High-resolution Imaging Instrument Research Articles

Validation of MODIS Temperature and Emissivity Products Based on Ground-Based Mid-Wave Hyperspectral Imaging Measurement in the Northwestern Plateau Region of Qinghai, China

The climatic fluctuations in northern China exhibit remarkable variability, making it imperative to harness the power of MODIS data for conducting comprehensive investigations into the influences of desertification, desert expansion, and snow and ice melting phenomena. Consequently, the rigorous evaluation of MODIS land surface temperature (LST) and land surface emissivity (LSE) products takes on a momentous role, as this provides an essential means to ensure data accuracy, thereby instilling confidence in the robustness of scientific analyses. In this study, a high-resolution hyperspectral imaging instrument was utilized to measure mid-wave hyperspectral images of grasslands and deserts in the northwest plateau region of Qinghai, China. The measured data were processed in order to remove the effects of sensor noise, atmospheric radiation, transmission attenuation, and scattering caused by sunlight and atmospheric radiation. Inversion of the temperature field and spectral emissivity was performed on the measured data. The inverted data were compared and validated against MODIS land surface temperature and emissivity products. The validation results showed that the absolute errors of emissivity of grassland backgrounds provided by MCD11C1 in the three mid-wave infrared bands (3.66–3.840 μm, 3.929–3.989 μm, and 4.010–4.080 μm) were 0.0376, 0.0191, and 0.0429, with relative errors of 3.9%, 2.1%, and 4.8%, respectively. For desert backgrounds, the absolute errors of emissivity were 0.0057, 0.0458, and 0.0412, with relative errors of 0.4%, 4.9%, and 3.9%, respectively. The relative errors for each channel were all within 5%. Regarding the temperature data products, compared to the inverted temperatures of the deserts and grasslands, the remote sensing temperatures provided by MOD11L2 had absolute errors of ±2.3 K and ±4.1 K, with relative errors of 1.4% and 0.7%, respectively. The relative errors for the temperature products were all within 2%.

Longitudinal structures of zonal wind in the thermosphere by the ICON/MIGHTI and the main wave sources

In this study, the neutral wind observations from the Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) instrument onboard Ionospheric CONnections (ICON) are used to investigate the longitudinal structure of zonal wind between 100 and 300 km during daytime. The four-peaked structure in the longitudinal distribution between June and August is visually clear in the whole altitudinal range. The longitudinal wavenumber 1–4 patterns (WN1–WN4) are extracted, and the altitude–month distributions of WN1–WN4 and their contributions to the longitudinal structure are compared. The amplitudes of WN3 and WN4 show seasonal dependence, and the amplitude of WN4 exhibits obvious vertical propagation from the mesosphere and lower thermosphere (MLT) to the upper thermosphere in summer and autumn. WN1 is an important contributor to the longitudinal structure, WN4 is the primary contributor in the lower altitude ranges in summer and autumn at three latitudes. The contributions of WN3 (WN1) increase holistically with latitude in summer (spring, autumn, and winter). And the main wave sources of WN1–WN4 are further investigated in the 100–106 km and 210–300 km altitude regions. The main wave sources of WN1 and WN2 have complex variations with altitude, latitude, and season, while WN3 (WN4) is clearly influenced by DE2 (DE3 and SE2).Graphical

Comparison of TIDI Line of Sight Winds With ICON-MIGHTI Measurements.

The Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite has been making observations of the mesosphere and lower thermosphere (MLT) region for two decades. The TIMED Doppler Interferometer (TIDI) measures the neutral winds using four orthogonal telescopes. In this study, the line of sight (LOS) winds from individual telescopes are compared to the measurements from the Ionospheric Connection Explorer's (ICON's) Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) instrument from 90 to 100km altitude during 2020. With the MIGHTI vector winds projected onto the LOS direction of each TIDI telescope, coincidences of the two data sets are found. The four telescopes perform differently and the performance depends on the satellite configuration and local solar zenith angle. Measurements from the coldside telescopes, Telescope 1 (Tel1) and Telescope 2 (Tel2), are better correlated with the MIGHTI winds in general with Tel2 having higher correlation coefficients across all conditions. The performance of Tel1 is comparable to that of Tel2 during backward flight while showing systematic errors larger than the average wind speeds during forward flight. The warmside LOS winds from Telescope 3 (Tel3) and Telescope 4 (Tel4) vary widely in magnitude, especially on the nightside. Compared with MIGHTI winds, the Tel4 measurements have the weakest correlation, while the Tel3 performance is comparable to that of the coldside telescopes during the ascending phase but deteriorates during the descending phase. Based on the TIDI/MIGHTI comparisons, figures of merit are generated to quantify the quality of measurements from individual telescopes in different configurations.

