Satellite Launch Research Articles

The system for near-real time air pollution monitoring over cities based on the Sentinel-5P satellite data

Introduction. Air pollution heterogeneity and rapid urbanization impose numerous constraints on available near-surface air quality monitoring. The solution for effective warning comes with the integration of different data, including remote sensing. Satellite data cannot answer whether dangerous pollution levels are observed; however, it provides a complete picture and may detect air pollution transportation towards or away from cities. The possibilities for effective near-real time (NRTI) monitoring have significantly improved with the launch of the Sentinel-5P satellite. The study aimed to describe the developed system for NRTI air pollution monitoring over Kharkiv, Kryvyi Rig, Kyiv, and Odesa based on NO2 and CO data derived from the Sentinel-5P satellite. Data and methodology. The NRTI System was developed for tropospheric NO2 and total CO column number densities based on the Sentinel-5P NRTI products. After satellite scanning of Ukrainian territory, the NRTI System goes live in 2-3 hours. It is fully automatic, and modules were written using Python, VB.NET, and batch-scripting. Results. The NRTI System includes four main phases: preparatory, source data downloading, processing and post-processing with visualization, archiving, and result distribution among users. Source data filtering with a quality assurance index and downscaling with linear kriging interpolation were developed. The output of the NRTI System is data in regular grids with a spatial resolution of 0.02o×0.02o. Based on the NRTI System work during October – December 2021, we conducted preliminary analyses to understand the possibilities of data usage. Higher NO2 content was observed in Kyiv and Kharkiv, where traffic emissions play a crucial role in air quality worsening. The use of daily time series allowed the detection of an increase in NO2 variance during the heating season, as well as plume distribution from cities to rural areas due to the prevailing wind. CO content is more homogeneous; however, higher values were observed in industrial Kryvyi Rig and Odesa. It is emphasized the huge impact of shipping CO emissions on air quality in Odesa. The temporal averaging of the NRTI System output allowed us to define the most polluted districts within the cities of interest. We intend to continue developing the presented NRTI System and develop the same algorithms for all cities with populations greater than 500 000 people in order to provide operational air pollution monitoring based on satellite data.

Simulation of a Future SLR Satellite to Improve Low‐Degree Gravity Estimates

AbstractThe Gravity Recovery and Climate Experiment (GRACE; 2002–2017) and GRACE Follow‐On (2018‐present) have observed Earth's monthly mass change with unprecedented spatial resolution. These missions have long relied on satellite laser ranging (SLR) measurements to replace the C2,0 coefficient, which GRACE recovers poorly. Recent work has also shown the need for SLR‐determined C3,0 when GRACE operates with a single accelerometer. However, it was not until the 2012 launch of the Laser Relativity Satellite that the SLR data gained the sensitivity to recover C3,0 accurately. These low‐degree gravity coefficients represent large‐scale mass transport and small changes in their values have implications for ice sheet, ocean mass, and water storage estimates. To fully exploit SLR's utility for time‐variable gravity (TVG), future satellite orbits should be selected to maximize their sensitivity to the gravity field. In this work, we present results from a simulation study of a hypothetical SLR satellite in which we generate 1 year of data to satellites placed across varying inclinations. We also simulate seven current SLR satellites to show realistic improvements from the new satellite. When compared to the known truth input, a low‐inclination satellite (<∼ 45°) most improves the low‐degree gravity terms, especially the even zonals which show a significant decorrelation. From this, we investigate recovery of the annual variability in the simulated signal and find recovery of the sine component improves by up to 41%. This has important implications when considering future SLR satellites in the context of TVG.

