The ongoing development of High Energy Laser (HEL) weapon systems is leading to a new suite of potential anti-satellite (ASAT) capabilities among both spacefaring and non-spacefaring nations. Powerful ground-based HEL systems may be used to dazzle or damage sensors or disable entire satellites. Such uses offer several advantages over other counterspace capabilities. HEL weapons could be used both in an offensive and a defensive manner and may be difficult to attribute to a specific actor. Furthermore, in some cases the physical effects are reversible, and the use of HEL may significantly limit the creation of space debris compared to other ASAT capabilities. The very long slant-paths through the turbulent atmosphere, coupled with the necessity to track and engage fast-moving objects in Low Earth Orbit (LEO) makes this particular application an interesting cross-over between typical HEL technology, astronomical instrumentation, satellite and space debris laser ranging, and laser satellite communication. In this paper we will review some of the scenarios and physical effects that may be expected from HEL systems used as an ASAT capability. We show that HEL systems of even moderate powers may pose severe risks to the sensors of imaging satellites passing overhead. We also find that the laser fluence delivered to a satellite on a single passage could easily reach the damage thresholds of many of the components that a satellite needs in order to function. A fourth scenario in which HEL is used to provide a negative impulse to alter the orbit or even de-orbit a small LEO satellite seems unlikely but merits some attention as a potential future capability.
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