Electrical anomalies on spacecraft due to hypervelocity impacts
One of the main challenges in satellite design is dealing with the threat from the space environment. Numerous spacecraft anomalies are reported on a regular basis and in most of these cases, it is extremely difficult to diagnose the cause of these anomalies/failures. Hypervelocity impacts from meteoroids and orbital debris has recently emerged as possible catalysts for electrical anomalies observed on spacecraft. In this paper, we present a case study and statistical analysis of hypervelocity impact-induced electrical anomalies. We present data showing anomalous currents in the power distribution system on the JASON-1 satellite following a hypervelocity impact. A statistical analysis is carried out using 2413 anomalies from the Ascend satellite anomaly database and 5033 anomalies from the anomaly database maintained in the 1990s by the National Geophysical Data Center (NGDC). We find that there is no correlation between the flux of shower meteoroids and incidence of anomalies. For geostationary satellites, we use NASA's Meteoroid Engineering Model to calculate the flux of sporadic meteoroids at different locations in the orbit and find that the incidence rate of anomalies is significantly higher in regions with high average meteoroid flux. These results serve as a strong indicator of electrical damage caused by electromagnetic emissions from meteoroid impacts.
The importance of the annual meteoroid streams to spacecraft and their detectors
In modelling dust fluxes to spacecraft surfaces and detectors, it is often assumed for simplicity that the influx is isotropic. The most popular working model used is that of Grun et al. (1985) which gives annual mean fluxes to a spinning flat plate detector at 1 AU. However, particular spacecraft orientations can highlight anisotropies in the natural meteoroid environment. This paper considers one source of anisotropy by isolating the contribution to the annual mean flux from the major annual meteoroid streams. Flux (mass) distributions are derived for 50 annual streams, and it is found that the streams contribute to ∼10% of the annual mean flux as seen by typical Low Earth Orbit (LEO) foil detectors at the (potentially hazardous) fmax = 1 mm size regime (i.e. impacts that can penetrate 1 mm aluminium). Strong temporal variations are also seen, relevant to short-exposure missions.
Electromagnetic properties of impact-generated plasma, vapor and debris
Plasma, vapor and debris associated with an impact or explosive event have been demonstrated in the laboratory to produce radiofrequency and optical electromagnetic emissions that can be diagnostic of the event. Such effects could potentially interfere with communications or remote sensing equipment if an impact occurred, for example, on a satellite. More seriously, impact generated plasma could end the life of a satellite by mechanisms that are not well understood and not normally taken into account in satellite design. For example, arc/discharge phenomena resulting from highly conductive plasma acting as a current path across normally shielded circuits may have contributed to the loss of the Olympus experimental communications satellite on August 11, 1993. The possibility of significant storm activity during the Leonid meteor showers of November 1998, 1999 and 2000 (impact velocity, 72 km/s) has heightened awareness of potential vulnerabilities from hypervelocity electromagnetic effects to orbital assets. The concern is justified. The amount of plasma, electrostatic charge and the magnitude of the resulting currents and electric fields scale nearly as the cube of the impact velocity (∝ ν2.6). Even for microscopic Leonid impacts, the amount of plasma approaches levels that could be dangerous to spacecraft electronics. The degree of charge separation that occurs during hypervelocity impacts scales linearly with impactor mass. The resulting magnetic fields increase linearly with impactor radius and could play a significant role in our understanding of the paleomagnetism of planetary surfaces.