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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

ERS-1 SAR data processing

To take full advantage of the synthetic aperature radar (SAR) to be flown on board the European Space Agency's Remote Sensing Satellite (ERS-1) (1989) and the Canadian Radarsat (1990), the implementation of a receiving station in Alaska is being studied to gather and process SAR data pertaining in particular to regions within the station's range of reception. The current SAR data processing requirement is estimated to be on the order of 5 minutes per day. The Interim Digital Sar Processor (IDP) which was under continual development through Seasat (1978) and SIR-B (1984) can process slightly more than 2 minutes of ERS-1 data per day. On the other hand, the Advanced Digital SAR Processore (ADSP), currently under development for the Shuttle Imaging Radar C (SIR-C, 1988) and the Venus Radar Mapper, (VMR, 1988), is capable of processing ERS-1 SAR data at a real time rate. To better suit the anticipated ERS-1 SAR data processing requirement, both a modified IDP and an ADSP derivative are being examined. For the modified IDP, a pipelined architecture is proposed for the mini-computer plus array processor arrangement to improve throughout. For the ADSP derivative, a simplified version is proposed to enhance ease of implementation and maintainability while maintaing real time throughput rates. These processing systems are discussed and evaluated.

Leung, K.↗
NASA NTRS1993

Intercomparison of haloe and ER-2 aircraft H2O and CH4 observations collected during the second Airborne Arctic Stratospheric Experiment (AASE-II)

HALOE observations of H2O and CH4 are compared with in situ techniques aboard the ER-2 aircraft during the northern winter of 1991/92, in particular for the dates 911208, 920108, 920217, 920222, and 920320 when the spatial coincidences are close, within +/- 1 deg latitude and +/- 12 deg longitude. The results reveal the limitations of comparing high resolution in situ aircraft data with a remote sounding limb scanner. Of the five comparison dates, three had HALOE/ER-2 coincidences which occurred near the edge of the Arctic vortex; the vertical variability in the HALOE results and the horizontal variability in the ER-2 observations on these days show that the vortex edge is not a region where exact agreement can be expected except by chance. On a 4th comparison date, there was substantial overlap away from the vortex edge, although for some species the aircraft data show considerable variability near the coincidence point. On the 5th comparison date, the ER-2 had no overlap in altitude with the lowest HALOE observations; however, a short linear interpolation over about 1 km altitude results in smooth composite profiles. Generally speaking the agreement between HALOE and the ER-2 at overlap altitudes is about 12 percent in the case of water vapor, which shows low horizontal and vertical variability. The agreement for methane, with limited data having altitude overlap, is better than 6 percent.

Tuck, A. F.↗
NASA NTRS1992

ERS-1 and Almaz ocean wave monitoring experiments

Preliminary results from two ocean wave monitoring experiments conducted in 1991 using the high-altitude ERS-1 synthetic aperture radar (SAR) and the low-altitude ex-USSR Almaz 1 SAR are presented. ERS-1 imagery of the Gulf Stream supports the idea that a future wide-swath scansar will be a valuable tool for monitoring large-scale ocean dynamics at high resolution. A direct comparison of ERS-1 and Almaz 1 ocean wave spectra shows major deficiencies in the ERS-1 high range-to-velocity ratio R/V sensor that are partially resolved with the lower-altitude Almaz platform. Optimum wave imaging from space will require both a low R/V and low off-nadir angle.

Beal, R. C.↗
NASA NTRS1993

The Grand Banks ERS-1 SAR wave spectra validation experiment

As part of the ERS-1 validation program, the ERS-1 Synthetic Aperture Radar (SAR) wave spectra validation experiment was carried out over the Grand Banks of Newfoundland (Canada) in Nov. 1991. The principal objective of the experiment was to obtain complete sets of wind and wave data from a variety of calibrated instruments to validate SAR measurements of ocean wave spectra. The field program activities are described and the rather complex wind and wave conditions which were observed are summarized. Spectral comparisons with ERS-1 SAR image spectra are provided. The ERS-1 SAR is shown to have measured swell and range traveling wind seas, but did not measure azimuth traveling wind seas at any time during the experiment. Results of velocity bunching forward mapping and new measurements of the relationship between wind stress and sea state are also shown.

