current measurements in rivers by spaceborne along track insar the global monitoring of river discharges is a technologically challenging problem with important applications in a variety of disciplines due to the limited availability and or quality of river runoff data from many regions an increasing use of remote sensing techniques is highly desirable altimeter specialists have already demonstrated water level retrievals in rivers from available data the along track interferometric synthetic aperture radar along track insar ati capabilities of state of the art imaging radars on satellites such as the german terrasar x which was launched on june 15 2007 also permit high resolution line of sight surface current measurements in this paper we evaluate the potential of current measurements in rivers by spaceborne ati on the basis of fundamental theoretical considerations existing spaceborne insar data from the shuttle radar topography mission srtm and simulated terrasar x data we show that an srtm derived line of sight surface current field in the elbe river germany agrees well with numerical hydrodynamic model results the data quality is sufficient to resolve characteristic lateral variations of the currents in the river around a pronounced main flow channel assuming that the flow direction is usually aligned with the river bed even a quasi 2d total surface current field can be derived simulations indicate that terrasar x was even better suited for current measurements in rivers depending on width surface roughness and relative flow direction of a river current estimates with an accuracy better than 0 1 m s were possible with an effective spatial resolution of a few hundred meters to kilometers

advanced remote sensing of internal waves by spaceborne along track insar a demonstration with terrasar x since the seasat mission in 1978 satellite based synthetic aperture radar sar images have been used to study oceanic internal waves internal waves become visible in sar images because their orbital currents modulate the surface roughness while this leads to an accurate spatial representation of internal wave patterns the complexity of the imaging mechanism makes it difficult to derive actual currents and internal wave amplitudes from sar signatures we demonstrate in this paper how a more robust parameter retrieval is possible with along track interferometric sar insar data that resolve amplitudes and temporal phase changes of the backscattered signal together the latter of which are directly related to the scatterers line of sight velocities our example data set which was acquired by terrasar x in dual receive antenna mode at dongsha south china sea exhibits strong signatures of internal waves in the interferogram amplitude and phase we use a simple internal soliton parameterization and a numerical radar imaging model to find a plausible combination of internal wave parameters which leads to good agreement between simulated and observed signatures testing the sensitivity of radar amplitude and phase signatures to various parameters we show that along track insar data should generally permit more accurate and less ambiguous internal wave parameter retrievals than conventional sar images

curiosity at gale crater mars characterization and analysis of the rocknest sand shadow the rocknest aeolian deposit is similar to aeolian features analyzed by the mars exploration rovers mers spirit and opportunity the fraction of sand 150 micrometers in size contains 55 crystalline material consistent with a basaltic heritage and 45 x ray amorphous material the amorphous component of rocknest is iron rich and silicon poor and is the host of the volatiles water oxygen sulfur dioxide carbon dioxide and chlorine detected by the sample analysis at mars instrument and of the fine grained nanophase oxide component first described from basaltic soils analyzed by mers the similarity between soils and aeolian materials analyzed at gusev crater meridiani planum and gale crater implies locally sourced globally similar basaltic materials or globally and regionally sourced basaltic components deposited locally at all three locations

decorrelation in interferometric radar echoes a radar interferometric technique for topographic mapping of surfaces implemented utilizing a single synthetic aperture radar sar system in a nearly repeating orbit is discussed the authors characterize the various sources contributing to the echo correlation statistics and isolate the term which most closely describes surficial change they then examine the application of this approach to topographic mapping of vegetated surfaces which may be expected to possess varying backscatter over time it is found that there is decorrelation increasing with time but that digital terrain model generation remains feasible the authors present such a map of a forested area in oregon which also includes some nearly unvegetated lava flows such a technique could provide a global digital terrain map

predicted diurnal variation of the deuterium to hydrogen ratio in water at the surface of mars caused by mass exchange with the regolith regolith on mars exchanges water with the atmosphere on a diurnal basis and this process causes significant variation in the abundance of water vapor at the surface while previous studies of regolith atmosphere exchange focus on the abundance recent in situ experiments and remote sensing observations measure the isotopic composition of the atmospheric water we are therefore motivated to investigate isotopic water exchange between the atmosphere and the regolith and determine its effect on the deuterium to hydrogen ratio d h of the atmosphere we model transport of water in the regolith and regolith atmosphere exchange by solving a transport equation including regolith adsorption condensation and diffusion the model calculates equilibrium fractionation between hdo and h 2o in each of these processes the fractionation in adsorption is caused by the difference in the latent heat of adsorption and that of condensation is caused by the difference in the vapor pressure together with a simple bulk aerodynamic boundary layer model we simulate the diurnal variation of the d h near the planetary surface we find that the d h can vary by 300 1400 diurnally in the equatorial and mid latitude locations and the magnitude is greater at a colder location or season the variability is mainly driven by adsorption and desorption of regolith particles and its diurnal trend features a drop in the early morning a rise to the peak value during the daytime and a second drop in the late afternoon and evening tracing the water vapor flow into and out from the regolith the predicted d h variation can be tested with in situ measurements as such our calculations suggest stable isotope analysis to be a powerful tool in pinpointing regolith atmosphere exchange of water on mars

direct measurements of ocean surface velocity from space interpretation and validation the median doppler shift of radar echoes is analyzed in measurements by envisat s advanced synthetic aperture radar asar over the ocean this doppler centroid differs from a predicted signal based on the predicted motion of the satellite and earth this anomaly converted to a surface doppler velocity u d appears to be of geophysical origin two wide swath images over the gulf stream around cape hatteras suggest that u d contains high resolution information on surface currents while on a global scale u d is found to vary with the wind speed in the range direction a simple quantitative forward model is proposed based on a practical two scale decomposition of the surface geometry and kinematics the model represents the effect of the wind through the wave spectrum and gives u d u 10 u c with u 10 and u c as the 10 m wind speed and quasi eulerian current in the line of sight of the radar projected on the sea surface respectively and as a coefficient function of the wind speed wave development and radar geometry it is found that for an incidence angle of 23 0 3 for moderate winds and fully developed seas this model is validated with a global data set of asar wave mode observations with colocated model winds acquired over the global ocean during the years 2003 and 2004 the doppler signal therefore provides the signed parameter u d that can be used to reduce the wind direction ambiguity in the inversion of high resolution wind fields from sar imagery a qualitative validation of current effects is shown for the english channel where tidal currents dominate thus it should be possible to combine this previously ignored geophysical doppler signal with traditional information on sea surface roughness in order to provide very high resolution wind and current fields

towards wide swath high resolution mapping of total ocean surface current vectors from space airborne proof of concept and validation two dimensional high resolution maps of total surface current vectors obtained for the first time with an airborne demonstrator of the innovative wavemill instrument concept are validated against hf radar data and compared with output from the polcoms high resolution coastal ocean circulation model wavemill is a squinted along track interferometric sar system optimized for ocean surface current vector retrieval that operates at moderate incidence angles 30 and is compatible with spaceborne implementation this paper represents the first comprehensive validation of the current retrieval capabilities of squinted along track sar interferometry in support of its development as a future european space agency earth explorer mission wavemill airborne data were acquired in october 2011 in liverpool bay off the west coast of great britain in light southerly wind 5 5 m s and maximum tidal ebbing flow 0 7 m s conditions contributions to the measured sar interferometric phase by surface gravity waves known as the wind wave induced artefact surface velocity wasv were removed using our best estimate of wind conditions and the mouche et al 2012 empirical correction derived from envisat asar validation of the 1 5 km resolution wavemill current vectors against independent current measurements from hf radar gives very encouraging results with wavemill biases and precisions typically better than 0 05 m s and 0 1 m s for surface current speed and better than 10 and 7 for current direction the sensitivity of the current retrieval to the wind vector used to compute the wasv is estimated a 1 m s error bias in wind speed has minimal impact on the quality of the retrieved currents in contrast the choice of wind direction is critical a bias of 15 in the direction of the wind vector degrades the accuracy of the airborne current speed against the hf radar by about 0 2 m s this highlights the need for future instruments to provide calibrated sar normalised radar cross section data to support retrieval of wind and current vectors simultaneously comparisons of polcoms surface currents with hf radar data indicate that the model reproduces well the overall temporal evolution of the tidal current correlation of spatial fields against hf radar over two tidal cycles of 0 9 but that the model features a systematic 1 h delay in the timing of the maximum ebbing flow in eastern parts of the domain near the mersey bar light buoy at the maximum ebb flow the model underestimates the current speed bias of 0 2m s with respect to the hf radar and wavemill data at the time of the flights both the hf radar and wavemill data reflect much greater snapshot spatial variability of the ocean surface current field than is present in the model resulting in poor correlation of instantaneous spatial fields 0 5 between polcoms and the hf radar data the wavemill data reveal high spatial variability of ocean surface currents at fine scales which are not visible in the 4km resolution hf radar data wavemill detects several strong 1 1 5m s localized current jets associated with deeper bathymetry channels in shallow waters 10 m that are too narrow or too close to land to be observed by the hf radar the study confirms the value of synoptic wide swath maps of high resolution ocean surface current vectors for coastal applications and to validate and develop high resolution ocean circulation models

