Scott Hensley

• PhD Mathematics
• National Aeronautics and Space Administration

In the framework of the comparison of Synthetic Aperture Radar (SAR) imagery from the Magellan space mission and the VISAR and VenSAR radar instruments which will be onboard the forthcoming VERITAS and EnVision missions to Venus, the problem of the disparity between the resolutions of the images arises when attempting to define a test statistic wit...

The Instrumentation and Future Technologies Technical Committee’s (IFT-TC) second summer school took place in Auckland, New Zealand, from 30 January to 3 February 2023. The IFT Remote Sensing Summer Schools (IFT-R3S) aim to promote future research in remote sensing; connect Master students, junior Ph.D. students, recent graduates, and young profess...

In this work we discuss various selected mission concepts addressing Venus evolution through time. More specifically, we address investigations and payload instrument concepts supporting scientific goals and open questions presented in the companion articles of this volume. Also included are their related investigations (observations & modeling) an...

Photogeologic principles can be used to suggest possible sequences of events that result in the present planetary surface. The most common method of evaluating the absolute age of a planetary surface remotely is to count the number of impact craters that have occurred after the surface formed, with the assumption that the craters occur in a spatial...

The NASA Discovery-class mission VERITAS, selected in June 2021, will be launched toward Venus after 2027. In addition to the science instrumentation that will build global foundational geophysical datasets, VERITAS proposed to conduct a technology demonstration for the Deep Space Atomic Clock (DSAC-2). A first DSAC successfully operated in low-Ear...

Global success of utilizing X/C/L-band InSAR (Interferometric Synthetic Aperture Radar) to survey ground deformation over non-forested terrain in the past two decades, has raised interest in monitoring forested lands, where relatively short-wavelength X/C/L SAR acquisitions often experience strong decorrelation and downgraded InSAR quality. To addr...

The NASA Discovery-class mission VERITAS, selected in June 2021, will be launched towards Venus in 2027. In addition to the science instrumentation that will build global foundational geophysical datasets, VERITAS proposed to conduct a technology demonstration for the Deep Space Atomic Clock (DSAC-2). A first DSAC successfully operated in low-Earth...

EnVision was selected as ESA's 5th Medium-class mission in the Agency's Cosmic Vision plan, targeting a launch in the early 2030s. EnVision's overarching science questions are to explore the full range of geoscientific processes operating on Venus. It will investigate Venus from its inner core to its atmosphere at an unprecedented scale of resoluti...

On June 10, 2021, the European Space Agency (ESA) announced the selection of EnVision as its newest medium-class science mission. EnVision's overarching science questions are to explore the full range of geoscientific processes operating on Venus [1, 2]. It will investigate Venus from its inner core to its atmosphere at an unprecedented scale of re...

Deep understanding of planetary habitability requires identifying key factors that govern the surface environment over time. Venus is the ultimate control case for understanding how Earth developed and maintained conditions suited to life. Venus very likely had elements essential to habitability such as past surface water and a dynamo. Tectonism an...

The Ka-Band Radar Interferometer (KaRIn) instrument on the Surface Water and Ocean Topography (SWOT) mission is a single-pass synthetic aperture radar (SAR) interferometer tasked with, among others, measuring ocean topography to within a few centimeters over kilometer scale resolutions. A SAR interferometer relies on very precise phase difference m...

In 2015 and 2016, the AfriSAR campaign was carried out as a collaborative effort among international space and National Park agencies (ESA, NASA, ONERA, DLR, ANPN and AGEOS) in support of the upcoming ESA BIOMASS, NASA-ISRO Synthetic Aperture Radar (NISAR) and NASA Global Ecosystem Dynamics Initiative (GEDI) missions. The NASA contribution to the c...

Synthetic aperture radar (SAR) tomography (TomoSAR) is a multibaseline interferometric technique that estimates the power spectrum pattern (PSP) along the perpendicular to the line-of-sight (PLOS) direction. TomoSAR achieves the separation of individual scatterers in layover areas, allowing for the 3D representation of urban zones. These scenes are...

The airborne glacier and ice surface topography interferometer (GLISTIN-A) is a single-pass radar interferometer developed for accurate high-resolution swath mapping of dynamic ice surfaces. We present the first validation results of the operational sensor, collected in 2013 over glaciers in Alaska and followed by more exhaustive collections from G...

Within the context of potential future InSAR missions, we describe (1) the desired characteristics of the earth deformation observables as outlined in the recent NASA earth science decadal survey,(2) additional desirable capabilities of a future observing system that could provide a quantum leap in geodetic quality, and (3) different imaging scenar...

