The First MAXI/GSC Catalog in the High Galactic-Latitude Sky

by on 9 June 2015in Earth Science and Remote Sensing No comment

We present the first unbiased source catalog of the Monitor of All-sky X-ray Image (MAXI) mission at high Galactic latitudes ( $vert bvert$ $>$ 10 $^{circ}$ ), produced from the first 7-month data (2009 September 1 to 2010 March 31) of the Gas Slit Camera in the 4–10 keV band. We have developed an analysis procedure to detect faint sources from the MAXI data, utilizing a maximum likelihood image fitting method, where the image response, background, and detailed observational conditions are taken into account. The catalog consists of 143 X-ray sources above the 7 $sigma$ significance level with a limiting sensitivity of $sim $ 1.5 $times$ 10 $^{-11} $ erg cm $^{-2} $ s $^{-1}$ (1.2 mCrab) in the 4–10 keV band. Among them, we have identified 38 Galactic/LMC/SMC objects, 48 galaxy clusters, 39 Seyfert galaxies, 12 blazars, and 1 galaxy. Four other sources are confused with multiple objects, and one remains unidentified. The log $ N$ –log $ S$ relation of extragalactic objects is in good agreement with the HEAO-1 A-2 result, although the list of the brightest AGNs in the entire sky has significantly changed since that produced 30 yr ago.

Related URLs:
http://pasj.oxfordjournals.org/content/63/sp3/S677.abstract
http://pasj.oxfordjournals.org/content/63/sp3/S677.full.pdf

International Space Station Agricultural Camera (ISSAC) Sensor Onboard the International Space Station (ISS) and Its Potential Use on the Earth Observation

by on 9 June 2015in Earth Science and Remote Sensing No comment

Recently launched and installed inside the Window Observational Research Facility (WORF) in the International Space Station (ISS), the International Space Station Agricultural Camera (ISSAC) sensor is an area-scan multi-spectral optical imaging system built by students and faculty at the University of North Dakota (UND). Radiometric calibration was conducted before launch and performance validation was evaluated with radiance extracted from Landsat5 TM image that was overpassed nearly at the same time as ISSAC overpass. Ground truth measurement with Analytical Spectral Devices (ASD, ASD Inc., Boulder CO) was also carried out over fairly homogenous regions of interest such as bare soil, gravel parking lot, crop and short grass pastures. Using the 6S radiative transfer model, radiances measured at the top-of-the atmosphere were converted into surface reflectance. Atmospheric corrected surface reflectance from ISSAC images was compared with the spectrum of ground ASD measurement. The results for both radiance and surface reflectance show fairly good agreements. This indicates that ISSAC would be a prospective candidate that would be able to fill the temporal gaps of Landsat 16-day revisit cycle. Higher rate of temporal opportunities from ISSAC sensor will result in significant improvement on decision making for users especially in time sensitive disaster management, farming practices or environmental issues occurred in short time frame.

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Comparison of ozone profiles between Superconducting Submillimeter-Wave Limb-Emission Sounder and worldwide ozonesonde measurements

by on 9 June 2015in Earth Science and Remote Sensing No comment

We compared ozone profiles measured by the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) with those taken at worldwide ozonesonde stations. To assess the quality of the SMILES version 2.3 ozone data for 16–30 km, 601 ozonesonde profiles were compared with the coincident SMILES ozone profiles. The agreement between SMILES and ozonesonde measurements was generally good within 5%–7% for 18–30 km at middle and high latitudes but degraded below 18 km. At low latitudes, however, the SMILES ozone data showed larger values (~6%–15% for 20–26 km) than those at middle and high latitudes. To explain this bias, we explored some possible issues in the ozonesonde measurement system. One possibility is due to a pressure bias in radiosonde measurements with a pressure sensor, but it would be within a few percent. We also examined an issue of the ozonesonde's response time. The response time was estimated from ozonesonde measurements with ascending and descending profiles showing clear difference, by using the time lag correction method to minimize the difference between them. Our estimation shows 28 s on average which is a similar value derived by prelaunch preparation. By applying this correction to the original profiles, we found a negative bias of the ascending ozonesonde measurement more than 7% at 20 km in the equatorial latitude where the vertical gradient of ozone is steep. The corrected ozonesonde profiles showed better agreement with the SMILES data. We suggest that the response time of ozonesondes could create a negative bias, particularly in the lower stratosphere at equatorial latitudes.

Related URLs:
http://dx.doi.org/10.1002/2013JD021094
http://onlinelibrary.wiley.com/doi/10.1002/2013JD021094/abstract

Observations of molecular oxygen Atmospheric band emission in the thermosphere using the near infrared spectrometer on the ISS/RAIDS experiment

by on 9 June 2015in Earth Science and Remote Sensing No comment

Observations of airglow emission using the RAIDS (Remote Atmospheric and Ionospheric Detection System) instruments on the International Space Station Kibo module are reported and compared to a photochemical model of the emission process. Launched in Sept. 2009, RAIDS performed routine observations of the O2(b1Σ → X3Σ) Atmospheric band (O2 A-band) transition during solar minimum conditions from October 2009 to December 2010. Limb brightness of the (0,0), (0,1) and (1,1) vibration band emissions were measured in the altitude range 80 to 180 km with the Near Infrared Spectrometer (NIRS) instrument, one of eight limb viewing instruments in the RAIDS experiment. Comparison of observed brightness profiles with the model shows very good agreement for the (0,0) and (0,1) bands. The model underestimates the (1,1) brightness profiles throughout the region, especially near the peak. Reasonable variations of composition and selected rate constants do not account for the underestimation of (1,1) band brightness. A contributing factor could be in the assumption of detailed balance and the accepted energy transfer pathways that redistribute energy between the v = 0 and v = 1 states.

