Being protected from space
Waste disposal is not just a problem down here on earth. Nearly sixty years on from the launch of the first Soviet satellite, Sputnik, signalling the beginning of the space exploration age, space is also called upon to tackle the problem of managing orbital debris.
The definition of space waste covers spent rocket stages, satellite fragments, flakes of paint, powders, material expelled from rocket engines and lots more besides. It might be a question of small objects or entire satellites or vector rockets that no longer work. Most of the debris is concentrated in low orbits between 500 and 2,000 km up. Its presence in space around our planet has increased out of all proportion in the last few years and become a growing problem as it poses a risk to operating satellites that, in turn, could produce other debris. This presence represents a danger to the safety of both the space infrastructure in orbit and earth's inhabitants.
As far back as 1991, NASA consultant Donald J. Kessler hypothesised a scenario where the volume of space debris in low orbit around the Earth would become so great as to cause repeated collisions, with a chain reaction that would make space exploration and even the use of satellites impossible for many future generations.
For many years, the U.S. Department of Defence has undertaken the task of monitoring and producing an up to date catalogue of space traffic: the US Space Catalog, that keeps track of the movement of the objects in orbit starting from a diameter as low as 50 cm and the data of this can be provided on a discretional basis to other nations and space agencies. Nonetheless, the growth in the risks caused by space waste has also prompted the European Union to gear up with an ambitious monitoring and surveillance project for orbiting satellites. In January 2015 a programme called SST – Space Surveillance and Tracking – was launched as part of the European Space Situational Awareness Programme. This programme requires each member state to make the data regarding the traffic of space objects in its possession available. All the data will flow into a single centre, to be processed and made available to the operators involved.
Following the European Union agreement, an agreement was signed in mid-June 2015 by the heads of the Italian, French, German and British space agencies at the International Paris Air Show at Paris-Le Bourget, to set up a consortium with the aim of providing monitoring and surveillance to the institutional users and the satellite operators of EU Member Countries. The aim of the consortium is to guarantee Europe greater autonomy in space surveillance, something for which it is still dependent on data provided by the United States.
Tests in Italy
In Italy, testing in this sector had already begun a number of months before the European level agreements. In January 2015, thanks to the cooperation with the Air Force's IV Brigade – Telecommunication and Systems for Air Defence and Flight Assistance, a test was carried out in which the Selex ES RAT-31/DL FADR (Fixed Air Defence Radar) played the leading role. The system has become the backbone for the air surveillance of NATO countries, over the years.
The test, that successfully recorded the trajectory of a number of small satellites showed the advantages of using radar in the search of space debris. In comparison to the benefits of optical telescopes the radar has a number of significant advantages. The radar is able to operate in any weather conditions whether day or at night even when there is no sunlight striking the orbiting object of interest (a telescope only detects objects illuminated by the sun against the background of the night sky). Furthermore, while astronomical techniques depend on measuring the sunlight reflected or the natural radiation emitted from an object, a radar transmits on an agreed frequency and the comparison between the characteristics of the signal transmitted and that received make it possible to deduce some physical and dynamic properties of the observed object more easily, thereby determining its position with great precision and instantly.
Furthermore, thanks to a number of technological improvements Selex ES has made in development for the RAT 31 D/L radar system, the company has also shown how it is possible to increase the capacity confirmed at the testing stage for the tracking of satellites and even smaller fragments in a short time frame.
The testing campaign has given results that confirm the great potential of the FADR in this field, even opening up the possibility of exploiting other Air Defence radar system networks across Europe (including numerous RAT-31/DLs installed in Austria, Poland, Hungary, the Czech Republic, Germany and other Countries) to provide satellite monitoring and surveillance services (SST).