Professor Craig Underwood

Research Interests

• Radiation Environment & Effects (Cosmic Rays, Van Allan Belts, Space Weather, Atmospheric Radiation)
• Remote Sensing Instrumentation (UV-VIS-NIR multi- and hyper-spectral imaging, Thermal IR imaging, UV-VIS-NIR radiometry and SWIR atmospheric spectroscopy, low-power SAR Radar, GNSS Reflectometry)
• Micro-Nano-Satellite Technologies (SNAP, PalmSat, AAReST, RDV and Docking Systems)
• Planetary Exploration (Mars VTOL Aerobot, Ramon Spectroscopy)
• Space Power Systems (Supercapcitors, Thin-Film Solar PV, RTGs, solar-thermal power)
PhD Topics are available in any of these or related areas.


The Group's personnel and their research interests can be seen here.


Craig heads the Environments and Instrumentation Group within the Surrey Space Centre, which has the remit of developing the instruments, systems and data processing techniques needed to investigate the Earth and other planetary environments from space. A particular focus of the group is on the development of low-mass, low-volume and low-power “micro-instrumentation” suitable for use on micro/nano-satellite technology platforms. Current research activities include the analysis of the space and atmospheric radiation environments and their effects on commercial-off-the-shelf (COTS) avionic technologies; the development of miniaturised instrumentation for ionising-radiation detection, UV-VIS-NIR and thermal-IR satellite remote sensing; micro-satellite-based radar imaging; a Mars VTOL unpopulated micro-air-vehicle, and micro-nano-satellite technologies.

 

Radiation Environment & Effects
Over the past 25 years Craig has gained considerable expertise in understanding the space radiation environment and its effects in low, medium and high Earth orbit (out to 60,000 km). The deleterious effects of the ionising radiation environment is of particular concern when using COTS technologies in space, thus, particular emphasis has been given to a programme of monitoring “space weather” in terms of the high energy proton and heavy-ion cosmic-ray environment these spacecraft encounter, and to observing and analysing its effects – particularly with regard to single-event effects - upon the COTS devices on-board. The extended period of research has enabled a wide variety of conditions to be observed ranging across an entire solar cycle, and standard models to be verified or challenged. He was the first to show clearly the effect of the SAA trapped proton environment on COTS memories operating in LEO (UoSAT-2), and through his work with QinetiQ using the QinetiQ’s CREDO (UoSAT-3) and his own CRE (KITSAT-1, PoSAT-1) instruments has shown the limitations of the AP8 and CREME models. He is now performing similar work for the MEO environment through the analysis of flight data from Surrey’s CEDEX and QinetiQ’s MERLIN payloads flown on GIOVE-A. It has recently delivered two miniaturised radiation monitors (MuREM, RM) for the UK’s TechDemoSat-1 mission, launched in 2014. These payloads comprise solid-state (RadFET) dosimeters, ionizing dose-rate-diode detectors, and PIN-diode –based multi-channel analysers for measuring proton and heavy-ion LET spectra. The work has also been applied to the aerospace sector via the SPACERANE project.


Remote Sensing Instrumentation
Optical: Craig has had a long-term interest in remote sensing instrumentation design: He developed stratospheric ozone monitoring UV radiometers for the FASAT-Alfa (1995) and FASAT-Bravo (1998) satellites, and an ultra-compact Earth-observation CMOS video camera for the Thai Paht (1998) satellite. He also provided the pre-flight optical and radiometric calibration of the tri-band (NIR, Red, Green) imaging sensors for the Disaster Monitoring Constellation (DMC) Satellites: AlSAT-1 (2002, UK-DMC (2003) and NigeriaSat (2003).
With his PhD students, Craig has developed prototype designs for a micro-bolometer array-based thermal-IR imager (B.  Olerich, 2005) and for a UV spectrometer for monitoring volcanic plumes (SO2) and ozone (J. Fernandez-Saldivar, 2008).  He has a strong interest in the application of Spatial Heterodyne Spectroscopy (SHS) and, through PhD studies, has applied this technique to an ultra-compact Ramon spectrometer for the analysis of Martian rocks (T. Nathanial,2011) and to the SWIR detection and measurement of atmospheric CO2 (I. Ikpaya, 2013). He is also interested in compact hyperspecteral instruments for micro-sat and UAV application.


Radar: He has proposed a bistatic Synthetic Aperture Radar (SAR) imaging concept for micro-satellites (2000) and, through PhD programmes, has developed the concept of applying low-power CWFM bi-static and mono-static SAR to micro-sat platforms (~100-150kg) (O. Mitchell, 2001; T. Wanwiwake, 2011; N. Ahmed, 2012; A. Cai, 2013). He also worked on the airborne demonstrator for the NovaSAR S-Band SAR (2010).
He has also supported PhD research into GNSS Reflectometry (P. Jales, 2013; E. Simons, 2014;  J. Tye); Image Data Compression (P. Hou, 1999); Machine Vision for Pose and Relative Orbit estimation (A. Cropp, 2001); and working with the National Physical Laboratory is researching Vicarious Calibration/Validation of Remote Sensing Instruments and Radiometric Uncertainty modelling (A. Bialek, J. Gorrono).
Micro-Nano-Satellite Technologies.


