International Journal of Space Science and Engineering (10 papers in press)
Radiance Enhancement and Shortwave upwelling Radiative Flux methods for efficient detection of cloud scenes
by Rehan Siddiqui, Rajinder K. Jagpal, Sanjar M. Abrarov, Brendan M. Quine
Abstract: The description, interpretation and imagery of cloud scenes by remote sensing datasets from Earth-orbiting satellites have become a great debate for several decades. Presently, there are many models for cloud detection and its classifications have been reported. However, none of the existing models can efficiently detect the clouds within the small band of shortwave upwelling radiative wavelength flux (SWupRF) in the spectral range from 1100 nm to 1700 nm. Therefore, in order to detect the clouds more efficiently, a method known as the radiance enhancement (RE) can be implemented (Siddiqui et al., 2015; Siddiqui et al., 2016b; Siddiqui, 2017). Satellite remote sensing database is one of the most essential parts of research for monitoring different atmospheric changes. This article proposes a new approach how with RE and SWupRF to distinguish cloud and non-cloud scenes by space orbiting Argus 1000 spectrometer utilizing the GENSPECT line-by-line radiative transfer simulation tool for space data retrieval and analysis (Quine and Drummond, 2002; Jagpal, 2011; Siddiqui et al., 2015; Siddiqui, 2017). This approach may be used within the selected wavelength band of Argus 1000 spectrometer in the range from 1100 nm to 1700 nm to calculate the integrated SWupRF synthetic spectral datasets. We used the collected Argus observations starting from 2009 to investigate the radiative flux and its correlation with cloud and non-cloud scenes (Siddiqui et al., 2017). Our results show that the both, RE and SWupRF model, are capable of identifying most of the cloudy scenes except for some thin clouds that cannot be identified reasonably with high confidence due to complexity of the atmospheric system. Based on our analysis, we suggest that the relative correlation between SWupRF and RE within a small wavelength band can be a promising technique for estimating the solar and thermal energy balance involving cloud layers.
Keywords: radiance enhancement; cloud detection; radiative transfer; shortwave; upwelling flux; micro-spectrometer; remote sensing.
Kinematic analysis of a lightweight periodic dielectric structure of pearls for RF coaxial power cables for space applications
by Gerald Kress, Holger Karstensen, Michael Mattes, David Raboso
Abstract: The desire to reduce the mass per unit length and to increase phase stabilityrnof coaxial radio-frequency (RF) power cables for space application motivates to replace solid dielectric with a periodic chain of hollow pearls. The design of the dielectric pearls must allow for bending exibility of the cable even if they are made from a stiff material such as silicon glass. An important requirement of RF power cables for space applications is their phase stability, which is in uenced by the material-dielectric-constant tolerance over a large temperature range as well as by changes in geometry. This paper presents a closed-form model based on rigid-body motion to predict the kinematic response of dielectric pearls to the bending of the cable. Particularly, the model maps the eccentricity of the inner and outer conductors with respect to each other and the axial strain of thernbent cable along its centerline.
Keywords: dielectric; co-axial RF power cable; space applications; kinematics; closed-form modeling.
Coherency Evaluation of GNSS MBOC Pilot and Data Signal in Joint Tracking
by Xue Wang
Abstract: The MBOC signal uses a modulation in which the pilot and the data signals are separated. However, these modulation methods have evolved a variety of joint receiving algorithms. The paper introduces the optimal design strategy for MBOC signal joint tracking, in which the amplitude and phase outputs in the loop phase discriminator are linear composite with the weight coefficients. According to the different modulations of each GNSS system, these composite coefficients are determined by the signals modulation phase relationship and power relationship. Through the BDS data verification, the advantages of joint tracking are demonstrated. The influences of signal coherency in the joint tracking process are analysed. The coherencies of between each signal code and code-to-carrier in GPS L1C, BDS B1C, and GALILEO E1C signals are evaluated by high Carrier-to-Noise ratio signal, which is acquired with the National Time Service Center CAS 40-meter antenna Signal in Space Quality Assessment System. The results verify the GNSS signal in space meets joint tracking requirements.
Keywords: GNSS MBOC signal; joint tracking; codes coherency; code-to-carrier coherency; Signal in Space Quality Assessment.
