Space science, a general term that embraces scientific investigations conducted in space distant from the earth. (By this definition, neither optical nor radio astronomy, using telescopes on earth, is a part of space science, although astronomical research using the same devices aboard satellites or space probes would be; from a scientific point of view, this distinction is not meaningful, but for practical purposes it is convenient.) The problem of designing and conducting space experiments is established by the requirements of space vehicles, because the instruments themselves are transported above interfering layers of the atmosphere, and in some instances, to (or closer to) other bodies in the solar system. This is highly meaningful with respect to particles and electromagnetic fields present in space, because satellites and space probes can detect them and measure their intensity at the locations under consideration.
The term "space science" also raises the question of what is meant by "space". No completely satisfactory definition is available because the universe is a continuum, which means that definitions of space in earth terms are arbitrary. Although the atmosphere is an essential feature of the Earth, its mass distribution or density does not afford the basis for a definition of space. Even though, for example, 99 per cent of the atmosphere (by mass) lies below an altitude of 20 mi. (miles), the atmosphere actually extends far beyond this altitude, merging imperceptibly into the interplanetary medium.
The scientific challenges and tasks, as man stands at the threshold of a new age of study of the cosmos, are probably equal to all that has gone before. We need only consider that atmospheric attenuation limits the earthbound observer to a small portion of the electromagnetic spectrum; a great additional area of space will be accessible to instruments flown outside the earth's atmosphere. With the aid of artificial satellites and space probes, fields, radiation, and particles in interplanetary space and in the vicinity of the Earth, the Moon, and the nearer planets become accessible to direct observation for the first time.
Effect of Satellite Size and Mass. The greater the mass of a satellite, the greater is its energy and the longer is its life. Size is significant in terms of the amount of surface area presented to the particles in space. For a given mass, the smaller the satellite is, the longer will be its life. This is because there will be fewer collisions with particles in space and less loss of satellite energy through the atmospheric friction produced.
Tracking the Satellite. Tracking is carried out by radio, visually, or optically to obtain observations which cap be used to compute future positions of the satellite and to determine its orbit. Data of interest are the times of the observations and two elements of the satellite's position, such as the elevation and azimuth angles.
MARS ON EARTH
A trip to Mars is out of the question now, but an island in the Canadian Arctic could soon provide the following interesting thing. The Mars Society, an international group of space enthusiasts, is planning to build a simulated Mars station on Devon Island in Canada. This island has been chosen as the best site for an artificial Martian base, because it has a great resemblance to the Red Planet, as Mars is sometimes called.
Like Mars, it is extremely cold and dry, and is covered with rocky ridges, valleys and even craters which appeared after the impacts with meteorites. Of course, there are great differences too, but there are as many similarities as one will never find anywhere on Earth.
It is planned to complete the Mars Research station by summer 2000. It will simulate the conditions that anyone living on real Mars in future will have to get used to. The station will also let scientists and engineers test different devices and equipment that will be very important for survival on Mars.
To do analogues of space exploration under extreme conditions on Earth is really a very promising research problem.