Craig began Surrey's nano-satellite activities in 1995, through setting and supervising a series of student projects aimed at developing a "soccer ball" sized spacecraft. As Chief Architect of the SNAP concept, he played a pioneering role in developing the UK’s first operational nano-satellite, SNAP-1, Surrey's 6.5 kg nano-satellite, launched in June 2000, which carried out experiments in autonomous orbital manoeuvring and remote inspection of other spacecraft. For his work on SNAP, Craig and the Surrey Space Centre achieved the award of “Finalist” in the 2001 Flight International Awards in the Space and Missiles Category. He subsequently developed the PalmSat, ~1kg pico-satellite concept in 2000, designed to play a similar rôle, and he is currently the UK PI for the AAReST multiple-mirror space telescope demonstrator concept, working with CalTech/NASA-JPL, where he is also developing a novel electro-magnetic rendezvous and docking system. AAReST is designed to demonstrate the autonomous in-orbit construction of a space telescope using multiple-mirror elements, which can change shape to form a coherent optical surface. Craig has also worked on Super-Capacitor based power systems (T. Shimizu, 2013); Thin-film solar PV systems; data-handling and RF systems (V.Asenek, 1998; S. Maqbool, 2006).
Planetary Exploration


Away from orbit, Craig is working on a vertical take-off and landing (VTOL) “flying wing” aerobot concept for the exploration of Mars (J. Fielding, 2004; H. Song, 2008; W. Zhao, 2013; N. Collins, current). He has also worked on studies for Lunar microsatellite missions, spaceborne radio astronomy, Mars sample returns and NEO investigations,

Teaching

Over the last 30 years, Craig has played a key role in developing and teaching Surrey's Spacecraft Engineering post-graduate, undergraduate and industrial-training courses. He was the recipient of the Department of Electrical and Electronic Engineering’s Tony Jeans Inspirational Teaching Prize, 2013. Currently he teaches:


• Level 1 (FHEQ 4) Mathematics
• Level 2 (FHEQ 5) Space Engineering and Mission Design
• Level 3 (FHEQ 6) Space Systems Design
• Level M (FHEQ 7) Spacecraft Systems Design
• Level M (FHEQ 7) Launch Vehicles and Propulsion
• Level M (FHEQ 7) Space Environment and Protection
• Short Course: Spacecraft Systems Design

Contact Me

E-mail:
Phone: 01483 68 9809

Find me on campus
Room: BA U

Publications

Highlights

  • Bridges CP, Taylor B, Horri N, Underwood CI, Kenyon S, Barrera-Ars J, Pryce L, Bird R. (2013) 'STRaND-2: Visual Inspection, Proximity Operations & Nanosatellite Docking'. Big Sky, MT USA: IEEE/AIAA Aerospace Conference 2013
  • Taylor BO, Underwood CI, Vacanti G, Maddox E. (2011) 'The Interplanetary Electron Model (IEM)'. IEEE IEEE Transactions on Nuclear Science, Las Vegas, NV, USA: NSREC 2011 6 (58), pp. 2785-2792.

    Abstract

    A new Interplanetary electron environment model based on statistical analyses of historical datasets is presented. The model reports generates confidence limits for solar electron fluences in a similar fashion to existing Solar proton models, as well as peak event fluxes and fluences. Electrons of Jovian origin are also modeled based on simplified diffusive transport equations to provide predicted fluxes for locations within the ecliptic plane.

  • Bridges CP, Kenyon S, Underwood CI, Sweeting MN. (2011) 'STRaND: Surrey Training Research and Nanosatellite Demonstrator'. International Academy of Astronautics Proceedings of the1st IAA Conference on University Satellite Missions and CubeSat Workshop, Rome, Italy: 1st IAA Conference on University Satellite Missions and CubeSat Workshop
  • Taylor B, Underwood CI, Ryden KA, Morris PA. (2009) 'A GIOVE Derived Galileo Electron Spectrum and Comparison to Models'. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC IEEE TRANSACTIONS ON NUCLEAR SCIENCE, Quebec City, CANADA: 56 (6), pp. 3423-3428.
  • Taylor B, Underwood C, Evans HDR, Daly E, Ryden KA, Santin G. (2008) 'Galileo GIOVE-A MEORAD Results and Analysis'. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 55 (6), pp. 3151-3157.
  • Ryden KA, Morris PA, Ford KA, Hands ADP, Dyer CS, Taylor B, Underwood CI, Rodgers DJ, Mandorlo G, Gatti G, Evans HDR, Daly EJ. (2008) 'Observations of Internal Charging Currents in Medium Earth Orbit'. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC IEEE TRANSACTIONS ON PLASMA SCIENCE, 36 (5), pp. 2473-2481.
  • Wang R, Crocombe AD, Richardson G, Underwood CI. (2008) 'Energy dissipation in spacecraft structures incorporating bolted joints operating in macroslip'. ASCE-AMER SOC CIVIL ENGINEERS JOURNAL OF AEROSPACE ENGINEERING, 21 (1), pp. 19-26.

Journal articles

  • Lamb D, Underwood C, Barrioz V, Gwilliam R, Hall J, Baker M, Irvine S. (2017) 'Proton Irradiation of CdTe Thin Film Photovoltaics Deposited on Cerium-Doped Space Glass'. Wiley Progress in Photovoltaics, 25 (12), pp. 1059-1067.

