Micrometeoroid impact charge yield for common spacecraft materials

Abstract

The impact ionization charge yield is experimentally measured from four common materials used in space and specifically on the two STEREO spacecraft (germanium-coated black Kapton, beryllium copper, multilayer insulation, and solar cells). Cosmic dust particle impacts on spacecraft have been detected by electric field and plasma and radio wave instruments. The accurate interpretation of these signals is complicated by many factors, including the details of the spacecraft antenna system, the local spacecraft plasma environment, and our understanding of the physics of the impact process. The most basic quantity, the amount of charge liberated upon impact, is generally considered poorly constrained and is suspected to depend on the target material. Here we show that for common materials used on spacecraft this variability is small for impacts around 10 km/s, and the impact charge yield can be approximated by 80 fC for a 1 pg projectile. At higher speeds (∼50 km/s), variation of up to a factor of 5 is observed. The measured yields in the 10-50 km/s range are compared to measurements and predictions from the literature and are found to be lower than predicted by at least a factor of 12 at 10 km/s and at least a factor of 1.7 at 50 km/s. Impact charge is also found to depend on angle of incidence; the data suggest a maximum at 45 • .

Dust impact signals on the wind spacecraft

“…In this figure, II means data from Iglseder and Igenbergs [], McMc is from McBride and McDonnell [], QPPRh is from Goldsworthy et al [], and BFeAu is iron on gold from Burchell et al []. “Coll” is measurements for solar cells from Collette et al []. The single point (diamond) is the measurement at the highest velocity we have found, 94 km/s, [ Ratcliff and Allahdadi, ].…”

“…This would imply a picture which is quite different for signal generation by oblique impacts. However, laboratory experiments, including the recent ones of Collette et al [], show only small effects (a factor of 2) for oblique impacts. Nevertheless, a more thorough understanding of the physics of oblique impacts might contribute to explaining the varieties of signals shown in Figure .…”

Floating potential perturbations due to micrometeoroid impacts: Theory and application to S/WAVES data

“…Hypervelocity impact experiments on materials relevant for STEREO spacecraft have been performed recently by Collette et al [], providing relationships between the total charge generated Q and the mass and velocity of the impacting particle. For impacts on the multilayer thermal coating that covers most of the spacecraft's surfaces, the relationship reads .…”

Experimental setup for the laboratory investigation of micrometeoroid ablation using a dust accelerator

“…An impact detector is a common way of detecting dust particles through impact ionization (see, for example, Auer 28 and Collette et al 29 ). The impact detector consists of a tungsten coated charge collection plate (also connected to a CSA) with a biased high-throughput grid in front of it.…”

“…every other PMT channel was collected) and channels prior to the first light signal are not shown. Specifically, due to the limited light channels the data acquisition is able to record with the current setup (29), the light signals which were saved for the event in Figure 13 were arranged in the following way. The first channel was saved, followed by the third, fifth, etc.…”