Sunday C. Ekpo

A System Engineering Analysis of Highly Adaptive Small Satellites

Spacecraft systems have undergone tremendous system-level transformations following advances in subsubsystems, subsystems, and systems designs and technologies. Furthermore, the ever expanding space applications and entrants necessitate a holistic review of current spacecraft system engineering (SE) margins. This paper seeks to examine contemporary space systems engineering procedures and develop a corresponding SE analysis tool for next-generation small satellites. Mass and power budgets are the considered SE margins. Case studies of highly adaptive small satellites (HASS) for a meteorology mission in low earth orbit are presented. HASS have demonstrated mass-, power-, and cost-savings with advanced capabilities than the conventional ones. The presented SE procedure can be extended to any spacecraft category and mission. As a capability-based SE analysis tool, it will enable the design and development of lightweight, reliable, adaptive, optimal, multifunctional, and economical satellites. This will enhance the provision of space systems that have postmission reapplications capability.

Impact of Noise Figure on a Satellite Link Performance

Small satellite link performance analysis is critical for assessing the adequacy of a transmitter to successfully transfer data at the desired rate. This is especially obvious when considering highly adaptive small satellite systems that exhibit static and active/dynamic power requirements. This paper presents the impact of noise figure on the carrier and data links performances of a highly adaptive small satellite application. The noise figures of a MMIC LNA, designed using GaAs technology operating within the C- and X-bands, were used to study the link performance of a planetary mission. An existing Magellan spacecraft link performance was considered in this study. The analysis reveals that designing a broadband LNA to have a ripple of less than 0.1 dB within its operating bandwidth is essential for a less than 2 dB drop in the carrier and data links margins. This fixes a 6.8 K receiver noise temperature swing margin for reliable, dynamic, broadband and adaptive space operations.

A system-based design methodology and architecture for highly adaptive small satellites

System-level conception, design and analysis are fundamental to ensuring the reliability and operability of complex systems. The ever-expanding and demanding global space activity requires, amongst other performance metrics, multifunctional, reconfigurable and adaptive system architectures. Consequently, there is need for developing a systems engineering tool/platform for assessing multipurpose space applications and decommissioned satellite systems reapplication. This paper presents a system-based design methodology and architecture for highly adaptive small satellites (HASSs). The developed HASS methodology beacons on the basic systems engineering design process and generalised information network analysis (GENA) model. The HASS methodology and architecture address the space mission and conceptual design objectives. The iterative process provides options for mission(s) definition and combinations and space system transformation. It also allows the designer to choose from available device technologies for specific and integrated applications with allowance for trade-offs and evaluation. Depending on the unique attributes of interest, the small satellite subsystem components can be selected for a specific mission. Furthermore, mission-defined quality of service metrics are assigned prior to the system trade space exploration. HASS-based multicriteria studies are then performed for qualifying the optimal system architectures. This adaptive space system-level platform allows the designer to optimize device technologies, systems and subsystems configurations and architectures in an integrated environment. The attendant benefits, are reduced design, launch and operations costs, reliability, adaptive remote monitoring and support for broadband and/or multimedia applications.

4 – 8 GHz LNA design for a highly adaptive small satellite transponder using InGaAs pHEMT technology

The ever increasing global space activity is characterised by emerging space systems, operation and applications challenges. Hence, reliable RF and microwave receivers for in-orbit highly adaptive small satellites are needed to support reconfigurable multimedia/broadband applications in real-time with optimal performance. Though other parameters of the small satellite communication system may be critical, the noise level of the receiver determines the viability, reliability and deliverability of the project. Thus, a good design that delivers low noise performance, high gain and low power consumption for multipurpose space missions is inevitable. This paper describes a 0.15µm InGaAs pseudomorphic high electron mobility transistor amplifier with low noise and high gain in the frequency band 4 – 8 GHz. The monolithic microwave integrated circuit LNA design presented here shows the best performance known using this technology; noise figure of 0.5 dB and gain of 37 ± 1 dB over the characterised bandwidth.

A system engineering consideration for future-generations small satellites design

The conventional point-based satellite system engineering design procedure is insufficient to address the dynamic operations and post-mission reuse of capability-based small satellites. Emerging space systems and missions require an adaptive architecture(s) that can withstand the radiation-prone flight environment and respond to in-situ environmental changes using onboard resources while maintaining its optimal performance. This proactive and reactive response requirement poses an enormous conceptual design task in terms of the trade space - which can be too large to explore, study, analyse and qualify - for a future-generation adaptive small satellite system. This paper involves a careful study of the current and emerging space system technologies, architectures and design concepts for realising adaptive small satellites for future space applications. Adaptive multifunctional structural units (AMSUs) that eliminate subsystem boundaries and enable five levels of inorbit customisations at the system level have been qualified for highly adaptive small satellites (HASSs). The initial system engineering (SE) analyses reveal that the HASS system has mass, cost and power savings over the conventional small satellite implementation. The reported novel research findings promise to enable capability-based, adaptive, cost-effective, reliable, multifunctional, broadband and optimal-performing space systems with recourse to post-mission re-applications. Furthermore, the results show that the developed system engineering design process can be extended to implement higher satellite generation missions with economies of scale.