chemistry mineralogy and grain properties at namib and high dunes bagnold dune field gale crater mars a synthesis of curiosity rover observations the mars science laboratory curiosity rover performed coordinated measurements to examine the textures and compositions of aeolian sands in the active bagnold dune field the bagnold sands are rounded to subrounded very fine to medium sized 45 500 m with 6 distinct grain colors in contrast to sands examined by curiosity in a dust covered inactive bedform called rocknest and soils at other landing sites bagnold sands are darker less red better sorted have fewer silt sized or smaller grains and show no evidence for cohesion nevertheless bagnold mineralogy and rocknest mineralogy are similar with plagioclase olivine and pyroxenes in similar proportions comprising 90 of crystalline phases along with a substantial amorphous component 35 15 yet bagnold and rocknest bulk chemistry differ bagnold sands are si enriched relative to other soils at gale crater and h 2o s and cl are lower relative to all previously measured martian soils and most gale crater rocks mg ni fe and mn are enriched in the coarse sieved fraction of bagnold sands corroborated by visible near infrared spectra that suggest enrichment of olivine collectively patterns in major element chemistry and volatile release data indicate two distinctive volatile reservoirs in martian soils 1 amorphous components in the sand sized fraction represented by bagnold that are si enriched hydroxylated alteration products and or h 2o or oh bearing impact or volcanic glasses and 2 amorphous components in the fine fraction 40 m represented by rocknest and other bright soils that are fe s and cl enriched with low si and adsorbed and structural h 2o

remote sensing of ocean wave spectra by interferometric synthetic aperture radar the two dimensional power spectra of ocean waves are of great interest not only to oceanographers but also in practical applications such as wave forecasting trans oceanic ship routing and design of coast and offshore installations remote sensing of ocean surface waves can be difficult using conventional synthetic aperture radar sar techniques but waves can be observed clearly by sar in the interferometric configuration insar 1 2 this improvement is due to the ability of insar to provide images of the local surface velocity field in contrast to conventional sar for which the imaging process is related indirectly to the complex modulation of the surface reflectivity by longer waves and currents here we show that insar can be used to obtain wavenumber spectra that are in agreement with power spectra measured in situ this new method thus has considerable potential to provide instantaneous spatial information about the structutre of ocean wave fields

on the statistics of the phase of microwave backscatter from the ocean surface in this paper we describe what we believe is the first study of the distribution of the phase of microwave fields backscattered from the ocean surface scatterometry data from the synthetic aperture radar and x band ocean nonlinearities experiment conducted on the german north sea research platform forschungsplatform nordsee in november 1990 have been analyzed to reveal the distribution of phase differences as a function of time lag a theoretical model for these statistics is presented based on modulated gaussian fields this theoretical model is shown to be in good agreement with the measured statistics from this agreement we conclude that the backscattered fields have a gaussian distribution on short time scales but are modulated in amplitude and frequency by the long surface waves these results are of more than purely academic interest with direct applications to the design and analysis of interferometric synthetic aperture radars a relatively new class of instruments that may be capable of providing high resolution maps of ocean surface currents from aircraft or satellites

satellite radar interferometry for monitoring ice sheet motion application to an antarctic ice stream satellite radar interferometry sri provides a sensitive means of monitoring the flow velocities and grounding line positions of ice streams which are indicators of response of the ice sheets to climatic change or internal instability the detection limit is about 1 5 millimeters for vertical motions and about 4 millimeters for horizontal motions in the radar beam direction the grounding line detected by tidal motions where the ice goes afloat can be mapped at a resolution of 0 5 kilometer the sri velocities and grounding line of the rutford ice stream antarctica agree fairly well with earlier ground based data the combined use of sri and other satellite methods is expected to provide data that will enhance the understanding of ice stream mechanics and help make possible the prediction of ice sheet behavior

sea surface velocity vector retrieval using dual beam interferometry first demonstration the dual beam interferometer consists of two interferometric synthetic aperture radars insars one squinted at 20 spl deg forward of broadside and the other 20 spl deg aft to allow measurement of vector surface velocity with only a single aircraft pass estimates of surface velocity vectors in the coastal region during high tidal flow are presented the data were gathered over the barrier islands west of fort myers florida as part of a march 2004 deployment whereas no detailed bathymetry data were available high quality aerial photography appears to be a useful tool in inferring bottom topography and possible current obstructions the retrieved velocity field clearly follows the expected outflow pattern while comparisons with tidal current magnitudes predicted by the u s national ocean service do reveal discrepancies of up to 0 5 m s these differences are most likely due to the contribution of ocean surface waves to the overall insar velocity measurement velocity retrievals for the same area based on the data from different tracks show good consistency the results constitute the first demonstration of vector retrieval of the surface velocity field with a single pass insar system and confirm the robustness of the dual beam interferometry principle

energy density directional spectra of a nearshore wave field measured by interferometric synthetic aperture radar the nearshore wave field within monterey bay california is studied using remote sensing imaging by an interferometric synthetic aperture radar insar and simultaneous ground based measurements it is shown that insar imagery of the ocean surface offers some advantages over conventional synthetic aperture radar because of the direct imaging mechanism of insar quantitative information about the complicated wave field can be obtained the insar derived directional energy density spectra and the corresponding ground based spectra compare well

remote sensing of ocean waves by along track interferometric synthetic aperture radar a new wave retrieval method for the along track interferometric synthetic aperture radar at insar phase image is presented the new algorithm named parametric retrieval algorithm pra uses the full nonlinear mapping relations it differs from previous retrieval algorithms in that it does not require a priori information about the sea state or the wind vector from scatterometer data instead it combines the observed at insar phase spectrum and assumed wind vector to estimate the wind sea spectrum the method has been validated using several c band and x band hh polarized at insar observations collocated with spectral buoy measurements in this paper x band and c band hh polarized at insar phase images of ocean waves are first used to study at insar wave imaging fidelity the resulting phase spectra are quantitatively compared with forward mapped in situ directional wave spectra collocated with the at insar observations subsequently we combine the parametric retrieval algorithm pra with x band and c band hh polarized at insar phase images to retrieve ocean wave spectra the results show that the ocean wavelengths wave directions and significant wave heights estimated from the retrieved ocean wave spectra are in agreement with the buoy measurements

remote sensing of ocean waves the surface wave process program experiment an airborne synthetic aperture radar sar has been used as an interferometer to obtain direct calibrated measurements of the ocean wind wave directional spectrum flights over the same area from three different directions produced reasonably consistent results the sar derived wave data agree well with simultaneous observations by a conventional wave measuring system and with a novel in situ acoustic doppler system

x band sea surface coherence time inferred from bistatic sar interferometry coherence time plays an important role in ocean surface observation by means of synthetic aperture radar sar for x band the autocorrelation function acf of the backscatter from the sea surface has been predicted using models up to now there exist only few experimental data and an empirical analysis of the sea surface coherence time based on a larger amount of data is missing in this paper we show how space based bistatic sar along track interferometry is used for the first time to measure the acf we achieve this by statistical analysis of the interferometric scene coherence as a function of the along track interferometric time lag instead of indirect estimation from the doppler bandwidth we use many data acquisitions of opportunity for that purpose thereby exploiting the diversity of along track baselines between the two sar sensors of the tandem x satellite formation the acf is related to the temporal decorrelation which is not directly observable we extract this component by quantifying and compensating for all other sources of decorrelation that contribute to the observed coherence

