We explore how well crowded field point-source photometry can be accomplished with Sloan Digital Sky Survey (SDSS) data. For this purpose, we present a photometric pipeline based on DoPHOT (Schechter et al. 1993), and tuned for analyzing crowded-field images from the SDSS. Using Monte Carlo simulations we show that the completeness of source extraction is above 80% to an i band AB magnitude of ...

High-accuracy Low Earth Orbit (LEO) satellite clock and orbital products are preconditions to realize LEO augmentation for high-accuracy GNSS-based positioning on the ground. There is a high correlation between orbit parameters in kinematic Precise Determination (POD) process. While future satellites planned be equipped with better clocks, benefits of modeling high-stability clocks not yet thor...

The excitation of Rossby waves on the edge of the stratospheric polar vortex, due to time-dependent topographic forcing, is studied analytically and numerically in a simple quasigeostrophic f-plane model. When the atmosphere is compressible, the linear response of the vortex is found to have two distinct components. The first is a spectrum of upward-propagating waves that are excited by forcing...

It is with great sorrow that we write about the demise of Leo Sachs, the Otto Meyerhof Professor of Molecular Biology, friend, colleague and brilliant scientist. Leo was born in Leipzig, Germany in 1924, emigrated with his family from Nazi Germany to England in 1933, and reached Israel in 1952. He began studying agricultural botany at the University of Wales, became fascinated by genetics and d...

We set new limits on the mass of the Milky Way, making use of the latest kinematic information for Galactic satellites and halo objects. Our sample consists of 11 satellite galaxies, 137 globular clusters, and 413 field horizontal-branch (FHB) stars up to distances of 10 kpc from the Sun. Roughly half of the objects in this sample have measured proper motions, permitting the use of their full s...

Sequential satellite microwave images of tropical cyclones readily lend themselves to morphing applications, which allow for a straightforward visualization of the storms' structural trends. P olar and other low-Earth-orbiting (LEO) satellites provide critical data for use in weather analysis and forecasting. However, the temporal sampling issue leads to the common problem of interpreting seque...

Measuring greenhouse gas (GHG) profiles with global coverage and high accuracy and vertical resolution in the upper troposphere and lower stratosphere (UTLS) is key for improved monitoring of GHG concentrations in the free atmosphere. In this respect a new satellite mission concept adding an infrared-laser part to the already well studied microwave occultation technique exploits the joint propa...