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In the JAXA PDF Hayabusa2 Information Fact Sheet (Ver. 2. 3, 2018. 07. 05, found here) on slide/page number 53 there is a diagram labeled Re-entry sequence overview and in the top right corner is depicted the sample recovery capsule descending in Earth's lower atmosphere suspended from a parachute.

The caption says:

Cloth parachute (with laser-reflective cloth)

Question(s):

  1. In this case, or in any case have lasers been used or at least planned to be used on laser-reflective parachutes for tracking and/or recovery?

  2. What is "laser-reflective cloth" anyway? Is this standard practice for spacecraft reentry parachutes or is this a unique instance or first-ever use?

"bonus points" for any information about the reflectivity being specific to lasers. I'm guessing they include the word "laser" just to help us understand how it might be used, rather than to suggest it's specifically designed to be reflective for laser light, but maybe there are specific enhancements that I don't know about.

Screen shot from "Hayabusa2 Information Fact Sheet, Ver. 2. 3, 2018. 07. 05"

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I think it is a retroreflective material like that used for High-visibility_clothing. There are reflective tape originally developed by 3M. A reflective coating of tiny glas spheres is used as retroreflectors. The surface should reflect radiation (usually light) back to its source with minimum scattering.

Using retroreflectors in space has a long tradition. They were placed on the Moon by Apollo 11, 14 and 15, the Lunokhod 1 and Lunokhod 2 rovers, but also on Mars Perseverance rover. Also on many satellites for Satellite laser ranging.

The reflective cloth should be used only at certain places of the parachute. Using it at the top of the chute does not make sense. Best places are those being vertical to the laser beam like the red rectangle shown in the image.

You need a material reflecting visible light, it works with light from incandescent bulbs, electronic flashes and lasers too. A very narrow laser beam is useful for long distances. Lasers light is just better focused than other artificial light. Lasers may produce very short pulses of high intensity as need for ranging over a large distance with a high precision and resolution.

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  • $\begingroup$ "Using retroreflectors in space has a long tradition" How so? Examples? Any thoughts on why they mention "laser" in the description? $\endgroup$ – uhoh Dec 7 '20 at 11:39
  • $\begingroup$ None of those examples are cloth suitable for parachutes. $\endgroup$ – uhoh Dec 7 '20 at 14:26
  • $\begingroup$ You may use a cloth for parachutes and coat it (partially) with the reflective "paint" containing the glas spheres. $\endgroup$ – Uwe Dec 7 '20 at 14:57
  • $\begingroup$ "Is this standard practice for spacecraft reentry parachutes or is this a unique instance or first-ever use?" You're answering a different and very general question which hasn't been asked here. $\endgroup$ – uhoh Dec 7 '20 at 15:02

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