synergistic surface current mapping by spaceborne stereo imaging and coastal hf radar 1 well validated optical and radar methods of surface current measurement at high spatial resolution nominally 100 m from space can greatly advance our ability to monitor earth s oceans coastal zones lakes and rivers with interest growing in optical along track stereo techniques for surface current and wave motion determinations questions of how to interpret such data and how to relate them to measurements made by better validated techniques arise here we make the first systematic appraisal of surface currents derived from along track stereo sun glitter atssg imagery through comparisons with simultaneous synoptic flows observed by coastal hf radars working at frequencies of 13 9 and 24 5 mhz which return averaged currents within surface layers of roughly 1 m and 2 m depth respectively at our tsushima strait japan test site we found that these two techniques provided largely compatible surface current patterns with the main difference apparent in current strength within the northwest southern comparison region the magnitudes of the atssg current vectors derived for 13 august 2006 were on average 22 40 higher than the corresponding vectors for the 1 m 2 m depth radar these results reflect near surface vertical current structure differences in the flow components sensed by the two techniques and disparities in instrumental performance the vertical profile constructed here from atssg hf radar and adcp data is the first to resolve downwind drift in the upper 2 m of the open ocean the profile e folding depth suggests stokes drift from waves of 10 m wavelength visible in the images

water and chlorine content in the martian soil along the first 1900 m of the curiosity rover traverse as estimated by the dan instrument the presence of hydrated phases in the soil and near surface bedrock of gale crater is thought to be direct evidence for water rock interaction in the crater in the ancient past layered sediments over the gale crater floor are thought to have formed in past epochs due to sediment transport accumulation and cementation through interaction with fluids and the observed strata of water bearing minerals record the history of these episodes the first data analysis of the dynamic albedo of neutrons dan investigation on board the curiosity rover is presented for 154 individual points of active mode measurements along 1900 m of the traverse over the first 361 martian solar days in gale crater it is found that a model of constant water content within subsurface should be rejected for practically all tested points whereas a two layer model with different water contents in each layer is supported by the data a so called direct two layer model water content increasing with depth yields acceptable fits for odometry ranges between 0 and 455 m and beyond 638 m the mean water h2o abundances of the top and bottom layers vary from 1 5 to 1 7 wt and from 2 2 to 3 3 wt respectively while at some tested spots the water content is estimated to be as high as 5 wt the data for odometry range 455 638 m support an inverse two layer model water content decreasing with depth with an estimated mean water abundance of 2 1 0 1 wt and 1 4 0 04 wt in the top and bottom layers respectively

computing ocean surface currents over the coastal california current system using 30 min lag sequential sar images as compared with conventional methods for measuring ocean surface currents spaceborne synthetic aperture radar sar offers cloud penetrating ocean current observation capability at high spatial resolution while some studies have shown the potential of sar for studying ocean surface currents through feature tracking they have only analyzed a few images to demonstrate the basic measurement technique and no concise general technique has been developed this paper shows the application of the maximum cross correlation mcc method to generate ocean surface currents from nearly two years of available sequential spaceborne c band sar imagery from the envisat asar and ers 2 advanced microwave instrument sar sensors over the coastal california current system the data processing strategies are discussed in detail and results are compared with hf radar measured currents one dimensional wavenumber spectra of the sar derived surface currents agree with the k 2 power law as predicted by submesoscale resolution models comparisons with hf radar currents show encouraging results with mcc sar vectors oriented slightly counterclockwise relative to hf radar vectors mcc sar surface currents are found to have larger magnitudes than hf radar currents approx 11 cm s which may be due to the fact that sar penetrates only a few centimeters into the ocean surface whereas hf radar currents are averaged over the top 1 m of the ocean surface the larger part of this magnitude difference is contained in the along shore component which can be attributed to higher hf radar accuracy in the direct radial cross shore measurements as compared with along shore components derived from multiple cross shore radial measurements

neutron background environment measured by the mars science laboratory s dynamic albedo of neutrons instrument during the first 100 sols 1 the dynamic albedo of neutrons dan instrument on board mars science laboratory has been operating successfully since the landing and has been making measurements regularly along curiosity s traverse at the surface dan measures thermal e 0 4 ev and epithermal neutrons 0 4 ev e 1 kev while operating in two different modes active and passive the active mode uses a pulsed neutron generator png to study the geological characteristics of the subsurface in the passive mode dan measures the background neutron environment this paper presents results of measurements in the passive mode from landing through to sol 100 and provides an interpretation of the data based on extensive monte carlo simulations the main observations are summarized as follows 1 the thermal neutron counts vary strongly along the rover traverse while the epithermal counts do not show much variation 2 the neutrons from the multi mission radioisotope thermoelectric generator mmrtg are a larger contributor to the dan passive data than the galactic cosmic ray gcr induced neutrons 3 for the mmrtg neutrons both the thermal and the epithermal counts increase as a function of the subsurface water content 4 on the other hand for the gcr induced neutrons the thermal counts increase but the epithermal counts decrease as a function of the subsurface water content and 5 relative contributions by the mmrtg and gcr to the dan thermal neutron counts at the rocknest site where the rover was stationed from sol 59 to sol 100 are estimated to be 60 and 40 respectively

measurements of sea surface currents in the baltic sea region using spaceborne along track insar the main challenging problems in ocean current retrieval from along track interferometric ati synthetic aperture radar sar are phase calibration and wave bias removal in this paper a method based on differential insar dinsar technique for correcting the phase offset and its variation is proposed the wave bias removal is assessed using two different doppler models and two different wind sources in addition to the wind provided by an atmospheric model the wind speed used for wave correction in this work is extracted from the calibrated sar backscatter this demonstrates that current retrieval from ati sar can be completed independently of atmospheric models the retrieved currents from four tandem x tdx acquisitions over the oresund channel in the baltic sea are compared to a regional ocean circulation model it is shown that by applying the proposed phase correction and wave bias removal a good agreement in spatial variation and current direction is achieved the residual bias between the ocean model and the current retrievals varies between 0 013 and 0 3 m s depending on the doppler model and wind source used for wave correction this paper shows that using sar as a source of wind speed reduces the bias and root mean squared error rmse of the retrieved currents by 20 and 15 respectively finally the sensitivity of the sea current retrieval to doppler model and wind errors are discussed

first analysis of terrasar x along track insar derived current fields we present the first analysis of surface current fields derived from terrasar x along track interferometric synthetic aperture radar along track insar ati data the images were acquired over the mouth of the elbe river germany during six satellite overpasses in spring and summer 2008 using the experimental aperture switching mode of terrasar x in this mode the phased array synthetic aperture radar sar antenna is split into two halves for receiving but in contrast to the dual receive antenna mode which uses two independent receivers in parallel a single receiver is multiplexed to process signals from the two antenna halves in an alternating manner at a doubled pulse repetition frequency the effective ati baseline is on the order of 0 8 m the sar ati raw data processing is described in another paper in this issue this paper focuses on the conversion of the basic interferograms into line of sight surface current fields which includes an elimination of ship signatures identification and correction as far as possible of imaging artifacts additional filtering and smoothing and a subtraction of contributions of wave motions to detected velocities according to a theoretical model we evaluate the quality of the results by comparison with current fields from a numerical flow model and with available in situ data the ati performance of terrasar x is found to be basically consistent with theoretical expectations after applying the same data processing algorithms to all six images mean differences between terrasar x derived currents and reference currents in our main test area range from 0 11 to 0 08 m s in five of the six cases with one outlier at 0 42 m s the spatial current variations within the terrasar x derived current fields are consistent with the model in three cases but unrealistically strong variations across the images are found in the other three cases we attribute this to shortcomings of our preliminary raw data processing algorithms which can probably be fixed after some more detailed analysis and testing the results obtained so far encourage us to believe that our internal performance goal of a typical current measuring accuracy of 0 1 m s at an effective spatial resolution better than 1 km can be met

estimating ocean coherence time using dual baseline interferometric synthetic aperture radar a new technique for measuring the coherence time of the ocean surface at radar wavelengths has been developed and tested this technique requires an interferometric synthetic aperture radar system with at least two unique baselines along the direction of platform motion the coherence time of the surface may be presented as a high resolution coherence time map this technique was tested using the jpl airsar along track interferometer measurements of the ocean coherence at the l band were made at high spatial resolution under a variety of conditions a new operating technique that results in the required two baselines is described some parametric analysis is performed pertaining to the design of such a system a representative interferometric data set acquired at the strait of messina in 1991 is presented to illustrate the technique the interferometric phase data reveal and measure tidal currents flowing through the strait while the coherence time image shows considerable structure not visible in the backscatter or phase image coherence times in and around the strait were measured to be of the order of 0 1 s at the l band which is in agreement with previous estimates and measurements