A deterministic multifunctional architecture for highly adaptive small satellites

A deterministic multifunctional architecture design approach for a highly adaptive small satellite system is proposed in this paper. It enables five levels of design customisation of all categories of highly adaptive small satellites; adaptive functional modules implement higher-level customised and reconfigurable mission functions. Each adaptive multifunctional structural unit (AMSU) supports the subsystem functions as a ‘structural and functional block’ and comes either as a baseline or hybrid. Associated functional sub subsystem components are contained in each AMSU. This removes the conventional structural and functional subsystem boundaries. A meteorology spacecraft mission using a highly adaptive nanosatellite reveals, besides more advanced mission capabilities, 0.6 kg and 1 W mass- and power-savings respectively over a conventional nanosatellite system implementation. This novelty results in adaptive, reconfigurable and multifunctional architectures with economies of scale, timely launch, system-level reliability, flexible integration and test options, cost-effective mass production, post-mission reapplication and optimal performance at the desired mission objectives.

Performance evaluation of free space optical communication under the weak turbulence regime

This paper experimentally investigates the performance of an FSO communications system by increasing the link length under an indoor laboratory controlled turbulence condition. A plane mirror is used to increase the link length by means of optical beam reflection. The experimental results show that the turbulence strength is highly dependent on the link length. The measured scintillation index (SI) for a link of 6 meters long with no reflection is 0.043, which increases to 0.56 with reflection for a link of 12 meters. Furthermore, the Q-factor is measured as a performance metric for the FSO link with and without the reflected beams for different SI values. The results show that the performance of the FSO link with reflection deteriorates very rapidly with the Q-factor being halved compared at SI of 0.01.

Acoustic signal gain enhancement and speech recognition improvement in smartphones using the REF beamforming algorithm

Smartphones deploy multiple microphones to reduce background noise, reverberation and interferences. This paper presents the regulated Frost beamformer (REF) for acoustic gain enhancement and speech recognition improvement in smartphones. Conventional and adaptive beamformers were investigated with recourse to the acoustic transducer specifications of the Samsung Galaxy S2 device. The REF algorithm outperforms the time delay and Frost beamformers by over 5 dB and 2 dB respectively. Moreover, the minimum array gain is 5 dB (REF) as opposed to the floor gain of 2 dB. Compared with the delay-and-sum and Frost beamformers, the output waveform of the REF beamformer is the closest to the desired signal.

A service based wireless sensor networks architecture for high value-added process monitoring

Current research in high value-added manufacturing processes, such as the Micro Injection Molding (μIM) process, focuses on the monitoring of the machine process data., which could potentially affect the quality of the end product. Up until now, machine process monitoring has been limited to the machine level and has often bypassed the ambient environmental factors and pre manufacturing factors, which could have direct impact on the end product quality. In light of this, extending the monitoring of high value-added processes to include the ambient manufacturing environment would have numerous benefits in terms of process monitoring accuracy, material condition and product quality. In this paper, we present a novel Service Orientated Architecture (SOA) for monitoring a high value-added manufacturing process and its ambient environment using Wireless Sensor Networks (WSN). The proposed architecture applies the SOA to a network of wireless sensor nodes installed in the uIM machine and the industrial micro-molding environment. Here we present; the generic architectural design, system integration, user interfaces, and initial test results for an experimental testbed system.

A Multicriteria Optimisation Design of SPSE for Adaptive LEO Satellites Missions Using the PSI Method

The spacecraft power system engineering (SPSE) analysis for the radiation-prone space environment is a major critical satellite engineering definition for realising successful mission and post-mission capabilities. The dynamic operations and post-mission applications of capability-based small satellites require an adaptive architecture(s) which exhibits an enormous conceptual system engineering design task in terms of the trade space – which can be too large to explore, study, analyse and qualify – for a reliable and sustainable mission. This paper involves a multicriteria optimisation design of the SPSE subsystems for adaptive LEO satellites missions using the parameter space investigation (PSI) method. A three-axis stabilised 10-kg nanosatellite is considered for a meteorological spacecraft (METSAT) mission at 800 km altitude. The initial case study SE parameters considered include the required payload power and spacecraft power and mass contingencies. The PSI method allows for a large-scale multicriteria optimisation of dynamic engineering systems. This was implemented in the multicriteria optimisation and vector investigation (MOVI) software. Specific power profiles for LEO satellites were used for the mathematical modelling of the highly adaptive nanosatellite (HAN) system in LEO. In the multicriteria optimisation process, 2765 design vectors entered the test table out of which 2762 formed the feasible solutions set. The PSI was conservatively designed to yield 10 pareto optimal solutions; a pareto optimal solution of 12.36 W for the payload subsystem yielded HAN mass and power margins of 1.84 kg and 2.37 W respectively. From the analysis, the solar array capability was found to deliver 24.23 W for the mission; this forms the beginning-of-life design point. The actual on-orbit mass of the HAN system (with enhanced capabilities including post-mission reuse) was found to be 9.2 kg as opposed to a conventional 10-kg nanosat implementation. The findings serve to eliminate undue space-borne equipment oversizing and advance the state-of-the-art in the conceptual design of future-generations spacecraft at the subsystem and system levels. Adaptive space systems promise to enable capability-based, dynamic, costeffective, reliable, multifunctional, multipurpose and optimal-performing space systems with recourse to post-mission re-applications. Furthermore, the PSI-MO results show that HASS architectures can be extended to implement higher satellite generation missions with economies of scale.