Commercial Satellite Research Articles

Chinese Capabilities as a Global Space Power

Since the early 1960s, China has been enhancing national power and, in this regard, Chinese space capabilities play a pivotal role. Today, China is second among spacefaring counties, behind the United States, as a measure of human spaceflight, as well as in commercial and military satellite systems. Chinese space technology, in contrast to developed nations, is comparatively cost-effective; China is sharing it with developing nations for their space programs, consequently expanding the pool of spacefaring states. Most significantly, China’s nuclear, military, and space capabilities provide it with an opportunity to reassert itself as a global power, enhancing its strategic outreach and preventing adversaries from contemplating strategies against it.

China's Uranium Enrichment Complex

New public information allows a fresh estimate of China's current and under-construction uranium enrichment capacity. This paper uses open source information and commercial satellite imagery to identify and offer estimates of the capacity of China's 10 operating enrichment facilities, located at 4 sites, using centrifuge technology most likely based on adapting Russian technology. The total currently operating civilian centrifuge enrichment capacity is estimated to be about 4.5 million separative work units/year (SWU/year), with additional capacity estimated to be about 2 million SWU/year under construction. Also China could have an enrichment capacity of around 0.6 million SWU/year for non-weapon military uses (i.e., naval fuel) or dual use. These estimates are much larger than previous public estimates of China's total enrichment capacity. Further expansion of enrichment capacity may be likely since China will require about 9 million SWU/year by 2020 to meet the enriched uranium fuel needs for its planned nuclear power reactor capacity of 58 gigawatts-electric (GWe) by 2020 under its policy of self-sufficiency in the supply of enrichment services.

Design and Numerical Assessment of a Passive Electron Emitter for Spacecraft Charging Alleviation

In this paper, we examine the theoretical basis for using passive unheated electron field emitters to control hazardous levels of spacecraft charging. We present the experimental evidence related to the capabilities of passive and low-power active field emitters. The concept of passive field emitters is detailed looking at their characteristics and location on a model satellite typical of a commercial geostationary satellite. The assessment is performed by means of numerical simulations. The generation and extraction of electrons is simulated at micrometric scale. Their flow is modeled at spacecraft scale to assess spacecraft absolute and differential charging alleviation. The system shows good promise limiting the inverted voltage gradient situations, observed especially on solar panels where cover glasses are more positive than solar cells. This situation is known as very risky in flight, possibly leading to sustained secondary arcing powered by the photovoltaic solar arrays themselves. Finally, we review how existing design practice would be modified by the presence of such passive emitters.

Integrated Tradespace Analysis of Space Network Architectures

Methods to design space communication networks at the link level are well understood and abound in the literature. Nevertheless, models that analyze the performance and cost of the entire network are scarce, and they typically rely on computationally expensive simulations that can only be applied to specific network designs. This paper presents an architectural model to quantitatively optimize space communication networks given future customer demands, communication technology, and contract modalities to deploy the network. The model is implemented and validated against NASA’s Tracking and Data Relay Satellite System. It is then used to evaluate new architectures for the fourth-generation Tracking and Data Relay Satellite System given the capabilities of new optical and Ka-band technologies, as well as the possibility to deploy network assets as hosted payloads. Results indicate that optical technology can provide a significant improvement in the network capabilities and lifecycle cost, especially when placing these terminals on board commercial satellites as hosted payloads. The cost savings and benefit improvements of such an architecture are discussed and quantified.

Validation of DigitalGlobe WorldView-3 Earth imaging satellite shortwave infrared bands for mineral mapping

WorldView-3 (WV-3) is a newly launched (August 2014) high-spatial resolution commercial multispectral satellite sensor with eight visible to near-infrared bands (0.42 to 1.04 μ m ) and eight shortwave infrared (SWIR) bands (1.2 to 2.33 μ m ). Previous analyses using hyperspectral imagery (HSI) data of Cuprite, Nevada, to simulate WV-3’s eight SWIR bands demonstrated identification and mapping of a wide variety of minerals, including kaolinite, alunite, buddingtonite, muscovite, calcite, and hydrothermal silica. These results, using partial unmixing, showed mineral occurrences similar to those mapped using full resolution HSI data and established WV-3’s potential as a valuable new mineral mapping tool. Confusion matrix analyses using the HSI data as ground truth did indicate, however, some difficulties with mapping spectrally similar minerals using the multispectral data. Follow-up mineral mapping, using on-orbit WV-3 data acquired September 19, 2014, for Cuprite, Nevada, and the same algorithms and methods used for WV-3 simulation, indicates that the WV-3 sensor is performing as expected. WV-3 SWIR data analyses closely match expectations for mineral mapping as predicted by the simulation. While not as capable as an HSI sensor, WV-3’s carefully selected eight SWIR bands provide new remote mineral mapping capabilities not available from any other spaceborne multispectral system.