likely frost events at gale crater analysis from msl rems measurements abstract we provide indirect evidence for the formation of frost at the surface of gale crater by analyzing the highest confidence data from simultaneous measurements of relative humidity and ground temperature during the first 1000 sols of the mars science laboratory msl mission we find that except for sol 44 frost events could have occurred only between sols 400 and 710 corresponding to the most humid and coldest time of the year from early fall to late winter in particular measurements at dingo gap during sols 529 535 at an unnamed place during sols 554 560 at kimberley during sols 609 617 and at an unnamed place during sols 673 676 showed the largest likelihood of the occurrence of frost events at these four locations the terrain is composed of fine grained and loosely packed material with thermal inertia values of 200 si units much lower than the 365 50 si units value found at the landing ellipse this is important because terrains with exceptionally low thermal inertia favor the formation of frost by lowering minimum daily ground temperatures an order of magnitude calculation to determine the thickness of the frost layer at these four locations results in values of tenths of m while the precipitable water content is a few pr m therefore surface frost events can have important implications for the local water cycle at gale crater in addition frost is the most likely type of water that can be temporarily found in bulk amounts on the surface of mars at low latitudes and therefore can cause weathering influencing the geology of gale crater

radar interferometry and its application to changes in the earth s surface geophysical applications of radar interferometry to measure changes in the earth s surface have exploded in the early 1990s this new geodetic technique calculates the interference pattern caused by the difference in phase between two images acquired by a spaceborne synthetic aperture radar at two distinct times the resulting interferogram is a contour map of the change in distance between the ground and the radar instrument these maps provide an unsurpassed spatial sampling density 100 pixels km 2 a competitive precision 1 cm and a useful observation cadence 1 pass month 1 they record movements in the crust perturbations in the atmosphere dielectric modifications in the soil and relief in the topography they are also sensitive to technical effects such as relative variations in the radar s trajectory or variations in its frequency standard we describe how all these phenomena contribute to an interferogram then a practical summary explains the techniques for calculating and manipulating interferograms from various radar instruments including the four satellites currently in orbit ers 1 ers 2 jers 1 and radarsat the next chapter suggests some guidelines for interpreting an interferogram as a geophysical measurement respecting the limits of the technique assessing its uncertainty recognizing artifacts and discriminating different types of signal we then review the geophysical applications published to date most of which study deformation related to earthquakes volcanoes and glaciers using ers 1 data we also show examples of monitoring natural hazards and environmental alterations related to landslides subsidence and agriculture in addition we consider subtler geophysical signals such as postseismic relaxation tidal loading of coastal areas and interseismic strain accumulation we conclude with our perspectives on the future of radar interferometry the objective of the review is for the reader to develop the physical understanding necessary to calculate an interferogram and the geophysical intuition necessary to interpret it

sea surface imaging with an across track interferometric synthetic aperture radar the sinewave experiment an across track interferometric synthetic aperture radar insar is used to image ocean waves across track insar data were acquired during the sar innterferometry experiment for validation of ocean wave imaging models sinewave in the north sea using an airborne x band radar with horizontal polarization a wind sea system was imaged at different flight levels and with different flight directions with respect to the ocean wave propagation direction simultaneously ocean wave spectra were measured by a directional wave rider buoy thus the experiment data comprises synthetic aperture radar sar intensity coherence and phase images together with in situ measurements as shown in a recent theoretical study by schulz stellenfleth and lehner 2001 across track insar provides distorted bunched digital elevation models dems of the sea surface using sinewave data the dem bunching mechanism is verified with in situ ocean wave measurements available for the first time it is shown that significant waveheight as well as one dimensional 1d wavenumber spectra derived from bunched dems and buoy data are in good agreement for small nonlinearities peak wave directions and peak wavelength detected in bunched dems and sar intensity images are compared with the buoy spectrum peak rotations of up to 30 spl deg with respect to the buoy spectrum are found depending on flight direction and flight level two dimensional 2d spectra of bunched dems corresponding coherency maps and sar intensity images are intercompared the signal to noise ratio snr of bunched dem spectra is shown to be about 5 to 10 db higher than the snr of sar intensity image spectra

ocean surface features and currents measured with synthetic aperture radar interferometry and hf radar this paper describes the results of the first quantitative comparison between high resolution ocean surface current fields extracted from interferometric synthetic aperture radar insar measurements and those from a high frequency hf ocean surface current radar oscr system data from each of these radar systems along with supporting measurements from shipboard and buoy mounted sensors were collected during the high resolution remote sensing experiment high res on june 20 1993 on the continental shelf off the coast of cape hatteras north carolina both components of the surface current were obtained from the insar system at roughly 10 m resolution from two orthogonal flight legs over the region separated in time by about 30 min the oscr system measured two dimensional surface current vectors at about 1 km resolution over this same region while the usns bartlett was collecting hydrographic samples and near surface current measurements two dimensional wave spectra as well as meteorological and additional current measurements were collected at two buoys within the experimental area we discuss in the paper two techniques for eliminating the effect of surface wave motion on the insar current estimates one method relies on some knowledge of the local wind and wave field and the use of a microwave scattering model the other method makes use of a few in situ current measurements spaced at different range locations across the insar image using either of these techniques we find that the agreement between the insar and oscr current estimates is generally very good furthermore the insar current and magnitude imagery show the presence of undulating surface features where abrupt changes in the current speed and direction occurred the ship surveys indicate that these features were caused by the collision of water masses of different density we show for the first time in this paper a high resolution area extensive vector surface current map derived from the insar of the two dimensional flow in the vicinity of these features our results demonstrate convincingly that high resolution oceanic surface current vectors can be derived from insar current measurements and that these measurements may be very beneficial for detailed studies of the dynamics of small scale surface features in regions of strong current divergences or shears

theoretical evaluation of several possible along track insar modes of terrasar x for ocean current measurements the german satellite terrasar x scheduled for launch in late 2006 will permit high resolution ocean current measurements by along track interferometric sar along track insar in various experimental modes of operation using different sections of its x band sar antenna array with a total length of 4 8 m as individual receive antennas depending on antenna and receive chain settings effective insar time lags of about 0 17 to 0 29 ms can be realized in combination with different noise levels single look resolutions swath widths and incidence angles we give an overview of the characteristics of the possible insar modes and evaluate their suitability for current measurements on the basis of simulated data products our results indicate that the quality of interferometric stripmap data from terrasar x will be clearly superior to the quality of the existing data acquired over the dutch coast during the shuttle radar topography mission accurate current retrievals can be expected at effective spatial resolutions on the order of 500 m however in modes using a multiplexed single receive chain the effective swath width of stripmap data will be limited to only 15 km while dual receive chain operation offers a swath width of 30 km for stripmap data and promises a reasonable data quality even for scansar data with a maximum swath width of 100 km finally we consider fundamental relations between along track baseline instrument noise and resulting insar phase noise to discuss the potential for current measuring performance improvements of terrasar x follow on satellites

estimates of currents in the nearshore ocean region using interferometric synthetic aperture radar microwave remote sensing of the ocean surface using synthetic aperture radar sar is of great interest due to its high resolution and the potential of nearly instantaneous coverage of large areas the experience accumulated in ocean imaging by sar indicates that there are substantial difficulties in interpretation of the obtained images of ocean wave systems ocean surface currents are almost impossible to obtain from sar imagery the present paper reports on measurements of ocean surface currents based on imaging of the nearshore regions of the monterey bay using an interferometric sar the method is a modification of the conventional sar which employs two spatially separated antennas this modification allows one to construct an interferogram from the two complex images obtained by each antenna which provides direct mapping of the observed surface velocities the present results demonstrate the advantages of this novel technique in studying nearshore ocean surface dynamics in particular spatial distribution of the longshore current velocity is presented

results from the dynamic albedo of neutrons dan passive mode experiment yellowknife bay to amargosa valley sols 201 753 abstract the mars science laboratory curiosity rover dynamic albedo of neutrons dan experiment detects neutrons for the purpose of searching for hydrogen in the shallow subsurface of mars dan has two modes of operation active and passive in passive mode the instrument detects neutrons produced by galactic cosmic ray interactions in the atmosphere and regolith and by the rover s multi mission radioisotope thermoelectric generator dan passive data from yellowknife bay to amargosa valley sols 201 through 753 are presented and analyzed here water equivalent hydrogen weh estimates from this portion of curiosity s traverse range from 0 0 wt up to 15 3 wt typical uncertainties on these weh estimates are 0 5 wt but in some cases can be as high as 4 0 wt depending on the specific circumstances of a given measurement here we also present a new way of reporting results from the passive mode of the experiment the dan passive geochemical index dpgi this index is sensitive to some key geochemical variations but it does not require assumptions about the abundances of high thermal neutron absorption cross section elements which are needed to estimate weh dpgi variations in this section of the traverse indicate that the shallow regolith composition is changing on both the local meters and regional 100 s of meters scales this variability is thought to be representative of the diverse composition of source regions for sediments within the crater floor kolmogorov smirnov tests on the populations of weh estimates and dpgi values demonstrate there are statistically significant differences between nearly all of the geologic units investigated along the rover s traverse we also present updated previous dan passive results from bradbury landing to john klein that make use of revised dan active mode results for calibration however no qualitative changes in the interpretations made in tate et al 2015b are incurred

