The space debris problem is becoming increasingly serious, transforming its scale and quality. The development of countermeasure technologies is progressing, but it is not keeping pace with the progress of the problem. This introductory article describes the laser technology issues that need to be addressed, referring to the debris environment as we know it today, the measures being taken to improve it, and the untouched problems.

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The energy efficiency of accelerating debris is particularly important in laser debris removal techniques. A calculation model depends on the laser focusing intensity, wavelength, and pulse width to evaluate the efficiency which is maximized when the ablation switches from evaporation to plasma generation. Based on this consideration, laser pulse energy can be evaluated based on the shape and mass of the debris to be removed.

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The removal and recovery of space debris has become a major international problem. Various artifacts (space debris), generated during space exploration, exist in the Earth’s orbit and pose a major obstacle to space activities. The removal of such debris by laser has been proposed and studied for more than 20 years, although it has not yet been implemented due to the elementary technology of a high-power laser irradiation system. The following extremely advanced and cutting-edge technologies are required: a high-power laser technology with a high repetition rate; a technology that focuses light on an object more than 1000 km away; a technology that compensates for atmospheric fluctuations; and a tracking technology that keeps the irradiated objects moving at high speed. This paper describes the possibility of space debris removal using ground-based lasers and reports on the current status of the required high-power lasers.

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To remotely and accurately irradiate laser beams on micro space debris moving at high speeds in space, mechanical beam control poses major challenges in terms of response speed and dynamic stability. In response to this issue, basic research is being conducted on digital phase conjugated-light technology that enables retro-directive tracking by real-time wavefront control using a CCD camera and a spatial phase modulator. This paper introduces the current technology and prospects for improving the wavefront reproduction accuracy and the response time performance and supporting high output power.

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Space-based laser technology is expected to be an effective approach for removing tumbling space debris. This paper presents a comprehensive analysis of the detumbling process for large debris, highlighting the advantages of using Active Debris Removal (ADR) with lasers. By examining specific case studies and conducting detailed simulations, the research demonstrates how laser application can successfully stabilize large space debris. The findings underscore the significant potential of laser-based ADR to mitigate the escalating issue of space debris. This approach offers a promising solution to enhance the safety and sustainability of space operations. Furthermore, the study suggests that laser-based ADR could play a critical role in preserving the orbital environment for future space missions, ensuring the long-term viability of space activities. We are actively developing this technology to address the challenges posed by space debris.

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Laser ablation technology is a promising method for contactless debris removal. The challenges of using laser ablation thrusts include the thrust’s small magnitude and its directional constraint. Thrust is generated along the inward direction of the irradiation surface’s normal vector, requiring prior control of the debris attitude so that the irradiation surface aligns with the orbital velocity direction. For attitude control, the thrust directional constraint translates to a torque directional constraint. For orbit control, the small magnitude of the laser ablation thrust gradually deviates from the relative orbit. Consequently, the service satellite must maneuver to maintain a relative orbit and ensure consistent laser irradiation. To tackle these problems, this paper introduces an attitude control method using angular momentum feedback and a relative orbit control method that repeatedly returns to a desired relative orbit using an analytical solution.

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Even space debris smaller than 10 cm can cause fatal damage to satellites. The number of such “lethal nontrackable” objects is estimated to be over a million. A laser-based active debris removal method can solve this problem. In this study, we show that the error in orbit prediction can be at most 2 cm in 30 seconds. We also show that taking the Moon’s gravity into account to the trajectory calculation improves the orbit prediction error about 20%. We also discuss the direction of the ablation recoil force. This direction is shown to be critical to the success of debris removal.

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