Publications by Karen Aplin

Comment on "a robust floating nanoammeter" [Rev. Sci. Instrum. 79, 126102 (2008)]

Review of Scientific Instruments 80 (2009)

KL Aplin, KL Smith

European Venus Explorer (EVE): An in-situ mission to Venus

Experimental Astronomy 23 (2009) 741-760

E Chassefière, O Korablev, T Imamura, KH Baines, CF Wilson, DV Titov, KL Aplin, T Balint, JE Blamont, CG Cochrane, C Ferencz, F Ferri, M Gerasimov, JJ Leitner, J Lopez-Moreno, B Marty, M Martynov, SV Pogrebenko, A Rodin, JA Whiteway, LV Zasova, J Michaud, R Bertrand, JM Charbonnier, D Carbonne, P Raizonville

The European Venus Explorer (EVE) mission was proposed to the European Space Agency in 2007, as an M-class mission under the Cosmic Vision Programme. Although it has not been chosen in the 2007 selection round for programmatic reasons, the EVE mission may serve as a useful reference point for future missions, so it is described here. It consists of one balloon platform floating at an altitude of 50-60 km, one descent probe provided by Russia, and an orbiter with a polar orbit which will relay data from the balloon and descent probe, and perform science observations. The balloon type preferred for scientific goals is one which oscillates in altitude through the cloud deck. To achieve this flight profile, the balloon envelope contains a phase change fluid, which results in a flight profile which oscillates in height. The nominal balloon lifetime is 7 days-enough for one full circumnavigation of the planet. The descent probe's fall through the atmosphere takes 60 min, followed by 30 min of operation on the surface. The key measurement objectives of EVE are: (1) in situ measurement from the balloon of noble gas abundances and stable isotope ratios, to study the record of the evolution of Venus; (2) in situ balloon-borne measurement of cloud particle and gas composition, and their spatial variation, to understand the complex cloud-level chemistry; (3) in situ measurements of environmental parameters and winds (from tracking of the balloon) for one rotation around the planet, to understand atmospheric dynamics and radiative balance in this crucial region. The portfolio of key measurements is complemented by the Russian descent probe, which enables the investigation of the deep atmosphere and surface. © Springer Science+Business Media B.V. 2008.

Field emission performance of multiwalled carbon nanotubes for a low-power spacecraft neutraliser

Acta Astronautica 64 (2009) 875-881

KL Aplin, BJ Kent, W Song, C Castelli

GAUGE: The grAnd unification and gravity explorer

Experimental Astronomy 23 (2009) 549-572

G Amelino-Camelia, K Aplin, M Arndt, JD Barrow, RJ Bingham, C Borde, P Bouyer, M Caldwell, AM Cruise, T Damour, P D'Arrigo, H Dittus, W Ertmer, B Foulon, P Gill, GD Hammond, J Hough, C Jentsch, U Johann, P Jetzer, H Klein, A Lambrecht, B Lamine, C Lämmerzahl, N Lockerbie, F Loeffler, JT Mendonca, J Mester, W-T Ni, C Pegrum, A Peters, E Rasel, S Reynaud, D Shaul, TJ Sumner, S Theil, C Torrie, P Touboul, C Trenkel, S Vitale, W Vodel, C Wang, H Ward, A Woodgate

An infrared filter radiometer for atmospheric cluster-ion detection.

Rev Sci Instrum 79 (2008) 106107-

KL Aplin, RA McPheat

Motivated by the detection of infrared absorption bands from atmospheric cluster ions in laboratory experiments, a narrowband filter radiometer has been constructed for ion detection in the atmosphere. It uses a filter centered at 9.15 mum wavelength with 5% bandwidth, protected by a diamond-like-carbon coated germanium auxiliary filter, and fitted to a standard pyrradiometer. A sensitivity of (29.3+/-0.1) microV/(W m(-2)) has been determined in a laboratory calibration using a blackbody source. Atmospheric experiments show that the filter radiometer, when used with a stable, low-noise amplifier, can respond to cluster-ion fluctuations. The filter radiometer's sensitivity to atmospheric ion changes is (0.47+/-0.05) (mW m(-2))/(ions cm(-3)).