Design and Experiment of High-Resolution Multispectral Polarization Imaging System

This paper addresses the objectives in a complex context: the polarization mathematical and physical model of the basic components of the target/background is constructed by simulation modeling. The image fusion experiment is carried out based on a two-dimensional wavelet transformation. A high-resolution polarization imaging instrument was developed, and static experiments were carried out with polarization, infrared, and visible cameras. The result shows that using polarization imaging detection technology to detect physical evidence targets in complex backgrounds can effectively improve target contrast. It can enrich the target information, improve image quality, and improve target detection accuracy.

Demonstration of an imaging technique for the measurement of PSF elongation caused by Atmospheric Dispersion

ABSTRACT Elongation of the point spread function (PSF) due to atmospheric dispersion becomes a severe problem for high-resolution imaging instruments, if an atmospheric dispersion corrector is not present. In this work, we report on a novel technique to measure this elongation, corrected or uncorrected, from imaging data. By employing a simple diffraction mask, it is possible to magnify the chromatic elongation caused by the atmosphere and thus make it easier to measure. We discuss the theory and design of such a mask and report on two proof of concept observations using the 40-cm Gratama telescope at the University of Groningen. We evaluate the acquired images using a geometric approach, a forward modelling approach and from a direct measurement of the length of the PSF. For the first two methods, we report measurements consistent with atmospheric dispersion models to within 0.5 arcsec. Direct measurements of the elongation do not prove suitable for the characterization of atmospheric dispersion. We conclude that the addition of this type of diffraction mask can be valuable for measurements of PSF elongation. This can enable high-precision correction of atmospheric dispersion on future instruments.

Development of a quasi-coaxis dual-energy flat spectral response X-ray imaging instrument for measuring hotspot electron temperature.

The measurement of hotspot electron temperature is a paramount technique of implosion physics research in inertial confinement fusion. This study proposes a novel quasi-coaxis dual-energy flat spectral response high-resolution X-ray imaging instrument comprising a dual-channel total-reflection Kirkpatrick-Baez microscope and two flat non-periodic multilayer mirrors, which can image at 6.4 ± 0.5 and 9.67 ± 0.5 keV simultaneously. Various theoretical simulations were performed to verify the performance and feasibility of the imaging instrument, which was assembled and characterized in a laboratory. Experimental results show that the imaging instrument could achieve a high spatial resolution of 5 µm in a ± 150 µm field of view (FOV), the root mean square(RMS) deviation values of the measured reflection efficiency are 1.71% and 1.82% for the 6.4 keV and 9.67 keV imaging channels, respectively, in the ± 150 µm FOV.

The Single-mode Complex Amplitude Refinement (SCAR) coronagraph

Context. The recent discovery of an Earth-mass exoplanet around the nearby star Proxima Centauri provides a prime target for the search for life on planets outside our solar system. Atmospheric characterization of these planets has been proposed by blocking the starlight with a stellar coronagraph and using a high-resolution spectrograph to search for reflected starlight off the planet. Aims. Due to the large flux ratio and small angular separation between Proxima b and its host star (≲10−7 and ≲2.2λ/D respectively; at 750 nm for an 8 m-class telescope) the coronagraph requires high starlight suppression at extremely-low inner working angles. Additionally, it must operate over a broad spectral bandwidth and under residual telescope vibrations. This allows for efficient use of spectroscopic post-processing techniques. We aim to find the global optimum of an integrated coronagraphic integral-field spectrograph. Methods. We present the Single-mode Complex Amplitude Refinement (SCAR) coronagraph that uses a microlens-fed single-mode fiber array in the focal plane downstream from a pupil-plane phase plate. The mode-filtering property of the single-mode fibers allows for the nulling of starlight on the fibers. The phase pattern in the pupil plane is specifically designed to take advantage of this mode-filtering capability. Second-order nulling on the fibers expands the spectral bandwidth and decreases the tip-tilt sensitivity of the coronagraph. Results. The SCAR coronagraph has a low inner working angle (∼1λ/D) at a contrast of < 3 × 10−5 for the six fibers surrounding the star using a sufficiently-good adaptive optics system. It can operate over broad spectral bandwidths (∼20%) and delivers high throughput (> 50% including fiber injection losses). Additionally, it is robust against tip-tilt errors (∼0.1λ/D rms). We present SCAR designs for both an unobstructed and a VLT-like pupil. Conclusions. The SCAR coronagraph is a promising candidate for exoplanet detection and characterization around nearby stars using current high-resolution imaging instruments.