    Abstract

    Space photovoltaics is dominated by multi-junction (III-V) technology. However, emerging applications will require solar arrays with; high specific power (kW/kg), flexibility in stowage and deployment and a significantly lower cost than the current III-V technology offers. This research demonstrates direct deposition of thin film CdTe onto the radiation-hard cover glass that is normally laminated to any solar cell deployed in space. Four CdTe samples, with 9 defined contact device areas of 0.25 cm2, were irradiated with protons of 0.5 MeV energy and varying fluences. At the lowest fluence, 1×1012 cm-2, the relative efficiency of the solar cells was 95%. Increasing the proton fluence to 1×1013 cm-2 and then 1×1014 cm-2 decreased the solar cell efficiency to 82% and 4% respectively. At the fluence of 1×1013 cm-2, carrier concentration was reduced by an order of magnitude. Solar Cell Capacitance Simulator (SCAPS) modelling obtained a good fit from a reduction in shallow acceptor concentration with no change in the deep trap defect concentration. The more highly irradiated devices resulted in a buried junction characteristic of the external quantum efficiency, indicating further deterioration of the acceptor doping. This is explained by compensation from interstitial H+ formed by the proton absorption. An anneal of the 1×1014 cm-2 fluence devices gave an efficiency increase from 4% to 73% of the pre-irradiated levels, indicating that the compensation was reversible. CdTe with its rapid recovery through annealing, demonstrates a radiation hardness to protons that is far superior to conventional multi-junction III-V solar cells.

  • Lamb D, Underwood C, Barrioz V, Gwilliam R, Hall J, Baker M, Irvine S. (2017) 'Proton irradiation of CdTe thin film photovoltaics deposited on cerium‐doped space glass'. Wiley Progress in Photovoltaics, 25 (12), pp. 1059-1067.

    Abstract

    Space photovoltaics is dominated by multi‐junction (III‐V) technology. However, emerging applications will require solar arrays with high specific power (kW/kg), flexibility in stowage and deployment, and a significantly lower cost than the current III‐V technology offers. This research demonstrates direct deposition of thin film CdTe onto the radiation‐hard cover glass that is normally laminated to any solar cell deployed in space. Four CdTe samples, with 9 defined contact device areas of 0.25 cm2, were irradiated with protons of 0.5‐MeV energy and varying fluences. At the lowest fluence, 1 × 1012 cm−2, the relative efficiency of the solar cells was 95%. Increasing the proton fluence to 1 × 1013 cm−2 and then 1 × 1014 cm−2 decreased the solar cell efficiency to 82% and 4%, respectively. At the fluence of 1 × 1013 cm−2, carrier concentration was reduced by an order of magnitude. Solar Cell Capacitance Simulator (SCAPS) modelling obtained a good fit from a reduction in shallow acceptor concentration with no change in the deep trap defect concentration. The more highly irradiated devices resulted in a buried junction characteristic of the external quantum efficiency, indicating further deterioration of the acceptor doping. This is explained by compensation from interstitial H+ formed by the proton absorption. An anneal of the 1 × 1014 cm−2 fluence devices gave an efficiency increase from 4% to 73% of the pre‐irradiated levels, indicating that the compensation was reversible. CdTe with its rapid recovery through annealing demonstrates a radiation hardness to protons that is far superior to conventional multijunction III‐V solar cells.

  • Gorrono J, Banks A, Fox N, Underwood CI. (2017) 'Radiometric inter-sensor cross-calibration uncertainty using a traceable high accuracy reference hyperspectral imager'. Elsevier ISPRS Journal of Photogrammetry and Remote Sensing, 130, pp. 393-417.

    Abstract

    Optical earth observation (EO) satellite sensors generally suffer from drifts and biases relative to their pre-launch calibration, caused by launch and/or time in the space environment. This places a severe limitation on the fundamental reliability and accuracy that can be assigned to satellite derived information, and is particularly critical for long time base studies for climate change and enabling interoperability and Analysis Ready Data. The proposed TRUTHS (Traceable Radiometry Underpinning Terrestrial and Helio-Studies) mission is explicitly designed to address this issue through re-calibrating itself directly to a primary standard of the international system of units (SI) in-orbit and then through the extension of this SI-traceability to other sensors through in-flight cross-calibration using a selection of Committee on Earth Observation Satellites (CEOS) recommended test sites. Where the characteristics of the sensor under test allows, this will result in a significant improvement in accuracy. This paper describes a set of tools, algorithms and methodologies that have been developed and used in order to estimate the radiometric uncertainty achievable for an indicative target sensor through in-flight cross-calibration using a well-calibrated hyperspectral SI-traceable reference sensor with observational characteristics such as TRUTHS. In this study, Multi-Spectral Imager (MSI) of Sentinel-2 and Landsat-8 Operational Land Imager (OLI) is evaluated as an example, however the analysis is readily translatable to larger-footprint sensors such as Sentinel-3 Ocean and Land Colour Instrument (OLCI) and Visible Infrared Imaging Radiometer Suite (VIIRS). This study considers the criticality of the instrumental and observational characteristics on pixel level reflectance factors, within a defined spatial region of interest (ROI) within the target site. It quantifies the main uncertainty contributors in the spectral, spatial, and temporal domains. The resultant tool will support existing sensor-to-sensor cross-calibration activities carried out under the auspices of CEOS, and is also being used to inform the design specifications for TRUTHS.

  • Gorrono J, Fomferra N, Peters M, Gascon F, Underwood CI, Fox N, Kirches G, Brockmann C. (2017) 'A Radiometric Uncertainty Tool for the Sentinel 2 Mission'. MDPI AG Remote Sensing, 9 (178)

    Abstract

    In the framework of the European Copernicus programme, the European Space Agency (ESA) has launched the Sentinel-2 (S2) Earth Observation (EO) mission which provides optical high spatial resolution imagery over land and coastal areas. As part of this mission, a tool (named S2-RUT, from Sentinel-2 Radiometric Uncertainty Tool) has been developed. The tool estimates the radiometric uncertainty associated with each pixel in the top-of-atmosphere (TOA) reflectance factor images provided by ESA. This paper describes the design and development process of the initial version of the S2-RUT tool. The initial design step describes the S2 radiometric model where a set of uncertainty contributors are identified. Each of the uncertainty contributors is specified by reviewing the preand post-launch characterisation. The identified uncertainty contributors are combined following the guidelines in the ‘Guide to Expression of Uncertainty in Measurement’ (GUM) model and this combination model is further validated by comparing the results to a multivariate Monte Carlo Method (MCM). In addition, the correlation between the different uncertainty contributions and the impact of simplifications in the combination model have been studied. The software design of the tool prioritises an efficient strategy to read the TOA reflectance factor images, extract the auxiliary information from the metadata in the satellite products and the codification of the resulting uncertainty image. This initial version of the tool has been implemented and integrated as part of the Sentinels Application Platform (SNAP).