Electrical properties of ions in the atmosphere of Titan

Journal of Physics: Conference Series 142 (2008)

NR Owen, KL Aplin, PA Stevens

An electric field sensor to measure charged dust on the Marco Polo asteroid sample return mission

International Astronautical Federation - 59th International Astronautical Congress 2008, IAC 2008 3 (2008) 1741-1748

KL Aplin, EC Sawyer, AJ Coates, DJ Parker, GH Jones, NE Bowles, MS Whalley

The Marco Polo mission has been selected by the European Space Agency (ESA) as a candidate for launch under the Cosmic Vision programme in -2017. The mission ultimately aims to understand the origins of the planets and even life itself, by returning a sample of material from a primitive asteroid, representative of the early Solar System. Particles on the surface of the asteroid are readily charged by photoelectric emission. Preliminary calculations suggest that photoelectric fields of tens of volts per metre are expected, and electrostatic transport, levitation, and even complete ejection from the asteroid's gravitational field seem likely for typical particles at the proposed candidate asteroids. The electrical and charged particle environment at the asteroid surface is therefore expected to be significant for sample selection and characterisation. The Asteroid Charge Experiment (ACE), comprising an electric field sensor to detect charged dust particles, and an electron spectrometer to measure both photoelectrons and electrons from the solar wind, is described here. ACE will also be able to determine the relative electrostatic potentials of the spacecraft and asteroid surface, which will quantify the electrical effects of the sampling process itself on the asteroid environment.

Electromagnetic wave propagation in the surface-ionosphere cavity of Venus

Journal of Geophysical Research E: Planets 113 (2008)

F Simões, M Hamelin, R Grard, KL Aplin, C Béghin, J-J Berthelier, BP Besser, J-P Lebreton, JJ López-Moreno, GJ Molina-Cuberos, K Schwingenschuh, T Tokano

Inexpensive optically isolated nanoammeter for use with micro-Newton electric propulsion technology

Journal of Propulsion and Power 24 (2008) 891-895

KL Aplin, KL Smith, JG Firth, BJ Kent, MS Alexander, JPW Stark

Schumann resonances as a means of investigating the electromagnetic environment in the solar system

Space Science Reviews 137 (2008) 455-471

F Simões, M Rycroft, N Renno, Y Yair, KL Aplin, Y Takahashi

Investigating earth's atmospheric electricity: A role model for planetary studies

Space Science Reviews 137 (2008) 11-27

KL Aplin, RG Harrison, MJ Rycroft

The historical development of terrestrial atmospheric electricity is described, from its beginnings with the first observations of the potential gradient to the global electric circuit model proposed by C.T.R. Wilson in the early 20th century. The properties of the terrestrial global circuit are summarised. Concepts originally needed to develop the idea of a global circuit are identified as "central tenets", for example, the importance of radio science in establishing the conducting upper layer. The central tenets are distinguished from additional findings that merely corroborate, or are explained by, the global circuit model. Using this analysis it is possible to specify which observations are preferable for detecting global circuits in extraterrestrial atmospheres. Schumann resonances, the extremely low frequency signals generated by excitation of the surface-ionosphere cavity by electrical discharges, are identified as the most useful single measurement of electrical activity in a planetary atmosphere. © 2008 Springer Science+Business Media B.V.

Planetary atmospheric electricity

Space Science Reviews 137 (2008) 5-10

RG Harrison, KL Aplin, F Leblanc, Y Yair

Electrification is a fundamental process in planetary atmospheres, found widely in the solar system. It is most evident through lightning discharges, which can influence an atmosphere's chemical composition, but electrification also affects the physical behaviour of aerosols and cloud droplets that determine an atmosphere's radiative balance. In the terrestrial atmosphere, lightning has been implicated in the origin of life. © 2008 Springer Science+Business Media B.V.

