Directed energy laser weapons are becoming more common on the global battlefield, with an increasing prevalence of both Earth-based and space-based platforms expected in the future. The thermal impact of these laser weapons can be significant and understanding the potential for thermally induced physical damage as a function of power, beam focus and time on target is critical to mission planning. Testing is often understood to be the standard for truth in this regard, but it can be difficult to depend entirely on laboratory or field testing, especially when adversarial targets and/or challenging environments are the focus of such studies. For example, the thermal impacts of directed energy laser weapons on foreign targets in inaccessible environments can be challenging to understand via testing alone. The need to understand the thermal impact of directed energy laser weapons in situations where testing is difficult or impossible motivates the use of transient thermal prediction software. Adversarial targets in inaccessible environments can be simulated, and scientific studies can be performed by varying laser power, beam focus and time on target. Additionally, the effectiveness of possible countermeasures can be evaluated by simulating with and without the countermeasure and computing the reduction in thermal impact due to the design change of interest. In this paper we report on a methodology for simulating the transient thermal impact of laser weapons on orbiting satellites. We demonstrate how critical factors such as power level, beam focus and time on target can be included. We report time-dependent physical temperatures and show how the efficacy of countermeasures can be evaluated.
Space-Domain Awareness (SDA) via remote thermal imaging, where thermal-waveband EO/IR sensors are employed to observe orbiting satellites, has benefits over conventional visible/short-wave imaging. For example, LWIR sensors provide capability for both daytime and nighttime imaging, since temperature emissions and reflections are the basis of such observation (as opposed to optical sensors which rely on reflected light). To understand the capability that thermally dominant wavebands such as LWIR and MWIR can play in SDA, a robust simulation capability must be developed to predict signatures across the relevant spectrum. The computational complexity required for radiative transfer simulation is typically greater for satellite-focused thermal modeling in comparison to shortwave, reflected light-dominant wavebands. In this work, we employ MuSES to demonstrate the prediction of both internal and external temperature distributions for 3D satellite models. MuSES uses dynamic orbital boundary conditions to simulate transient solar loading, thermal radiation from Earth and to space, as well as radiative and conductive heat transfer from internal components such as electronics. Additionally, the coupled thermal/electrical multi-physics solvers in MuSES can incorporate realistic solar panel efficiency and battery cell charge/discharge cycling. Surfaces are attributed with spectral optical surface properties across the waveband(s) of interest to generate radiance maps via BRDF-based ray tracing of the predicted 3D temperature distributions. This allows radiometric signal levels of both the target and background, and subsequently contrast metrics of interest, to be generated with sensor simulations of space-based imaging platforms. Signature prediction is the primary output of this process, and in this study, we use our described methodology to demonstrate the inclusion of solar panel efficiency, battery charging/discharging and internal heat sources impact surface temperature distributions and infrared signatures during observations of satellites in LEO and GEO. A sensitivity study is performed to determine the significance that several satellite design choices can have on resultant signatures.
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