  • Hands A, Lei F, Ryden KA, Dyer C, Underwood CI, Mertens C. (2016) 'New Data and Modelling for Single Event Effects in the Stratospheric Radiation Environment'. IEEE IEEE Transactions on Nuclear Science, 64 (1), pp. 587-595.

    Abstract

    The upper atmosphere is a transition region between the neutron-dominated aviation environment and satellite environment where primary protons and ions dominate. We report high altitude balloon measurements and model results characterising this radiation environment for single event effects (SEE) in avionics. Our data, from the RaySure solid-state radiation monitor, reveal markedly different altitude profiles for low linear energy transfer (LET) and high LET energy depositions. We use models to show that the difference is caused by the influence of primary cosmic ray particles, which induce counts in RaySure via both direct and indirect ionization. Using the new Model of Atmospheric Ionizing Radiation Effects (MAIRE), we use particle fluxes and LET spectra to calculate single event upset (SEU) rates as a function of altitude from ground level to the edge of space at 100 km altitude. The results have implications for a variety of applications including high altitude space tourism flights, UAVs and missions to the Martian surface.

  • Lamb DA, Irvine SJC, Clayton AJ, Kartopu G, Barrioz V, Hodgson SD, Baker MA, Grilli R, Hall J, Underwood CI, Kimber R. (2016) 'Characterization of MOCVD Thin-Film CdTe Photovoltaics on Space-Qualified Cover Glass'. IEEE IEEE Journal of Photovoltaics, 6 (2), pp. 557-561.

    Abstract

    This paper details the AM0 conversion efficiency of a metal-organic chemical vapor phase deposition thin-film cadmium telluride (CdTe) solar cell deposited onto a cerium-doped cover glass (100 μm). An AM0 best cell conversion efficiency of 12.4% (0.25-cm2 contact area) is reported. An AM0 mean efficiency of 12.1% over eight cells demonstrated good spatial uniformity. Excellent adhesion of the cell structure to the cover glass was observed with an adhesive strength of 38 MPa being measured before cohesive failure of the test adhesive. The device structure on cover glass was also subject to severe thermal shock cycling of +80 °C to -196 °C, showing no signs of delamination and no deterioration of the photovoltaic (PV) performance.

  • Hands A, Ryden K, Underwood C, Rodgers D, Evans H. (2015) 'A New Model of Outer Belt Electrons for Dielectric Internal Charging (MOBE-DIC)'. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 62 (6), pp. 2767-2775.
  • Underwood C, Pellegrino S, Lappas VJ, Bridges CP, Baker J. (2015) 'Using CubeSat/micro-satellite technology to demonstrate the Autonomous Assembly of a Reconfigurable Space Telescope (AAReST)'. PERGAMON-ELSEVIER SCIENCE LTD ACTA ASTRONAUTICA, 114, pp. 112-122.
  • Lamb DA, Irvine SJC, Clayton AJ, Barrioz V, Kartopu G, Baker MA, Underwood CI, Grilli R, Kimber R, Hall J. (2015) 'Lightweight and low-cost thin film photovoltaics for large area extra-terrestrial applications'. INST ENGINEERING TECHNOLOGY-IET IET RENEWABLE POWER GENERATION, 9 (5), pp. 420-423.
  • Ryden KA, Hands ADP, Underwood CI, Rodgers DJ. (2015) 'Internal Charging Measurements in Medium Earth Orbit Using the SURF Sensor: 2005-2014'. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC IEEE TRANSACTIONS ON PLASMA SCIENCE, 43 (9), pp. 3014-3020.
  • Zhao W, Underwood C. (2014) 'Robust transition control of a Martian coaxial tiltrotor aerobot'. PERGAMON-ELSEVIER SCIENCE LTD ACTA ASTRONAUTICA, 99, pp. 111-129.
  • Maqsood, M, Gao S, Brown TWC, Unwin M, de vos Van Steenwijk R, Xu JD, Underwood CI. (2014) 'Low-Cost Dual-Band Circularly Polarized Switched-Beam Array for Global Navigation Satellite System'. IEEE Transactions on Antennas and Propagation, 62 (4), pp. 1-8.

    Abstract

    This paper presents the design and development of a dual-band switched-beam microstrip array for Global Navigation Satellite System (GNSS) applications such as ocean reflectometry and remote sensing. In contrast to the traditional Butler matrix, a simple, low cost, broadband and low insertion loss beam switching feed network is proposed, designed and integrated with a dual band antenna array to achieve continuous beam coverage of ±25° around the boresight at the L1 (1.575 GHz) and L2 (1.227 GHz) bands. To reduce the cost, microstrip lines and PIN diode based switches are employed. The proposed switched beam network is then integrated with dual-band step-shorted annular ring (S-SAR) antenna elements in order to produce a fully integrated compact-sized switched beam array. Antenna simulation results show that the switched beam array achieves a maximum gain of 12 dBic at the L1 band and 10 dBic at the L2 band. In order to validate the concept, a scaled down prototype of the simulated design is fabricated and measured. The prototype operates at twice of the original design frequency i.e. 3.15 GHz and 2.454 GHz and the measured results confirm that the integrated array achieves beam switching and good performance at both bands.