Implementing polarization shift keying over satellite - system design and measurement results

Summary Polarization shift keying (PolSK) is a digital modulation technique using the state of polarization of an electromagnetic wave as the signalling quantity. PolSK comes from fibre communications, where the channel offers two orthogonal states of polarization. This article develops on the idea to adapt this technology to satellite communications, where similar channel conditions exist. For this purpose, a digital PolSK modem was implemented on a programmable logic board. A proposal for constellation design as well as thoughts on synchronization of PolSK over satellite is presented. The modem was used to demonstrate a 16-state Polarization Shift Keying link over a commercial satellite in Ku band. Measurements have been conducted in a back-to-back setup on intermediate frequency and on a Ku band transponder simulator to assess the impact of path-length differences, carrier recovery and non-linearity. Copyright © 2015 John Wiley & Sons, Ltd.

Special issue: Shining a light on future broadband satellite systems: optical and quantum space communications systems and technologies

Optical space communications have moved from the Research & Development (R&D) stage and are now ready to be applied in commercial satellite communication systems, bringing with them significant advantages such as much higher data rates, low probability of intercept, no restriction for frequency use, lower payload volume and mass, and less power consumption requirements. The European Space Agency has demonstrated laser communications from an airborne platform to ground stations, further establishing that high-throughput laser communications are feasible and ready for commercial service, and the European Data Relay System is relying on optical inter satellite links for its commercial data relay service. The US fundedTransformational Satellite Communications System program, developed and partially validated highly successful inter-satellite laser optical links, proving the efficacy and efficiency of laser communications. In Japan, there is a lot of activity on optical communications by satellite, and China has declared an intention to develop a quantum satellite. Researchers in Austria and Spain are working on applications of quantum communications, and the UK has recently announced an investment to convert quantum-physics research into commercial products. A new generation of proposed satellite constellations has intent to develop a service addressing the high bandwidth data and next-generation service needs of carriers, enterprises, and government agencies around the world, based entirely on optical wave technology. We would like to invite papers addressing these and other related topics:

Change in the glacier extent in Turkey during the Landsat Era

We report the latest study for small glaciers, using Turkey as an example, and update previous studies of glaciers in Turkey from the 1970s to 2012–2013. We used seventy-two Landsat scenes from the Multispectral Scanner (MSS), Return Beam Vidicon-3 (RBV-3), Thematic Mapper (TM), Enhanced Thematic Mapper plus (ETM+), and Operational Land Imager (OLI); five Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images; and forty-one commercial satellite images. IKONOS, Quickbird-2, GeoEye-1, and WorldView-1 and -2 commercial satellite images were used to evaluate mapping accuracies, to understand debris-covered glacial margins, to map glacier margins in shadows, and to better determine the area of the smaller glaciers in Turkey. We also used nine Landsat-5 simultaneously acquired TM and MSS images to more accurately process MSS imagery from the 1970s. The area of the glaciers in Turkey decreased from 25km2 in the 1970s to 10.85km2 in 2012–2013. By 2012–2013, five glaciers had disappeared, six were less than 0.5km2, one was 0.8km2, and only two were 3.0km2 or larger. No trends in 1980 to 2012 annual precipitation, 1980 to 2012 winter precipitation, and 1980 to 2008 cloud cover extent were found, while surface temperatures increased, with summer minimum temperatures showing the greatest increases. We attribute glacier recession in Turkey from the 1970s to 2012–2013 to increasing summer minimum temperatures with no changes in precipitation or cloud cover over this time period.

