International Journal of Remote Sensing

Kramer, Herbert J.; Cracknell, Arthur P.

doi: 10.1080/01431160801914952pmid: N/A

This article gives a global overview of some aspects of small satellite developments since the launch of Sputnik‐1 50 years ago. These developments are offering new opportunities for remote sensing. *. Based on a paper presented at the International Workshop on Earth Observation Small Satellites for Remote Sensing Applications, Kuala Lumpur, Malaysia, 20–23 November 2007. The earliest satellites were small but, as time went on, the satellites that were flown were developed to serve several different projects and they became larger and more expensive and took a long time to design, build and be launched. One of the extreme examples was Envisat. For these large satellites compromises often had to be made between different objectives and different instruments. A failure of the whole system meant the death of many different projects. The future is likely to see more small satellites, each of which is dedicated to a particular mission objective and carries a single instrument. Through this approach more and more countries around the world are becoming involved in Earth observation from space, not just in using the data from the major established systems but also in constructing their own systems. There were some small, low‐cost satellites in the early days, but they were overlooked or considered toys by the space community. The first microsatellites were built by enthusiasts of the amateur radio community and launched in the early 1960s. The invention/introduction of the microprocessor in the 1970s represented a quantum jump for the onboard capabilities of a spacecraft. This technology introduction represented a prime catalyst in the development of microsatellites since it enabled small physical structures in support of sophisticated data handling applications. The engineering of microsatellites, which emerged in the early 1980s, took a radical change of approach from the custom design of traditional spacecraft, namely a design‐to‐capability scheme to achieve cost reductions by focusing on available, and existing technologies using a general purpose bus and ‘off‐the‐shelf’ components and instruments. The new approach of small satellite design was pioneered by Surrey Satellite Technology Ltd (SSTL) of Surrey University, UK. SSTL's lead has now been followed by various companies and space agencies throughout the world. A key feature of this work is the development of microsatellite technology transfer programmes, providing partnerships and on‐the‐job training of engineers and scientists of foreign national organizations in cooperative programmes – in particular to those who were not in a position to start or afford their own space projects – to participate in the development of their own microsatellites. In addition to discussing these developments, this article also covers small satellite classification, small satellite initiatives in the USA, small satellite development in the rest of the world, some aspects of the technology and applications of small satellites, and small satellites developed by universities, particularly the CubeSats programme. Today, small satellites are changing the economics of space. These spacecraft embrace cutting edge Commercial Off‐The‐Shelf (COTS) technology, permitting novel and less‐expensive ways to perform meaningful observation missions, although there are various technical challenges. There are several synthetic aperture radar (SAR) and hyperspectral imaging missions on small satellites in operation and in planning.

Xue, Yong; Li, Yingjie; Guang, Jie; Zhang, Xiaoye; Guo, Jianping

doi: 10.1080/01431160801914945pmid: N/A

The small satellite renaissance began in the 1980s and is changing the economics of space. Technological trends have supported the advancement of small satellites in the 1–500 kg range. The number of countries actively participating has grown substantially during the past years. Satellite constellations (groups of satellites working in concert) are emerging as a powerful and effective application. In this paper, we focus on the small satellites than can perform remote sensing or Earth observation tasks. An overview is presented of the small satellite literature on Earth observation. The aim of the survey is threefold: an introduction for those new to the field, an overview for those working in the field and a reference for those searching for literature on a specific application for Earth observation. Small satellite programmes are classified according to the geographic regions. The small satellite industry and small satellite systems are addressed. In terms of applications, small satellite constellations are discussed in more detail. Finally, future developments are put forward. Telegeoprocessing combined with grid computing will provide the infrastructure and technologies for the development of Processing on Demand for Small Satellite Constellation systems.

Grasso, Lewis D.; Sengupta, Manajit; Dostalek, John F.; Brummer, Renate; Demaria, Mark

doi: 10.1080/01431160801891820pmid: N/A

During the next decade, data from a new generation of US geostationary and polar orbiting satellites will become available. To prepare for these data, representative imagery of these satellites is desirable. Two independent methods have been developed to create imagery from future satellites before they are placed into orbit. One method uses data from current operational and experimental satellites. Data obtained this way are referred to as simulated imagery. Another method generates satellite imagery by using numerical models. Data obtained by this method are referred to as synthetic imagery. Each method has some weaknesses that can be overcome by using both methods together. Synthetic imagery for two future US sensors is introduced in this paper. Emphasis is placed on a severe thunderstorm event.