Determining the thermomechanical image shift for the MIGHTI instrument on the NASA-ICON satellite.

The Michelson Interferometer for Global High-Resolution Thermospheric Imaging (MIGHTI) instrument on NASA's Ionospheric Connection Explorer's mission will measure neutral winds in the Earth's thermosphere. We investigate how thermal changes to the instrument's optical bench affect the relative position of the image recorded by the camera. The thermal shift is measured by fitting the image of a series of reference notches and determining their current position on the camera with subpixel precision. Analyzing ground-based calibration data, we find that the image position is not affected within the uncertainty of the analysis for the applied thermal changes. We also address the question of the analysis uncertainty with signal-to-noise ratio.

Tracking Pharmacodynamics of Vascular Targeted Therapy with Photoacoustic Imaging.

HomeRadiology: Imaging CancerVol. 2, No. 1 PreviousNext Research HighlightsFree AccessTracking Pharmacodynamics of Vascular Targeted Therapy with Photoacoustic ImagingGary D. LukerGary D. LukerGary D. LukerPublished Online:Jan 31 2020https://doi.org/10.1148/rycan.2020204004MoreSectionsPDF ToolsImage ViewerAdd to favoritesCiteTrack CitationsPermissionsReprints ShareShare onFacebookTwitterLinked In Take-Away Points■ Major Focus: To investigate feasibility of noninvasive photoacoustic imaging for quantifying pharmacodynamics of vascular-targeted therapy in tumors.■ Key Result: Photoacoustic imaging measured time- and dose-dependent effects of an investigation of a vascular disrupting agent in two preclinical models of cancer.■ Impact: Photoacoustic imaging can successfully monitor pharmacodynamics of tumor vasculature during therapy, supporting applications in drug development and clinical translation for precision medicine.Imaging methods to analyze pharmacodynamics, the activity of a compound on its therapeutic target, potentially will increase development of new drugs for cancer and enable precision therapy for patients. Vascular disrupting agents represent a new class of anticancer compounds designed to target immature blood vessels typically associated with tumors. Success of these agents remains limited by a viable peripheral rim of cancer cells perfused by adjacent normal blood vessels and intertumor differences in susceptibility to hypoxia. Photoacoustic imaging, which uses low-intensity, nonionizing laser pulses to generate ultrasound waves for an image, provides an excellent method to image tumor blood vessels based on sensitive, high-contrast detection of hemoglobin. Using a high-resolution photoacoustic imaging instrument, Johnson et al measured the effects of the vascular disrupting agent OXi4503 in two different mouse models of colon cancer. In both models, photoacoustic imaging revealed initial ablation of internal blood vessels and subsequent regrowth of tumor vasculature over 16 days of treatment. For well-perfused tumors with extensive immature blood vessels, reductions in tumor blood vessels correlated highly with reductions in tumor volume over time. While poorly perfused tumors with larger, more mature blood vessels showed modest reductions in tumor blood vessels, changes in tumor vasculature did not predict effects on tumor volume. Treatment failures in poorly perfused tumors mirror past studies demonstrating resistance of such tumors to vascular disrupting therapy. Photoacoustic imaging also measured dose-dependent reductions in tumor blood vessels, establishing an approach to optimize doses and dosing schedules. These results establish photoacoustic imaging as a preclinical imaging method to advance development of vascular-targeted therapies. Furthermore, since photoacoustic instruments have entered clinical testing, this research supports future clinical applications of photoacoustic methods for pharmacodynamic imaging.Highlighted ArticleJohnson SP, Ogunlade O, Lythgoe MF, Beard P, Pedley RB. Longitudinal photacoustic imaging of the pharmacodynamics effect of vascular targeted therapy on tumors. Clin Cancer Res 2019;25:7436–7447. doi: 10.1158/1078-0432.CCR-19-036Highlighted ArticleJohnson SP, Ogunlade O, Lythgoe MF, Beard P, Pedley RB. Longitudinal photacoustic imaging of the pharmacodynamics effect of vascular targeted therapy on tumors. Clin Cancer Res 2019;25:7436–7447. doi: 10.1158/1078-0432.CCR-19-036 Crossref, Medline, Google ScholarArticle HistoryPublished online: Jan 31 2020 FiguresReferencesRelatedDetailsRecommended Articles Irreversible Electroporation versus Radiofrequency Ablation: A Comparison of Local and Systemic Effects in a Small-Animal ModelRadiology2016Volume: 280Issue: 2pp. 413-424Midterm Safety and Efficacy of Irreversible Electroporation of Malignant Liver Tumors Located Close to Major Portal or Hepatic VeinsRadiology2017Volume: 285Issue: 3pp. 1023-1031Local-Regional Treatment of Hepatocellular Carcinoma: A Primer for RadiologistsRadioGraphics2022Volume: 42Issue: 6pp. 1670-1689Nonthermal Ablation by Using Intravascular Oxygen Radical Generation with WST11: Dynamic Tissue Effects and Implications for Focal TherapyRadiology2016Volume: 281Issue: 1pp. 109-118Animal Models of Hepatocellular Carcinoma for Local-Regional Intraarterial TherapiesRadiology: Imaging Cancer2022Volume: 4Issue: 4See More RSNA Education Exhibits Novel Image-Guided Micro-Invasive Percutaneous Treatments of Breast Lesions: Where Do We Stand?Digital Posters2019Imaging Features at the Periphery – Hemodynamics, Pathophysiology and Impact on LI-RADS CategorizationDigital Posters2020A Practical Guide of Locoregional Treatment for Patients with Hepatocellular CarcinomaDigital Posters2019 RSNA Case Collection Adult colo-colonic intussusceptionRSNA Case Collection2020Cerebral Cavernous Venous MalformationRSNA Case Collection2021Pseudocirrhosis of Hepatic Breast MetastasesRSNA Case Collection2020 Vol. 2, No. 1 Metrics Altmetric Score PDF download