Technology Trends and Challenges of Antennas for Satellite Communication Systems

Communication is one of the most essential activities of mankind and there is no doubt that satellite communications have made a tremendous stride in this matter. The goal has been to create uninterrupted, seamless, high throughput connectivity no matter where. The fact that this is all possible is because of the existence of electromagnetic waves: Antennas play a pivotal role in advanced functionality, efficient usage of the bandwidth, and cost effective deployment of this technology. The trends of the technological development of antennas for a wide range of commercial satellite communication services and the challenges faced in their development are chronologically reviewed. Various antenna concepts are summarized and future challenges are projected. A rather comprehensive list of references is included to assist the reader with further reading beyond this paper.

An ultra-wide bandwidth-based range/GPS tight integration approach for relative positioning in vehicular ad hoc networks

Relative position awareness is a vital premise for the implementation of emerging intelligent transportation systems, such as collision warning. However, commercial global navigation satellite systems (GNSS) receivers do not satisfy the requirements of these applications. Fortunately, cooperative positioning (CP) techniques, through sharing the GNSS measurements between vehicles, can improve the performance of relative positioning in a vehicular ad hoc network (VANET). In this paper, while assuming there are no obstacles between vehicles, a new enhanced tightly coupled CP technique is presented by adding ultra-wide bandwidth (UWB)-based inter-vehicular range measurements. In the proposed CP method, each vehicle fuses the GPS measurements and the inter-vehicular range measurements. Based on analytical and experimental results, in the full GPS coverage environment, the new tight integration CP method outperforms the INS-aided tight CP method, tight CP method, and DGPS by 11%, 15%, and 24%, respectively; in the GPS outage scenario, the performance improvement achieves 60%, 65%, and 73%, respectively.

A global reference database from very high resolution commercial satellite data and methodology for application to Landsat derived 30 m continuous field tree cover data

The methodology for selection, creation, and application of a global remote sensing validation dataset using high resolution commercial satellite data is presented. High resolution data are obtained for a stratified random sample of 500 primary sampling units (5km × 5km sample blocks), where the stratification based on Köppen climate classes is used to distribute the sample globally among biomes. The high resolution data are classified to categorical land cover maps using an analyst mediated classification workflow. Our initial application of these data is to evaluate a global 30m Landsat-derived, continuous field tree cover product. For this application, the categorical reference classification produced at 2m resolution is converted to percent tree cover per 30mpixel (secondary sampling unit)for comparison to Landsat-derived estimates of tree cover. We provide example results (based on a subsample of 25 sample blocks in South America) illustrating basic analyses of agreement that can be produced from these reference data. Commercial high resolution data availability and data quality are shown to provide a viable means of validating continuous field tree cover. When completed, the reference classifications for the full sample of 500 blocks will be released for public use.

Earth Orbiting Support Systems for commercial low Earth orbit data relay: Assessing architectures through tradespace exploration

As small satellites and Sun Synchronous Earth Observation systems are assuming an increased role in nowadays space activities, including commercial investments, it is of interest to assess how infrastructures could be developed to support the development of such systems and other spacecraft that could benefit from having a data relay service in Low Earth Orbit (LEO), as opposed to traditional Geostationary relays. This paper presents a tradespace exploration study of the architecture of such LEO commercial satellite data relay systems, here defined as Earth Orbiting Support Systems (EOSS). The paper proposes a methodology to formulate architectural decisions for EOSS constellations, and enumerate the corresponding tradespace of feasible architectures. Evaluation metrics are proposed to measure benefits and costs of architectures; lastly, a multicriteria Pareto criterion is used to downselect optimal architectures for subsequent analysis. The methodology is applied to two case studies for a set of 30 and 100 customer-spacecraft respectively, representing potential markets for LEO services in Exploration, Earth Observation, Science, and CubeSats. Pareto analysis shows how increased performance of the constellation is always achieved by an increased node size, as measured by the gain of the communications antenna mounted on EOSS spacecraft. On the other hand, nonlinear trends in optimal orbital altitude, number of satellites per plane, and number of orbital planes, are found in both cases. An upward trend in individual node memory capacity is found, although never exceeding 256Gbits of onboard memory for both cases that have been considered, assuming the availability of a polar ground station for EOSS data downlink. System architects can use the proposed methodology to identify optimal EOSS constellations for a given service pricing strategy and customer target, thus identifying alternatives for selection by decision makers.

