Three GOCE-based gravity field solutions have been computed by ESA’s high-level processing facility and were released to the user community. All models are accompanied by variance-covariance information resulting either from the least squares procedure or a Monte-Carlo approach. In order to obtain independent external quality parameters and to assess the current performance of these models, a s...

Effective satellite mission operations are directly impacted by the ability to generate accurate and precise orbit predictions. High precision orbit determination processes rely on detailed force models to propagate an orbit solution and predict future orbit behavior. While gravity forces are typically well understood, the modeling of non-conservative forces is often more challenging, causing i...

the recent dedicated satellite gravimetry missions have provided huge amount of high quality gravity data with global coverage. from computational point of view, estimation of the unknown gravity field parameters is a highly demanding task due to the sheer number of observations and the unknown coefficients. different computational schemes have been proposed to tackle the problem. since the ear...

The population of deep space resident space objects (RSOs) are tracked with sparse resources and thus tracking data are only collected on these objects for a relatively small fraction of their orbit revolution (i.e. a short-arc). This contributes to commonly mistagged or uncorrelated RSOs, and their associated trajectory uncertainties (covariances) to be less physically meaningful. The case of ...

We report on the preliminary determination of the visual orbit of the double-lined spectroscopic binary system BY Draconis with data obtained by the Palomar Testbed Interferometer in 1999. BY Dra is a nearly equal-mass double-lined binary system whose spectroscopic orbit is well known. We have estimated the visual orbit of BY Dra from our interferometric visibility data fit both separately and ...

The effects of aerodynamic perturbation forces on the orbital life of low altitude Low Earth Orbit (LEO) satellites are investigated, with a focus on the secular perturbations caused by lift and drag. The secular effects can be divided into the circularization of the orbit for both lift and drag perturbation forces, and the decrease of the orbit semimajor axis for drag perturbation. A study of ...

The first three ionization potentials of americium are calculated using ab initio spin-orbit configuration interaction techniques. These results are favorably compared with experimental and theoretical work. The lowest two ionization potentials are accurately determined using wavefunctions constructed as simple single and double substitutions from a self-consistent field reference configuration...

By August 2016, 5 new-generation BeiDou satellites (BeiDou-3) have successfully been launched. The observations of a very limited number of 9 International GNSS (Global Navigation Satellite System) Monitoring and Assessment Service (iGMAS) stations and 52 Multi-GNSS Experiment (MGEX) stations from 16 July to 14 August 2016 are processed to determine the orbits of BeiDou-3 and BeiDou-2 satellite...

We present a procedure for determination of positions and orbital elements, and associated uncertainties, of outer Solar System planets. The orbit-fitting procedure is greatly streamlined compared to traditional methods because acceleration can be treated as a perturbation to the inertial motion of the body. These techniques are immediately applicable to Kuiper Belt Objects, for which recovery ...