Impact of Geometry Sensitive Satellites on the Navigation Performance of Ground Based Augmented GPS
by Irfan Sayim, Haoxiang Lang, Dan Zhang
Abstract: This paper discussed the impact of geometry sensitive of satellites on the navigation performance of Ground Based Augmentation System (GBAS). The nominal number of satellites (space vehicles, or SVs), defined in RTCA/DO-229E, in the Global Positioning System (GPS) constellation was used in the analysis. In the quantification of GBAS navigation performance (i.e., the protection level or PL computed at aircraft), full constellation, and one and two SV outage scenarios were applied through the search process within all combinations of healthy SV geometries (i.e., subsets of SVs in view). It was observed that some SV combinations, subset geometries obtained after depletion of constellation, reduced GBAS navigation performances significantly. These geometries were treated as unsafe for an initiation of intended aircraft precision approach and landing. Further, SVs affecting the integrity and the availability of GBAS in this manner were identified as geometry sensitive. The impact of geometry sensitive SVs on the GBAS navigation performance were quantified and ranked per outage cases.
Keywords: Ground Based Augmented Systems (GBAS); Satellite Outages; Navigation integrity; Vertical Protection Levels (VPL); Vertical Alert Limit (VAL); GBAS Availability.
Kalman Filter and Satellite Attitude Control System Analytical Design
by Yuri Kim
Abstract: Certain robust form of suboptimal Kalman-Busy Filter (KBF), with Bounded Grows of Memory (FBGM) is considered for satellite Attitude Control System (ACS) design purposes. At the first step of the design, at the preliminary (conceptual model CM or low fidelity model - LFM) design it can be used to synthesize the system state estimator/observer and the controller and to evaluate system feasibility and potentially achievable performance. Further steps of the design, take into account some realistic constrains and restrictions, and develop this LFM, by adding more detail elements, to complex, non-linear and not-stationary high fidelity model (HFM). This model (HFM) should be analyzed from the System Engineering point of view, during design review, prototyping, manufacturing, testing and qualification. However, the CM, as the basic reference, still keeps its significance to the end of the system life time cycle. rnIf the conceptual design was performed professionally by the experienced developer, it is usually sound and robust, and the LFM can be considered as a generic model that would not be drastically changed when developing the HFM model. Rather some additional elements and constrains would be introduced, but not making unfit previous analysis. rnMore than that, with small additions synthesized at the conceptual design phase state estimator and controller can be directly implemented in the Flight System. However, even experienced specialist is not assured against mistakes and misinterpretations sometimes leading to wrong solutions. Also junior developers can be involved, students should have a solid methodology based on an objective criteria rather than on the tutor experience and intuition. All this presents the actuality of the consideration presented below. It is in the scope of the linear, time invariant systems under assumptions of the linear KBF theory. If these assumptions are applicable then presented results can be implemented or, at least used as a reference, to guide developers through the system developing process.
Keywords: analytical design; dynamic system; satellite attitude control system (ACS); Kalman Filter; controller; estimator; filter; white noise; optimal estimation and control.
Conceptual Thermal Design of a Network of Solar-powered Boardsat- and CubeSat-based Landed Spacecraft on Mars
by Dukhang Lee, Thomas Young, Hugh Podmore, John E. Moores, Regina S.K. Lee
Abstract: In this paper, we assess the feasibility of the neoPASCAL thermal design by performing thermal analysis. NeoPASCAL is a network of compact solar-powered landers on Mars which aim to validate Mars General Circulation Models (GCMs) by measuring the diurnal variations in surface pressure. It is a modern revision of the original Pascal mission proposed in 1996, with each science station being ten times smaller in size and mass (a kg or less) by using miniaturised commercial off-the-shelf (COTS) electronic components and satellite platforms (i.e., Boardsat and CubeSat platforms). Despite the harsh thermal environments, the analysis shows that the Boardsat-based model can survive at ≤ ±60° latitude by using a large flexible-solar-cells-attached sail that was originally designed to attain soft landing. If successful, such a network would provide an unprecedented set of global meteorological data that can be used to investigate various meteorological phenomena including the general circulation.
Keywords: Mars lander; thermal design; picosat; low-cost planetary mission.