  • Shimizu T, Underwood C. (2013) 'Super-capacitor energy storage for micro-satellites: Feasibility and potential mission applications'. PERGAMON-ELSEVIER SCIENCE LTD ACTA ASTRONAUTICA, 85, pp. 138-154.
  • Cai A, Underwood C, Sweeting MN. (2013) 'Height reduction using mutual coupling for the multimode horn phased array'. 2013 7th European Conference on Antennas and Propagation, EuCAP 2013, , pp. 3585-3589.
  • Taylor B, Underwood C, Dyer A, Ashton C, Rason S, Browning J. (2012) 'The micro radiation environment monitor (MuREM) and SSTL radiation monitor (SSTL RM) on TechDemoSat-1'. IEEE Transactions on Nuclear Science, 59 (4 PART 1), pp. 1060-1065.

    Abstract

    Two new miniaturized scientific radiation monitoring payloads are presented prior to their first flight on the TechDemoSat-1 Spacecraft. They are capable of monitoring the space radiation environment and its effects on radiation-sensitive devices. Micro radaion environment monitor (MuREM) and Surrey Satellite Technology radiation monitor (SSTL RM) carry RADFET dosimeters, dose-rate-sensitive photodiodes, and p-i-n diode particle detectors. SSTL RM is also connected to external RADFET sensors placed around the spacecraft, while MuREM carries a radiation effects payload consisting of COTS devices that will be monitored while exposed to the space radiation environment. © 2012 IEEE.

  • Di Bari R, Brown TWC, Gao S, Underwood C. (2011) 'Dual-Polarized Printed S-Band Radar Array Antenna for Spacecraft Applications'. IEEE IEEE Antennas and Wireless Propagation Letters, 10, pp. 987-990.

    Abstract

    A novel dual-polarized broadband antenna array for S-band is presented. This antenna is composed of 6 × 2 microstrip antenna elements with a hybrid feed-line network providing an isolation ≥ 18.6 dB between the H- and V-ports. The operative bandwidth is from 3.15 to 3.25 GHz, and the peak measured gain is approximately 19 dBi. The array is suitable for spacecraft operation because of the selected materials, its low profile (~8 mm thickness), and light weight. It has potential applications in synthetic aperture radar (SAR), remote sensing, and wireless communications.

  • Di Bari R, Brown T, Gao S, Notter M, Hall D, Underwood C. (2011) 'Dual-Polarized Printed S-Band Radar Array Antenna for Spacecraft Applications'. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS, 10, pp. 987-990.
  • Gao S, Clark K, Unwin M, Zackrisson J, Shiroma WA, Akagi JM, Maynard K, Garner P, Boccia L, Amendola G, Massa G, Underwood C, Brenchley M, Pointer M, Sweeting MN. (2009) 'Antennas for Modern Small Satellites'. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC IEEE ANTENN PROPAG M, 51 (4), pp. 40-56.
  • Taylor B, Underwood CI, Ryden KA, Morris PA. (2009) 'A GIOVE Derived Galileo Electron Spectrum and Comparison to Models'. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC IEEE TRANSACTIONS ON NUCLEAR SCIENCE, Quebec City, CANADA: 56 (6), pp. 3423-3428.
  • Taylor B, Underwood C, Evans HDR, Daly E, Ryden KA, Santin G. (2008) 'Galileo GIOVE-A MEORAD Results and Analysis'. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 55 (6), pp. 3151-3157.
  • Ryden KA, Morris PA, Ford KA, Hands ADP, Dyer CS, Taylor B, Underwood CI, Rodgers DJ, Mandorlo G, Gatti G, Evans HDR, Daly EJ. (2008) 'Observations of Internal Charging Currents in Medium Earth Orbit'. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC IEEE TRANSACTIONS ON PLASMA SCIENCE, 36 (5), pp. 2473-2481.
  • Wang R, Crocombe AD, Richardson G, Underwood CI. (2008) 'Energy dissipation in spacecraft structures incorporating bolted joints with viscoelastic layers'. PROFESSIONAL ENGINEERING PUBLISHING LTD PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART G-JOURNAL OF AEROSPACE ENGINEERING, 222 (G2), pp. 201-211.
  • Wang R, Crocombe AD, Richardson G, Underwood CI. (2008) 'Energy dissipation in spacecraft structures incorporating bolted joints operating in macroslip'. ASCE-AMER SOC CIVIL ENGINEERS JOURNAL OF AEROSPACE ENGINEERING, 21 (1), pp. 19-26.
  • Taylor B, Underwood C, Evans HDR, Ryden K, Rodgers D, Daly EJ, Mandorlo G, Falcone M, Morris PA, Prieto RG. (2007) 'Results from the Galileo giove - A radiation monitors and comparison with existing radiation belt models'. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC IEEE TRANSACTIONS ON NUCLEAR SCIENCE, Athens, GREECE: 54 (4), pp. 1076-1081.
  • Crocombe AD, Wang R, Richardson G, Underwood CI. (2006) 'Estimating the energy dissipated in a bolted spacecraft at resonance'. PERGAMON-ELSEVIER SCIENCE LTD COMPUTERS & STRUCTURES, 84 (5-6), pp. 340-350.