NASADEM is a near-global elevation model that is being produced primarily by completely reprocessing the Shuttle Radar Topography Mission (SRTM) radar data and then merging it with refined ASTER GDEM elevations. The new and improved SRTM elevations in NASADEM result from better vertical control of each SRTM data swath via reference to ICESat elevat...

NASADEM is a near-global elevation model that is being produced primarily by completely reprocessing the Shuttle Radar Topography Mission (SRTM) radar data and then merging it with refined ASTER GDEM elevations. The new and improved SRTM elevations in NASADEM result from better vertical control of each SRTM data swath via reference to ICESat elevat...

Measuring ice surface topography over the major ice caps of Greenland and Antarctica is crucial to quantifying and understanding the effect of climate change on the Earth's environment. Multiple sensors including radars, lidars, and optical systems have been utilized in making these measurements. To integrate data from these multiple sensors into a...

In order to provide surface geodetic measurements with “landslide-wide” spatial coverage we develop and validate a method for the characterization of 3D surface deformation using the unique capabilities of the UAVSAR airborne repeat-pass radar interferometry system. We apply our method at the well-studied Slumgullion Landslide, which is 3.9 km long...

Radiometric correction of radar images is essential to produce accurate estimates of biophysical parameters related to forest structure and biomass. We present a new algorithm to correct radiometry for 1) terrain topography and 2) variations of canopy reflectivity with viewing and tree-terrain geometry. This algorithm is applicable to radar images...

The mechanical properties of glacier beds play a fundamental role in regulating the sensitivity of glaciers to environmental forcing across a wide range of timescales. Glaciers are commonly underlain by deformable till whose mechanical properties and influence on ice flow are not well understood but are critical for reliable projections of future g...

The papers from this special issue were presentd at the 10th European Conference on Synthetic Aperture Radar (EUSAR), which was held from June 2¿¿¿6, 2014 in Berlin, German. EUSAR is the largest conference worldwide entirely dedicated to the development of synthetic aperture radar technologies, techniques, and applications. For the last 20 years, t...

Change detection using synthetic aperture radar (SAR) data is useful in emergency situations and unfavorable weather conditions. In this letter, change detection using multitemporal polarimetric Uninhabited Aerial Vehicle SAR data is investigated in an urban environment. The most robust polarimetric parameters are determined, and change detection t...

Estimation of forest height from combined polarimetric and interferometric synthetic aperture radar (Pol-InSAR) measurements has been the focus of radar remote sensing studies in the past decade. The simplicity of the random-volume-over-ground (RVoG) model makes it one of the most widely used candidates for estimating canopy height. However, the po...

Coastal lands and nearshore marine areas are productive and rapidly changing places. However, these areas face many environmental challenges related to climate change and human-induced impacts. Space-borne remote sensing systems may be restricted in monitoring these areas because of their spatial and temporal resolutions. In situ measurements are a...

This paper addresses the important yet unresolved problem of estimating forest properties from polarimetric-interferometric radar images affected by temporal decorrelation. We approach the problem by formulating a physical model of the polarimetric-interferometric coherence that incorporates both volumetric and temporal decorrelation effects. The m...

The relevance of this challenging still unresolved development of multi-band equatorially orbiting fully polarimetric POLinSAR satellite configurations to the entire terrestrial globe will be highlighted. Special attention will be given to generation of global weather phenomena, supply of an ever more relevant stable food base, extraction of minera...

Magellan, a NASA mission to Venus in the early 1990s, mapped nearly the entire surface of Venus with an S-band (12 cm) synthetic aperture radar and microwave radiometer and made radar altimeter measurements of the topography, [1]. These measurements revolutionized our understanding of the geomorphology, geology and geophysical processes that have s...

Tectonic motion across the Los Angeles region is distributed across an intricate network of strike-slip and thrust faults that will be released in destructive earthquakes similar to or larger than the 1933 M6.4 Long Beach and 1994 M6.7 Northridge events. Here we show that LA regional thrust, strike-slip, and oblique faults are connected and move co...

Differential SAR interferometry, a popular technique for measuring displacements of the Earth's surface, is potentially influenced by changes in soil moisture. Different mechanisms for this impact have been proposed, but its magnitude, sign and even presence remain poorly understood. In this study the dependence of the phase, the coherence magnitud...