synthetic aperture radar interferometry to measure earth s surface topography and its deformation synthetic aperture radar interferometry insar from earth orbiting spacecraft provides a new tool to map global topography and deformation of the earth s surface radar images taken from slightly different viewing directions allow the construction of digital elevation models of meter scale accuracy these data sets aid in the analysis and interpretation of tectonic and volcanic landscapes if the earth s surface deformed between two radar image acquisitions a map of the surface dis placement with tens of meters resolution and subcentimeter accuracy can be con structed this review gives a basic overview of insar for earth scientists and presents a selection of geologic applications that demonstrate the unique capabilities of insar for mapping the topography and deformation of the earth

inferring surface currents within submerged vegetated deltaic islands and wetlands from multi pass airborne sar abstract water flow patterns across coastal and deltaic wetlands affect biogeochemical cycling denitrification organic carbon burial and coastal landscape evolution our understanding of such patterns across these important landscapes is incomplete however because of the inherent difficulty of conducting spatially and temporally dense ground or boat based surveys in shallow vegetated terrain we conducted an airborne l band synthetic aperture radar sar acquisition campaign on wax lake delta louisiana usa in may 2015 to investigate whether water velocities and flow patterns over kilometer scales can be determined from remote sensing thirteen sar flight lines over the delta region were acquired in 3 h with six different flight directions concurrently with a small boat campaign we show that sar azimuth displacement due to doppler shift can be used to estimate the surface water flow relative to the static and submerged vegetation interspersed on delta islands using a simple bragg wave scattering model and accounting for the bragg wave s free velocity and wind drift at wax lake delta we find that 0 40 m s water velocities within the main deltaic channels slow to 0 1 0 2 m s as flow spreads laterally across and converges within the vegetated islands coinciding with shallow

modelling of yingxiu beichuan fault zone based on refined dinsar data of 2008 wenchuan earthquake abstract differential interferometric synthetic aperture radar dinsar provides an essential constraint for forward modelling of seismic faulting however the crucial evidence of deformation along the very near vicinity of a seismic fault is often missing because chaotic ruptures destroy the insar signal coherence such is the case of the yingxiu beichuan fault zone of the 2008 wenchuan earthquake we developed an adaptive local kriging alk interpolation method to produce a refined dinsar dataset which continues without the interruption of decoherence gaps thus the 3d configuration of the seismic faulting can be better constrained for forward modelling using the poly3d software through parameter fine tuning in a sequence of trial and error simulation the best fitting between the simulated interferogram and the alk refined dinsar interferograms is achieved using a structural model of the yingxiu beichuan fault zone which comprises a total of 14 segments with dip angles varying from 20 to 60 in the south west to 40 to 70 in the north east some major fault segments are composed of multiple planes with varying dip angles the model reveals that in the much disputed beichuan pengguan area the yingxiu beichuan fault links with the pengguan fault which dips to the nw at 30 at a depth of 13 km these two structures are interpreted as representing the foreland propagation of the yingxiu beichuan fault by footwall collapse a process that in the vicinity of the pengguan fault involves the transfer of displacement from the older yingxiu beichuan fault to the younger pengguan fault

interferometric radar measurement of ocean surface currents we describe a new method of measuring surface currents using an interferometric synthetic aperture radar an airborne implementation has been tested over the san francisco bay near the time of maximum tidal flow resulting in a map of the east west component of the current only the line of sight component of velocity is measured by this technique where the signal to noise ratio was strongest statistical fluctuations of less than 4 cm s 1 were observed for ocean patches of 60 60 m

mapping the agulhas current from space an assessment of asar surface current velocities 1 over 2 years of surface current information collected in the agulhas current region and derived from the doppler centroid anomalies of envisat s advanced synthetic aperture radar asar are examined the sources of errors and potential use of asar surface current velocities for oceanographic research are assessed asar surface current velocities are compared to surface drifter data and merged altimetry observations maps of sea surface temperature are used to establish the asar s capacity to capture the synoptic circulation discrepancies between observed and predicted asar velocities result predominantly from inadequate wind corrections combined with radar incidence angles below 30 occasionally observed wind induced outliers cause a bias in the estimated asar velocities but do not affect the ability of the asar to systematically image regions of strong surface current flow and shear time averaged maps of asar derived surface current velocity seem able to accurately capture the position as well as the intensity of the agulhas current the ability of the asar to pick up the smaller features of the circulation along the shelf break also shows that variability along the agulhas bank is of the same order of magnitude as that observed in the agulhas retroflection asar surface current velocities offer a very good complement to altimetry in regions where the mean dynamic topography is poorly resolved the quasi synoptic nature of asar acquisitions combined with the relatively high resolution of asar surface current velocities also make it attractive for studies of submesoscale processes and western boundary current dynamics

mapping small elevation changes over large areas differential radar interferometry a technique that uses synthetic aperture radar sar images to measure very small 1 cm or less surface motions with good resolution 10 m over large swaths 50 km is presented along with experimental results the method could be used for accurate measurements of many geophysical phenomena including swelling and buckling in fault zones residual displacements from seismic events and prevolcanic swelling the method is based on sar interferometry where two images are made of a scene by simultaneously flying two physically separated antennas then the phases of corresponding pixels are differenced and altitude formation is deduced from some simple computation and image rectification it is also possible to use one antenna flown twice over the same scene then if the second flight exactly duplicates the track of the first an interesting possibility occurs there would be no phase changes between the images at all unless there was a physical change in the scene such as ground swelling that would alter the distance from some resolution element to the antenna since the phase changes all occur at the short carrier wavelength the basic limitation on sensitivity is only the phase noise in the system when the two imaging passes are made from flight tracks that are separated which is the case with the seasat images used here it is no longer possible to distinguish surface changes from the parallax caused by topography however with some additional computation a third image made at some other baseline may be used to remove the topography and leave only the surface changes this method was applied using seasat data to an imaging site in imperial valley california where motion effects were observed that were ascribed to the expansion of water absorbing clays phase change images of this area are shown along with associated ground truth about the presence of water problems with the technique are explored along with a discussion of future experimental possibilities on upcoming sar missions like earth observing system eos earth resources satellite ers 1 sir c and the venus imaging radar magellan

mars science laboratory dynamic albedo of neutrons passive mode data and results from sols 753 to 1292 pahrump hills to naukluft plateau abstract the dynamic albedo of neutrons instrument dan onboard the mars science laboratory msl uses 3he proportional counters to detect neutrons escaping the martian surface this neutron leakage flux can be used to estimate the amount of hydrogen in the shallow martian regolith during sols 753 through 1292 of the msl mission the rover traversed from pahrump hills to the naukluft plateau and acquired slightly less than 2000 h of neutron count rate data covering 3 km of traverse and 125 waypoints along that traverse here we present an analysis of these data including new procedures to leverage the oversampling of the instrument within its own spatial footprint water equivalent hydrogen weh estimates and dan passive geochemical index dpgi values the average water equivalent hydrogen estimate for this region of the traverse is 1 6 wt with a standard deviation of 1 1 wt these results show that curiosity transitioned into a relatively lower weh content region as it left the plains of gale crater and began ascending the hills at the base of mt sharp we also show that the weh populations of the geologic units investigated during this time murray and stimson formations are statistically different both from each other and the previously studied aeolis palus sediments smooth hummocky bedded fractured eolian rugged and striated light toned additionally dan passive weh estimates agree with measurements from other msl instruments in this region and are consistent with decreasing phyllosilicate abundance with increasing elevation

