ESA Science & Technology - Publication Archive
The European space Agency (ESA) undertook a bold experiment with the Mars Express mission: to develop rapidly a low cost platform for planetary exploration. The myriad scientific achievements of this mission prove the success of the experiment. ESA took a second bold step by adapting the Mars platform for the Venus Express mission, and doing so rapidly and most cost-effectively. While the differences in Venus and Mars necessitated several changes in instrumentation, there are many objectives that remain the same at the two planets. When we issued a call to the MEX and VEX communities for a volume of brief articles covering the latest results from these two missions, the response from those examining the interaction of the solar wind and energetic particles with the planets was most swift. The authors were asked to keep their presentations to four published pages. The guest editor in turn attempted to shepherd these papers through the reviewing process quickly. In those instances where the editor had a conflict of interest, R. J. Strangeway assumed the duties of the editor.
The articles that passed review before the press deadline are included therein. They include discussions of the various plasma boundaries at Venus and Mars, the nature of their plasma environments, the discovery of energetic neutral particles, the configuration of the magnetic field near the planets, space weather and the loss of atmosphere. Papers included contain both modeling and observational work and are written by some of the newest members of the community as well as many of the veteran research scientists. We especially thank the referees of these papers who responded promptly to help speed these early results to the readers of Planetary and Space Science.
Venus Express is the first dedicated mission to Venus in over a decade. It was built by the European Space Agency, launched from Baikonur on a Soyuz-Fregat launcher on 9 November 2005. It arrived at Venus on 11 April 2006 and is in a polar orbit, with a period of ~24 hours. Since arrival its suite of instruments has been collecting data on the atmosphere and magnetosphere. In this focus, eight Letters describe the results obtained so far, while a Progress paper by Svedhem et al. gives an overview of the mission.
The Planetary Fourier Spectrometer (PFS) is an infrared spectrometer optimised for atmospheric studies, with a short-wavelength (SW) channel covering the spectral range 1800-11400 cm-1 (0.9-5.5 mm) and a long-wavelength (LW) channel covering 250-1800 cm-1 (5.5-45 mm). Both channels have a uniform spectral resolution of 1.3 cm-1. It is the first Fourier spectrometer at Venus covering the 1-5 mm range. The SW field of view is about 1.6º FWHM, and 2.8º FWHM for the LW, which corresponds to spatial resolutions of 7 km and 12 km, respectively, when Venus is observed from a height of 250 km. PFS can provide unique data for improving our knowledge not only of the atmosphere properties but also the surface properties (temperature) and surface-atmosphere interaction (volcanic activity).
The SW channel uses a PbSe detector cooled to 200-220K, while the LW channel is based on a pyroelectric (LiTaO3) detector working at room temperature. The intensity of the interferogram is measured at every 112 nm displacement of the mirrors (corresponding to 450 nm optical path difference), by using a laser diode monochromatic light interferogram (a sine wave), whose zero crossings control the double pendulum motion. PFS works primarily around the pericentre of the orbit, only occasionally observing Venus from large distances. Each measurement takes 4 s, with a repetition time of 11.5 s. By working for about 1.5 h around pericentre, a total of 460 measurements per orbit can be acquired, plus 60 for calibrations. PFS can take measurements at all local times, facilitating the retrieval of surface temperatures and atmospheric vertical temperature profiles on both the day and night sides.