Peña, M. A.

doi: 10.1080/01431160801908137pmid: N/A

This work addresses the remotely sensed urban heat sink formation in Santiago City, Chile. The main aim was to analyse the relationship that surface temperature exhibits with land cover types, as well as with vegetation cover fraction, surface moisture and albedo of Santiago City and its rural surroundings. Information was extracted from the processing of Landsat Enhanced Thematic Mapper Plus (ETM+) data. Surface temperature of the main land cover classes and correlation coefficients between surface temperature and the above‐mentioned surface parameters were analysed. The results show that the hottest surfaces are mainly concentrated in the northern rural valley, wherein the predominance of bare or sparsely vegetated land covers determine a low vegetation cover fraction and surface moisture content. The correlation coefficients obtained confirm the higher warming rate that the rural valley exhibits in comparision with the city temperatures at the image acquisition time, which is one of the main causes of urban heat sink formation.

Wentz, Elizabeth A.; Nelson, David; Rahman, Atiqur; Stefanov, William L.; Roy, Shoursaseni Sen

doi: 10.1080/01431160801905497pmid: N/A

This study presents the results of classifying land use/land cover for Delhi, India using an expert system approach. For this study Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data of 22 September 2003 were used. The research goals of this project are two‐fold. In one respect, the research goal is to report on the extent covered by urbanization using the classified image. Thirteen different land‐cover categories were identified with an 85.55% overall classification accuracy based on 256 random points for validation and 50 on the ground observations. Secondly, we report on our efforts to duplicate an expert system model previously developed for Phoenix Arizona as a generalized approach for urban land use classification. Results suggest that while some of the methodology could be duplicated, there are local factors (e.g. data availability and specific land features) that required the approach to be modified.

Wang, Yong; Allen, Thomas R.

doi: 10.1080/01431160801932525pmid: N/A

An edge extraction model has been developed that uses multitemporal satellite synthetic aperture radar data to delineate shorelines in estuaries. Using Japanese ALOS PALSAR HH data acquired in December 2006 and JERS‐1 L‐HH SAR data in December 1994, we mapped shorelines of the outer Pamlico Peninsula, Dare County, North Carolina, USA, spanning 12 years. To assess the validity and accuracy of the delineation, we compared (a) 1994 shorelines versus those derived from the 1993 digital orthophotographs, and (b) 2006 shorelines versus field data collected in February 2007. With promising results, we then analysed and quantified the shoreline changes between 1994 and 2006 on the north, east, and south sides of the Peninsula. Virtually no discernible changes on the north and south sides were found. However, significant landward migration in the middle to southern portion on the east shore was observed. Spatial retreat of shorelines varied greatly, with the maximum rate averaged over a span of 12 years exceeding 11 m year−1. The results support further monitoring of shorelines in estuaries using active remote sensing and the potential for the methodology developed to identify erosional hotspots.

Masiri, Itsara; Nunez, Manuel; Weller, Evan

doi: 10.1080/01431160801930255pmid: N/A

A 10‐year solar radiation climatology is developed for the Great Barrier Reef region using data from the Geostationary Meteorological Satellite (GMS). The method uses a look‐up table based on the STREAMER radiative transfer model for a tropical atmosphere. One outstanding feature appears in the summer and autumn climatologies which exhibit distinct maxima in the southern end of the study area, between latitudes 18° S and 26° S. There is a small but statistically significant increase in solar radiation over the 10‐year study period, with maximum values of just under 1% per decade. The radiation climatology was used to examine previous coral bleaching episodes, and in particular the largest mass bleaching episode that occurred in 2002. Results show that the area of maximum bleaching corresponded closely to the area of maximum solar insolation. Sea surface temperature and solar radiation were used in a variance analysis to discriminate bleached from unbleached reefs. Solar radiation is a better discriminator for inshore areas, but temperature is better at discriminating offshore reefs. Possible reasons for this difference are discussed.

