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.
Examination of spacecraft anomalies provides insight into complex space environment
Abstract Spacecraft operations are affected by a variety of natural and manmade features that create significant ambiguity as to root cause determination for many anomalies and failures of satellites. The natural space environment comprises dynamic radiation, energetic atomic particles, and particulates (micrometeoroids and orbital debris) that vary temporally and spatially across relevant Earth orbits. Some of the failure mechanisms are further obfuscated by intricate local interactions, the fact that failures are often the result of more than one environmental effect, and lack of diagnostic sensors onboard spacecraft. At the same time, manmade influences on spacecraft anomalies and failures include design, manufacture, integration/installation, parts quality, testing completeness, and operations. These manmade aspects of the anomaly/failure attribution process are equally daunting as much of the relevant information is either not collected or not widely distributed for a variety of reasons. This paper details these dimensions of the anomaly/failure attribution process and provides data from a variety of operational examples to illustrate quantitative and specific actions to enhance the anomaly/failure attribution process short-term and long-term.
Pyrite multiple-sulfur isotope evidence for rapid expansion and contraction of the early Paleoproterozoic seawater sulfate reservoir
Abstract Earthʼs oxygenation is often described in terms of two unidirectional steps at the beginning and end of the Proterozoic Eon, separated by a long-lived intermediate redox state. Recent work defines a more complicated path to oxygenation, exemplified by an apparent drop in oxidation state following the early Paleoproterozoic Lomagundi carbon isotope excursion. The timing of this proposed drop in oxidation state is not well constrained, and it is not clear how it relates to redox conditions during the remainder of the Proterozoic. Here we present a study of pyrite multiple-sulfur isotopes, supported by Fe speciation and organic carbon isotopes, from early Paleoproterozoic black shales. We find evidence for the rapid expansion of the seawater sulfate reservoir during the Great Oxidation Event at ca. 2.3 Ga followed by a subsequent contraction in the size of the seawater sulfate reservoir at ca. 2.05 Ga. This scenario is consistent with the emerging view of a rise and fall in surface oxidation state during the early Paleoproterozoic. Comparison of our new data to other records of the seawater sulfate reservoir suggests that the elevated sulfate concentrations that characterize the early Paleoproterozoic did not return until the late Neoproterozoic.