Rf

Jamming/Blackout

Communications tolerance to interference/scintillation.

Multiple links, processing, modulation and frequency choices.

Prior to the end of the Cold War, fixed ground control stations were high priority targets of ICBM-launched nuclear weapons. Therefore, satellites needed to be autonomous or capable of being controlled by multiple mobile ground control stations, or utilize a combination of the two survivability features. In the Post-Cold War era, these survivability features are less important Nevertheless, the following principles of survivability are still relevant Mobile ground stations are survivable because ICBMs cannot find targets whose Earth coordinates are unknown and continually changing. By deploying mobile ground stations so they are separate from one another, we allow a single nuclear weapon to kill, at most, one ground station.

TABLE 8-11. Satellite System Survivability Options. Many options exist, each adding cost and design complexity.

Option

Cost*

Effectiveness

Features

Satellite Hardening

2-5%

Very good

Trapped electron shielding, prompt radiation shielding, tatchup screening, radiation-tolerant electronics, degraded electronic parts deratings

Redundant Nodes

Cost of extra node

Good

Essential functions performed by 2 or more nodes (e.g., satellites with overlapping coverage but separated by greater than 1 lethal diameter range)

Onboard Decoys

1-10%

Good, depending upon type of threat guidance

Credible decoys simulating both radar and optical signatures of the satellite; decoys are launched when an attack Is detected (detection system required)

Maneuver Capability

10-20%

Good, depending upon type of threat guidance

Thrust levels depend on satellite altitude (warning time), nature of threat, threat detection efficiency; additional satellite weight for high acceleration

Self

Defense

20-40%

Very good

Kinetic energy kill homing missiles represent most likely first system

Escort Defense

Cost of 1 sat

Very good

Kinetic km homing missiles represent most likely first system; directed energy (e.g., high-energy laser or high-power microwave system) Is future possibility

Autonomous Operations

3-8%

Provides protection against loss of ground station

Autonomous orbit control (e.g., station-keeping for geosynchronous orbits), momentum control, redundant unit control (fault detection) and substitution

Mobile Ground Control Stations

2 to 3 times cost of large gmd. staL

Veiy good; provides survivable ground control station network

Multiple mobile ground control stations; while one is controlling, one is tearing down, one Is setting up, and one Is changing its location; survivability is achieved by physical location uncertainty.

Surv. Mobile Gmd. Term.

20-30% of fixed terminal

Very good; provides low-cost ground-control optlont

Hardened against high-altitude EMP, nuclear biological chemical warfare. Jamming, small arms fire. Survivability enhanced by physical location uncertainty.

Onboard Attar* Reporting System

1-5%

Essential for total system survivability

System records/reports time, Intensity, or direction of all potentially hostile events (e.g., RF, laser, nuclear, pellet impacts, and spoofing or takeover attempts); allows appropriate military response to hostilities

'Percent of total satellite cost tSurvhrable with nrdn. essential com. connectivity.

'Percent of total satellite cost tSurvhrable with nrdn. essential com. connectivity.

Onboard systems for attack reporting tell ground-control stations that a satellite is being attacked and what the attack parameters are. Without such information, ground operators may assume a spacecraft fault or natural accident has occurred, rather than an attack. Thus, controllers could act incorrectly or fail to act when necessary. More importantly, national command authorities need timely information telling of any attack on our space assets.

Decoys are an inexpensive way to blunt an antisatellite attack. They simulate the satellite's optical or RF signature and deploy at the appropriate moment, thus diverting the attack toward the decoys. Decoys must be credible (provide a believable radar or optical simulation of the satellite) and must properly sense an attack to know the precise moment for the most effective deployment We can also defeat a homing anti-satellite by including optical or RF jammers to nullify or confuse its homing system. Such jammers weigh little and, depending on how well we know the parameters of the homing system, can be very effective.

A satellite can maneuver, or dodge, an antisatellite attack if it has thrusters for that purpose. Of course, almost every satellite has thrusters for attitude control and orbit changes. Thrusters for maneuvers are more powerful, generating higher accelerations and causing the need for stiffer, stronger solar arrays or other appendages. These extra requirements lead to weight penalties. In addition, we must supply more propellant, trading off the increased propellant weight against the increased survivability.

A satellite can defend itself against an antisatellite attack if that capability is included in the design. One possible approach is to include a suite of optical or radar sensors and small, lightweight missiles. The sensors would detect the onset of an attack, determine approximate location and velocity of the attacker, and launch the self-guided, homing missiles to kill the attacker. Of course, we would have to consider weight, power, inertial properties, and other design factors, but a self-defense system is a reasonable way to help a high-value spacecraft survive. Alternatively, we could deploy an escort satellite carrying many more missiles and being much more able to detect, track, and intercept the antisatellite attack. An escort satellite would cost more than active defense on the primary satellite, but the latter* s weight and space limitations may demand it

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