Composition and measurement of charged atmospheric clusters

Space Science Reviews 137 (2008) 213-224

KL Aplin

Why we need to go to Venus: The future of European Venus exploration

International Astronautical Federation - 59th International Astronautical Congress 2008, IAC 2008 3 (2008) 1622-1629

C Wilson, E Chassefière, T Imamura, O Korablev, K Baines, D Titov, K Aplin, TS Balint, J Blamont, C Ferencz, C Cochrane, F Ferri, M Gerasimov, J Leitner, J Lopez-Moreno, B Marty, M Martynov, S Pogrebenko, A Rodin, J Whiteway, L Zasova

Venus is the most Earthlike planet we know besides our own, in terms of its size and distance from its parent star. It was probably formed from the same materials as the Earth and Mars, at a similar time - why then has it become so different?To address this key question, a team of 170+ scientists from around the world formulated the European Venus Explorer (EVE) mission proposal to the European Space Agency's Cosmic Vision Programme in 2007. Although it was not chosen in the 2007 selection round for programmatic reasons, it was rated a high priority for the future European Space Science so we take this opportunity to reiterate the science goals which motivated the EVE mission, and to discuss the status of technological and programmatic developments required to address these goals.

A Michelson interferometer system for testing the stability of a piezo-electric actuator intended for use in space

Journal of Physics: Conference Series 85 (2007)

KL Aplin, KF Middleton

Water vapour changes and atmospheric cluster ions

Atmospheric Research 85 (2007) 199-208

RG Harrison, KL Aplin

Properties of small ions in atmospheric air have been investigated using a modern ion spectrometer with co-located meteorological and atmospheric electrical measurements, in urban air at Reading during May and June, (days 147-154) 2005. The ion spectrometer's programmed measurement sequence determined the mean ion currents and their variability, permitting derivation of positive and negative ion number concentrations, and their associated mean mobilities, on a ∼ 30 min cycle. The ion measurements were validated by comparing the derived air conductivity with the nearby atmospheric electrical potential gradient, and both these independently measured parameters correlated closely under fair weather conditions. Histograms of the mean mobility for positive (μ+) and negative (μ-) ions across the 7 days of measurement showed μ- > μ+, i.e. that the negative ion mass was less than that of positive ions. Adjacent air humidity measurements were used to analyse the mobility data. Using the median water vapour pressure of 4.1 hPa as a threshold, the mean μ+ was found to be significantly lower when vapour pressures were above the threshold, but there was no significant change in μ- with vapour pressure. As the effect on positive ions remains present in strong sunlight, weak sunlight, and darkness, it is unlikely to be solely of photochemical origin but, more probably, related to changes in ion hydration. There is therefore an asymmetric response of positive and negative ions to water vapour. This will influence the aerosol electrification in fogs and clouds, and modify the radiative response of hydrated ion clusters. © 2007 Elsevier B.V. All rights reserved.

Clouds in atmospheric physics [1]

48 (2007)

G Harrison, R Bingham, K Aplin, B Kellett, K Carslaw, J Haigh

Solar and cosmic ray physics and the space environment: Studies for and with LISA

AIP Conference Proceedings 873 (2006) 172-178

DNA Shaul, KL Aplin, H Araújo, R Bingham, JB Blake, G Branduardi-Raymont, S Buchman, A Fazakerley, LS Finn, L Fletcher, A Glover, C Grimani, M Hapgood, B Kellet, S Matthews, T Mulligan, WT Ni, P Nieminen, A Posner, JJ Quenby, P Roming, H Spence, T Sumner, H Vocca, P Wass, P Young

With data analysis preparations for LISA underway, there has been renewed interest in studying solar, cosmic ray and environmental physics for, and using LISA. The motivation for these studies is two fold. The primary incentive is to predict and consequently minimize the impact of disturbances associated with these factors, to maximize LISA's gravitational wave scientific yield. The second stimulus is the unique opportunity that is afforded by LISA's long-baseline 3-spacecraft configuration for studies of solar, cosmic ray and environmental physics. Here we present an overview of recent progress in these studies. © 2006 American Institute of Physics.

Variability in long-duration operation of silicon tip field emission devices

Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures 24 (2006) 1056-1060

KL Aplin, BJ Kent, L Wang, HF Lockwood, J Rouse, R Stevens

Investigation of fabrication uniformity and emission reliability of silicon field emitters for use in space

Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures 24 (2006) 1072-1075

L Wang, KL Aplin, SE Huq, BJ Kent, R Stevens, A Malik, HO Blom, IM Loader, GR Thomas