Hierarchical Domain-Based Multicontroller Deployment Strategy in SDN-Enabled Space–Air–Ground Integrated Network

The space–air–ground integrated network (SAGIN) is considered to be a significant framework for realizing the vision of “6G intelligent connection of all things.” A typical SAGIN consists of three parts: a space-based network composed of various orbiting satellites, an air-based network composed of aircraft, and a traditional ground-based network. Considering the cost of satellite launch, the network needs to be flexible and controllable. In order to ensure that the ground can handle satellite anomalies in real time by program, it is necessary to introduce in-orbit programmable networks, such as the software-defined network (SDN). In the network management architecture, if the controller plane in the SDN adopts the flat management scheme, the expansion of the control plane is limited due to the low efficiency of data synchronization among controllers. Compared with controller deployments on terrestrial networks, multicontroller deployments in the SAGIN face the following problems: the dynamic change of the satellite network topology, the large-scale network nodes, the increase or decrease in the number of aerial vehicles, and the unbalanced distribution of ground users. Therefore, it is of great significance to study how to optimize the deployment of multiple controllers in the SDN-enabled SAGIN. This article introduces an SDN into the SAGIN and designs a hierarchical domain-based SDN-enabled SAGIN architecture. A multicontroller deployment strategy for the hierarchical domain-based SDN-enabled SAGIN is proposed. First, we divide the SDN control plane into two layers, i.e., the primary controller layer is deployed on the ground network and the secondary on the space-based network. The SDN data plane is composed of space-based, air-based, and ground-based networks. Second, considering the average network delay and the controller load, a multiobjective optimization model is constructed. To determine the number of controllers and the relative positions of switch nodes and controllers, the clustering algorithm based on <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> -means is adopted to initially divide the data plane. Finally, to improve the global search ability of the algorithm, a multiobjective optimization algorithm based on a genetic algorithm is adopted. The simulation results show that the proposed strategy is effective in reducing the average network delay and improving the controller load balance. Compared to other algorithms, the average network delay is reduced by 13.3% and the controller load is improved by 10.33%.

Design of a non-cooperative target capture mechanism for capturing satellite launch adapter ring

Space debris is growing dramatically, which poses a serious threat to space exploration activities. Especially the large non-cooperative target, such as malfunctioning satellites. This paper proposes a capture mechanism for the launch adapter ring that is usually available on satellites as the capture object, which used for in-orbit capture of malfunctioning satellites. Firstly, introduce the design conditions, the overall design plan, carry out the mechanical mechanism design, sensor system configuration, electrical system design, and explain the capture process. Secondly, analyze the capture tolerance. Thirdly, by establishing the kinematics model of the captured finger, use D-H parameter method for kinematic analysis, and analyze the dynamic in the capturing process. In addition, the control strategy is proposed, and the clamping force model, friction identification model, and servo control strategy are established. Then, the prototype is manufactured, and the clamping force, stiffness, capture loads, and capture tolerance are tested. Finally, the air-floating platform is used to verify the capture test of the launch adapter ring in a microgravity environment. The experimental results show that the developed capture mechanism meets the design conditions and has the ability to capture launch adapter ring of satellites in orbit.

Thermo/mechanical design for embedding ALPIDE pixel sensor chip in a High-Energy Particle Detector space module

The High-Energy Particle Detector (HEPD) module is designed to measure the pitch angle and energy of electrons and protons fluxes trapped in the Earth Magnetosphere with energies 3-100 MeV and 30-300 MeV respectively. Because of the launch of the CSES-02 satellite, an interesting option for improving the HEPD is to endow the tracking module with ALPIDE monolithic active pixel, specifically developed for the ITS upgrade of ALICE experiment at CERN. In this work we present the project of a modular and compact particle tracker made of 5 turrets, making use of 150-pixel sensors equipped with Hybrid Integrated Circuit (HIC) and supported by Carbon Fiber Reinforced Plastics (CFRPs) staves housed in an aluminum case. All envisaged solutions have been validated with an intense campaign of qualification tests, concerning vibrations and thermal stresses. The HEPD-02 tracker project foreruns the massive usage of CFRPs for space initiatives both of scientific and exploratory nature.

