Space Debris and Other Threats From Outer Space Read Online Free PDF Page A

protective measures need to be employed to protect satellites and orbital spacecraft from these occasional blasts, some of which are violent enough to threaten not only not only satellites in orbit but as noted earlier electrical grids, electronic equipment, and facilities on the ground. In short, CMEs, in the most severe cases, can endanger much of the modern infrastructure on Earth. This means not only power grids but pipeline systems and highly distributed computers and telecommunications networks as well. Just think of the consequences if all the microprocessors on all the vehicles and aircraft in the world were to be blown out by a super-massive solar eruption.
    Chapter 7 will focus on solar and cosmic radiation and can likewise present hazards to space assets as well as people right here on Planet Earth as well. Widening holes in the ozone layer allow through truly harmful X-ray radiation in the Polar Regions. Solar and cosmic ultraviolet radiation travels essentially at the speed of light or close to 300,000 km/second or 186,000 miles/second. Solar eruptions that contain super charged electron ions as well as alpha and beta particles travel at huge velocities. Despite this great speed these eruptions nevertheless travel on the order of a 100 times slower than the speed of light or energetic gamma rays. This is indeed fortunate. The speed differential allows solar flares and CMEs to be detected via solar observatories and space-based sensors so that satellites and key facilities can be powered down and electrical systems switched off to protect against the “big hits” from these solar storms or super space weather events. Without this type of warning system hundreds of orbiting spacecraft worth hundreds of billions of dollars could be at risk and essential satellite operations lost for communications, navigation, remote sensing, weather forecasting, and military-related services.
    Chapter 8 examines how potentially hazardous asteroids (PHAs) and comets pose an ongoing risk to humans, and Chap. 9 addresses what is currently being done to address and forestall these potentially calamitous events. These NEOs are rarely of large enough size to actually pose a major threat, but on average—about every 50–100 million years—these natural orbital debris can truly clobber Earth and its inhabitants. The good news is that we believe that we have identified some 90 % of the potentially hazardous asteroids that are 1,000 m or more in diameter and might come within 9 million miles (or 14.4 million km) of Earth. The bad news is that it is estimated that there are another 10 % of these large threats still to be identified and some 80 % of such asteroids some 100–1,000 m in size to be cataloged. An asteroid of this smaller size could still hit us with the force of tens of thousands of atomic bombs. What is perhaps most important of all is to understand that impacts of objects in this size range are much more frequent than every million years. In fact the chance of a Tunguska-size impact this century is in the order of 1 in 10 to 1 in 5. Later in this book we address the so-called Torino Scale, that is sort of like the Richter Scale for potentially hazardous asteroids. This chart indicates both the likelihood of strikes and the type of damage various-sized NEOs might cause if they hit Earth.
    And there are also a large number of potentially hazard comets still to be detected as well. Currently the odds seem to be in our favor, but there are a number of specific asteroids we are tracking with particular concern.
    In the short term a much more serious threat for spacecraft are the millions of meteorites and micro-meteorites that can strike and disable a spacecraft. There are a series of recurring meteor showers that pose high levels of risk, but damage from a meteor or even a meteorite can occur at any time. Indeed it is estimated that about 15 % of the strikes on satellites today are from micro-meteorites and not