Vachon, P. W.↗
NASA NTRS1993

Arctic geodynamics: Continental shelf and deep ocean geophysics. ERS-1 satellite altimetry: A first look

An overall review of the Arctic Geodynamics project is presented. A composite gravity field model of the region based upon altimetry data from ERS-1, Geosat, and Seasat is made. ERS-1 altimetry covers unique Arctic and Antarctic latitudes above 72 deg. Both areas contain large continental shelf areas, passive margins, as well as recently formed deep ocean areas. Until 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 north of Iceland are shown. The gravity anomalies around Svalbard (Spitsbergen) and Bear island are particularly large, indicating large isostatic anomalies which remain from the recent breakup of Greenland from Scandinavian. Recently released gravity data from the Armed Forces Topographic Service of Russia cover a portion of the Barents and Kara seas. A comparison of this data with the ERS-1 produced gravity field is shown.

Anderson, Allen Joel↗
NASA NTRS1994

Precise orbit analysis and global verification results from ERS-1 altimetry

A technique which employs dual satellite crossover measurements from ERS-1 and Topology Ocean Experiment (TOPEX)/Poseidon together with laser tracking data and single satellite crossover measurements for ERS-1 precision orbit determination is described. The accuracy assessment of the resulting ERS-1 orbit is provided. Results of global verification of the ERS-1 Ocean Products (OPR02) and the Interim Geophysical Data Records (IGDR) data products in terms of altimeter bias, time lag bias and sea state bias are presented.

Shum, C. K.↗
NASA NTRS1996

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

We compare volume mixing ratio profiles of N2O, O3, NO(y), H2O, CH4, and CO 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. ATMOS and ER-2 observations of (N2O) show good agreement, as do measured correlations of (O3), (NO(y)), (H2O), and (CH4) with (N2O). Thus a consistent measure of the hydrogen (H2O, CH4) content of the lower stratosphere is provided by the two platforms. The similarity of (NO(y)) determined by detection of individual species by ATMOS and the total (NOy) measurement on the ER-2 provides strong corroboration for the accuracy of both techniques. A 25% discrepancy in lower stratospheric (CO) observed by ATMOS and the ER-2 remains unexplained. Otherwise, the agreement for measurements of long-lived tracers demonstrates the ability to combine ATMOS data with in situ observations for quantifying atmospheric transport.

Chang, A. Y.↗
NASA NTRS1997

Biweekly Maps of Wind Stress for the North Pacific from the ERS-1 Scatterometer

The European Remote-sensing Satellite (ERS-1) was launched in July 1991 and contained several instruments for observing the Earth's ocean including a wind scatterometer. The scatterometer measurements were processed by the European Space Agency (ESA) and the Jet Propulsion Laboratory (JPL). JPL reprocessed (Freilich and Dunbar, 1992) the ERS-1 backscatter measurements to produced a 'value added' data set that contained the ESA wind vector as well as a set of up to four ambiguities. These ambiguities were further processed using a maximum-likelihood estimation (MLE) and a median filter to produce a 'selected vector.' This report describes a technique developed to produce time-averaged wind field estimates with their expected errors using only scatterometer wind vectors. The processing described in this report involved extracting regions of interest from the data tapes, checking the quality and creating the wind field estimate. This analysis also includes the derivation of biweekly average wind vectors over the North Pacific Ocean at a resolution of 0.50 x 0.50. This was done with an optimal average algorithm temporally and an over-determined biharmonic spline spatially. There have been other attempts at creating gridded wind files from ERS-1 winds, e.g., kriging techniques (Bentamy et al., 1996) and successive corrections schemes (Tang and Liu, 1996). There are several inherent problems with the ERS-1 scatterometer. Since this is a multidisciplinary mission, the satellite is flown in different orbits optimized for each phase of the mission. The scatterometer also shares several sub-systems with the Synthetic Aperture Radar (SAR) and cannot be operated while the SAR is in operation. The scatterometer is also a single-sided instrument and only measures backscatter along the right side of the satellite. The processing described here generates biweekly wind maps during the wktwo years analysis period regardless of the satellite orbit or missing data.