apparent thermal inertia and the surface heterogeneity of mars abstract thermal inertia derivation techniques generally assume that surface properties are uniform at horizontal scales below the footprint of the observing instrument and to depths of several decimeters consequently surfaces with horizontal or vertical heterogeneity may yield apparent thermal inertia which varies with time of day and season to investigate these temporal variations we processed three mars years of mars global surveyor thermal emission spectrometer observations and produced global nightside and dayside seasonal maps of apparent thermal inertia these maps show broad regions with diurnal and seasonal differences up to 200 j m 2 k 1 s 1 2 at mid latitudes 60 s to 60 n and 600 j m 2 k 1 s 1 2 or greater in the polar regions we compared the seasonal mapping results with modeled apparent thermal inertia and created new maps of surface heterogeneity at 5 resolution delineating regions that have thermal characteristics consistent with horizontal mixtures or layers of two materials the thermal behavior of most regions on mars appears to be dominated by layering with upper layers of higher thermal inertia e g duricrusts or desert pavements over fines prevailing in mid latitudes and upper layers of lower thermal inertia e g dust covered rock soils with an ice table at shallow depths prevailing in polar regions less common are regions dominated by horizontal mixtures such as those containing differing proportions of rocks sand dust and duricrust or surfaces with divergent local slopes other regions show thermal behavior that is more complex and not well represented by two component surface models these results have important implications for mars surface geology climate modeling landing site selection and other endeavors that employ thermal inertia as a tool for characterizing surface properties

experimental and numerical study of asperity degradation in the direct shear test abstract in this paper the shear behaviour and mechanisms of asperity degradation of rock joints under direct shear tests were studied using numerical and experimental approaches pfc2d was used for numerical simulations in which the intact material is simulated by a dense packing of circular particles bonded together at their contact points and by breakage of these bonds under loading regimes the damage process is simulated the joint interfaces were simulated by a newly developed modified smooth joint model in which micro scale slip surfaces are applied at contacts between particles of upper and lower blocks of the shear box in order to study the ability of this numerical approach in reproducing the shearing mechanisms and asperity degradation of rock joints in direct shear tests a comparative study was carried out against the physical experiments experimental and numerical direct shear tests were carried out on saw tooth triangular joints with the base angles of 20 and 30 under different normal stresses three shearing mechanisms of sliding surface wear and asperity shearing off were observed in these experiments the comparison of the shear behaviour and mechanisms of asperity degradation of physical and numerical experiments showed that the results of numerical models are in good agreement with physical experiments and this numerical approach can reproduce the shear behaviour of rock joints under different loading conditions

on the derivation of coseismic displacement fields using differential radar interferometry the landers earthquake we present a map of the coseismic displacement field resulting from the landers california june 28 1992 earthquake derived using data acquired from an orbiting high resolution radar system we achieve results more accurate than previous space studies and similar in accuracy to those obtained by conventional field survey techniques data from the ers 1 synthetic aperture radar instrument acquired in april july and august 1992 are used to generate a high resolution wide area map of the displacements the data represent the motion in the direction of the radar line of sight to centimeter level precision of each 30 m resolution element in a 113 km by 90 km image our coseismic displacement contour map gives a lobed pattern consistent with theoretical models of the displacement field from the earthquake fine structure observed as displacement tiling in regions several kilometers from the fault appears to be the result of local surface fracturing comparison of these data with global positioning system and electronic distance measurement survey data yield a correlation of 0 96 thus the radar measurements are a means to extend the point measurements acquired by traditional techniques to an area map format the technique we use is 1 more automatic 2 more precise and 3 better validated than previous similar applications of differential radar interferometry since we require only remotely sensed satellite data with no additional requirements for ancillary information the technique is well suited for global seismic monitoring and analysis

an experimental investigation of wave measurements using a dual beam interferometer gulf stream as a surface wave guide 1 a dual beam interferometric synthetic aperture radar measures remotely two radial components of the ocean surface current from a single flight pass combining two passes over the same area all three orthogonal components of the surface velocity can be retrieved an experiment is conducted near the gulf stream gs boundary a sharp change of the surface velocity of about 1 m s over a 500 m lateral distance is measured the wind and wave condition is dominated by a 14 s swell system and low wind velocity the wave variance inside gs is about twice the wave variance outside the gs in the present data set the difference in the wave variance is considerably higher than that can be expected from wave current interaction an ocean current system with strong shears such as the gs is a wave guide and can trap waves with the right combinations of wavelengths and propagation directions numerical calculations suggest that the wave properties of the data set may satisfy the conditions of wave trapping by the gs the standing wave pattern on the gs side of the sharp velocity front indicative of the long swell bouncing off the current front also offers support for the wave guide hypothesis in this respect the gulf stream can be considered the nature s hydraulic breakwater that can attenuate about 50 of the incident wave energy generated by storms its role in protecting the u s coastlines in the atlantic ocean cannot be overstated

local variations of bulk hydrogen and chlorine equivalent neutron absorption content measured at the contact between the sheepbed and gillespie lake units in yellowknife bay gale crater using the dan instrument onboard curiosity data gathered with the dynamic albedo of neutron dan instrument onboard rover curiosity were analyzed for variations in subsurface neutron flux and tested for possible correlation with local geological context a special dan observation campaign was executed in which 18 adjacent dan active measurements were acquired every 0 75 1 0 m to search for the variations of subsurface hydrogen content along a 15 m traverse across geologic contacts between the sheepbed and gillespie lake members of the yellowknife bay formation it was found that several subunits in sheepbed and gillespie lake could be characterized with different depth distributions of water equivalent hydrogen weh and different chlorine equivalent abundance responsible for the distribution of neutron absorption elements the variations of the average weh at the top 60 cm of the subsurface are estimated at up to 2 3 chlorine equivalent neutron absorption abundances ranged within 0 8 1 5 the largest difference in weh and chlorine equivalent neutron absorption distribution is found between sheepbed and gillespie lake

ocean surface current retrieval from space the sentinel 2 multispectral capabilities abstract the sentinel 2 multispectral instrument msi collects multiple spectral band images corresponding to specific sensing wavelengths and spatial resolutions i e 10 m 20 m and 60 m respectively images are collected one at the time with a given time lag between observations under favorable conditions spatio temporal characteristics of propagating ocean surface waves can thus uniquely be retrieved a method for surface current vector field reconstruction is then developed demonstrated over different deep ocean regions the retrieved surface current fields well compare with medium resolution ocean circulation model or derived velocities from altimeter measurements at finer scales the surface wave conservation law is recovered with the associated relationship between current vorticity and wave ray curvature over shallow water regions the wave propagation properties well follow sea depth variations consistent with etopo1 data finally time lag between detector bands can also be exploited to estimate speed and direction properties of detected surface wave breaking whitecaps an analysis of velocity reconstruction errors further reveals that sentinel 2 msi inter channel co registration is realized with an accuracy better than 0 1 pixel overall these results confirm very promising capabilities of optical imagery to provide direct surface current velocity measurements from space over relatively large areas o 100 km with a spatial resolution down to o 1 km

current measurements by sar along track interferometry from a space shuttle we present one of the first studies on ocean current retrievals from interferometric synthetic aperture radar insar data acquired during the shuttle radar topography mission srtm in february 2000 the insar system of srtm was designed for high resolution topographic mapping of the earth s land surfaces using two sar antennas on a space shuttle with a cross track separation of 60 m an additional along track antenna separation of 7 m resulted in an effective time lag of about 0 5 ms between the two images which could theoretically be exploited for target velocity retrievals however the feasibility of ocean current measurements with srtm has been questionable since the time lag was much shorter than the theoretical optimum about 3 ms at x band and the signal to noise ratio over water was quite low nevertheless some x band insar images of coastal areas exhibit clear signatures of tidal flow patterns as an example we discuss an image of the dutch wadden sea we convert the insar data into a line of sight current field which is then compared with results of the numerical circulation model kustwad for tidal phases close to the conditions at the time of the srtm overpass we obtain correlation coefficients of up to 0 6 and rms differences on the order of 0 2 m s furthermore we find that srtm resolves current variations down to spatial scales on the order of 1 km this is consistent with predictions of a numerical insar imaging model remaining differences between srtm and kustwad derived currents can be attributed mainly to residual motion errors in the srtm data as well as to a limited representation of the conditions at the time of the srtm overpass in the available kustwad results

monitoring the surface inflow of atlantic water to the norwegian sea using envisat asar 1 sea surface range doppler velocities from nearly 1200 envisat advanced synthetic aperture radar asar acquisitions between 2007 and 2011 covering the norwegian sea the north sea and the skagerrak sea have been examined after systematic corrections the inflow of atlantic water to the norwegian sea via the two branches of the norwegian atlantic current is investigated distinct expressions of the eastern branch the norwegian atlantic slope current are revealed with a speed of 20 40 cm s and a clear manifestation of topographic steering along the 500 m isobath the western branch the norwegian atlantic front current is also depicted but with lower surface velocities moreover parts of the norwegian coastal current are also detected with time averaged speed reaching up to 40 cm s at a spatial resolution of 10 km the root mean square errors of these velocities are estimated to be less than 5 cm s the range doppler velocity retrievals are assessed and compared to other direct and indirect estimates of the upper ocean current including surface lagrangian drifters moored recording current meter measurements and surface geostrophic current inverted from several mean dynamic topography fields the results are promising and demonstrate that the synthetic aperture radar based range doppler velocity retrieval method is applicable to monitoring the temporal and spatial variations of ocean surface circulation provided the imaging geometry is favorable

