Results 81 to 90 of about 4,818 (307)

Optimal on-off cooperative manoeuvers for long-term satellite cluster flight

, 2014
When a group of satellites is equipped with a particulary simple propul- sion system, e.g. cold-gas thrusters, constraints on the thrust level and total propellant mass renders cluster-keeping extremely challenging.
Gurfil, Pini, Mazal, Leonel, Mingotti, Giorgio   +2 more
core   +1 more source

Orbital dynamics of earth-orbiting 'smart dust' spacecraft under the effects of solar radiation pressure and aerodynamic drag [PDF]

, 2010
This paper investigates how the perturbations due to asymmetric solar radiation pressure, in presence of Earth's shadow, and atmospheric drag can be balanced to obtain long-lived Earth centered orbits for swarms of SpaceChips, without the use of active ...
COLOMBO, CAMILLA, Colin McInnes, Mcinnes, Colin, Camilla Colombo, Colombo, C., McInnes, C.R.   +5 more
core   +1 more source

Understanding and Modeling the Dynamics of Storm‐Time Atmospheric Neutral Density Using Random Forests

Space Weather
Atmospheric neutral density is a crucial component to accurately predict and track the motion of satellites. During periods of elevated solar and geomagnetic activity atmospheric neutral density becomes highly variable and dynamic.
K. Murphy, A. J. Halford, V. Liu, J. Klenzing, J. Smith, K. Garcia‐Sage, J. Pettit, I. J. Rae   +7 more
doaj   +1 more source

Comparative cranial biomechanics reveal macroevolutionary trends in theropod dinosaurs, with emphasis on Tyrannosauroidea

The Anatomical Record, EarlyView.
Abstract Tyrannosaurus is viewed as a model organism in vertebrate paleontology, with numerous studies analyzing its feeding biomechanics. Nonetheless, the evolution of this feeding performance has been under‐addressed in Tyrannosauroidea, especially in basal tyrannosauroids. Here we used muscle‐force reconstruction and finite element analysis (FEA) to
Evan Johnson‐Ransom, Paul Gignac, Daniel E. Barta, Ryan N. Felice, Eric Snively   +4 more
wiley   +1 more source

Orbital dynamics of "smart dust" devices with solar radiation pressure and drag

, 2011
This paper investigates how perturbations due to asymmetric solar radiation pressure, in the presence of Earth shadow, and atmospheric drag can be balanced to obtain long-lived Earth centred orbits for swarms of micro-scale 'smart dust' devices, without ...
Colombo, Camilla, McInnes, Colin
core   +1 more source

Inter‐ and intraspecific variation in theropod dinosaur dental microwear and its palaeoecological implications

The Anatomical Record, EarlyView.
Abstract Differences in skull and tooth morphology, stomach contents, and estimated bite force between medium‐to‐large sized (≥100 kg) predatory theropod dinosaurs have long been suspected to correlate with differences in their diets and dietary guilds (e.g., hypercarnivory, piscivory).
Cassius Morrison, James Gregory, Christopher Jackson, Jordan Bestwick, Katlin Schroeder, Samuel J.L. Gascoigne, Paul Bills, Laura B. Porro, Philip D. Mannion, Paul M. Barrett   +9 more
wiley   +1 more source

Influences of Space Weather Forecasting Uncertainty on Satellite Conjunction Assessment

Space Weather
A significant increase in the number of anthropogenic objects in Earth orbit has necessitated the development of satellite conjunction assessment and collision avoidance capabilities for new spacecraft.
William E. Parker, Mervyn Freeman, Gareth Chisham, Andrew Kavanagh, Peng Mun Siew, Victor Rodriguez‐Fernandez, Richard Linares   +6 more
doaj   +1 more source

Evaluation of the DTM-2009 thermosphere model for benchmarking purposes

Journal of Space Weather and Space Climate, 2012
Aims: The Drag Temperature Model (DTM) is a semi-empirical model describing the temperature, density, and composition of the Earth’s thermosphere. DTM2009 and DTM2000, and the COSPAR reference models NRLMSISE-00 and JB2008, are evaluated in order to ...
Guijarro Nuria, Olmedo Estrella, Sánchez-Ortiz Noelia, Bruinsma Sean L.   +3 more
doaj   +1 more source

Benchmarking Forecasting Models for Space Weather Drivers

Space Weather, 2020
Space weather indices are commonly used to drive operational forecasts of various geospace systems, including the thermosphere for mass density and satellite drag.
Richard J. Licata, W. Kent Tobiska, Piyush M. Mehta   +2 more
doaj   +1 more source

Exploring the cranial morphology and possible convergences of Triassic non‐crocodylomorph pseudosuchians (Archosauria: Pseudosuchia) with other sauropsids through linear morphometrics

The Anatomical Record, EarlyView.
Abstract Triassic pseudosuchians had highly diversified cranial morphologies. These archosaurs occupied diverse ecological roles, ranging from terrestrial predators and herbivores to semiaquatic ambush predators and possible waders. Here, we apply linear cranial morphometrics to assess possible convergences with other sauropsids from the clades ...
Rafael Terras, Rodrigo Temp Müller, Leonardo Kerber, Mirian Carbonera   +3 more
wiley   +1 more source