Conference papers

  • Ahmad G, Brown T, Underwood C, Loh T. (2017) 'Millimetre Wave Reflectarray Antenna Unit Cell Measurements'. Institution of Engineering and Technology LAPC 2017 Proceedings, Loughborough, UK: The Loughborough Antennas & Propagation Conference (LAPC 2017)
    [ Status: Accepted ]

    Abstract

    Reflectarray antennas are a potential candidate solution to realize high gains at millimetre waves (mm-waves). A reflectarray contains a large number of spatially illuminated unit cells. The performance of a good reflectarray design is manifested by the behaviour of its comprising unit cells. An established technique to characterise a unit cell is by placing it inside a waveguide to achieve periodic boundary conditions. This usually requires custom waveguide products; making the tests difficult and expensive. Additionally, when the unit cells are reconfigurable as in a smart reflectarray it is hard to take the DC bias lines out of the waveguide without using custom made waveguide parts. This contribution address the issue of unit cell placement inside the waveguide and proposes simple unit cell structures to avoid custom made waveguide parts. The idea was verified by measuring a series of unit cells at mm-waves in various configurations and a practically acceptable agreement was found. The proposed structures greatly simplify the reconfigurable unit cell testing.

  • Ahmad G, Underwood C, Brown T, Loh T. (2017) 'Role of Surface Waves in Improving the Reflection Properties of a Millimetre Wave Reflectarray Unit Cell'. The Institution of Engineering and Technology LAPC 2017 Proceedings, Loughborough, UK: The Loughborough Antennas & Propagation Conference (LAPC 2017)
    [ Status: Accepted ]

    Abstract

    A steady increasing trend towards millimetre waves (mm-waves) for next generation communication has initiated an intensive research in the field of mm-wave antenna technologies. Reflectarray antennas being one of the potential candidates offer significant advantages over parabolic and phased array antennas at mm-wave bands. In a well-designed reflectarray, the overall performance is mainly determined by its comprising unit cell(s). Most of the recent reflectarray designs are based on printed microstrip technology. It is well known that surface waves get generated in printed microstrip technology and contribute to loss in the radiated signal power in the intended direction. This paper analyses the effect of surface waves in the reflection properties of a printed microstrip millimetre wave reflectarray unit cell. The analytical results are compared with measured data at 32 GHz and an excellent agreement was observed. It was observed that surface waves, though generally considered to have malign effects in antennas, play a significant positive role in the reduction of reflection loss magnitude at unit cell level.

  • Taylor BO, Duke R, Stewart B, Massimiani C, Djamane F, Bridges CP, Aglietti GS, Lassakeur A, Amine Ouisb M, Cherif Ladouze M, Meftah K, Underwood CI, Chikouche A, Hamed D. (2017) 'AlSat-Nano: Knowledge Transfer to Operational Partnership'. International Astronautical Federation 68th International Astronautical Congress Proceedings, Adelaide, Australia: 68th International Astronautical Congress (IAC)

    Abstract

    The AlSat-Nano mission is a joint endeavour by the UK and Algeria to build and operate a 3U CubeSat. The project was designed to provide training to Algerian students, making use of UK engineering and experience. The CubeSat was designed and built by the Surrey Space Centre (SSC) of the University of Surrey and hosts three UK payloads with operations run by the Algerian Space Agency (ASAL). The educational and CubeSat development were funded by the UK Space Agency (UKSA), whilst the UK payloads were self-funded. Launch and operations are funded by ASAL. This paper illustrates the development of the programme, the engineering of the satellite and the development of collaborative operations between the SSC and ASAL.

  • Ahmad G, Loh T, Brown TWC, Underwood CI. (2017) 'On the Phase Selection of Millimeter Wave Quantized Reflectarrays'. IEEE Proceedings of the 2017 International Applied Computational Electromagnetics Society Symposium, National University of Singapore Suzhou Research Institute, Suzhou, China: 2017 International Applied Computational Electromagnetics Society Symposium

    Abstract

    Microstrip printed reflectarrays are becoming a potential replacement of parabolic reflector and phased array antennas due to their simple design, low cost and ease of manufacture to attain high gain and wide angle beam pointing at millimeter waves (mm-waves). Significant challenges are faced while implementing continuous phase reflectarrays at mm-waves. However, discretizing the required reflection phase provides a practically implementable solution. This contribution addresses the selection of phase states and its scattering in a phase discretized mm-wave reflectarray. The performance of two 1.5 bit phase quantized reflectarrays having closely spaced geometrical features is analyzed at 60 GHz. This study provides a better understanding to achieve a wider bandwidth response in practically implementable mm-wave reflectarrays.

  • Eckersley S, Saunders C, Lobb D, Johnston G, Baud T, Sweeting MN, Underwood CI, Bridges CP, Chen R. (2017) 'Future Rendezvous and Docking Missions enabled by low-cost but safety compliant Guidance Navigation and Control (GNC) architectures'. British Interplanetary Society Proceedings of The 15th Reinventing Space Conference, Strathclyde University Technology & Innovation Centre, Glasgow, Scotland: The 15th Reinventing Space Conference, 24-26 October 2017, Glasgow, Scotland