SYNTHETIC APERTURE RADAR↗
NASA NTRS1996

A Comparison of Measurements from ATMOS and Instruments Aboard the ER-2 Aircraft: Tracers of Atmospheric Transport

We compare volume mixing ratio profiles of N2O, O3, NO(y) H2O, CH4, and CO 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. ATMOS and ER-2 observations of [N2O] show good agreement, as do measured correlations of [O3], [NO(y)], [H2O], and [CH4] with [N2O]. Thus a consistent measure of the hydrogen (H2O, CH4) content of the lower stratosphere is provided by the two platforms. The similarity of [NO(y)] determined by detection of individual species by ATMOS and the total [NO(y)] measurement on the ER-2 provides strong corroboration for the accuracy of both techniques. A 25% discrepancy in lower stratospheric [CO] observed by ATMOS and the ER-2 remains unexplained. Otherwise, the agreement for measurements of long-lived tracers demonstrates the ability to combine ATMOS data with in situ observations for quantifying atmospheric transport.

Chang, A. Y.↗
NASA NTRS2000

Hurricane Bonnie Landfalling Observed from ER-2 Doppler Radar on 26 August 1998 During CAMEX-3

The NASA ER-2 and DC-8 aircraft collected remote sensing and in situ data sets from Hurricane Bonnie (23, 24, and 26 August 1998) during the Convection And Moisture Experimental-3 (CAMEX-3). Bonnie was an exceptional case where NASA and NOAA had five aircraft sampling both upper levels and lower altitudes. The ER-2 was instrumented with the ER-2 Doppler XBand radar (EDOP) and several radiometers ranging from visible to lower frequency microwaves. EDOP is a fixed dual-beam radar (nadir and forward-looking beams) which allows computation of both vertical and alongtrack horizontal winds. The hurricane secondary circulation is typically difficult to measure at upper levels due to aircraft altitude limitations and sensitivity of the lower altitude airborne radars. EDOP is in principle, well suited to measure these components of the wind. When ER-2 flies across the approximate center of the hurricane circulation, the along-track winds derived from EDOP, are approximately equal to the hurricane radial flow comprising the secondary circulation. Assuming that the hydrometeor fallspeeds can be approximated, the radial and vertical wind components of the secondary circulation can be measured. Since the hydrometeor motions can be estimated with more confidence in the higher altitude ice regions (i.e., graupel and mixed phase are complicated at lower altitudes), the derived radial and vertical winds have higher accuracy at upper levels. On the other hand, the reflectivities are extremely low at higher altitudes, resulting in fewer Doppler velocity estimates.

Heymsfield, G. M.↗
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 5-6dB. 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 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.↗
DOE OSTI2020

Materials Data on Er(AlGe)2 by Materials Project

Al2ErGe2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Er is bonded to six equivalent Ge atoms to form distorted ErGe6 octahedra that share corners with twelve equivalent AlGe4 tetrahedra, edges with six equivalent ErGe6 octahedra, and edges with six equivalent AlGe4 tetrahedra. All Er–Ge bond lengths are 2.98 Å. Al is bonded to four equivalent Ge atoms to form distorted AlGe4 tetrahedra that share corners with six equivalent ErGe6 octahedra, corners with six equivalent AlGe4 tetrahedra, edges with three equivalent ErGe6 octahedra, and edges with three equivalent AlGe4 tetrahedra. The corner-sharing octahedra tilt angles range from 20–56°. There are three shorter (2.55 Å) and one longer (2.57 Å) Al–Ge bond lengths. Ge is bonded to three equivalent Er and four equivalent Al atoms to form a mixture of distorted corner and edge-sharing GeEr3Al4 pentagonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Er(IO3)3 by Materials Project

