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6.3.1 Introduction: particle physics from ground to space

The Universe is the ultimate laboratory to understand the laws of nature. Under the action of the fundamental forces, lasting infinitesimal times or billion of years, matter and energy reach most extreme conditions. Using sophisticated instruments capable to select the signals reaching us from the depths of space and of time, we are able to extract information otherwise not obtainable with the most sophisticated ground based experiments. The results of these observations deeply influence the way we today look at the Universe and at our place in the Universe. During hundreds of thousand of years we have observed the sky only using our eyes, accessing in this way only a very small part of electromagnetic radiation able to traverse the atmosphere, the visible light. The first telescope observations by Galileo in 1609 dramatically changed our understanding of the solar system, yet were based only on the visible part of the electromagnetic spectrum. Only during the second half of the XX th century we started to access wider parts of the spectrum. After the end of the war, using the new technologies related to radar, the scientists developed the radio telescopes to record to first radio images of the galaxy. But only in the 60’s, with the advent of the first man made satellites, we began to access the much wider e.m. spectrum, including infrared, UV, X-ray and γ-ray radiation. A similar situation happened with the charged cosmic radiation. Cosmic Rays, discovered by Hess in 1912 [1] using electrometers operated on atmospheric balloons, for about 40 years were the subject of very intense studies. The discovery of a realm of new particles using CR experiments, gave birth to particle physics and to high energy physics, successfully performed since the 50’s at particle accelerators. However, the study of the cosmic radiation performed within the atmosphere, deals only with secondary particles. The primary radiation can only be studied with stratospheric balloons or using satellites. In 1958 Van Allen [2] and collaborators studied for the first time the charged cosmic radiation trapped around the Earth, and since, the measurement of Cosmic Rays from space has become an important tool for the study of the Universe. A third, more recent example is the search for gravitational waves (GW), a process which is ongoing right now. Direct observation of gravitational waves would be an important discovery confirming General Relativity predictions. Since the pioneering attempts of Weber [3] in the 60’s, using resonating bars, the GW community has developed in the 90’s a network of O(1) km arms, ground based interferometers to search for GWs in the frequency range 10 Hz to 100s of Hz. The expected signal, however, is extremely rare, since GW are expected much more abundantly in the frequency range O(0.001) Hz to a O(1) Hz. This range can be studied with a 5 · 10 6 km arm, space based interferometer, as the proposed ESA/NASA LISA mission. Over time, particle detectors developed on ground have been adapted or designed to be used on stratospheric balloons and on space born experiments. Space, however, is a hostile environment and launching a payload is a very expensive enterprise. For these reasons, the design and the testing of a space born detector requires particular care. In this chapter we will deal with this topic. We begin discussing the properties of the space environment from the upper atmosphere, the transition from the atmosphere to the magnetosphere and from the magnetosphere to the deep interplanetary space. We then address the requirements for hardness and survivability of space born instrumentation.