Elements and ephemeris of Comet G 1906 (Thiele)

G. Ledyard Stebbins (1906-2000): an appreciation.

L Stebbins, born January 6, 1906, was deeply fond of nature all his life, starting with his experiences around Seal Harbor, Maine, when he was 4 years old. While he was still young, his mother contracted tuberculosis, and the family moved west to find a more healthy climate for her, first in Pasadena, then in Colorado Springs. An important formative period of Ledyard’s life was spent at Cate Sc...

g-Elements of matroid complexes

A g-element for a graded R-module is a one-form with properties similar to a Lefschetz class in the cohomology ring of a compact complex projective manifold, except that the induced multiplication maps are injections instead of bijections. We show that if k(∆) is the face ring of the independence complex of a matroid and the characteristic of k is zero, then there is a non-empty Zariski open su...

IRNSS Orbit Determination and Broadcast Ephemeris Assessment

The Indian Regional Navigation Satellite System (IRNSS) is an emerging satellite based navigation system offering an independent positioning and timing service over India and neighboring regions. Based on satellite laser ranging data collected by selected stations of the International Laser Ranging Service (ILRS) precise orbits have been determined for the first pair of inclined geosynchronous ...

Bivariate Blending Thiele-Werner’s Osculatory Rational Interpolation

A numerical time ephemeris of the Earth

We present a time ephemeris of the Earth, TE405, which approximates a relativistic time-dilation integral from 1600 to 2200 using numerical quadrature of quantities supplied by the recent JPL ephemeris, DE405. The integral is required to transform between terrestrial time, TT, and the (solar-system) barycentric time scales Teph or TCB. Teph is a linear transformation of TCB that represents the ...