SDUST2021GRA: global marine gravity anomaly model recovered from Ka-band and Ku-band satellite altimeter data

Abstract. With the launch of altimetry satellites with different observation frequencies and different survey missions, it is necessary to integrate multi-satellites altimeter data to establish a new global marine gravity anomaly model. Based on Ka-band sea surface heights (SSHs) from SARAL/AltiKA and Ku-band SSHs from other satellites (including HY-2A) in geodetic missions and exact repeat missions, the global marine gravity anomaly model of SDUST2021GRA on a 1′ × 1′ grid is derived. Gridded deflections of vertical (DOV) are determined from along-track geoid gradients by the least squares collocation method, in which the noise variances of along-track geoid gradients are obtained by the iteration method for Ka-band geodetic mission and by the SSH crossover discrepancies for other altimetry missions. SDUST2021GRA is recovered from the gridded DOVs by the inverse Vening Meinesz formula, and analyzed by comparing with the recognized marine gravity anomaly models of DTU17 and SIO V30.1. Finally, the accuracy of SDUST2021GRA, DTU17, and SIO V30.1 is assessed by preprocessed shipborne gravity anomalies. In conclusion, the differences between SDUST2021GRA and recognized models are small, indicating the reliability of SDUST2021GRA. The differences are mainly concentrated between −5 and 5 mGal, which accounts for more than 95 % of the total number. Assessed by shipborne gravity, the accuracy of SDUST2021GRA is 2.37 mGal globally, which is higher than that of DTU17 (2.74 mGal) and SIO V30.1 (2.69 mGal). The precision advantage of SDUST2021GRA is mainly concentrated in offshore areas. HY-2A-measured altimeter data have an important role on gravity anomaly recovery in areas with complex coastlines and many islands. SDUST2021GRA is concluded to reach an international advanced level for the altimeter-derived marine gravity model, especially in the offshore area. The SDUST2021GRA model data are freely available at https://doi.org/10.5281/zenodo.6668159 (Zhu et al., 2022).

Route Plans for UAV Aerial Surveys according to Different DEMs in Complex Mountainous Surroundings: A Case Study in the Zheduoshan Mountains, China

Accurate and error-free digital elevation model (DEM) data are a basic guarantee for the safe flight of unmanned aerial vehicles (UAVs) during surveys in the wild, especially in moun-tainous areas with large topographic undulations. Existing free and open-source DEM data gen-erally cover large areas, with relatively high spatial resolutions (~90, 30, and even 12.5 m), but they do not have the advantage of timeliness and cannot accurately reflect current and up-to-date topographical information in the survey area. UAV pre-scanning missions can provide highly accurate and recent terrain data as a reference for UAV route planning and ensure security for subsequent aerial survey missions; however, they are time consuming. In addition, being limited to the electric charge of the UAV, pre-scanning increases the human, financial, and time consumption of field missions, and it is not applicable for field aerial survey missions in reality, unless otherwise specified, especially in harsh environments. In this paper, we used interferometric synthetic aper-ture radar (InSAR) technology to process Sentinel-1a data to obtain the DEMs of the survey area, which were used for route planning, and other free and open-source DEMs were also used for flightline plans. The digital surface models (DSMs) were obtained from the structure of the UAV pre-scan mission images, applying structure for motion (SfM) technology as the elevation reference. Comparing the errors between the InSAR-derived DEMs and the four open-source DEMs based on the reference DSM to analyze the practicability of flight route planning, the results showed that among the four DEMs, the SRTM DEM with a spatial resolution of 30 m performed best, which was considered as the first reference for UAV route plans when the survey area in complex mountainous regions is covered with a poor or inoperative network. The InSAR-derived DEMs from the Sentinel-1 images have great potential value for UAV flight planning, with a large perpendicular baseline and short temporal baseline. This work quantitatively analyzed the errors among the different DEMs and provided a discussion regarding UAV flightline plans based on external DEMs. This can not only effectively reduce the manpower, materials, and time consumption of field operations, improving the efficiency of UAV survey tasks, but it also broadens the use of InSAR technology. Furthermore, with the launch of high-resolution SAR satellites, InSAR-derived DEMs with high spatial and temporal resolutions provide an optimistic and credible strategy for UAV route planning with small errors.

