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Even a low failure rate means that dozens of satellites could lose control and become debris. Because they are located in an operational orbit, they pose a serious problem. Therefore, a few active debris removal (ADR) ideas have been proposed, which is to tow and de-orbit debris satellites with rescue satellites similar to tugboats for shipwrecks. In these cases, physical contact, such as towing by wire, is a prerequisite. Mechanical coupling between satellites involves risks such as the collision between satellites and loss of attitude control at the time of coupling. Since no cooperation between the two satellites is not desirable, mechanical contact is very difficult when the debris has high angular momentum. On the other hand, the contactless debris removing idea, to irradiate debris satellites with lasers and use of the laser ablation induced impulse, has been proposed. In this approach ti, is important to accumulate data on how much impulse is generated by the plasma plume produced by laser ablation in a vacuum. A compact and efficient measurement device to measure this impulse has been developed. In this study, we investigated impulses generated by a 10ns Q-switched Nd:YAG laser (1064nm) and its second harmonic generation (SHG, 532nm) using a metal as a target for laser irradiation. The results show that the fundamental (1064nm) laser of about 100W can generate enough thrust to deorbit space debris with comparable mass to a small satellite from 1000km to 500km altitude in a year. SHG can be converted to impulse more efficiently than 1064nm. The use of 532nm alone, including the SHG generation efficiency, has less impact on the impulse generation effect than the use of 1064nm fundamental alone, without SHG. It was pointed out that the energy of the Nd:YAG laser effectively uses generation of impulse when the remaining fundamental components that could not be converted to SHG could be used to irradiate to generate ablation. Although the use of SHG is not effective in terms of 1064nm fundamental power including SHG generation efficiency, it is demonstrated that the energy of the Nd:YAG laser can be efficiently utilized by using the remaining fundamental components that could not be converted to SHG.
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