repeat pass sar interferometry for land cover classification a methodology using sentinel 1 short time series abstract in this paper we explore the potential of repeat pass interferometric sar insar for land cover classification purposes we introduce a novel approach for the generation of large scale thematic maps based on the use of multi temporal data acquired over short observation intervals short time series a larger interferometric coherence loss is expected with the increasing time difference between two interferometric acquisitions this phenomenon is normally indicated as temporal decorrelation whose amount differs depending on the type of imaged target on ground the basic idea is therefore to accurately model the evolution in time of the temporal decorrelation and use the estimated parameters together with backscatter as input features for the random forest machine learning classification algorithm the work has been carried out on the case study of land cover mapping over central europe considering sentinel 1 c band interferometric stacks acquired over a time span of about one month three different land cover classes have been considered artificial surfaces as e g urban areas forests and non forested areas as the ensemble of low vegetation bare soil and agricultural areas the results show a level of agreement above 91 when compared to the corine land cover map product of 2012 which has been used as external reference for both training and testing of the classification algorithm

wind wave induced velocity in ati sar ocean surface currents first experimental evidence from an airborne campaign conventional and along track interferometric ati synthetic aperture radar sar sense the motion of the ocean surface by measuring the doppler shift of reflected signals measurements are affected by a wind wave induced artefact surface velocity wasv which was modelled theoretically in past studies and has been estimated empirically only once before with envisat asar by mouche et al 2012 an airborne campaign in the tidally dominated irish sea served to evaluate this effect and the current retrieval capabilities of a dual beam sar interferometer known as wavemill a comprehensive collection of wavemill airborne data acquired in a star pattern over a well instrumented validation site made it possible for the first time to estimate the magnitude of the wasv and its dependence on azimuth and incidence angle from data alone in light wind 5 5 m s and moderate current 0 7 m s conditions the wind wave induced contribution to the measured ocean surface motion reaches up to 1 6 m s upwind with a well defined 2nd order harmonic dependence on direction to the wind the magnitude of the wasv is found to be larger at lower incidence angles the airborne wasv results show excellent consistency with the empirical wasv estimated from envisat asar these results confirm that sar and ati surface velocity estimates are strongly affected by wasv and that the wasv can be well characterized with knowledge of the wind knowledge and of the geometry these airborne results provide the first independent validation of mouche et al 2012 and confirm that the empirical model they propose provides the means to correct airborne and spaceborne sar and ati sar data for wasv to obtain accurate ocean surface current measurements after removing the wasv the airborne wavemill retrieved currents show very good agreement against adcp measurements with a root mean square error rmse typically around 0 1 m s in velocity and 10 in direction this article is protected by copyright all rights reserved

remote sensing of ocean currents a method of remotely measuring near surface ocean currents with a synthetic aperture radar sar is described the apparatus consists of a single sar transmitter and two receiving antennas the phase difference between sar image scenes obtained from the antennas forms an interferogram that is directly proportional to the surface current the first field test of this technique against conventional measurements gives estimates of mean currents accurate to order 20 percent that is root mean square errors of 5 to 10 centimeters per second in mean flows of 27 to 56 centimeters per second if the full potential of the method could be realized with spacecraft then it might be possible to routinely monitor the surface currents of the world s oceans

insar imagery of surface currents wave fields and fronts the authors demonstrate the ability of interferometric radar imagery to determine both relative and absolute surface velocities in the open ocean absolute phase calibration is accomplished by noting the azimuthal displacement of range travelling targets demonstrating for the first time that under favourable circumstances phase calibration can be achieved in open ocean in the absence of ground truth the high resolution of radar imagery permits observation of sharp velocity discontinuities e g the gulf stream boundary and the wave field the recent sir c x sar shuttle missions dramatically emphasize the experimental and observational aspects of space based radar the combination of absolute velocities high spatial resolution and wide area coverage suggest that interferometric radar imagery can provide a unique and powerful aid both for studies of global circulation patterns and detailed analysis of slope shelf water interactions with ocean currents in particular the authors employ this measurement of the surface currents and wave field near a velocity front to help refine and bound results of their modeling of calculated radar images of the front the results of this paper are compared with available ground truth

water abundance of dunes in gale crater mars from active neutron experiments and implications for amorphous phases we report the water abundance of bagnold dune sand in gale crater mars by analyzing active neutron experiments using the dynamic albedo of neutrons instrument we report a bulk water equivalent hydrogen abundance of 0 68 0 15 wt which is similar to measurements several kilometers away and from those taken of the dune surface thus the dune is likely dehydrated throughout furthermore we use geochemical constraints including bulk water content to develop compositional models of the amorphous fraction for which little information is known we find the amorphous fraction contains 26 to 64 wt basaltic glass and up to 24 wt rhyolitic glass suggesting at least one volcanic source for the dune material we also find a range of hydrated phases may be present in appreciable abundances either from the incorporation of eroded aqueously altered sediments or the direct alteration of the dune sand

azimuth falloff effects in two antenna sar measurements of ocean wave spectra estimates of ocean wave spectra obtained from conventional synthetic aperture radar sar images suffer from the azimuth falloff effect which limits the range of azimuth wavenumbers that can be observed by such systems this effect was earlier predicted to be modified by the use of a second receive antenna which is displaced from the first in the along track direction the authors present experimental evidence which is consistent with these theoretical predictions and suggests that the azimuth falloff limitations inherent in conventional sar systems can be overcome by the use of two or more appropriately spaced antennas

evolved gas analyses of sedimentary rocks and eolian sediment in gale crater mars results of the curiosity rover s sample analysis at mars instrument from yellowknife bay to the namib dune the sample analysis at mars instrument evolved gas analyzer sam ega has detected evolved water h2 so2 h2s no co2 co o2 and hcl from two eolian sediments and nine sedimentary rocks from gale crater mars these evolved gas detections indicate nitrates organics oxychlorine phase and sulfates are widespread with phyllosilicates and carbonates occurring in select gale crater materials coevolved co2 160 248 2373 820 gc co2 g and co 11 3 320 130 gc co g suggest organic c is present in gale crater materials five samples evolved co2 at temperatures consistent with carbonate 0 32 0 05 0 70 0 1 wt co3 evolved no amounts to 0 002 0 007 0 06 0 03 wt no3 evolution of o2 suggests oxychlorine phases chlorate perchlorate 0 05 0 025 1 05 0 44wt clo4 are present while so2 evolution indicates the presence of crystalline and or poorly crystalline fe and mg sulfate and possibly sulfide evolved h2o 0 9 0 3 2 5 1 6 wt h2o is consistent with the presence of adsorbed water hydrated salts interlayer structural water from phyllosilicates and possible inclusion water in mineral amorphous phases evolved h2 and h2s suggest reduced phases occur despite the presence of oxidized phases nitrate oxychlorine sulfate carbonate sam results coupled with chemin mineralogical and apxs elemental analyses indicate that gale crater sedimentary rocks have experienced a complex authigenetic diagenetic history involving fluids with varying ph redox and salt composition the inferred geochemical conditions were favorable for microbial habitability and if life ever existed there was likely sufficient organic c to support a small microbial population

improved ocean surface velocity precision using multi channel sar this paper investigates new approaches to estimating the motion of the dynamic ocean surface using a multi channel synthetic aperture radar msar with m phase centers arranged in an along track configuration the objective of this paper is to determine the processing methods that produce the finest velocity resolution an issue that arises due to the finite coherence time of radar backscatter produced by the sea surface the investigation is carried out both theoretically using synthesized data produced from a modeled msar covariance matrix as well as experimentally using images collected with a 16 channel system three processing methods are considered linear regression along with a multi baseline phase progression estimation of the velocity centroid and coherent averaging of the shortest baseline interferograms both the theoretical and experimental results indicate that simple averaging of the shortest baseline interferograms often produces the best velocity precision