    Abstract

    Proximity flight systems for rendezvous-and-docking, are traditionally the domain of large, costly institutional manned missions, which require extremely robust and expensive Guidance Navigation and Control (GNC) solutions. By developing a low-cost and safety compliant GNC architecture and design methodology, low cost GNC solutions needed for future missions with proximity flight phases will have reduced development risk, and more rapid development schedules. This will enable a plethora of on-orbit services to be realised using low cost satellite technologies, and lower the cost of the services to a point where they can be offered to commercial as well as institutional entities and thereby dramatically grow the market for on-orbit construction, in-orbit servicing and active debris removal. It will enable organisations such as SSTL to compete in an area previously exclusive to large institutional players. The AAReST mission (to be launched in 2018), will demonstrate some key aspects of low cost close proximity “co-operative” rendezvous and docking (along with reconfiguration/control of multiple mirror elements) for future modular telescopes. However this is only a very small scale academic mission demonstration using cubesat technology, and is limited to very close range demonstrations. This UK National Space Technology Programme (NSTP-2) project, which is being carried out by SSTL and SSC, is due to be completed by the end of November 2017 and is co-funded by the UK Space Agency and company R&D. It is aiming to build on the AAReST ("Autonomous Assembly of a Reconfigurable Space Telescope") mission (where appropriate), and industrialise existing research, which will culminate in a representative model that can be used to develop low-cost GNC solutions for many different mission applications that involve proximity activities, such as formation flying, and rendezvous and docking. The main objectives and scope of this project are the following:  Definition of a reference mission design (based on a scenario that SSTL considers credible as a realistic scenario) and mission/system GNC requirements.  Develop a GNC architectural design for low cost missions applications that involve close proximity formation flying, rendezvous and docking (RDV&D) - i.e. “proximity activities”  Develop a low cost sensor suite suitable for use on proximity missions  Consider possible regulatory constraints that may apply to the mission The SSTL/SSC reference mission concept is a

  • Ahmad G, Brown TWC, Underwood CI, Loh T. (2017) 'An efficient algorithm for electrically large reflectarray antenna design automation'. IEEE Proceedings of the 2017 International Workshop on Electromagnetics: Applications and Student Innovation Competition, London, United Kingdom: 2017 International Workshop on Electromagnetics: Applications and Student Innovation Competition, pp. 133-134.

    Abstract

    Reflectarrays are becoming a potentially attractive replacement of parabolic reflectors for high gain requirements. A large reflectarray consists of thousands of elements. To predict their performance a simulation model is required which is very cumbersome to build manually due to a large number of elements. It takes exhaustive efforts, keen attention to details and significant amount of time to build such a simulation model. When several iterations of modelling are required it worsens the issue even further. We have presented here an algorithm as an automated solution to this problem by interfacing Matlab® with an electromagnetic simulation software. It is very generic, time efficient and makes the modelling easy with least intervention of the designer.

  • Ahmad G, Brown TWC, Underwood CI, Loh T. (2017) 'How coarse is too coarse in electrically large reflectarray smart antennas?'. IEEE Proceedings of the 2017 International Workshop on Electromagnetics: Applications and Student Innovation Competition, London, United Kingdom: 2017 International Workshop on Electromagnetics: Applications and Student Innovation Competition, pp. 135-137.

    Abstract

    Millimeter wave (mm-wave) bands are becoming potentially attractive candidates for next generation communication systems. It is envisioned that high gain smart antennas will be one of the key enabling technologies for such systems. At mm-wave bands, where electrical size of an individual antenna becomes very small, the inclusion of a reconfigurable mechanism in the antenna becomes a great challenge due to real estate constraints. In these scenarios a designer has to decide on the number of bits in a phase shifter for antenna beam steering which will result in an optimum design. This contribution addresses the issue of phase quantization in mm-wave high gain reflectarray smart antennas to achieve an optimum performance. Implementing coarse phase quantization greatly reduces the complexity at mm-wave bands. A case study is presented to highlight the effects of coarse phase quantization using various numbers of bits.

  • Gorrono J, Banks A, Gascon F, Fox N, Underwood CI. (2016) 'Novel techniques for the analysis of the TOA radiometric uncertainty'. Proceedings of SPIE, Edinburgh, United Kingdom: SPIE Conference on SECURITY+DEFENCE AND REMOTE SENSING
    [ Status: Accepted ]

    Abstract

    In the framework of the European Copernicus programme, the European Space Agency (ESA) has launched the Sentinel-2 (S2) Earth Observation (EO) mission which provides optical high spatial -resolution imagery over land and coastal areas. As part of this mission, a tool (named S2-RUT, from Sentinel-2 Radiometric Uncertainty Tool) estimates the radiometric uncertainties associated to each pixel using as input the top-of-atmosphere (TOA) reflectance factor images provided by ESA. The initial version of the tool has been implemented — code and user guide available1 — and integrated as part of the Sentinel Toolbox. The tool required the study of several radiometric uncertainty sources as well as the calculation and validation of the combined standard uncertainty in order to estimate the TOA reflectance factor uncertainty per pixel. Here we describe the recent research in order to accommodate novel uncertainty contributions to the TOA reflectance uncertainty estimates in future versions of the tool. The two contributions that we explore are the radiometric impact of the spectral knowledge and the uncertainty propagation of the resampling associated to the orthorectification process. The former is produced by the uncertainty associated to the spectral calibration as well as the spectral variations across the instrument focal plane and the instrument degradation. The latter results of the focal plane image propagation into the provided orthoimage. The uncertainty propagation depends on the radiance levels on the pixel neighbourhood and the pixel correlation in the temporal and spatial dimensions. Special effort has been made studying non-stable scenarios and the comparison with different interpolation methods

