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Why satellite communications could be denied/degraded

Despite their overwhelming usefulness, satellite systems are vulnerable to a number of naturally occurring disturbances, such as ionospheric and tropospheric disturbances, rain fade (particularly in certain microwave frequency bands) and outages due to Sun-transit and eclipse. In addition to those naturally occurring disturbances, satellite communications are also vulnerable to interception and geolocation from anywhere within their footprint (43 per cent of the Earth’s surface for geostationary orbit and 5 per cent for low-Earth orbit).

Although those vulnerabilities can be managed and are not likely to lead to complete loss of communications, there are a number of major vulnerabilities that could lead to significant degradation or complete denial of satellite communications. ⁹

High-altitude nuclear detonation

The detonation of a nuclear warhead (surface burst, air burst or high-altitude-burst) poses a significant threat in many contexts due to a large number of undesirable effects including overpressure (blast), ground shock, nuclear radiation, electromagnetic pulse, post-event ionospheric disturbances and thermal radiation. Of those effects, electromagnetic pulse has a potentially catastrophic effect on satellites because of the very high electric and magnetic fields that can be rapidly induced into electrical equipment.

The short duration of a high-power electromagnetic pulse creates very high voltages and currents in unprotected electrical circuits, destroying sensitive devices. The pulse poses a significant threat to the very sensitive electronic equipment on satellites, exacerbated by the intense thermal radiation which has no atmosphere to attenuate it as it propagates through space from the detonation point to the satellite. Damage can range from faults and failures in isolated sub-systems to total system failure.

A high-altitude burst has even wider-ranging effects, and a high-altitude electromagnetic pulse can produce significant damage in the user terminals of the ground segment of a satellite communication system, as well as any control facility.

During the Cold War, the Soviet Union developed a system that was to be launched into low-Earth polar orbit and then de-orbited for attack with a nuclear warhead.¹⁰ A south-to-north polar orbit was chosen to avoid the US ballistic missile defenses oriented towards the north.¹¹ More recently, a number of experts have warned that two of North Korea’s satellites in polar orbit may carry nuclear warheads designed for a high-altitude electromagnetic pulse attack.¹²

Space weather

There are three types of space-weather storms: geomagnetic storms, radiation storms and radio blackouts.¹³,¹⁴ There have been a significant number of large solar storms since they were first observed in 1859—the Carrington event. In 2012, a large Carrington event occurred on the opposite side of the Sun, producing a very large solar flare—had it occurred a week earlier, the Sun would have been facing the Earth, with an effect that would have crippled satellite communications, GNSS, and severely damaged the power grid.¹⁵ Such a storm occurring today would cause widespread damage, with a likely impact exceeding US$2 trillion (20 times the costs of Hurricane Katrina) in just the continental US electricity distribution systems alone.^16,17 Smaller events occur more frequently, such as that which affected the Hydro-Quebec power grid on 13-14 March 1989 at a cost of some C$13.2 billion. ¹⁸ Although such events have been rare, it is estimated that there is a 12 per cent chance that such a storm will impact Earth in the next ten years¹⁹ or, in terms of time, historical records suggest a return period of 50 years for a Quebec-level storm and 150 years for a Carrington event.²⁰

The catastrophic effects of an extreme space-weather event are largely due to the widespread loss of electric power. If power remains available, there will be intermittent loss of HF-based systems, minimal impact to radio-relay and cellular services, interference or intermittent loss of GNSS navigation signals, and no significant impact on electronic devices.²¹ However, severe geomagnetic storms can affect satellite attitude control systems, and solar radiation storms can render satellite systems useless—examples include the Anik satellite in the late 1980s, AT&T’s Telstar 401 satellite in January 1997, two Telesat Canada satellites in January 1994, and Intelsat 511 in October 1995.²² Geomagnetic storms can also heat the atmosphere increasing drag on satellites in low earth orbit and can cause uncontrolled re-entry²³.

Jamming

Given that a geostationary orbit satellite is visible from some 43% of the Earth’s surface, satellite communications are vulnerable to jamming, particularly on the uplink, and the jammer does not even have to be in the same area as the targeted ground stations. Low-Earth orbit satellites have a much lower exposure to the Earth’s surface and the jammer would need to follow the satellite as it passed overhead.

