Reflections on human presence in space.

Humankind's exploration of Space has until now been understood as analogous to that of planet Earth: sending out crews to far-off, unknown lands in the hope of finding supplies of food, water or energy along with shelter and living-space. But Space is turning out to be much less hospitable than our earthly milieu in terms of resources as well as energy costs. It seems appropriate to ask what level of adaptation is needed for humans to travel and live in the cosmos, and to assess if the next logical step should necessarily be a programme of conquest analogous to that of the Moon--for example, towards Mars. Should we not rather be making more use of Earth's immediate neighbourhood, namely the sphere of a million of kilometres we call "Greater Earth"? In the same way, it is appropriate to ask questions about the conception of human beings which will from now on sustain the conquest of Space. The astronaut of the last forty years is the direct heir of the explorers of Ancient and Modern times; now, through the influence of science and technology, humanity has been put "into motion" not only geographically, but also in its most essential foundations: culture, psychology, philosophy. If the development of telepresence technology now gives us the ability to talk about a "Greater Human Being", it is chiefly through freedom of choice for oneself, for humanity and even for Earth.     

Adaptive Pulse Doppler Ambiguity Resolution

This paper demonstrates and tests a new algorithm for extracting velocity information from a pulse Doppler radar signal. The system is adaptive and performs weil in the presence of target scintillation. This paper also shows a special steady-state version of the adaptive algorithm. lt is computationally attractive and produces near optimal velocity estimates.     

Yohkoh observations of the solar corona

The Yohkoh soft X-ray telescope obtains several images every 90 minutes. Data from the declining phase of the solar cycle have been used to compare the X-ray signal with other indicators of activity and to study coronal heating. X-ray emission from a north polar coronal hole is found broadly consistent with results of previous EUV observations. In diffuse emission regions, temperature rises to around 2.2 MK and levels off in the height range 1.5 – 1.9 R_O. Such emission underlies streamers and may be the source of the low-speed solar wind. X-ray signatures for Coronal Mass Ejection (CME) events which involve the detection of reduced X-ray intensities in the corona, have been developed with Yohkoh data. CME observations are described     

Imaging the solar corona in the EUV

The SOHO (SOlar and Heliospheric Observatory) satellite was launched on December 2nd 1995. After arriving at the Earth-Sun (L1) Lagrangian point on February 14th 1996, it began to continuously observe the Sun. As one of the instruments onboard SOHO, the EIT (Extreme ultraviolet Imaging Telescope) images the Sun's corona in 4 EUV wavelengths. The He II filter at 304 Å images the chromosphere and the base of the transition region at a temperature of 5 − 8 × 10⁴ K; the Fe IX–X filter at 171 Å images the corona at a temperature of 1.3 × 10⁶ K; the Fe XII filter at 195 Å images the quiet corona outside coronal holes at a temperature of 1.6 × 10⁶ K; and the Fe XV filter at 284 Å images active regions with a temperature of 2.0 × 10⁶ K. About 5000 images have been obtained up to the present. In this paper, we describe also some aspects of the telescope and the detector performance for application in the observations. Images and movies of all the wavelengths allow a look at different phenomena present in the Sun's corona, and in particular, magnetic field reconnection.