Vanguard Magazine

www.vanguardcanada.com OCTOBER/NOVEMBER 2019 21 sPAce timeters in the orbits from Low Earth Or- bit (LEO) to Geostationary Orbit (GEO). These objects, the vast majority of which are classified as debris, are mostly the rem- nants of space objects such as defunct sat- ellites, discarded rocket stages, and debris created by collisions between space objects. Before 2007, the primary source of space debris was the explosion of old launch-ve- hicle upper stages. Upper stages are used to give satellites the final kick into the desired orbit and were most often left to slowly drift back down to Earth. However, these rocket bodies had a small remnant of fuel. Often, these rocket bodies would explode due to the heating of the enclosed propel- lant and material fatigue. However, because of the growth of com- mercial and private space activity, it is an- ticipated that debris will increase over the next few years, despite the international debris mitigation guidelines. According to one review on the state of space debris pub- lished in Science, "[i]n reality, the situation will undoubtedly be worse because space- craft and their orbital stages will continue to be launched." The key element of the space debris problem is the increase in the space ob- ject population in LEO. As the number of objects grows, the greater the chance for collisions increases, risking a cascade of collisions. This effect is referred to as the "Kessler Syndrome" and was famously portrayed in popular culture by the movie Gravity. In addition, the higher the alti- tude, the longer the space debris will re- main in orbit. Orbital debris below 600 kilometers returns to Earth and burns up within several years. However, at altitudes of 800 kilometers or higher, the orbital decay lasts decades, with debris not ex- pected to fall back to Earth before a cen- tury or more. Space operators can expect a sharp in- crease in the number of conjunction warn- ings as the number of catalogued objects increases. According to a presentation made at the Military Space Surveillance conference in London, England this past February, the Combined Space Opera- tions Center, operated by the USAF, is- sued 6.7 million satellite conjunction alerts last year. In addition, the Combined Space Operations Center only provides conjunction warnings on objects larger than 10 centimeters. Impact with an ob- ject 1 centimeter or larger will cause dam- age likely to destroy a satellite , and yet ob- jects of this size cannot be reliably tracked. Therefore, there is a large latent risk from unobserved debris with the highest risk to operational satellites coming from lethal and non-trackable debris. (in)Famous Debris Creation Events There are three prominent debris creation events that have added to the space debris problem. These are the intentional anti- satellite tests against the Chinese Fen Yun 1C satellite, the Mission Shakti conducted by India and the accidental collision of Kosmos-2251 and Iridium 33. The Fengyun 1C was destroyed in early

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