High-resolution Imaging Transit Photometry of Kepler-13AB

Abstract Using the high-resolution imaging instrument, ’Alopeke, at the Gemini-N telescope, we obtained simultaneous two-channel time-series observations of the binary exoplanet host star Kepler13-AB. Our optical observations were obtained during a transit event of the exoplanet Kepler-13b and light curves were produced using both speckle interferometric and aperture photometry techniques. Both techniques confirm that the transiting object orbits the star Kepler-13A while different transit depths are seen across the optical wavelength range, being ∼2 times deeper in the blue. These measurements, as well as mass determinations in the literature, are consistent with Kepler-13b being a highly irradiated gas giant with a bloated atmosphere. Our observations highlight the ability of high-resolution speckle imaging to not only assess binarity in exoplanet host stars but robustly determine which of the stars the transiting object actually orbits.

Calibration lamp design, characterization, and implementation for the Michelson Interferometer for Global High-Resolution Thermospheric Imaging instrument on the Ionospheric Connection satellite.

We describe the design and ground-based performance of the two-color calibration lamp for the Michelson Interferometer for Global High-Resolution Thermospheric Imaging (MIGHTI) instrument on the NASA Ionospheric Connection (ICON) satellite. The calibration lamp assembly contains radio frequency excited krypton and neon lamps, which generate emission lines at 557 and 630 nm, respectively, and which are used to monitor thermal drifts in the two MIGHTI Doppler asymmetric spatial heterodyne interferometers. The lamps are coupled to two mixed optical fiber bundles that deliver the calibration signals to the two MIGHTI optical units. The assembly starts reliably, consumes <8 W, and has passed environmental testing for the ICON satellite. The total mass of the lamp assembly is 1.8 kg. Special features of the assembly and its implementation are described along with results of life tests.

Two-channel high-resolution quasi-monochromatic X-ray imager for Al and Ti plasma.

High-resolution, high-sensitivity X-ray imaging is a real challenge in high-energy density plasma experiments. We present an improved design of the Fresnel ultra high-resolution imager instrument. Using an Ultra-High-Intensity (UHI) laser to generate hot and dense plasma in a small volume of an Al-Ti mixed target provides simultaneous imaging of both Al and Ti X-ray emission. Specifically, the Al Heβ (or Lyβ) and the Ti Heα lines are imaged with a resolution of (2.7 ± 0.3) μm and (5.5 ± 0.3) μm, respectively. It features two transmission Fresnel phase zone plates fabricated on the same substrate, each associated with a multilayer mirror for spectral selection. Their spatial resolution has been measured on the PTB synchrotron radiation facility laboratory at BESSY II and on the EQUINOX laser facility. Results obtained on an UHI experiment highlight the difference of emission zone sizes between Al and Ti lines and the versatility of this instrument.