Related URLs:
http://dx.doi.org/10.1029/2011JA016838

Validation of ozone data from the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES)

by on 9 June 2015in Earth Science and Remote Sensing No comment

The Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) onboard the International Space Station provided global measurements of ozone profiles in the middle atmosphere from 12 October 2009 to 21 April 2010. We present validation studies of the SMILES version 2.1 ozone product based on coincidence statistics with satellite observations and outputs of chemistry and transport models (CTMs). Comparisons of the stratospheric ozone with correlative data show agreements that are generally within 10%. In the mesosphere, the agreement is also good and better than 30% even at a high altitude of 73 km, and the SMILES measurements with their local time coverage also capture the diurnal variability very well. The recommended altitude range for scientific use is from 16 to 73 km. We note that the SMILES ozone values for altitude above 26 km are smaller than some of the correlative satellite datasets; conversely the SMILES values in the lower stratosphere tend to be larger than correlative data, particularly in the tropics, with less than 8% difference below ~24 km. The larger values in the lower stratosphere are probably due to departure of retrieval results between two detection bands at altitudes below 28 km; it is ~3% at 24 km and is increasing rapidly down below.

Related URLs:
http://dx.doi.org/10.1002/jgrd.50434
http://onlinelibrary.wiley.com/doi/10.1002/jgrd.50434/abstract

A New View of Coastal Oceans From the Space Station

by on 9 June 2015in Earth Science and Remote Sensing No comment

Understanding and quantifying the natural processes that occur along coasts are critical components of managing environmental resources and planning and executing coastal operations, from humanitarian relief to military actions. However, the coastal ocean is complicated, with dissolved and suspended matter that hinders water transparency, phytoplankton blooms that can be toxic, and bathymetry and bottom types that vary over spatial scales of tens of meters, all of which affect processes in an area that spans millions of square kilometers. A hyperspectral imager collects the spectrum of the light received from each pixel in an image. For environmental characterization the wavelength range typically spans the visible and shortwave infrared wavelengths, and the spectrum is collected in contiguous spectral intervals 1–10 nanometers wide. This spectral information is exploited to provide significantly more information about vegetation, minerals, and other components in the scene than can be retrieved from panchromatic or even multispectral imagery, which rely primarily on the shape of the object for detection [Goetz et al., 1985]. Such technology can also work over shallow seas. Over the past 2 decades, experiments with hyperspectral imagers on airborne platforms have demonstrated the ability to characterize the coastal environment [Davis et al., 2002, Davis et al. 2006] and produce maps of coastal bathymetry, in-water constituents, and bottom type.

Related URLs:
http://dx.doi.org/10.1029/2011EO190001

The Hyperspectral Imager for the Coastal Ocean (HICO™) environmental littoral imaging from the International Space Station

by on 9 June 2015in Earth Science and Remote Sensing No comment

The Hyperspectral Imager for the Coastal Ocean (HICO), launched to the International Space Station in September 2009, is the first spaceborne hyperspectral imager optimized for environmental characterization of the coastal ocean. Building on the heritage of airborne hyperspectral imagers, HICO; combines high signal-to-noise ratio, contiguous 10 nm wide spectral channels over the range 400 to 900 nm, and a scene size of 42 × 190 km to capture the scale of coastal dynamics. HICO; image data is being exploited to produce maps of coastal ocean properties including bathymetry, in-water suspended and dissolved matter, and bottom characteristics, offering a new remote sensing capability for coastal environments worldwide. In this paper we discuss the development and performance characteristics of the HICO™ imager, and present example HICO™ data products.

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Hyperspectral Imaging of River Systems

by on 9 June 2015in Earth Science and Remote Sensing No comment

The Navy has a requirement to rapidly and covertly characterize the coastal environment in support of Joint Strike Initiatives. Over the past 15 years we have demonstrated that spaceborne hyperspectral remote sensing is the best approach to covertly acquire data on shallow water bathymetry, bottom types, hazards to navigation, water clarity and beach and shore trafficability to meet those requirements. The long term goal of this work is to put a hyperspectral imager capable of making the appropriate measurements in space to demonstrate this capability.

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Hyperspectral imaging of rivers and estuaries

by on 9 June 2015in Earth Science and Remote Sensing No comment

The Hyperspectral Imager for the Coastal Ocean (HICO) is the first spaceborne imaging spectrometer designed to sample the coastal ocean. HICO samples selected coastal regions at 92 m ground sample distance with full spectral coverage (88 channels covering 400 to 900 nm) and a high signal-to-noise ratio to resolve the complexity of the coastal ocean. HICO has been operating on the International Space Station since October 2009 and collected over 8000 scenes for more than 50 users. We have been using HICO data to study major rivers and estuaries in the US and Asia. Our results show the advantages of HICO’s additional spectral channels and higher spatial resolution for studying these complex coastal waters. We use these data to suggest requirements for spatial and spectral sampling for future ocean color sensors.

Related URLs:
http://dx.doi.org/10.1117/12.2023401