A water coverage extraction approach to track inundation in the Saskatchewan River Delta, Canada

Tracking surface water coverage changes is a complicated task for many regions of the world. It is, however, essential to monitor the associated biological changes and bioproductivity. We present a methodology to track contemporary water coverage changes using optical remote sensing and use it to estimate historical summer water coverage in a large river delta. We used a geographical information system automated routine, based on the modified normalized difference water index, to extract the surface water coverage area (SWCA) from optical satellite data sets using the surface water extraction coverage area tool (SWECAT). It was applied to measure SWCA during drought and flood peaks in the Saskatchewan River Delta in Canada, from Landsat, SPOT and RapidEye images. Landsat results compared favourably with Canadian National Hydro Network (CNHN) GeoBase data, with deviations between SWCA classifications and the base CNHN GeoBase shapefile of ~2%. Difference levels between the extracted SWCA layer from Landsat and the higher resolution commercial satellites (SPOT and RapidEye) were also less than 2%. SWCA was tightly linked to discharge and level measurements from in-channel gauges (r2 > 0.70). Using the SWCA versus discharge relationship for the gauge with the longest record, we show that peak summer SWCA has declined by half over the last century, from 13% of our study area to 6%, with likely implications for fish and wildlife production.

Assessing absolute and relative accuracy of recreation‐grade and mobile phoneGNSSdevices: a method for informing device choice

The affordability/availability and portability of recreation‐grade receivers and mobile devices, compared with commercial survey Global Navigation Satellite Systems (GNSS), commonly referred to as Global Positioning System, make them worthy of consideration for student fieldwork and research. While empirical evidence of the relative accuracy of low‐costGNSSreceivers in open areas is currently limited, initial findings suggest that levels of relative accuracy, as opposed to absolute accuracy, make these devices an inexpensive and manageable technology for measuring the relative location of land features. Given the current speed at whichGNSStechnology advances, it is important to have an appreciation of any proposed device's accuracy. This paper presents a method for evaluating the levels of absolute and relative accuracy of various devices, which can inform the choice of device for particular survey‐based projects. It can also be used to indicate a ‘best practice’ approach to usingGNSSdevices in a research and study context, through an assessment of the factors influencing levels of relative accuracy, such as the length of time a device is left to settle before recording a point. In addition, this method can be a useful exercise in and of itself for helping students better understand absolute and relative accuracy, the capabilities of their own mobile hardware, and the potential use of recreation‐grade and mobile devices in a range of scenarios both within and beyond the academy.

Analysis of Atmosphere-Breathing Electric Propulsion

To extend the lifetime of commercial and scientific satellites in low Earth orbit (LEO) and below (100–250 km of altitude) recent years showed an increased activity in the field of air-breathing electric propulsion as well as beamed-energy propulsion systems. However, preliminary studies showed that the propellant flow necessary for electrostatic propulsion at these altitudes exceeds the mass intake possible within reasonable limits, and that electrode erosion due to oxygen flow might limit the lifetime of eventual thruster systems. The pulsed plasma thruster (PPT), however, can be successfully operated with smaller mass intake and at relatively low power. This makes it an interesting candidate for air-breathing application in LEO and its feasibility is investigated within this paper. An analysis of such an air-breathing PPT system shows that for altitudes between 150 and 250 km, drag compensation is at least partially feasible assuming a thrust-to-power ratio of 30 mN/kW and a specific impulse of 5000 s. Further, to avoid electrode erosion, inductively heated electrothermal plasma generator technology is discussed to derive a possible propulsion system that can handle gaseous propellant without unfavorable side effects. Current technology can be used to create an estimated 4.4 mN of thrust per 1 mg/s of mass flow rate, which is sufficient to compensate the drag for small satellites in altitudes between 150 and 250 km.

The U.S. Export Control of Commercial Satellites to China: Technology Trade Politics of Security and Economy

The U.S. Export Control of Commercial Satellites to China: Technology Trade Politics of Security and Economy

GLISA: geosynchronous laser interferometer space antenna concepts with off-the-shelf satellites.