This paper investigates the feasibility of using an airborne synthetic aperture radar (SAR) to validate spaceborne SAR data. This is directed at soil moisture sensing and the recently launched soil moisture active passive (SMAP) satellite. The value of this approach is related to the fact that vicarious targets such as rain forests and oceans calib...

Mechanical properties of glacier beds impose fundamental constraints on glacier flow across a wide range of timescales [1]. Despite their importance in governing glacier dynamics, basal mechanics are not well understood, particularly where glaciers are underlain by deformable till [2]. While some till samples have been retrieved from beneath severa...

The AirMOSS airborne SAR operates at UHF and produces fully polarimetric imagery [1]. The AirMOSS radar data are used to produce Root Zone Soil Moisture (RZSM) depth profiles. The absolute radiometric accuracy of the imagery, ideally of better than 0.5 dB, is key to retrieving RZSM, especially in wet soils where the backscatter as a function of soi...

Changes in soil moisture between two radar acquisitions can impact the observed coherence in differential interferometry: both coherence magnitude |γ| and phase ϕ are affected. The influence on the latter potentially biases the estimation of deformations. These effects have been found to be variable in magnitude and sign, as well as dependent on po...

Uninhabited aerial vehicle synthetic aperture radar (UAVSAR) is a reconfigurable polarimetric L-band SAR that operates in quad-polarization mode and is specifically designed to acquire airborne repeat-track SAR data for interferometric measurements. In this paper, we present details of the UAVSAR radar performance, the radiometric calibration, and...

We infer the horizontal velocity fields of the ice caps Langjökull and Hofsjökull, central Iceland, using repeat-pass interferometric synthetic aperture radar (InSAR). NASA's uninhabited aerial vehicle synthetic aperture radar (UAVSAR) acquired airborne InSAR data from multiple vantage points during the early melt season in June 2012. We develop a...

The Slumgullion landslide in southwestern Colorado, USA is a natural laboratory for studying the mechanics of landslide motion because of its rapid motion of up to 2 cm/day and its large spatial extent. We are using interferometric synthetic aperture radar (InSAR) analysis of COSMO-SkyMed™ (CSK) X-band satellite Spotlight images and UAVSAR L-band a...

Estimating the amount of above ground biomass in forested areas and the measurement of carbon flux through the quantification of disturbance and regrowth are critical to develop a better understanding of ecosystem processes. Well-resolved and globally consistent inventories of forest carbon must rely on remote sensing measurements, particularly fro...

Changes in soil moisture between the two radar acquisitions can impact the observed coherence 7 in differential interferometry: both correlation -γ- and phase φ are affected. The influence on the latter potentially biases the estimation of deformations. These effects have been found to be variable in magnitude and dependent on polarization, as oppo...

A one-dimensional digital beam-forming (DBF) algorithm that is suitable for onboard real-time implementation is described in this article. A couple of techniques for generating a set of DBF coefficients will be also proposed to improve radar system performance such as signal-to-noise ratio (SNR) and/or range ambiguity (as a part of multiplicative n...

A better understanding of ecosystem processes requires accurate estimates of forest biomass and structure on global scales. Recently, there have been demonstrations of the ability of remote sensing instruments, such as radar and lidar, for the estimation of forest parameters from spaceborne platforms in a consistent manner. These advances can be ex...

The 4 April 2010 M 7.2 El Mayor – Cucapah earthquake that occurred in Baja California, Mexico and terminated near the US Mexican border caused slip on the Imperial, Superstition Hills, and East Elmore Ranch faults. The pattern of slip was observed using radar interferometry from NASA's Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) in...

Since the 2007 National Academy of Science “Decadal Survey” report “Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond” [1], the National Aeronautics and Space Administration (NASA) has been studying concepts for a Synthetic Aperture Radar (SAR) mission to determine Earth change in three disciplines - eco...

Different mechanisms for the impact of soil moisture on interferometric radar data have been proposed, but its magnitude, sign and even presence have barely been studied empirically and thus remain poorly understood. In this study the dependence of the phase and coherence magnitude on soil moisture was inferred empirically with regression technique...

Estimates of above ground biomass density in forests are crucial for refining global climate models and understanding climate change. Although data from field studies can be aggregated to estimate carbon stocks on global scales, the sparsity of such field data, temporal heterogeneity and methodological variations introduce large errors. Remote sens...