The (R)evolution of Distributed Amplifiers: From Vacuum Tubes to Modern CMOS and GaN ICs

Broadband amplification of signals is desirable in many applications such as high-speed data communications, high-resolution imaging systems, optoelectronics, and instrumentation systems. Wide bandwidth is one of the prominent factors to be considered in designing such systems because it determines the system's ability to transfer high-data-rate information, transmit/receive short pulses, and process wide-band signals. Designing broadband amplifiers has always been challenging. The ever-increasing demand for higher data rates and low energy consumption in next-generation communication systems further complicates broadband amplifier design.

Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI): Monolithic Interferometer Design and Test.

The design and laboratory tests of the interferometers for the Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) instrument which measures thermospheric wind and temperature for the NASA-sponsored Ionospheric Connection (ICON) Explorer mission are described. The monolithic interferometers use the Doppler Asymmetric Spatial Heterodyne (DASH) Spectroscopy technique for wind measurements and a multi-element photometer approach to measure thermospheric temperatures. The DASH technique and overall optical design of the MIGHTI instrument are described in an overview followed by details on the design, element fabrication, assembly, laboratory tests and thermal control of the interferometers that are the heart of MIGHTI.

The MIGHTI Wind Retrieval Algorithm: Description and Verification.

We present an algorithm to retrieve thermospheric wind profiles from measurements by the Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) instrument on NASA's Ionospheric Connection Explorer (ICON) mission. MIGHTI measures interferometric limb images of the green and red atomic oxygen emissions at 557.7 nm and 630.0 nm, spanning 90-300 km. The Doppler shift of these emissions represents a remote measurement of the wind at the tangent point of the line of sight. Here we describe the algorithm which uses these images to retrieve altitude profiles of the line-of-sight wind. By combining the measurements from two MIGHTI sensors with perpendicular lines of sight, both components of the vector horizontal wind are retrieved. A comprehensive truth model simulation that is based on TIME-GCM winds and various airglow models is used to determine the accuracy and precision of the MIGHTI data product. Accuracy is limited primarily by spherical asymmetry of the atmosphere over the spatial scale of the limb observation, a fundamental limitation of space-based wind measurements. For 80% of the retrieved wind samples, the accuracy is found to be better than 5.8 m/s (green) and 3.5 m/s (red). As expected, significant errors are found near the day/night boundary and occasionally near the equatorial ionization anomaly, due to significant variations of wind and emission rate along the line of sight. The precision calculation includes pointing uncertainty and shot, read, and dark noise. For average solar minimum conditions, the expected precision meets requirements, ranging from 1.2 to 4.7 m/s.

HOW BRIGHT ARE PLANET-INDUCED SPIRAL ARMS IN SCATTERED LIGHT?

ABSTRACT Recently, high angular resolution imaging instruments such as SPHERE and GPI have discovered many spiral-arm-like features in near-infrared scattered-light images of protoplanetary disks. Theory and simulations have suggested that these arms are most likely excited by planets forming in the disks; however, a quantitative relation between the arm-to-disk brightness contrast and planet mass is still missing. Using 3D hydrodynamics and radiative transfer simulations, we examine the morphology and contrast of planet-induced arms in disks. We find a power-law relation for the face-on arm contrast (δ max) as a function of planet mass ( ) and disk aspect ratio (h/r): . With current observational capabilities, at a 30 au separation, the minimum planet mass for driving detectable arms in a disk around a 1 Myr, 1 star at 140 pc at low inclinations is around Saturn mass. For planets more massive than Neptune masses, they typically drive multiple arms. Therefore, in observed disks with spirals, it is unlikely that each spiral arm originates from a different planet. We also find that only massive perturbers with at least multi-Jupiter masses are capable of driving bright arms with as found in SAO 206462, MWC 758, and LkHα 330, and these arms do not follow linear wave propagation theory. Additionally, we find that the morphology and contrast of the primary and secondary arms are largely unaffected by a modest level of viscosity with . Finally, the contrast of the arms in the SAO 206462 disk suggests that the perturber SAO 206462 b at ∼100 au is about in mass.