Er(IO3)3 crystallizes in the monoclinic P2_1/c space group. The structure is two-dimensional and consists of one Er(IO3)3 sheet oriented in the (-1, 0, 2) direction. Er3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Er–O bond distances ranging from 2.28–2.41 Å. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Er3+ and one I5+ atom. The O–I bond length is 1.85 Å. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Er3+ and one I5+ atom. The O–I bond length is 1.85 Å. In the third O2- site, O2- is bonded in a distorted single-bond geometry to one I5+ atom. The O–I bond length is 1.86 Å. In the fourth O2- site, O2- is bonded in a bent 120 degrees geometry to one Er3+ and one I5+ atom. The O–I bond length is 1.84 Å. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to one Er3+ and one I5+ atom. The O–I bond length is 1.86 Å. In the sixth O2- site, O2- is bonded in a distorted single-bond geometry to one I5+ atom. The O–I bond length is 1.84 Å. In the seventh O2- site, O2- is bonded in a bent 150 degrees geometry to one Er3+ and one I5+ atom. The O–I bond length is 1.82 Å. In the eighth O2- site, O2- is bonded in a bent 120 degrees geometry to one Er3+ and one I5+ atom. The O–I bond length is 1.84 Å. In the ninth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Er3+ and one I5+ atom. The O–I bond length is 1.84 Å. There are three inequivalent I5+ sites. In the first I5+ site, I5+ is bonded in a 5-coordinate geometry to three O2- atoms. In the second I5+ site, I5+ is bonded in a 3-coordinate geometry to three O2- atoms. In the third I5+ site, I5+ is bonded in a 6-coordinate geometry to three O2- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Er(MnGe)2 by Materials Project

ErMn2Ge2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Er is bonded in a 8-coordinate geometry to eight equivalent Ge atoms. All Er–Ge bond lengths are 3.05 Å. Mn is bonded to four equivalent Ge atoms to form a mixture of edge and corner-sharing MnGe4 tetrahedra. All Mn–Ge bond lengths are 2.43 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Er, four equivalent Mn, and one Ge atom. The Ge–Ge bond length is 2.56 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Er(BiO2)3 by Materials Project

Er(BiO2)3 is Ilmenite-like structured and crystallizes in the trigonal R-3 space group. The structure is three-dimensional. there are two inequivalent Er3+ sites. In the first Er3+ site, Er3+ is bonded in an octahedral geometry to six equivalent O2- atoms. All Er–O bond lengths are 2.27 Å. In the second Er3+ site, Er3+ is bonded in an octahedral geometry to six equivalent O2- atoms. All Er–O bond lengths are 2.26 Å. Bi3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Bi–O bond distances ranging from 2.22–2.63 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to one Er3+ and three equivalent Bi3+ atoms to form a mixture of distorted edge and corner-sharing OErBi3 trigonal pyramids. In the second O2- site, O2- is bonded to one Er3+ and three equivalent Bi3+ atoms to form a mixture of distorted edge and corner-sharing OErBi3 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Er(ReO4)2 by Materials Project

Er(ReO4)2 crystallizes in the triclinic P1 space group. The structure is two-dimensional and consists of one Er(ReO4)2 sheet oriented in the (0, 0, 1) direction. Er3+ is bonded to six O2- atoms to form ErO6 octahedra that share corners with six equivalent ReO4 tetrahedra. There are three shorter (2.23 Å) and three longer (2.24 Å) Er–O bond lengths. Re+6.50+ is bonded to four O2- atoms to form ReO4 tetrahedra that share corners with three equivalent ErO6 octahedra. The corner-sharing octahedra tilt angles range from 19–20°. There is one shorter (1.75 Å) and three longer (1.78 Å) Re–O bond length. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to one Er3+ and one Re+6.50+ atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to one Er3+ and one Re+6.50+ atom. The O–Re bond length is 1.78 Å. In the third O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Er3+ and one Re+6.50+ atom. The O–Re bond length is 1.78 Å. In the fourth O2- site, O2- is bonded in a single-bond geometry to one Re+6.50+ atom. In the fifth O2- site, O2- is bonded in a single-bond geometry to one Re+6.50+ atom. The O–Re bond length is 1.75 Å. In the sixth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Er3+ and one Re+6.50+ atom. In the seventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Er3+ and one Re+6.50+ atom. In the eighth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Er3+ and one Re+6.50+ atom. The O–Re bond length is 1.78 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Er(Ni2P)2 by Materials Project

ErNi4P2 crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. Er is bonded in a 6-coordinate geometry to six equivalent P atoms. There are two shorter (2.80 Å) and four longer (2.83 Å) Er–P bond lengths. Ni is bonded in a 3-coordinate geometry to three equivalent P atoms. There are two shorter (2.30 Å) and one longer (2.31 Å) Ni–P bond lengths. P is bonded in a 9-coordinate geometry to three equivalent Er and six equivalent Ni atoms.

36 MATERIALS SCIENCE↗