Air-rocket space launch system - as Responsive Space System

ObjectivesThe study was to analyze the concept of Responsive Space Systems alternative launch and set of the nanomicro satellites into Low Earth Orbit. The analysis focused on aircraft-rocket space systems, where platform for launching a rocket with a satellite is an aircraft.The aircraft in the role of the platform provides opportunities, system thus the operator doesn't need bases or space ports in European conditions.MethodsAnalysis of the research area, focused on the review, critical analysis, evaluation of the available literature, resources. The work was supplemented with the results and recommendation of the research project recently carried out at the MUT.ResultsSystems were presented in view of the war in Ukraine. Existing operational and currently designed systems were reviewed. Article evaluated the aerial-rocket systems for launching objects into the LEO in the context of the system's operational costs and capabilities, potential market and further military and civilian applications also the needs of the Polish Armed Forces. Combat aircraft and rocket kits based on decommissioned from PAF fighters were proposed and valuated.ConclusionsImplementation of system gives autonomy from countries or companies offering space services, possibility of mastering new capabilities of placing satellite systems for security&amp;defense purposes. For the PAF, aircraft-rocket kits based on phased-out supersonic combat aircraft may be the start of the development and construction of the national Responsive Space System. The country's scientific-industrial base has competence to design&amp;build such a system. Polish Space Agency can act as an integrator of the system just as NASA did in the 1960s.

Optomechanical design and analysis of lens assembly for space application

This study illustrates how commercial off-the-shelf optics may be employed in space exploration cameras. The most frequent loads on optical systems are self-weight, which is caused by gravitational orientations, vibration, and temperature ranges, which is caused by exposure to quickly changing temperatures ranging from extremely cold to very hot and during launch. This study describes the modulation transfer function (MTF) performance of the selected lens assembly, followed by a top-down method to disassemble the optical parts of the commercial lens housing. The lens enclosure was designed and modelled by retaining the interelement lengths determined from physical measurement. The performance of the lens barrel and optical elements have also been validated in ANSYS using a quasi-static loading and thermoelastic condition. As a post-performance assessment owing to stress and vibrations during satellite launch, a tilt-separation simulation was conducted. As a result of this research, it has been demonstrated that optomechanical design of commercial lens assembly is feasible for use in space application camera systems.

Track detection of high-velocity resident space objects in Low Earth Orbit

The world’s economy has become heavily dependent on the services provided by satellites. With the exponential increase in satellite launches, the population of defunct or inactive hardware in space has grown substantially. This is especially true in sensitive orbits such as the Low Earth Orbit (LEO) and Geostationary Earth Orbit (GEO) regimes. These objects, collectively known as orbital debris, can reach speeds of up to 28 000km h−1 in LEO. At these orbital speeds, even the smallest of objects can pose a considerable threat to operational satellites or astronauts. This makes the monitoring, and detection, of these objects of the utmost importance. This work describes the latest detection strategy used in one of Europe’s largest Space Situational Awareness (SSA) installation; the BIstatic RAdar for LEo Survey (BIRALES) space debris radar. We present a novel bottom-up approach that makes use of single-linkage clustering to identify faint radar streaks in spectrogram data. Tests on synthetic data have shown that the detection strategy presented in this study obtains a higher detection rate when it is compared against existing methods. Unlike other approaches, this detection strategy, using the Multi-beam streak detection strategy (MSDS) algorithm, was still able to recall 90% of the track information at an Signal-to-Noise Ratio (SNR) of 2dB.