We discuss two geosynchronous gravitational wave (GW) mission concepts, which we generically name gLISA. One relies on the science instrument hosting program onboard geostationary commercial satellites, while the other takes advantage of recent developments in the aerospace industry that result in dramatic satellite and launching vehicle cost reductions for a dedicated geosynchronous mission. To achieve the required level of disturbance free-fall onboard these large and heavy platforms, we propose a new drag-free system, which we have named "two-stage" drag-free. It incorporates the Modular Gravitational Reference Sensor (developed at Stanford University) and does not rely on the use of μN thrusters. Although both mission concepts are characterized by different technical and programmatic challenges, individually they could be flown and operated at a cost significantly lower than those of previously envisioned gravitational wave missions, and in the year 2015 we will perform at JPL a detailed selecting mission analysis.

Quality assessment of ten fusion techniques applied on Worldview-2

Fusion or merging or pansharpening is the digital processing that combines the high spatial and multispectral information to obtain a fused multispectral image that retains the spatial information from the high resolution panchromatic image, as well as the spectral characteristics of the lower resolution multispectral image. Many fusion algorithms were developed and tested on different commercial satellite data such as Ikonos and Quickbird, however, the efficacy of these algorithms is weakly assessed on the new satellite images of Worldview-2 with very high spatial resolution. In the present study ten well known fusion techniques namely Color Normalized (CN), Ehlers, Gram-Schmidt, High Pass Filter (HPF), Local Mean Matching (LMM), Local Mean and Variance Matching (LMVM), Modified IHS (Modihs), Pansharp, PCA and Wavelet are used for the fusion of Worldview-2 panchromatic and multispectral data. Fused images were evaluated for spectral and spatial fidelity using visual inspection and different quality indexes such as the correlation coefficient (CC), ERGAS, the Universal Image Quality Index (Q), the Expanded Quality Index (Q4expand) and the Entropy values. Under each quality metric the fusion algorithms were ranked and best performances were indentified. It has been proved that all fusion algorithms have a different performance with the new multispectral bands of Worldview-2 in comparison to the classical ones. It has also been proved that almost all quality indices present a very strong dependency to the spatial resolution of the input data. The Q4expand quality index is proposed as the main quality discriminator since it gave the most robust results independently of the spectral and spatial input resolution. Pansharp algorithm took the lead in spatial enhancement while Ehlers and HPF are ranked in the first places for spectral preservation.

열해석 모델 간략화 및 동적특성에 관한 연구

A detailed satellite panel thermal model composed of more than thousands nodes can not be directly integrated into a spacecraft thermal model due to its node size and the limitation of commercial satellite thermal analysis programs. For the integration of the panel into the satellite thermal model, a reduced thermal model having proper accuracy is required. A thermal model reduction method was developed and validated by using a geostationary satellite panel. The temperature differences of main components between the detailed and the reduced thermal model were less than <TEX>$1^{\circ}C$</TEX> in steady state analysis. Also, the dynamic responses of the detailed and the reduced thermal model show very similar trends. Thus, the developed reduction method can be applicable to actual satellite thermal design and analysis with resonable accuracy and convenience.

Parameter-Based Performance Analysis of Object-Based Image Analysis Using Aerial and Quikbird-2 Images

Abstract. Opening new possibilities for research, very high resolution (VHR) imagery acquired by recent commercial satellites and aerial systems requires advanced approaches and techniques that can handle large volume of data with high local variance. Delineation of land use/cover information from VHR images is a hot research topic in remote sensing. In recent years, object-based image analysis (OBIA) has become a popular solution for image analysis tasks as it considers shape, texture and content information associated with the image objects. The most important stage of OBIA is the image segmentation process applied prior to classification. Determination of optimal segmentation parameters is of crucial importance for the performance of the selected classifier. In this study, effectiveness and applicability of the segmentation method in relation to its parameters was analysed using two VHR images, an aerial photo and a Quickbird-2 image. Multi-resolution segmentation technique was employed with its optimal parameters of scale, shape and compactness that were defined after an extensive trail process on the data sets. Nearest neighbour classifier was applied on the segmented images, and then the accuracy assessment was applied. Results show that segmentation parameters have a direct effect on the classification accuracy, and low values of scale-shape combinations produce the highest classification accuracies. Also, compactness parameter was found to be having minimal effect on the construction of image objects, hence it can be set to a constant value in image classification.