Proposal for the Implementation of the ALOHA Up-Conversion Interferometer on the CHARA Telescope Array

In this paper, we present a new concept of instrument for high resolution imaging in astronomy, involving the sum frequency generation in non-linear waveguides. The aim is to convert the infrared radiation emitted by an astronomical source to the visible spectral domain where the optical components are mature and efficient. We present the main experimental results obtained in laboratory, and propose a new design for this instrument for its implementation on the Center for High Angular Resolution Astronomy (CHARA) telescope array. Preliminary stability and photometric results obtained at CHARA are presented. Using these last measurements, we estimate the limiting magnitudes which could be reached by this interferometer in the H spectral band.

Adaptive optics optical coherence tomography forin vivomouse retinal imaging

Small animal models of retinal diseases are important to vision research, and noninvasive high resolution in vivo rodent retinal imaging is becoming an increasingly important tool used in this field. We present a custom Fourier domain optical coherence tomography (FD-OCT) instrument for high resolution imaging of mouse retina. In order to overcome aberrations in the mouse eye, we incorporated a commercial adaptive optics system into the sample arm of the refractive FD-OCT system. Additionally, a commercially available refraction canceling lens was used to reduce lower order aberrations and specular back-reflection from the cornea. Performance of the adaptive optics (AO) system for correcting residual wavefront aberration in the mice eyes is presented. Results of AO FD-OCT images of mouse retina acquired in vivo with and without AO correction are shown as well.

EFFECTS OF LOCAL PHASE ERRORS IN MULTI-LOOK SAR IMAGES

The synthetic aperture radar (SAR) is a widely used instrument for high-resolution imaging from aircraft or satellite platforms. In the paper, the problem of the defocusing of multi- look SAR images by uncompensated phase errors presented in the received data is analyzed. It is shown that the phase errors on a multi-look processing interval can be efiectively described in terms of local quadratic and local linear phase errors. Approximate analytical expressions are derived to describe the azimuth resolution degradation. Criteria for acceptable phase errors are given. The obtained results are verifled by numerical simulations. The approach is illustrated by two typical motion errors: slow de∞ections of a SAR platform trajectory from a reference ∞ight line and periodic trajectory deviations.

Disk-resolved photometry of Asteroid (2867) Steins

We present a new method to perform disk-resolved photometry in order to investigate the intrinsic photometric properties of the surface of small Solar System bodies. We adopt the standard approach where a shape model is combined with a photometric formalism – in practise the Hapke formalism – to remove the effects of topography and recover the photometric (Hapke) parameters of either the global surface or, in its most elaborated form, the spatial variations of these parameters across the surface. Our method operates in the space of the facets representing the three-dimensional shape of the body, whereas all past analysis have always been performed in the space of the image pixels although they are not intrinsic to the surface of the body. This has the advantage of automatically tracking the same local surface element on a series of images. We first apply our method to images of the nucleus of Comet 9P/Tempel 1 obtained by the High-Resolution Imager (HRI) instrument on board the Deep Impact spacecraft and our derived Hapke parameters are in good agreement with those published by Li et al. (Li, J.-Y. et al. [2007]. Icarus 187, 41–55) within their respective uncertainties. We confirm the presence of an extended region of higher roughness in the southern hemisphere of the nucleus and the higher albedo of the ice-rich regions identified by Sunshine et al. (Sunshine, J.M. et al. [2006]. Science 311, 1453–1455) near the equator. The photometric properties of Asteroid (2867) Steins are then studied from multi-spectral images obtained with the OSIRIS Wide Angle Camera (WAC) on board the Rosetta spacecraft during its flyby on 5 September 2008. Our analysis indicates that the surface is highly porous (∼84%) and that it exhibits both a shadow-hiding opposition effect (SHOE) and probably, a coherent-backscatter opposition effect (CBOE). The single scattering albedo is the highest (SSA=0.57) ever observed among small bodies visited by spacecrafts. Our modelled roughness parameter is indicative of a high microscale roughness. The surface of Steins may in fact exhibit a fractal surface with high roughness present on a large range of scales, from micrometers to centimeters. The geometric and Bond albedos are calculated with the Hapke parameters yielding Ap=0.39±0.02 and AB=0.24±0.01. This high albedo is consistent with an iron-poor surface composition similar to aubrite meteorites which are suspected to originate from the E-type asteroids. We find no photometric variations on the surface at the (limited) spatial resolution of the WAC images.