Urban land use and land cover classification with interpretable machine learning – A case study using Sentinel-2 and auxiliary data

The European Commission launch of the twin Sentinel-2 satellites provides new opportunities for land use and land cover (LULC) classification because of the ready availability of their data and their enhanced spatial, temporal and spectral resolutions. The rapid development of machine learning over the past decade led to data-driven models being at the forefront of high accuracy predictions of the physical world. However, the contribution of the driving variables behind these predictions cannot be explained beyond generalized metrics of overall performance. Here, we compared the performance of three shallow learners (support vector machines, random forest, and extreme gradient boosting) as well as two deep learners (a convolutional neural network and a residual network with 50 layers) in and around the city of Malmö in southern Sweden. Our complete analysis suite involved 141 input features, 85 scenarios, and 8 LULC classes. We explored the interpretability of the five learners using Shapley additive explanations to better understand feature importance at the level of individual LULC classes. The purpose of class-level feature importance was to identify the most parsimonious combination of features that could reasonably map a particular class and enhance overall map accuracy. We showed that not only do overall accuracies increase from shallow (mean = 84.64%) to deep learners (mean = 92.63%) but that the number of explanatory variables required to obtain maximum accuracy decreases along the same gradient. Furthermore, we demonstrated that class-level importance metrics can be successfully identified using Shapley additive explanations in both shallow and deep learners, which allows for a more detailed understanding of variable importance. We show that for certain LULC classes there is a convergence of variable importance across all the algorithms, which helps explain model predictions and aid the selection of more parsimonious models. The use of class-level feature importance metrics is still new in LULC classification, and this study provides important insight into the potential of more nuanced importance metrics.

Orbital launches and teams up with Beam

Orbital launches and teams up with Beam

Orbital launches and teams up with Beam

Orbital launches and teams up with Beam

Assessing the Potential of Qormino Processor for Embedded AI on Board a CubeSat

The launch of small satellites, CubeSats among others, is skyrocketing easing the development of Earth observation missions and the implementation of Space applications. At the same time, artificial intelligence (AI) and deep neural networks algorithms are enjoying impressive success for their results and the diverse applications they enable. The idea of combining nanosatellite standards with AI capabilities arises, thus, from a will to push the boundaries of Space systems further. Led by the Grenoble University Space Center (CSUG), the QlevEr Sat mission aims at embedding such an algorithm on board a CubeSat, to process data directly and send only the relevant results to the ground station. From the images taken with the Emerald sensor, forest/nonforest and cloud/noncloud segmentation maps are inferred with the Teledyne Qormino QLS1046-Space processor to monitor deforestation. A detailed benchmark of this processor is presented in this article and confirms its suitability for the mission. The specifically designed pixel-wise classification algorithm leverages the Qormino processor computing power to produce accurate high-resolution binary maps.

Analysis and Demonstration of First Cross-Support Interferometry Tracking in China Mars Mission

Delta-Differential One-Way Ranging (DeltaDOR) is widely used in deep spacecraft navigation, and cross support could enhance navigation accuracy with more interferometry baselines and longer baseline. In China Mars mission Tianwen-1, formal joint cross-support interferometry tracking between China Satellite Launch and TT&amp;C General (CLTC) and European Space Operations Center (ESOC) under commercial contract was conducted around the critical stages of the mission, such as Mars orbit insertion. Cross-support interferometry is a new challenge to CLTC, as the correlator for routine DeltaDOR measurements do not fit for cross support, because of observable definition, blind station clock searching, and so on. This paper discusses the new method and algorithm adopted in joint cross support, especially for spacecraft tone signal processing and clock estimation when correlating with the data of two stations from different agencies. Results of the cross-support interferometry tracking activities are also analyzed. Observables from CLTC and ESOC are consistent with each other, and the difference in observables is in the order of tens of ps. All the baselines are induced to evaluate the accuracy of the spacecraft orbit determined and predicted by CLTC, and the DeltaDOR residuals have a root-mean-square (RMS) better than 0.5 ns (the goal is 1 ns), which could enhance the confidence of the orbit accuracy and the effectiveness of control parameters during critical orbit operation.

