DSN support of Mars Observer

This article provides a summary of the DSN prelaunch, launch, and cruise support of the Mars Observer through Trajectory Correction Maneuver 2 (TCM-2) on 8 Feb. 1993. This summary includes planning, implementation, testing, DSN special configurations and DSN operational problems, and successes and challenges to date

Telecommunications and data acquisition systems support for Voyager missions to Jupiter and Saturn, 1972-1981, prelaunch through Saturn encounter

The Deep Space Network has supported the Voyager Project for approximately nine years, during which time implementation, testing, and operational support was provided. Four years of this time involved testing prior to launch; the final five years included network operations support and additional network implementation. Intensive and critical support intervals included launch and four planetary encounters. The telecommunications and data acquisition support for the Voyager Missions to Jupiter and Saturn are summarized

Tracking and data system support for the Viking 1975 mission to Mars. Volume 1: Prelaunch planning, implementation, and testing

The tracking and data acquisition support for the 1975 Viking Missions to Mars is described. The history of the effort from its inception in late 1968 through the launches of Vikings 1 and 2 from Cape Kennedy in August and September 1975 is given. The Viking mission requirements for tracking and data acquisition support in both the near earth and deep space phases involved multiple radar tracking and telemetry stations, and communications networks together with the global network of tracking stations, communications, and control center. The planning, implementation, testing and management of the program are presented

A new model for mixing by double-diffusive convection (semi-convection): I. The conditions for layer formation

The process referred to as "semi-convection" in astrophysics and "double-diffusive convection in the diffusive regime" in Earth and planetary sciences, occurs in stellar and planetary interiors in regions which are stable according to the Ledoux criterion but unstable according to the Schwarzschild criterion. In this series of papers, we analyze the results of an extensive suite of 3D numerical simulations of the process, and ultimately propose a new 1D prescription for heat and compositional transport in this regime which can be used in stellar or planetary structure and evolution models. In a preliminary study of the phenomenon, Rosenblum et al. (2011) showed that, after saturation of the primary instability, a system can evolve in one of two possible ways: the induced turbulence either remains homogeneous, with very weak transport properties, or transitions into a thermo-compositional staircase where the transport rate is much larger (albeit still smaller than in standard convection). In this paper, we show that this dichotomous behavior is a robust property of semi-convection across a wide region of parameter space. We propose a simple semi-analytical criterion to determine whether layer formation is expected or not, and at what rate it proceeds, as a function of the background stratification and of the diffusion parameters (viscosity, thermal diffusivity and compositional diffusivity) only. The theoretical criterion matches the outcome of our numerical simulations very adequately in the numerically accessible "planetary" parameter regime, and can easily be extrapolated to the stellar parameter regime. Subsequent papers will address more specifically the question of quantifying transport in the layered case and in the non-layered case.Comment: Submitted to Ap

Why did the Walleye Cross the Reservoir? Explaining Adult Walleye Use of the Missouri River Upstream of Canyon Ferry Reservoir to Toston Dam

Over the last decade, walleye (Sander vitreus) have been increasingly using the Missouri River upstream of Canyon Ferry Reservoir to Toston Dam, and Montana Fish, Wildlife, and Parks wants to understand why these walleye are moving upstream and how it could impact the existing fish community in the river. To understand if this expansion of habitat could be associated with spawning and/or foraging, we examined the composition and distribution of juvenile fish in the area. Specifically, the presence of juvenile walleye would indicate that adult walleye were using the river to spawn and/or if there were abundant prey fish available then adults might be increasingly using the river to feed. To ensure a representative data set, we divided the 23-mile-long stretch of river into three sampling sections. In each section, juvenile fish were sampled using beach seines and mini-fyke nets across pool, riffle, run, and backwater habitats. Each section was sampled twice during the summer of 2016, once in late July or early August and again in mid-August. We captured 26,510 fish, with yellow perch (Perca flavescens), white sucker (Catostomus catostomus) and longnose dace (Rhinichthys cataractae) being the most common species captured. Only 16 of these fish were juvenile walleye, all coming from sampling locations at the interface of the river floodplain and the reservoir; no juvenile walleye were found in the river upstream of this interface. Based on these results, it appears that walleye did not use the river to spawn. However high densities of yellow perch, one of the walleye’s favorite prey items, suggests that adult walleye are using this stretch of river to feed. Additionally, classification and regression tree results of habitat associations indicate that perch occurred in habitat with characteristics preferred by walleye, suggesting that walleye may impact the perch population the most in the future