The GeoSAR single-pass P-band and X-band IFSAR system was employed 09 April 2012 to acquire ice data over the city of Barrow, Alaska, extending into the Chukchi Sea to the west and the Beaufort Sea to the northeast. The acquisition covered two back-to-back flights obtaining high quality single-pass interferometric X-band and P-band data. Some of th...

Slow-moving landslides (earthflows) can dominate hillslope sediment flux and landscape erosion in hilly terrain with mechanically weak, fine-grained rock. Controls on the occurrence of slow-moving landslides are poorly constrained and need to be under stood for landscape evolution models, sediment budgets, and infrastructure and hazards planning. H...

5-9 March 2011 Kamoamoa fissure eruption along the east rift zone of Kīlauea Volcano, Hawai`i, followed months of pronounced inflation at Kīlauea summit. We examine dike opening during and after the eruption using a comprehensive interferometric synthetic aperture radar (InSAR) data set in combination with continuous GPS data. We solve for distribu...

The National Aeronautics and Space Administration's (NASA) proposed Soil Moisture Active Passive (SMAP) satellite mission ( ~ 2014) will include a radar system that will provide L-band multi-polarization backscatter at a constant incidence angle of 40 °. During the pre-launch phase of the project, there is a need for observations that will support...

Quantification of global carbon storage, carbon flux and disturbance in forested regions is of critical importance to refining our understanding of ecosystem processes, climate modeling and climate change. Remote sensing instruments, such as lidar and radar provide a means of obtaining highly accurate and well resolved biomass estimates over global...

We have studied the utility of high resolution synthetic aperture radar for levee monitoring using UAVSAR data collected over the dikes and levees in California's Sacramento-San Joaquin Delta and the lower Mississippi River. Our study has focused on detecting and tracking changes that are indicative of potential problem spots, namely deformation of...

This paper describes a physical model of the temporal changes that occur in vegetated land surfaces observed by a repeat-pass radar interferometer. We assume the temporal changes to be caused by a Gaussian-statistic motion of the vegetation elements, with motion variance changing along the vertical direction. We show that the temporal correlation b...

This paper investigates the ability of radar image segmentation to produce meaningful, structurally homogenous objects with respect to lidar-derived forest metrics. A comparative approach is taken to determine if radar-derived segments perform better in this respect than arbitrary, square segments or landcover-derived segments. It is found that seg...

Quantification of the various components of the carbon cycle budget is key to improved climate modeling and projecting anthropogenic affects on climate in the future. Estimating the levels of above ground biomass contained in the world's forests that comprise 86% of the planet's above ground carbon and monitoring the rate of change to these standin...

The world forest systems are dynamic and play an integral role in the Earth's carbon budget. Monitoring of these valuable assets is being mandated by the international community. The requirement of global forest inventories suggests that a global measurement methodology should be adopted and that a verification and validation strategy should be acc...

This paper describes comparison of digital elevation data derived from synthetic aperture radar (SAR) and stereo optical imagery used to understand temporal changes of tropical forest and to estimate tree height in tropical regions. Tree height information is important for forest management and global carbon cycle studies. An intereferometric SAR (...

In this paper we show our first POLINSAR results using the Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) developed by the Jet Propulsion Laboratory (JPL). UAVSAR is a L-band repeat-pass polarimetric and interferometric system designed for measuring vegetation structure and monitoring crustal deformations. In order to extract canopy h...

Rapid response to natural disasters resulting from events such as earthquakes, volcanoes, floods, and tsunamis or anthropogenically induced events such as oil spills often requires response time measured in hours to days. The type of information required spans information on the magnitude and location of damage needed by immediate response teams to...

A keystone of the Airborne Microwave Observatory of Subcanopy and Subsurface (AirMOSS) investigation is the P-band Synthetic Aperture Radar (SAR), which will provide calibrated polarimetric measurements that will be used to retrieve the root-zone soil moisture (RZSM) over regional scale (250 kha) areas imaged. The radar is based on JPL's L-band Uni...

We present an empirical assessment of the impact of temporal decorrelation on interferometric coherence measured over a forested landscape. A series of repeat-pass interferometric radar images with a zero spatial baseline were collected with UAVSAR (Uninhabited Aerial Vehicle Synthetic Aperture Radar), a fully polarimetric airborne L-band radar sys...

We automate F-BIDR stereo processing to obtain precise and extensive terrain data, complete with formal error calculation and updated ephemerides. Results will eventually be released to the community with a viewing/editing tool.

