Precise orbit and baseline determination for maneuvering low earth orbiters

GPS Solutions - Orbital maneuvers are usually performed as needed for low earth orbiters to maintain a predefined trajectory or formation-flying configuration. To avoid unexpected discontinuities...     

Book reviews

Mineralium Deposita -     

A basic-to-ultrabasic layered extrusion in east Elba

Detailed geochemical analyses were made on an ophiolitic basalt-gabbro-serpentinite series in east Elba, northern Italy.Close relationships in composition were determined for the rocks within this series. Chemistry and mineral distribution allow the supposition to be made that differentiation in a large basic submarine extrusion took place in situ and that early crystallized mineral phases separated by gravity. This resulted in the formation of a sequence of anorthosite, gabbro and peridotite (serpentinite) under a pillow-basalt cover. Gradual change in chemistry is an important diagnostic feature of this series.     

Rural Social Networks along Amazonian Rivers: Seeds,Labor and Soccer among Communities on the Napo River,Peru

Research on Amazonian communities has focussed more often on rural‐urban linkages than on links among rural communities. This is unsurprising, given the low density of population, limited intercommunity commerce, and importance of direct city‐market relations. Social relations among rural communities are also important in shaping rural livelihoods and lifeways. We report on the findings of a large‐scale census of communities in the Napo River basin in northeastern Peru (n=174). Data were gathered on intervillage crop seed acquisition and cooperative labor sharing as two key inputs in agriculture, and on intervillage soccer matches, which are integral to rural social life. We analyze the socio‐spatial networks of each practice, paying attention to settlement patterns, community ethnicity, and differential access to the uplands. We find that seeds and labor flow along soccer network lines. Rural social networks appear to be structured strongly by ethnicity (homophily) and reflect important complementarities between upland and lowland communities (weak ties).     

Trends in the frequency of synoptic types in central-southern Chile in the period 1961–2012 using the Jenkinson and Collison synoptic classification

Atmospheric circulation patterns in southern Chile (42° 30′ S) were studied in order to determine and analyse the most characteristic synoptic types and their recent trends, as well as to gain an understanding of how they are associated with low-frequency variability patterns. According to the Jenkinson and Collison (J&C) classification method, a 16-point grid of sea-level pressure data was employed. The findings reveal that some synoptic types show statistically significant trends with a 95% confidence level, positively for anticyclonic westerly hybrids (AW) and advective types for third and fourth quadrant wind flows (W, NW, and N) and negatively for SW and cyclonic hybrids (CS and CSW). A model has been constructed of the linear regression of some weather types with teleconnections that most affect Chile: the undetermined types (U), AW were associated with El Niño or the warm phase of the Pacific Decadal Oscillation (PDO), whereas the cyclonic northerly and cyclonic northeasterly types (CN and CNE) were associated with La Niña or cool phase of the PDO. The weather types associated with Antarctic Oscillation (AAO) in its positive phase are anticyclonic northerly and northeasterly and northerly advection types, while in its negative phase are cyclonic southwesterly and advection types.     

Multiscale Gravitational Field Recovery from GPS-Satellite-to-Satellite Tracking

The purpose of GPS-satellite-to-satellite tracking (GPS-SST) is to determine the gravitational potential at the earth's surface from measured ranges (geometrical distances) between a low-flying satellite and the high-flying satellites of the Global Positioning System (GPS). In this paper, GPS-satellite-to-satellite tracking is reformulated as the problem of determining the gravitational potential of the earth from given gradients at satellite altitude. The uniqueness and stability of the solution are investigated. The essential tool is to split the gradient field into a normal part (i.e. the first-order radial derivative) and a tangential part (i.e. the surface gradient). Uniqueness is proved for polar, circular orbits corresponding to both types of data (first radial derivative and/or surface gradient). In both cases gravity recovery based on satellite-to-satellite tracking turns out to be an exponentially ill-posed problem. Regularization in terms of spherical wavelets is proposed as an appropriate solution method, based on the knowledge of the singular system. Finally, the extension of this method is generalized to a nonspherical earth and a non-spherical orbital surface, based on combined terrestrial and satellite data.     

Shallow Circulations: Relevance and Strategies for Satellite Observation

Shallow circulations are central to many tropical cloud systems. We investigate the potential of existing and upcoming data to document these circulations. Different methods to observe or constrain atmospheric circulations rely on satellite-borne instruments. Direct observations of the wind are currently possible at the ocean surface or using tracer patterns. Satellite-borne wind lidar will soon be available, with a much better coverage and accuracy. Meanwhile, circulations can be constrained using satellite observations of atmospheric diabatic heating. We evaluate the commonalities and discrepancies of these estimates together with reanalysis in systems that include shallow circulations. It appears that existing datasets are in qualitative agreement, but that they still differ too much to provide robust evaluation criteria for general circulation models. This state of affairs highlights the potential of satellite-borne wind lidar and of further work on current satellite retrievals.