Rosetta CONSERT Data as a Testbed for In Situ Navigation of Space Probes and Radiosciences in Orbit/Escort Phases for Small Bodies of the Solar System

Many future space missions to asteroids and comets will implement autonomous or near-autonomous navigation, in order to save costly observation time from Earth tracking stations, improve the security of spacecraft and perform real-time operations. Existing Earth-Spacecraft-Earth tracking modes rely on severely limited Earth tracking station resources, with back-and-forth delays of up to several hours. In this paper, we investigate the use of CONSERT ranging data acquired in direct visibility between the lander Philae and the Rosetta orbiter, in the frame of the ESA space mission to comet 67P/Churyumov-Gerasimenko, as a proxy of autonomous navigation and orbitography science capability.

The Congressional Black Caucus and the Closure of NASA’s Satellite Tracking Station at Hartebeesthoek, South Africa

Keith Snedegar explores the impact of the civil rights movement on decisions related to NASA facilities outside the United States. Snedegar maintains that when Charles C. Diggs Jr., one of the founders of the Black Congressional Caucus, visited the NASA satellite tracking station at Hartesbeesthoek, South Africa, in 1971, he discovered a racially segregated facility where technical jobs were reserved for white employees and black Africans essentially performed menial labor. Upon his return to the United States, the Detroit congressman embarked on a two-year struggle, first to improve workplace equity at the tracking station, and later, for the closure of the facility. NASA administration under James Fletcher was largely indifferent to demands for change at the station. It was only after Representative Charles Rangel proposed a reduction in NASA appropriations did the agency announce plans to end its working relationship with the white minority regime of South Africa. NASA’s public statements suggested that a scientific rationale lay behind the station’s eventual closure in 1975, but this episode clearly indicates that NASA was acting only under political pressure, and its management remained largely insensitive to global issues of racial equality.

Relationship of baseline and maximum glucocorticoid concentrations to migration propensity: a field test with wild subadult brown trout (Salmo trutta)

There is considerable variation in glucocorticoid (GC) baseline status and stress responses of individuals, yet the cause and consequence of this variation remains ambiguous. Attempts to relate GC levels to fitness and life-history trade-offs have yielded variable results. In this study, we evaluated whether baseline and poststressor GC hormone concentrations predicted migration strategy (i.e., resident or migrant) and successful seaward migration in a partially migrating population of juvenile brown trout (Salmo trutta Linnaeus, 1758). Baseline (N = 99) or poststressor (N = 102) plasma cortisol concentrations were obtained from brown trout and they were tagged with passive integrated transponder (PIT) and released in a natural Danish stream. Subsequently, fish were tracked with PIT reader systems and the stream was resampled for resident individuals. GC levels were not found to be associated with recapture of resident individuals or migration propensity to our first tracking station (S1), but increased baseline (and not poststressor) GC levels were associated with increased passage from S1 to our second tracking station, which anecdotally was an area of high predation or challenge. Our study found no evidence to suggest that cortisol regulates the migration life history in juvenile brown trout, but intermediate increases in baseline GC (and not poststressor GC) levels may favor migration performance.