SweepSAR is a wide-swath synthetic aperture radar technique that is being studied for application on the future Earth science radar missions. This paper describes the design of an airborne radar demonstration that simulates an 11-m L-band (1.2–1.3 GHz) reflector geometry at Ka-band (35.6 GHz) using a 40-cm reflector. The Ka-band SweepSAR Demonstrat...

After a review of biomass estimation from interferometric SAR (InSAR) at all bands over the last 15 years, and a brief review of lidar biomass estimation, this paper discusses structure and biomass estimation from simultaneously acquired (not repeat-track) InSAR at L-band. We will briefly discuss the history of regression of biomass to InSAR raw ob...

A better understanding of ecosystem processes requires accurate estimates of forest biomass and structure on global scales. Recently, there have been demonstrations of the ability of remote sensing instruments, such as radar and lidar, for the estimation of forest parameters from spaceborne platforms in a consistent manner. These advances can be ex...

Biomass is identified by the United Nations Framework Convention on Climate Change (UNFCCC) as an essential climate variable needed to reduce uncertainties in our knowledge of the climate system [1]. Radar remote sensing is the most suitable tool to measure and map Earth's forest biomass, but current methods are limited by saturation issues (backsc...

We use the UAVSAR, an airborne fully polarimetric L-band radar system, to estimate forest canopy structure and biomass through radar backscatter and repeat-pass interferometry. UAVSAR provides backscatter images with a spatial resolution of 5m and is capable of repeat-pass interferometry. Our analysis also includes data from LVIS (Laser vegetation...

The UAVSAR Iceland campaign collected L-band, airborne, repeat-pass InSAR data over temperate ice caps Hofsjökull and Langjökull, located in central Iceland. Eleven different tracks were flown during the 5-day campaign in June 2009, acquiring enough InSAR data to generate approximately 400 interferograms with temporal baselines ranging from less th...

The improved spatiotemporal resolution of surface deformation from recent satellite and airborne InSAR measurements provides great potential to improve our understanding of faulting processes and earthquake hazard for a given fault system. A major plate boundary fault in central California, the central San Andreas fault (CSAF) displays a spectrum o...

On March 5, 2011, the Kamoamoa fissure eruption began along the east rift zone (ERZ) of Kilauea Volcano. It followed several months of pronounced inflation at Kilauea's summit and was the first dike intrusion into the ERZ since June 2007. The eruption began in the late afternoon of March 5, 2011 (Hawaii Standard Time; UTC-10:00 hrs) with rapid defl...

The vulnerability of the Gulf Coast has received increasing attention in the years since hurricanes Katrina and Rita. A quantitative geophysical basis for measuring, predicting, and understanding subsidence rates, their geographic distribution, and temporal variability, is necessary for long term protection of lives and property in addition to bein...

In April 2009, an airborne Ka-band single pass interferometric SAR (GLISTIN-A) was demonstrated as a modification to the UAVSAR system. GLISTIN-A was developed under the NASA International Polar Year program to demonstrate swath-mapping for ice-surface topography. Instrument performance confirmed swath widths over the ice between 5-7km, with height...

Geodetic Imaging with Interferometric Airborne Radar Scott Hensley and Cathleen Jones Jet Propulsion Laboratory, California Institute of Technology 4800 Oak Grove Dr, Pasadena CA 91109. Unlike spaceborne sensors both revisit time and viewing geometry can be optimized to a particular application. Airborne sensors such as GeoSAR for topographic measu...

Kilauea Volcano, Hawai`i, has a wealth of constantly changing magmatic and structural deformation processes. Interferometric synthetic aperture radar (InSAR) observations provide important constraints on the magmatic and structural source parameters that complement the more sparse in-situ networks of continuous GPS and tiltmeter observations. We pr...

Under ARIA (Advanced Rapid Imaging and Analysis) project at JPL and Caltech, we developed a prototype algorithm to detect surface property change caused by natural or man-made damage using InSAR coherence change. The algorithm was tested on building demolition and construction sites in downtown Pasadena, California. The developed algorithm performe...

In this paper we quantify the effects of temporal decorrelation in repeat pass synthetic aperture radar interferometry (InSAR). Temporal decorrelation causes significant uncertainties in vegetation parameter estimates obtained using various InSAR techniques, which are desired on a global scale. Because of its stochastic nature temporal decorrelatio...

The islands of the Sacramento-San Joaquin Delta have been subject to subsidence since they were first reclaimed from the estuary marshlands starting over 100 years ago, with most of the land currently lying below mean sea level. This area, which is the primary water resource of the state of California, is under constant threat of inundation from le...