TEC-EES Final Presentation Days 1998

15-16 September, 1998


ESA/ESTEC

Noordwijk, The Netherlands



Agenda

15 September, 1998 (click to view)

09:00 Introduction

E. Daly (ESA/ESTEC)

09:30 Trapped Radiation Environment Model Developments - Models for High Altitude and Models for Low Altitude (TREND-3) - TRP

Michel Kruglanski; BIRA-IASB (Belgium) with MPAe(D) and MSSL(UK)

Standard Models for the Trapped Radiation Belts are outdated and poorly suited to many present-day applications. This study addressed particular aspects of these problems. At high altitudes the main problem is the great variability in the environment over many timescales. Data from spacecraft including Meteosat, CRRES and ISEE were used to construct databases and subsequently models of energetic electron flux temporal and spatial characteristics. At low altitude, the standard model takes no account of strong directionality, has no explicit link to atmospheric density and is based on a very short dataset from an atypical solar maximum. This dataset was re-analysed, an anisotropy model constructed and models derived from analysis of more modern datasets.

10:45 Coffee

11:00 Radiation Environment Monitor Data Analysis - TRP

P. B�hler; Paul Scherrer Institute, Switzerland

ESA's Radiation Environment Monitors (REMs) are simple pairs of single shielded silicon diode detectors. One REM flew on the UK STRV-1b spacecraft in GTO and the other on MIR. The lifetime of the STRV instrument is about 4 years, far beyond the planned 1 year. Each REM is sensitive to protons with energies E > 30 MeV and to electrons with energies E>1.2MeV. The influence of solar-heliospheric events on the outer, electron, radiation belt is a strong feature of REM observations. We see recurrent radiation-belt effects due to the 27-day solar rotation period and associated recurrent fast solar wind (SW) streams. The arrival of a fast SW stream at the earth first causes a depletion of the outer belt high energy electron population, followed by a rapid (~few days) increase where the flux level reached depends on the SW peak velocity. Fluxes then slowly decay. The large electron injection of January 1997, which received wide media publicity, was seen. Summaries of the orbital dose measurements are presented. We have observed that the energetic electron environment exhibits strong seasonal variations. Despite the simplicity of the instrument, the REMs have provided a wealth of useful data showing that, with a long enough mission to monitor long-term effects, and flying in interesting, useful and relevant orbits, highly valuable data can be derived from such monitors. Current static models are inadequate for many contemporary mission and spacecraft design purposes. Further missions of this kind are planned and the instrument, mission, and data analysis procedures are described.

12:15 Complementary activities - future activities

13:00 Lunch

14:00 Engineering Tools for Internal Charging - TRP

D. Rodgers and L. Levy; DERA (UK), ONERA-DESP (F)

Internal charging occurs in spacecraft when energetic electrons stop in materials. It can lead to hazardous discharges. There is currently no easy way to quantify the susceptibility of materials to internal charging in a way which allows corrective actions, such as additional shielding or changes in properties, to be easily identified. A software tool, DICTAT, has been developed to enable spacecraft engineers to predict whether on-board dielectrics are vulnerable to electrostatic discharge. It simulates irradiation of simple shielded single-dielectric structures, calculating time-dependent internal electric fields, taking into account the effect on conductivity of electric field, dose rate and temperature. It includes a worst-case model of electron fluxes in the outer radiation belt, as well as interfaces with standard models. It automatically informs the user what amount of additional shielding is necessary to meet the specification. It can also simulate test set-ups. A complementary programme of laboratory tests has been carried out and the results from the code and the laboratory tests have been compared. Interfaces with Spenvis are being established.

15:15 Coffee

15:30 Space Weather, Spacecraft Anomalies and Spacecraft Charging Simulations - TRP

H. Koskinen and J.-E. Wahlund; FMI (Finland), IRF-Uppsala (S)

  • State of the art of space weather modelling; The state of the art in Europe regarding space weather activities is presented and recommendations for an ESA strategy in the field are given. The crucial problem of European simulation capability is discussed in depth together with a draft URD-SRD document for a software-based space weather forecast system with effort estimates. Finally, a space weather server containing an easy to browse catalogue of space weather resource with a good coverage of the European ones is presented.
  • Freja charging data analysis; The Swedish scientific spacecraft measurements are analysed in depth in order to characterise the charging environment on polar orbit relevant to modern European spacecraft technology. This led to the production of an up-to-date worst-case electron spectrum and of a WWW-based database of the Freja charging environment. A test of the ability of the POLAR code to model this was made, showing that improvement of the code is crucially needed (it was unable to predict the observations). [See http://www.geo.fmi.fi/spee/ ; http://www.irfu.se/]
  • Prediction of geostationary spacecraft anomalies and prototype anomaly index; A database of anomalies observed on a Swedish geostationary spacecraft was developed and used together with a Meteosat anomaly database to investigate the feasibility of forecasting spacecraft anomalies on the basis of space environment data and an artificial intelligence system. This led to the development of a prototype of a forecast system of spacecraft anomalies, successfully tested on two different spacecraft. Furthermore, it is shown that a significant fraction of these anomalies are due to the electron environment in the range 10-100 keV.

17:00 Complementary activities - future activities

16 September, 1998 (click to view)

09:00 Post-Flight Analysis of Spacecraft Surfaces: Meteoroids & Debris Impacts - General Budget

A. McDonnell and B. Carey; Unispace Kent (UK), SAS (B)

  • Post-flight investigation programme; Following the return from space of a solar array from the Hubble Space Telescope and the complete Eureca Spacecraft, a wide-ranging set of investigations was undertaken to identify and characterise all impact features on the surfaces. Many groups participated in these investigations. The impact features were used to deduce properties of the impacting population and thereby to contribute to the validation of space debris and meteoroid environment and damage models. MLI blankets, solar cells and other surfaces were examine and the investigations included residue analysis.
  • World-Wide-Web based database system - Madweb; A WWW-based system was developed containing a large part of the images of impact features taken, the chemical analysis results and the analysis reports of the various groups.

11:00 The ESABASE Software - Overview and Current Status - General Budget

F. Liard; ALSTOM/ETC (UK)

ESABASE is a general geometry modelling and analysis environment, integrating a set of applications for spacecraft preliminary design mainly in the area of environmental analysis. It allows geometry modelling including kinematics and pointing derived from orbital data. These facilities are important when the environment has directionality, or when its effects are affected by the spacecraft geometry and/or configuration. The main applications areas are: atomic oxygen impingement, microparticle (small-sized space debris and meteoroids) impacts, energetic particle radiation shielding, outgassing contamination, and sunlight exposure. An overview of the general capabilities will be given, and the current work on the software will be introduced.

12:00 Space Environment Information System (Spenvis) - GSTP

Daniel Heynderickx; BIRA-IASB (Belgium) with SAS(B) and PSI(CH)

The space environment (including radiation, plasma/charging, meteoroids & debris, atmosphere, magnetic fields) is causing increasing problems for spacecraft. Easier access to models and data are needed by engineers for efficient spacecraft and mission design. A comprehensive system has been developed containing models of most aspects of the space environment and their effects on spacecraft which is both easy to use by the non-specialist to make quantitative assessments for arbitrary projects, and has high-quality help and back-up information. The system is based on WWW technology. Access to data resources and other valuable information sources are being established. Intranet versions are available and a JAVA-based interface is under development.

13:00 Lunch

14:00 Demonstrations and Round-Table Discussion