  • Underwood CI, Pellegrino S, Lappas V, Bridges CP, Taylor BO, Chhaniyara S, Theodorou T, Shaw P, Arya M, Breckinridge J, Hogstrom K, Patterson K, Steeves J, Wilson L, Horri N. (2013) 'Autonomous Assembly of a Reconfigurable Space Telescope (AAReST) – A CubeSat/Microsatellite Based Technology Demonstrator'. American Institute of Aeronautics and Astronautics (AIAA) Proceedings of the 27th Annual AIAA/USU Conference on Small Satellites (SmallSat 2013), Logan, Utah, USA: 27th Annual AIAA/USU Conference on Small Satellites (SmallSat 2013)

    Abstract

    Future space telescopes with diameter over 20 m will require in-space assembly. High-precision formation flying has very high cost and may not be able to maintain stable alignment over long periods of time. We believe autonomous assembly is a key enabler for a lower cost approach to large space telescopes. To gain experience, and to provide risk reduction, we propose a demonstration mission to demonstrate all key aspects of autonomous assembly and reconfiguration of a space telescope based on multiple mirror elements. The mission will involve two 3U CubeSat-like nanosatellites (“MirrorSats”) each carrying an electrically actuated adaptive mirror, and each capable of autonomous un-docking and re-docking with a small central “9U” class nanosatellite core, which houses two fixed mirrors and a boom-deployed focal plane assembly. All three spacecraft will be launched as a single ~40kg microsatellite package.

  • Bridges CP, Taylor B, Horri N, Underwood CI, Kenyon S, Barrera-Ars J, Pryce L, Bird R. (2013) 'STRaND-2: Visual Inspection, Proximity Operations & Nanosatellite Docking'. Big Sky, MT USA: IEEE/AIAA Aerospace Conference 2013
  • Taylor BO, Underwood CI, Vacanti G, Maddox E. (2011) 'The Interplanetary Electron Model (IEM)'. IEEE IEEE Transactions on Nuclear Science, Las Vegas, NV, USA: NSREC 2011 6 (58), pp. 2785-2792.

    Abstract

    A new Interplanetary electron environment model based on statistical analyses of historical datasets is presented. The model reports generates confidence limits for solar electron fluences in a similar fashion to existing Solar proton models, as well as peak event fluxes and fluences. Electrons of Jovian origin are also modeled based on simplified diffusive transport equations to provide predicted fluxes for locations within the ecliptic plane.

  • Bridges CP, Kenyon S, Underwood CI, Sweeting MN. (2011) 'STRaND: Surrey Training Research and Nanosatellite Demonstrator'. International Academy of Astronautics Proceedings of the1st IAA Conference on University Satellite Missions and CubeSat Workshop, Rome, Italy: 1st IAA Conference on University Satellite Missions and CubeSat Workshop
  • Bridges C, Kenyon S, Underwood C, Lappas V. (2011) 'STRaND-1: The world's first smartphone nanosatellite'. 2nd International Conference on Space Technology, ICST 2011,
  • Ahmed N, Underwood CI. (2010) 'Software Defined LFM CW SAR Receiver for Microsatellites'. SPRINGER-VERLAG BERLIN SMALL SATELLITE MISSIONS FOR EARTH OBSERVATION, Berlin, GERMANY: 7th IAA International Symposium on Small Satellites for Earth Observation, pp. 311-320.
  • Smail S, Underwood CI. (2009) 'ELECTROMAGNETIC FLAT DOCKING SYSTEM FOR IN-ORBIT SELF-ASSEMBLY OF SMALL SPACECRAFT'. UNIVELT INC SPACEFLIGHT MECHANICS 2009, VOL 134, PTS I-III, Savannah, GA: AAS/AIAA 19th Space Flight Mechanics Meeting 134, pp. 173-183.
  • Saaj CM, Underwood CI, Noakes C, Park DWG, Moore T. (2008) 'The science and technology behind Galileo - Europe's GPS'. BRITISH INTERPLANETARY SOC JBIS-JOURNAL OF THE BRITISH INTERPLANETARY SOCIETY, London, ENGLAND: US/European/Asian Symposium of the British-Interplanetary-Society 61 (3), pp. 91-97.
  • Fernandez-Saldivar JA, Underwood CI, Mackin S. (2008) 'Comparison of atmospheric ozone measurements between NASA's Total Ozone Mapping Spectrometer (TOMS) and the FASAT-BRAVO Ozone Mapping Detector (OMAD)'. SPRINGER SMALL SATELLITES FOR EARTH OBSERVATION: SELECTED CONTRIBUTIONS, German Aerosp Ctr, Berlin, GERMANY: 6th IAA International Symposium on Small Satellites for Earth Observation, pp. 101-109.
  • Song H, Underwood C. (2007) 'A Mars VTOL aerobot - Preliminary design, dynamics and control'. IEEE 2007 IEEE AEROSPACE CONFERENCE, VOLS 1-9, Big Sky, MT: 2007 IEEE Aerospace Conference, pp. 204-217.
  • Fernandez-Saldivar JA, Underwood CI, Mackin S. (2007) 'Ozone depletion in the Austral spring from UV microsatellite instrument - art. no. 674503'. SPIE-INT SOC OPTICAL ENGINEERING REMOTE SENSING OF CLOUDS AND THE ATMOSPHERE XII, Florence, ITALY: Conference on Remote Sensing of Clouds and the Atmosphere XII 6745, pp. 74503-74503.
  • Fernandez-Saldivar JA, Underwood CI, Mackin S. (2006) 'Low-cost microsatellite UV instrument suite for monitoring ozone and volcanic sulphur dioxide'. SPIE-INT SOC OPTICAL ENGINEERING REMOTE SENSING OF CLOUDS AND THE ATMOSPHERE XI, Stockholm, SWEDEN: Conference on Remote Sensing of Clouds and the Atmosphere XI 6362

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