Measuring How Much Dust Spacecraft Kick Up When they Land

The arrival of spacecraft on alien worlds uses a number of different techniques from giant air bags to parachutes and small rockets. The use of rockets can pose a problem to onboard technology though as the dust kicked up can effect sensors and cameras and the landing site can be disturbed in the process. A team of researchers have developed a new instrument that can measure the dust that is kicked up on landing to inform future instrument design. 

Dust can have a significant impact on spacecraft during landing especially on bodies like the Moon and Mars. Both worlds have a fine layer of dust on the surface known as the regolith. On descent, landing thrusters can stir up large clouds of dust which reduces visibility having an impact on navigation systems, and reducing visibility. It can damage optical instruments causing scratches on lenses and accumulation of dust on solar panels. Particles can even stick to spacecraft through electrostatic adhesion leading to overheating and mechanical problems. 

There are existing systems and instruments available to analyse the dust cloud but those instruments rely upon visual imaging, x-ray or MRI technology. The research team at the University of Illinois have developed technology that can assess displaced dust clouds using radio waves of 3.8mm wavelength. This enables them to deal with particle clouds too dense for optical examination or too thin for the x-ray analysis. The new instrument sends out radio waves just like a radar, the waves travel through the cloud and a picture of the cloud is built up. 

The new technique relies upon the concept that the waves are generally larger than the dust particles. As they travel through the dust, they are slowed down by a tiny amount and this reduction in velocity enables the cloud to be modelled. If light waves were used, they could not pass through the dust. 

The Radar Interferometry for Landing Ejecta or RIFLE as it has been called began development back in 2020 when radar was identified as the right technology. The original concept employed absorption measurements instead of measurements of the speed of the signal but that had problems. Unfortunately there were problems with this approach; larger clouds would cause a weaker radar signal on measuring absorption, the cloud also caused problems acting like a lens to focus waves onto a receiver and affecting the measurements. The team then turned their attention upon interferometry instead.

The team found the results were far more accurate so worked upon the development of prototypes and a final working instrument. A funnel was used to create a thin curtain of dust of known concentration. They then used cameras with lights to cast shadows of the dust particles at high magnification. The dust concentrations were measured optically to enable the instrument to be calibrated for use. The team have now applied for a patent following the successful test phase. 

Source : New instrument uses radar to measure what the eye can’t see

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