Space for defence: A European vision

A common European defence policy is still at a very preliminary stage, and although some limited progress has recently been made, it is a politically sensitive issue. In contrast to scientific research or large industrial ventures such as aircraft development, where Europe has moved forward rather well, obstacles to further integration in defence and security matters are numerous. Space systems could be used to facilitate such integration as their duplication is costly and so much remains to be done in Europe in this field. A common European ‘vision’ for the role of space systems in security and defence thus needs to be developed. This article reviews the role of space in security and defence missions, the technology and industrial base Europe needs, and its capability and autonomy in achieving access to space. Space system vulnerability and the means of minimizing it are addressed, including measures to prevent the weaponization of space. The possible role of ESA in support of the European Defence Agency for defence space systems development is identified, along with the need for ad hoc organizations for operational exploitation. Ten recommendations are made that would permit progress at the European level, following the path already successfully achieved in the civilian domain.     

Solar Forcing of Climate. 2: Evidence from the Past

The nature of the climatic response to solar forcing and its geographical coherence is reviewed. This information is of direct relevance for evaluating solar forcing mechanisms and validating climate models. Interpretation of Sun-climate relationships is hampered by difficulties in (1) translating proxy records into quantitative climate parameters (2) obtaining accurate age assessments (3) elucidating spatial patterns and relationships (4) separating solar forcing from other forcing mechanisms (5) lacking physical understanding of the solar forcing mechanisms. This often limits assessment of past solar forcing of climate to identification of correlations between environmental change and solar variability. The noisy character and often insufficient temporal resolution of proxy records often exclude the detection of high frequency decadal and bi-decadal cycles. However, on multi-decadal and longer time scales, notably the ∼90 years Gleisberg, and ∼200 years Suess cycles in the ¹⁰Be and ¹⁴C proxy records of solar activity are also well presented in the environmental proxy records. The additional ∼1500 years Bond cycle may result from interference between centennial-band solar cycles. Proxy evidence for Sun-climate relations is hardly present for Africa, South America and the marine realm; probably more due to a lack of information than a lack of response to solar forcing. At low latitudes, equatorward movement of the ITCZ (upward component of the Hadley cell) occurs upon a decrease in solar activity, explaining humidity changes for (1) Mesoamerica and adjacent North and South American regions and (2) East Africa and the Indian and Chinese Monsoon systems. At middle latitudes equatorward movement of the zonal circulation during solar minima probably (co-)induces wet and cool episodes in Western Europe, and Terra del Fuego as well as humidity changes in Southern Africa, Australia, New Zealand and the Mediterranean. The polar regions seem to expand during solar minima which, at least for the northern hemisphere is evident in southward extension of the Atlantic ice cover. The forcing-induced migration of climate regimes implies that solar forcing induces a non linear response at a given location. This complicates the assessment of Sun-climate relations and calls for nonlinear analysis of multiple long and high resolution records at regional scale. Unfortunately nonlinear Sun-climate analysis is still a largely barren field, despite the fact that major global climate configurations (e.g. the ENSO and AO) follow nonlinear dynamics. The strength of solar forcing relative to other forcings (e.g. volcanism, ocean circulation patterns, tides, and geomagnetism) is another source of dynamic responses. Notably the climatic effects of tides and geomagnetism are hitherto largely enigmatic. Few but well-dated studies suggest almost instantaneous, climatic deteriorations in response to rapid decreases in solar activity. Such early responses put severe limits to the solar forcing mechanisms and the extent of this phenomenon should be a key issue for future Sun-climate studies.     

Influence of Bandwidth Restriction on the Signal-to-Noise Performance of a PCM/NRZ Signal

The influence of bandwidth restriction on the performance of a PCM transmission system is treated. In particular, the relationship is investigated between signal-to-noise, bandwidth, and bit-error probability of an NRZ (non-return-to-zero) signal. The detector used in the investigation contains a device that integrates the signal over the bit period. Theoretical results were obtained by a Fourier analysis of bandwidth-restricted signals and by an autocorrelation analysis of the bandwidth-restricted noise. Theoretical and experimental results are in good agreement.     

The 2010 US space policy: A view from Europe

The authors examine the principles, goals and guidelines in the new US NSP. While in general favourable to the overall direction of the policy, noting that Europe too has similar goals or, in some cases, should be adopting US ideas, they are sceptical about certain aspects, such as the greater emphasis on commercial partnerships with NASA and the continuing protectionist launch policy. Particular points of concern are the vagueness and lack of clear goals in the human spaceflight programme and the US position on space weaponization at the Conference on Disarmament. Nevertheless, they believe that a similar type of EU-wide policy should be developed by the European Commission.