Оцінка можливості застосування автофажних двигунів в системах відводу космічних об’єктів

This article is devoted ascent depreciation in an earth orbit of space crafts for different functions that allow to solve many problems connected with space activity, in particular, maintenance of wider use of space resources and more effective clearing of a near space from space debris. The last is particularly true for bulky space objects of a technogenic origin which can be deorbit from earth orbits by using the special means for deorbiting injection into the target orbit by launch vehicles. As the ascent of such means for deorbiting by orbital launch vehicle demands significant financial expenses, for their decreased application of easy autophagy launch vehicles with burned fuel tanks is offered. The basic making unit of such launch vehicles is an autophagy engine. The design of autophage engine design and the principle of its operation of the version with compulsory fuel supply to the combustion chamber are presented and the expediency of use of such an engine for small spaceships in case of the impossibility of application of rather heavy usual systems of storage and fuel supply is shown. However, now the weight of the accepted systems of compulsory fuel supply autophagy engines for spaceships remains significant for launch vehicles. As one of the alternative ways of a feed the engine of autophagy launch vehicle, the capability of submission by using the inertia of the most fuel charge is considered. The unit of the autophagy engine contains an evaporator and works in a pulse mode, supplying fuel supply between momentums at the moment of low pressure in the engine. The effect of retardation (easings), representing pressure decrease and engine thrusts in flight time is established. This effect is called by the forces of inertia acting on the sliding engine, and has экспоненциальную an easing picture. Considering the effect of retardation, a system of the equations for calculating kinematic and design data of the launch vehicle with the autophagy engine is offered. The received results of the research have scientific and practical value and can find wide applications in the design of schemes and deorbiting means.

Multi-Objective Evolutionary formulations for design of hybrid Earth observing constellations

With the recent advances in satellite miniaturization, communication and information technologies, and the advent of affordable small satellite launch services, there has been a paradigm shift in space exploration missions involving the transition from monolithic architectures formed by a large satellite to the concept of Distributed Spacecraft Missions (DSM), which fly multiple simpler and less costly satellites to offer increased capabilities such as better temporal, spatial, and angular sampling. Despite the potential to provide higher science return and novel data products, the orbit selection problem for Earth Observation DSMs requires a much more complex constellation design process, which involves several interrelated design variables and conflicting objectives. Because of this, prior work has focused mostly on relatively simple DSM architectures consisting of a single type of constellation, such as homogeneous Walker constellations. This paper presents a novel evolutionary formulation (i.e., chromosome and operators) in the context of Multi-Objective Evolutionary Algorithms (MOEA) that allows for the exploration of large tradespaces of non-Walker hybrid satellite constellations with diversity of orbital parameters. The idea behind this new formulation is that it allows to search through the space of different types of constellations – such as Walker formations, Sun-synchronous trains and string-of-pearls among others – and combinations thereof. This type of hybrid constellations have not been studied in detail. The methodology presented in this paper helps overcome the combinatorial explosion resulting when opening up the design space to include non-symmetrical configurations and relaxing constraints in the values of some orbital parameters (e.g. choosing a common altitude or inclination for all satellites forming the constellation). The proposed formulation is compared with a state-of-the-art evolutionary formulation using a variable-length chromosome in 5 different problems including the observation of symmetrical, asymmetrical, connected and disconnected regions of interest. Results show that the proposed formulations achieve better convergence and convergence rate than the state-of-the-art. The proposed method can reduce the effort required to design a problem formulation for each problem instance, while also reducing the risk of missing potentially good architectures due to formulations that are too restrictive and rely too much on previous experience and expertise.