retrieval of sea surface range velocities from envisat asar doppler centroid measurements the processing steps and error corrections needed to retrieve estimates of sea surface range doppler velocities from envisat advanced synthetic aperture radar wide swath medium resolution image products are presented retrieval accuracies based on examination of the corrected doppler shift measurements are assessed the root mean square errors of the doppler shift after bias corrections are found to be 4 7 and 3 9 hz in vv and hh polarizations respectively at 35 incidence angle this corresponds to horizontal doppler velocities of 23 and 19 cm s

an exact analytic representation of a regular or interferometric sar image of ocean swell the problem of obtaining quantitative data on spatial ocean wave spectra from the images of the ocean surface by either regular sar or along track interferometric sar insar is studied the dominant mechanism which allows imaging of ocean waves by sar insar is the so called velocity bunching this mechanism is essentially nonlinear the theoretical analysis of sar insar imagery of the ocean surface due to velocity bunching is performed and nonlinear solutions of the sar insar images of monochromatic waves and of the spectra of these images are obtained analytic expressions are presented which allow for the accurate simulation both sar and insar images of waves with arbitrary lengths heights and propagation directions it is demonstrated that a monochromatic wave expands in the sar insar images into an infinite number of harmonics in addition to the nonlinearity parameters of sar which is related to the velocity bunching mechanism it is shown that for complex insar the degree of nonlinearity depends also on separation time between the two antennas the results of the present study indicate that in addition to the prevailing practice to consider the phase component of the insar image an analysis of the imaginary part of the complex insar map of the ocean surface may provide some supplementary information beneficial in particular for rough sea

mineralogy of a mudstone at yellowknife bay gale crater mars sedimentary rocks at yellowknife bay gale crater on mars include mudstone sampled by the curiosity rover the samples john klein and cumberland contain detrital basaltic minerals calcium sulfates iron oxide or hydroxides iron sulfides amorphous material and trioctahedral smectites the john klein smectite has basal spacing of similar to 10 angstroms indicating little interlayer hydration the cumberland smectite has basal spacing at both similar to 13 2 and similar to 10 angstroms the larger spacing suggests a partially chloritized interlayer or interlayer magnesium or calcium facilitating h2o retention basaltic minerals in the mudstone are similar to those in nearby eolian deposits however the mudstone has far less fe forsterite possibly lost with formation of smectite plus magnetite late noachian early hesperian or younger age indicates that clay mineral formation on mars extended beyond noachian time

derivation of sea surface tidal current from spaceborne sar constellation data in this paper we demonstrate an application of spaceborne synthetic aperture radar sar constellation data to derive sea surface tidal current at high spatial resolution the maximum cross correlation mcc method which has been widely applied to optical remote sensing data to derive sea surface velocities is applied to x band sar data from terrasar x tsx and tandem x tdx which were operating in pursuit monostatic mode because of the short temporal interval of tsx and tdx s pursuit acquisitions temporal de correlation is minimized to derive tidal current fields that exhibit significant temporal and spatial variations in addition we combined data from tdx and another x band sar cosmo skymed to obtain a virtual sar constellation data pair which was also analyzed using the mcc method to derive the tidal current field case studies of hangzhou bay in the east china sea and amrum island in the north sea are presented the sar derived tidal current fields were compared to the results of numerical model simulations high frequency hf radar measurements and in situ measurements mcc coefficients that are greater than 0 8 are an appropriate threshold for the further derivation of tidal currents comparisons to finite volume community ocean model hf radar and general estuarine transport model results yield root mean square errors of 0 13 0 06 and 0 05 m s respectively measurements from three field stations were also compared to the mcc sar retrievals yielding differences of 0 3 0 07 and 0 09 m s

motion detection using near simultaneous satellite acquisitions a number of acquisition constellations for airborne or spaceborne optical images involve small time lags and produce near simultaneous images a type of data which has thus far been little exploited to detect or quantify target motion at the earth s surface these time lag constellations were for the most part not even meant to exhibit motion tracking capabilities or these capabilities were considered a drawback in this contribution we give the first systematic overview of the methods and issues involved in exploiting near simultaneous airborne and satellite acquisitions we first cover the category of the near simultaneous acquisitions produced by individual stereo sensors typically designed for topographic mapping with a time lag on the order of a minute over this time period we demonstrate that the movement of river ice debris sea ice floes or suspended sediments can be tracked and we estimate the corresponding water surface velocity fields similarly we assess cloud motion vector fields and vehicle trajectories a second category of near simultaneous acquisitions with much smaller time lags of at most a few seconds is associated with along track offsets of detector lines in the focal plane of pushbroom systems these constellations are demonstrated here to be suitable to detect motion of fast vehicles such as cars and airplanes or for instance ocean waves acquisition delays are third also produced by other constellations such as trains of satellites following each other and leading to time lags of minutes to tens of minutes which are in this contribution used to track icebergs and features of floating ice crystals on the sea and an algae bloom for all acquisition categories the higher the spatial resolution of the data and the longer the time lag the smaller the minimum speed that can be detected

mapping surface currents and waves with interferometric synthetic aperture radar in coastal waters observations of wave breaking in swell dominant conditions airborne and spaceborne interferometric synthetic aperture radars insars produce surface velocity measurements at very high spatial resolutions over a large area the data allow construction of the velocity strain field for highlighting ocean surface processes such as wave breaking and rip currents also coherence between signals from two interferometric channels is a descriptor of the correlation condition of the surface roughness that scatters back the radar signals and it is an indication of the ocean surface turbulence wave breaking is a major turbulence source causing surface roughness decorrelation thus the coherence parameter serves as an independent means for detecting wave breaking the results of breaking detection using roughness decorrelation and critical local acceleration are comparable in this paper the breaking fraction in swell dominant mixed seas along a cross shore transect is compared with several steepness parameters characterizing different length scales of surface waves the highest correlation coefficient from 0 90 to 0 99 is between the breaking fraction and windsea mean square slope contributed primarily by short waves this result reinforces the previous field observations showing that the length scales of breaking waves are much shorter than the energetic components near the spectral peak although dominant waves and the associated wave group modulation are important in triggering the breaking process the large spatial coverage of airborne or spaceborne operation further offers the opportunity to investigate evolution of the surface wave spectrum in high spatial subkilometer resolution this capability is very useful for monitoring the coastal wave and current environment

differentiation in impact melt sheets as a mechanism to produce evolved magmas on mars abstract asteroid bombardment contributed to extensive melting and resurfacing of ancient 3 5 ga mars evidence from the largest impact structures on earth and the moon suggests that vertically thick impact melt sheets experience chemical differentiation recently observed materials in gale crater are enriched in alkalis up to 14 wt na2o k2o and silica up to 67 wt sio2 with low mgo

the presence and stability of ground ice in the southern hemisphere of mars abstract we calculate new estimates of ground ice stability and the depth distribution of the ice table the depth boundary between ice free soil above and ice cemented soil below and compare these theoretical estimates of the distribution of ground ice with the observed distribution of leakage neutrons measured by the neutron spectrometer instrument of the mars odyssey spacecraft s gamma ray spectrometer instrument suite our calculated ground ice distribution contains improvements over previous work in that we include the effects of the high thermal conductivity of ice cemented soil at and below the ice table we include the surface elevation dependence of the near surface atmospheric humidity and we utilize new high resolution maps of thermal inertia albedo and elevation from mars global surveyor observations results indicate that ground ice should be about 5 times shallower than in previous predictions while results are dependent on the atmospheric humidity depths are generally between a few millimeters and a few meters with typical values of a few centimeters results are also geographically similar to previous predictions with differences due to the higher resolution of thermal inertia and the inclusion of elevation effects on humidity comparison with the measured epithermal neutron count rates in the southern hemisphere indicate that the geographic distribution of the count rate is best correlated with ground ice in equilibrium with 10 to 20 pr m precipitable micrometers column abundance of atmospheric water assuming a uniform distribution with co2 however given the uncertainties 5 to 30 pr m also may be viable this water abundance represents a longer term average over 100 to 1000 yr there is a high degree of correlation between the depth of the ice table and the epithermal count rate that agrees remarkably well with predicted count rates as a function of ice table depth these results indicate that ground ice in the upper meter of the martian soil is in diffusive equilibrium with the atmosphere since ground ice in this depth zone is expected to undergo saturation desiccation cycles with orbital variations this ice should be younger than about 500 kyr and was emplaced under similar cold and dry climate conditions of today remaining differences between the predicted depths of the ice table and those inferred from the neutron data are likely to be due to subpixel heterogeneity in the martian surface including the presence of rocks slopes and patches of soil with varying thermophysical properties