Search Publications
Elemental Abundances in the Solar Upper Atmosphere Derived by Spectroscopic Means
Feldman, U.; Widing, K. G.
The composition of the solar photosphere is believed to be uniform. Indeed a quantity that does not vary with solar surface location or with a particular solar feature, i.e., no observational evidence is available to indicate that the photospheric composition near the solar equator is different from the photospheric composition near the solar pole…
Atomic Deuterium/Hydrogen in the Galaxy
Linsky, Jeffrey L.
An accurate value of the D/H ratio in the local interstellar medium (LISM) and a better understanding of the D/H variations with position in the Galactic disk and halo are vitally important questions as they provide information on the primordial D/H ratio in the Galaxy at the time of the protosolar nebula, and the amount of astration and mixing in…
Dynamic Modelling of the Hipparcos Attitude
van Leeuwen, Floor; Fantino, Elena
We present a new method for a high-accuracy reconstruction of the attitude for a slowly spinning satellite. This method, referred to as the fully-dynamic approach, explores the possibility to describe the satellite's attitude as that of a rigid body subject to continuous external torques. The method is tried out on the Hipparcos data and is shown …
A Detailed Analysis of the Operational Orbit of the Hipparcos Satellite
van Leeuwen, Floor; Dalla Torre, Andrea
An analysis of the orbital evolution of the ESA's Hipparcos satellite is presented. Hipparcos operated between August 1989 and March 1993 in a highly elliptical orbit: a geostationary transfer orbit with increased perigee height. The requirements of the scientific mission included high accuracy knowledge of the position and velocity vectors of the…
Modelling the Torques Affecting the Hipparcos Satellite
van Leeuwen, Floor; Fantino, Elena
Reconstructed attitude data for the Hipparcos mission as obtained in the final stages of the data analysis for the published catalogue is used to derive detailed information on the dynamics of the satellite. Most elements of the inertia tensor of the satellite could be calibrated from the observed acceleration data, which are also used to reconstr…
Reconstructed 3-d magnetic field structure and hard X-ray two ribbons for 2000 Bastille-day event
Yan, Yihua; Huang, Guangli
The Bastille-day event in 2000 produced energetic 3B/X5.6 flare with a halo CME, which had great geo-effects consequently. This event has been studied extensively and it is considered that it follows the two-ribbon flare model. The flare/CME event was triggered by an erupting filament and TRACE observations showed formation of giant arcade structu…
The Operational Environment of the Hipparcos Mission
van Leeuwen, Floor; Penston, Margaret J.
We investigate links between the observational environment as experienced by the Hipparcos satellite and the performance of the spacecraft and payload instrumentation, with particular emphasis on finding out whether some of these effects may have been inadequately represented in instrument calibrations and could thus have affected the scientific r…
Introduction to a Further Examination of the Hipparcos Data
van Leeuwen, Floor; Fantino, Elena
We present an introduction to four papers on further analysis of the raw Hipparcos data. This analysis has lead to the recognition of how orbit, radiation and temperature conditions did or didn't affect the scientific results of the Hipparcos mission. It also led the way to a new reduction of the scientific data that shows from its initial results…
Variations of the magnetic fields in large solar flares
Donea, A. -C.; Schunker, H.
We present preliminary results from high resolution observations obtained with the Michelson Doppler Imager (MDI) instrument on the SOHO of two large solar flares of 14 July 2000 and 24 November 2000. We show that rapid variations of the line-of-sight magnetic field occured on a time scale of a few minutes during the flare explosions. The reversib…
Telescopic and Microscopic views of the magnetosphere: Multispacecraft observations
Baker, D. N.
The magnetospheric research community has long sought the capability to view the Sun-Earth system in a global way and to probe concurrently the microphysical details of key physical regions. This objective has now been substantially realized with the combination of the CLUSTER and IMAGE missions. With the additional use of SOHO, ACE, FAST, SAMPEX,…