Satellite Formation Flying control using an Innovative Technique Subject to Electromagnetic Acceleration
by Shafeeq Tealib, Yehia Abdel-Aziz, Mervat EL-Said Awad, Khalil Ibrahim. Khalil, Mohmed Radwan
Abstract: The electrostatic charge became a possible method to control both orbital and attitude motion without fuel consumption or reduce the fuel cost. This study needs to install an ion collector on the satellite to increase the level of charging as artificial charging. In this paper, we developed a linearized satellite relative motion and a combination of Lorentz forces provided by modulating spacecrafts electrostatic charge (magnetic and electric fields) that can be used to keep the desired relative distances and orientations considering J2 perturbation. The proposed controller contains a feedback control using a real-time fuel-optimal control approach is considered for satellite formation control in eccentric orbits based on the developed linear J2 dynamic model. Comprehensive simulation numerical results confirmed the capability of Lorentz force to correct the drift in the relative position of formation flying due to the effect of J2., these corrections depend on the value of charge to mass ratio and magnitude of the relative position.
Keywords: Lorentz-force; electrostatic charge; relative motion; Second zonal harmonics; Legendre pseudospectral.
Design and Analysis of Entry, Powered Descent Trajectory Envelopes and Manifold of Landing Points
by Melissa Onishi, Dilmurat Azimov
Abstract: This paper presents the design, analysis and construction of trajectory envelopes for viable descent and landing manoeuvres. A family of envelopes is generated by varying a vast range of terminal conditions allowed by the proposed design space based on previous Mars landing trajectories. The following phases are considered in the landing manoeuvre: exoatmospheric thrust phase, atmospheric transit phase and powered descent and landing phase. The paper investigates cases where two or three entry velocity components are defined as non-zero arbitrary constants to analyse the overall profile of the entry trajectory. Specific parameters are designated to satisfy the design space and achieve feasible landing. The continuity conditions at the junction points have been presented and analysed to provide smooth and continuous change of these parameters except for the control variables. The proposed design and construction of trajectory envelopes can be used in the mission design analysis for planetary landing missions. Simulations of the proposed manoeuvre trajectories are presented.
Keywords: entry; descent and landing; trajectory envelopes; powered descent.
Passive Vibration Suppression of Large Space Truss Structures by Viscous Damping
by Cheng Luo, Min Luo, Yaobing Wang, Wenbo Luo
Abstract: Viscous damping methods are commonly employed to suppress the vibration due to their simple design, low cost, and stable damping performance. However, the harsh space environment makes the normal viscous dampers suspicious to various failures. This paper proposes a novel and robust design of viscous damper to provide high damping under low-frequency vibration disturbance in space. The characterization of the damper at low-frequency and large displacement is first investigated by numerical analysis and then validated by experiments. Based on the results of the damper, this paper presents an optimal design strategy for the damping system of large space truss structures, which is critical for space mission because there is no sufficient damping in such space structures. The design is further optimized by weighted-sum that includes the damping characteristics of dampers and elastic flexibility of space truss structures. The effect of the damping system is demonstrated by the optimal design of a 60-bay truss structure. The results show that the damping ratios of the first three modes of the truss structure can be increased by over 10% with two viscous dampers. Comparisons between the structure with and without dampers demonstrate that significant vibration suppression at low-frequency bandwidth can be achieved satisfactorily.
Keywords: space truss structures; vibration suppression; viscous damper; weighted-sum optimization method.
MICROGRAVITY, ATMOSPHERE SOUNDING, ASTRONOMY, TECHNOLOGY VALIDATION - AN OVERVIEW OF SUBORBITAL ROCKETS' MISSIONS AND PAYLOADS
by Tomasz Noga, Rachita Puri
Abstract: Suborbital rockets have been used for research purposes for decades, and they are attractive for atmosphere sounding, microgravity research, astronomy and technology validation purposes. This paper aims to give an outline of the current state of suborbital rocket research efforts. We present a short overview of the history of suborbital research and give a general description of suborbital rockets as well as an overview of national and international research programs utilizing suborbital rockets. The topic of test ranges and recent commercialization efforts are described briefly. We divide the research into four general types technology validation, astronomy, microgravity and atmosphere sounding. Each type is described and a corresponding table of recently flown example missions is included. Additionally, use of suborbital rockets for education purposes is described. We comment on the future of suborbital research based on current trends and forecasts.
Keywords: suborbital flight; sounding rocket; microgravity; atmosphere sounding; technology validation; astrophysics onboard sounding rockets; suborbital research; suborbital research market.