Deronde, B.; Kempeneers, P.; Houhuys, R.; Henriet, J.‐P.; Van Lancker, V.

doi: 10.1080/01431160801891804pmid: N/A

Airborne imaging spectroscopy data (AISA Eagle and HyMap) were applied to classify the sediments of a sandy beach in seven sand type classes. On the AISA‐Eagle data, several classification strategies were tried out and compared with each other. The best classification results were obtained applying a linear discriminant classifier (LDC) in combination with feature selection based on sequential floating forward search (SFFS). The statistical LDC was used in a multiple binary approach. In the first step, the original bands were used in the classification, but transformation of the bands to wavelet coefficients enhanced the accuracy obtained. The combination of LDC with SFFS resulted in an overall accuracy of 82% (using three wavelet coefficients). Replacing the LDC with the non‐statistical SAM algorithm reduced the overall accuracy to 74% (using all bands or wavelet coefficients). When applying LDC, the optimal number of bands/wavelet coefficients to be used was defined: using more than two bands or three wavelet coefficients did not result in a higher classification accuracy. Finally, the HyMap data, featuring 126 bands in the VNIR‐SWIR range, were used to demonstrate that the VNIR range outperforms the SWIR range for this application.

Feng, H.; Vandemark, D.; Campbell, J. W.; Holben, B. N.

doi: 10.1080/01431160801918599pmid: N/A

Moderate Resolution Imaging Spectroradiometer (MODIS) marine and atmospheric products were evaluated using match‐ups of MODIS and in situ measurements collected by an above‐water radiometric system, the SeaWiFS Photometer Revision for Incident Surface Measurements (SeaPRISM), deployed near the Martha's Vineyard Coastal Observatory from 2004 to 2005. The products evaluated include the normalized water‐leaving radiance L wn in the visible and near‐infrared bands, and the aerosol optical thickness at 870 nm τa(870), and the Ångström exponent α(531). With a restricted match‐up criterion, the result shows that the MODIS‐retrieved L wn at 488, 531 and 551 nm agree very well with SeaPRISM measurements, giving mean per cent differences δ(%) of 3–7%, absolute mean per cent differences |δ|(%) of ∼16%, and coefficient of determination R 2 of 0.84–0.88. However, the MODIS‐retrieved L wn at 412 nm are underestimated significantly with δ(%), |δ|(%) and R 2 of −35%, 57% and 0.32, respectively, corresponding to a consistent overestimation and underestimation for the MODIS‐retrieved τa(870) and α(531), respectively. Temporal patterns of match‐ups revealing two distinct cases of the discrepancy of MODIS retrievals from in situ SeaPRISM measurements are discussed.

Tiwari, Supriya; Rai, Richa; Agrawal, Madhoolika

doi: 10.1080/01431160801961391pmid: N/A

This study examines the annual, seasonal and diurnal variations in the ambient concentrations of ozone at a suburban site of Varanasi, India, during 2002–2006. Prominent seasonal variations in ozone concentrations were recorded. Ozone concentrations were higher during the warmer months. Daytime 12‐hourly mean monthly ozone concentrations varied from 45.18 to 62.35 ppb during summer, from 28.55 to 44.25 ppb during winter and from 24 to 43.85 ppb during the rainy season from 2002 to 2006. Distinct diurnal variations in ozone concentrations were also observed. Daytime maxima in ozone concentration were recorded between 1200 and 1400 h, whereas morning and evening hours showed lower concentrations of ozone. Ozone concentrations in the atmosphere depended on several meteorological factors. Monthly average ozone concentration was significantly correlated with maximum temperature (p<0.001) and mean monthly temperature (p<0.05), maximum relative humidity (p<0.001), minimum relative humidity (p<0.001) and mean monthly relative humidity (p<0.001), and sunshine hours (p<0.001). Ozone concentrations in the ambient air have shown an increase in the past decade that was more in the winter and rainy seasons than in the summer. This study suggests that ozone concentrations around Varanasi were sufficiently high to cause significant damage to agricultural production. The present work can be extended to a regional level by incorporating modelling studies using recent remote sensing tools.