Further, jamming of a single low-Earth orbit satellite would invariably only affect those relatively small number of users in the footprint of the satellite being jammed. Military satellites can respond with anti-jamming techniques, such as spread spectrum and frequency hopping—commercial satellite systems are seeking to deploy similar capabilities. Unfortunately, the data rate drops considerably with anti-jam protection. Further, many satellites used by military forces are not classed as military satellites (so do not have anti-jam protection).

Cyber

Jamming attacks the receiver in the RF link between the satellite and the ground—either the uplink or the downlink. Cyberattacks, on the other hand, are on data carried by the RF links and on the systems that process and use that data resulting in data loss, disruption in communications services, and even loss of the satellite if control can be gained over crucial satellite command and control.^24,25

Physical destruction

Satellite ground stations are large installations for high-capacity networks and their locations are obvious. They are very fragile, so can be readily destroyed by conventional forces, terrorist activity or missiles. Physical destruction of the space segment by direct physical attack is difficult but the US, Russia and China have a declared anti-satellite capability, with India and Israel announcing developments leading to such a capability. Anti-satellite weapons include kinetic-energy weapons (missiles) or directed-energy (laser) weapons. In addition to deliberate physical attack, accidental damage can be caused by collisions with other space objects.

Kinetic energy weapons

Ballistic missiles have apogees such that their warhead could be detonated to coincide with a low-Earth orbit satellite. In 1985, the US fired an ASM-135 missile and destroyed the P78-1 Solwind satellite at an altitude of 525 kilometers and, in 2008, a malfunctioning US satellite was destroyed by a missile fired from a US warship.²⁶ In the early 1980s, the Soviet Union began development of an anti-satellite weapon launched from a modified MiG-31. In 2015 and 2016, Russia successfully tested its direct-ascent anti-satellite missile, PL-19 Nudol.²⁷ In 2007, China destroyed with a missile a defunct Fengyun weather satellite in polar orbit at an altitude of 865 kilometers, creating a vast cloud of debris that will pose a low-Earth orbit threat for many years. ²⁸ On 27 March 2019, India destroyed a Microsat-R satellite at an altitude of 283 kilometers.²⁹

Both China and Russia have reportedly developed weapon systems that could threaten geostationary satellites.^30,31 Russia has also developed a co-orbital anti-satellite interceptor capable of maneuvering alongside a satellite in polar orbit and firing its fragmentation weapon, reportedly testing the interceptor 20 times between October 1968 and June 1982.³²

Directed energy weapons

Laser-based directed-energy weapons are more attractive than kinetic-energy weapons because they are delivered at the speed of light, can fire multiple times, and can be quickly redirected. They are, however, line-of-sight weapons that suffer from atmospheric attenuation which limits the locations from which they can be operated—nonetheless, satellites can be damaged or disrupted through laser-induced heating out to geostationary-orbit altitudes.

The Soviet Union began experimenting with ground-based lasers in the 1970s and 1980s, reportedly blinding a number of US spy satellites. In 1984, a laser weapon was reportedly used to disrupt operations on space shuttle Challenger.³³ Reports in May 2010 indicated that Russia was developing a prototype laser based on an A-60 aircraft.³⁴ The US Airborne Laser program aimed to develop a Boeing 747-mounted 1.2-megawatt laser designed to destroy missiles but which could also target spacecraft. The aircraft successfully destroyed two test missiles in 2010³⁵ but the program was cancelled in 2011 as a result of funding cuts. More recently, a number of countries are reported to be developing on-orbit anti-satellite weapons, both laser and kinetic. ^36,37,38

Accidental damage

Accidental damage to satellites can be caused by collisions with other spacecraft, space debris, or with natural space objects such as meteors. Perhaps surprisingly, there has been only one major collision between satellites, when Iridium 33 collided with a non-operational Russian satellite in December 2009. The threat from space debris is significant, however, and many agencies across the world, including the ADF, have invested much effort in space situational awareness programs to assist in space domain management. Ultimately, as predicted by Kessler et al, the density of debris in low Earth orbit (LEO) may become sufficient to cause cascading collisions. ³⁹

The principal danger to satellites comes from micro-meteors under 0.05 millimeters in diameter. Although such particles have tiny mass, their high velocities mean they have considerable kinetic energy that can penetrate thin metal sheets and will sandblast solar panels, causing a significant degradation over time. Notable examples of meteor-caused damage include the Olympus 1 experimental satellite and Landsat 5, both of which suffered damage during annual Perseid meteor showers.