The small launch vehicle survey a 2021 update (The rockets are flying)

The 2010′s has seen a dramatic increase in potential small launch vehicle contenders, defined as rockets capable of carrying at most 1000 kg to Low Earth Orbit. Spurred on by government programs such as the European Horizon 2020 or the American DARPA Launch Challenge, and the rapid proliferation of CubeSats and nanosatellites, more than 100 different commercial, semi-commercial, and government entities worldwide are now working on new entrants of this class. To date the most successful small launcher, the Northrop Grumman Pegasus has launched 45 times, but its flight rate has dropped to less than one a year. At the same time launch opportunities on ESPA rings, secondary slots on larger launchers, and CubeSat missions as cargo to the International Space Station have proliferated. Despite this seemingly bleak market environment, new entrants have emerged looking for a new magic formula. Others are new commercial entries from unexpected markets such as China. All are inspired by the success of SpaceX and the desire to capitalize on the perceived demand caused by the mega constellations. This paper presents an overview of the small satellite launch systems under development today. Capabilities, stated performance goals, cost, and funding sources are compared where available. This paper is a yearly update of a paper originally presented at the 2015 Conference on Small Satellites (Frick and Niederstrasser, 2015) and subsequently at the 2016 International Astronautical Congresses (Frick and Niederstrasser, 2016). We also review the growing number of entrants that have dropped out since we first started this report. Despite the COVID-19 pandemic, the authors discovered fifteen new systems under development and one system became operational in the past 12 months. Two other systems attempted their first flight in 2021 but were unsuccessful. The author welcomes any comments, feedback, or corrections.

Fast spatial-spectral random forests for thick cloud removal of hyperspectral images

The long-term existence and extensive coverage of thick clouds have caused an amount of missing information in hyperspectral images (HSIs), hindering their applications greatly. Recently, with the continuous launch of new satellites, the increasing availability of HSIs provides more opportunities for using temporal information in cloud removal of HSIs. In this paper, a fast spatial-spectral random forests (FSSRF) method was proposed for removing clouds of HSIs. FSSRF is developed based on the advanced spatial-spectral random forests (SSRF) method that was developed to handle multispectral images. FSSRF greatly improves the computing efficiency while ensuring the accuracy of reconstruction. Experimental results on both GF-5 and EO-1 HSIs show that FSSRF is a much faster version than the original SSRF that uses directly all known bands of the temporally neighboring HSI with spatially complete coverage, and the accuracies of the two versions are similar. Compared with subSSRF (i.e., SSRF using several spectrally adjacent known bands for each cloudy band) and the popular MNSPI method, FSSRF can produce more accurate predictions. The evaluation from spectral dimension shows that FSSRF can recover the spectral characteristics of cloud pixels more satisfactorily. FSSRF has great potential in real-time cloud removal of HSIs due to its obvious advantages in balancing computational efficiency and accuracy.

Optimal Design of Hybrid Rocket Small Satellite Launchers: Ground Versus Airborne Launch

A three-stage hybrid rocket is considered as a small satellite launcher. The same engine is used in different numbers in each stage: six, three, and one in the first, second, and third stages, respectively. This design choice aims at an overall reduction of the launcher cost. The propellants are liquid oxygen and a paraffin-based fuel. The performance of different feed systems and launch options are evaluated: the feasibility of a ground launch is analyzed and compared to similar three-stage launchers with airborne launch using both a gas pressurized feed system and an electric turbopump feed system. The optimization procedure exploits a direct method to evaluate the best values of engine design parameters, whereas an indirect method optimizes the ascent trajectory once the engine design is given. Constant power and blowdown operation are, respectively, assumed for the electrical feed system and the gas pressurized feed system. The initial mass of the launcher is given (5000 kg), and the payload mass is maximized for a given insertion orbit. The initial thrust is fixed in order to have an initial acceleration equal to . The nozzle expansion ratio in the first-stage engines is reduced to avoid separation at liftoff in the ground case, and the third-stage engines are used at a lower vacuum thrust level to satisfy maximum acceleration constraints. The results show that the proposed small satellite launcher concepts are able to deliver payload masses in the range of 40–100 kg into the desired orbit.