2 aircraft during Nov. 1994. Good agreement is found between ATMOS and in situ correlations of [CFC-11], [CFC-12], and [SF6] with [N2O]. ATMOS measurements of [CCl4] are 15% high compared to ER-2 data, but agree within the systematic uncertainties. ATMOS observations of [HCl] vs [N2O] are within approximately 10% of ER-2 data for [HCl] > 1 ppbv, but exceed in situ measurements by larger fractional amounts for smaller [HCl]. ATMOS measurements of [ClONO2] agree well with values inferred from in situ observations of [ClO], [NO], and [O3]. The sum of [HCl] and [ClONO2] observed by ATMOS, supplemented by a minor contribution from [ClO] estimated with a photochemical model, is consistent with the levels of inorganic chlorine inferred from in situ measurements of chlorine source gases.

Chang, A. Y.↗
NASA NTRS2000

Topographic Phase Recovery from Stacked ERS Interferometry and a Low-Resolution Digital Elevation Model

A hybrid approach to topographic recovery from ERS interferometry is developed and assessed. Tropospheric/ionospheric artifacts, imprecise orbital information, and layover are key issues in recovering topography and surface deformation from repeat-pass interferometry. Previously, we developed a phase gradient approach to stacking interferograms to reduce these errors and also to reduce the short-wavelength phase noise (see Sandwell arid Price [1998] and Appendix A). Here the method is extended to use a low-resolution digital elevation model to constrain long-wavelength phase errors and an iteration scheme to minimize errors in the computation of phase gradient. We demonstrate the topographic phase recovery on 16-m postings using 25 ERS synthetic aperture radar images from an area of southern California containing 2700 m of relief. On the basis of a comparison with 81 GPS monuments, the ERS derived topography has a typical absolute accuracy of better than 10 m except in areas of layover. The resulting topographic phase enables accurate two-pass, real-time interferometry even in mountainous areas where traditional phase unwrapping schemes fail. As an example, we form a topography-free (127-m perpendicular baseline) interferogram spanning 7.5 years; fringes from two major earthquakes and a seismic slip on the San Andreas Fault are clearly isolated.

Sandwell, David T.↗
NASA NTRS2003

The Potato virus X TGBp3 protein associates with the ER network for virus cell-to-cell movement

Potato virus X (PVX) TGBp3 is required for virus cell-to-cell movement. Cell-to-cell movement of TGBp3 was studied using biolistic bombardment of plasmids expressing GFP:TGBp3. TGBp3 moves between cells in Nicotiana benthamiana, but requires TGBp1 to move in N. tabacum leaves. In tobacco leaves GFP:TGBp3 accumulated in a pattern resembling the endoplasmic reticulum (ER). To determine if the ER network is important for GFP:TGBp3 and for PVX cell-to-cell movement, a single mutation inhibiting membrane binding of TGBp3 was introduced into GFP:TGBp3 and into PVX. This mutation disrupted movement of GFP:TGBp3 and PVX. Brefeldin A, which disrupts the ER network, also inhibited GFP:TGBp3 movement in both Nicotiana species. Two deletion mutations, that do not affect membrane binding, hindered GFP:TGBp3 and PVX cell-to-cell movement. Plasmids expressing GFP:TGBp2 and GFP:TGBp3 were bombarded to several other PVX hosts and neither protein moved between adjacent cells. In most hosts, TGBp2 or TGBp3 cannot move cell-to-cell.

NASA Discipline Plant Biology↗
NASA NTRS1996

(abstract) Detection of Mesoscale Oceanic Phenomena in the Southern California Bight via ERS-1 SAR

ERS-1 SAR images are examined with the intent of identifying mesoscale oceanic phenomena in the Southern California Bight (SCB). The SCB is a region of dynamic physical and biological processes, and as such has long been studied. The ERS-1 SAR images are augmented with other remote sensing data, including SIR-C SAR, AVHRR, ERS-1 ATSR, and Space Shuttle hand-held photography. Analysis of these images has revealed a more dynamic mesoscale field than was previously suspected. Eddies with scales on the order of 20-30 km in diameter have been the most common mesoscale features evident, but the presence of oceanic fronts and internal waves, as well as atmospheric internal waves, have been documented as well. The multisensor data record will provide insight as to the underlying ocean and meterological conditions that lead to the prevalence especially of the eddies in this region.

Southern California Bight SCB remote sensing data ↗
NASA NTRS1993

(abstract) Monitoring Seasonal Change in Taiga Forests Using ERS-1 SAR Data

Sensitivity of radar backscatter to the dielectric and geometric character of forested regions suggests significant changes in backscatter are expected with season due to freezing temperatures, snow, wind, leaf fall, and drought. The first European Remote Sensing Satellite, ERS-1, offers a unique opportunity to monitor a complete seasonal cycle for the Alaskan taiga forest ecosystem with synthetic aperture radar. During the 3-day repeat Commissioning Phase of ERS-1, from August 1991to December 1991, ERS-1 SAR data were collected in the region of Manley Hot Springs, Alaska, along the Tanana River, west of Fairbanks. In parallel with the SAR data collection, meteorological data from three weather stations positioned in three forest stands were collected continuously along with in situ measurements of the dielectric and moisture properties of the canopy and of ground cover which were collected during each overflight. The in situ data were collected in floodplain forest stands dominated by balsam poplar, white spruce, and black spruce. These results from the Commissioning Phase as well as preliminary results from the 35-day Repeat Phase will be presented.

characteristics geometric characteristics moisture↗
NASA NTRS2008

Comparison of the KSC-ER Cloud-to-Ground Lightning Surveillance System (CGLSS) and the U.S. National Lightning Detection Network (NLDN)

The NASA Kennedy Space Center (KSC) and Air Force Eastern Range (ER) are located in a region of Florida that experiences the highest area density of lightning strikes to ground in the United States, with values approaching 16 fl/km 2/yr when accumulated in 10x10 km (100 sq km) grids (see Figure 1). Consequently, the KSC-ER use data derived from two cloud-to-ground (CG) lightning detection networks to detect hazardous weather, the "Cloud-to-Ground Lightning Surveillance System" (CGLSS) that is owned and operated by the Air Force and the U.S. National Lightning Detection Network (NLDN) that is owned and operated by Vaisala, Inc. These systems are used to provide lightning warnings for ground operations and to insure mission safety during space launches at the KSC-ER. In order to protect the rocket and shuttle fleets, NASA and the Air Force follow a set of lightning safety guidelines that are called the Lightning Launch Commit Criteria (LLCC). These rules are designed to insure that vehicles are not exposed to the hazards of natural or triggered lightning that would in any way jeopardize a mission or cause harm to the shuttle astronauts. Also, if any CG lightning strikes too close to a vehicle on a launch pad, it can cause time-consuming mission delays due to the extensive retests that are often required for vehicles and/or payloads when this occurs. If any CG lightning strike is missed or mis-located by even a small amount, the result could have significant safety implications, require expensive retests, or create unnecessary delays or scrubs in launches. Therefore, it is important to understand the performance of each lightning detection system in considerable detail.

Ward, Jennifer G.↗