TEC-EES Final Presentation Days 1999

14-15 December, 1999

Room Fresnel

ESA/ESTEC

Noordwijk, The Netherlands


Day 1

09:30 Introduction

09:45 The Space Environment Information System

10:30 Coffee

10:45 The ESABASE Software - Current status and New User Interface

11:30 Engineering Tools for Internal Charging

12:15 Spacecraft-Plasma Interactions - Status Report

12:25 Discussion

12:45 Lunch

14:00 Contamination Modelling - Outgassing / Vent Analysis Tool

14:45 Study of Smaller Impact Craters on HST Solar Cells

15:30 Coffee

15:45 Martian Environment Model Development - Status Report

15:55 REM Data Analysis and SREM Preparation

16:40 Space Environment Database Analysis Tool - Status Report

16:50 Discussion

17:15 end day 1

Day 2

09:15 Energetic Particle Shielding and Interaction Tools

10:00 Models of the Earth's Radiation Belts

10:45 Coffee

11:00 In-situ Impact Detectors in Space - Development and Data Analysis - Status Report

11:10 Spacecraft Anomaly Analysis and Prediction System - Status Report

11:20 Discussion:

  • Outlook on Environmental Effects and Recent Problems
  • Future Needs and Possible Activities
  • Other Matters

12:00 Lunch

14:00 Demonstrations and Further Discussions

 


INTRODUCTION

Space environments such as radiation, plasmas, atmospheres, meteoroids and debris are becoming increasing threats to space programmes.

  • Radiation environments have been a severe problem for recent science missions, are a serious threat to commercial and other application spacecraft and are a danger to man in space;
  • Plasma environments cause spacecraft charging, can interact with spacecraft to disrupt plasma observations, and are also generated by electric propulsion systems;
  • Neutral atmospheric environments need to be considered in mission planning both for Earth missions and for operations at other planets involving aero braking and atmospheric entry;
  • Meteoroids and debris continue to be a concern to manned missions, but are also a threat to sensitive elements of other types of spacecraft.

As part of the Space Environments and Effects Major Axis of the Technology Research Programme, several studies have been undertaken on various aspects of the domain. Some related activities have also been performed under GSTP and general budget funding.

On 14 and 15 December 1999, Final Presentation Days have been organised at ESTEC where these efforts will be reported. Abstracts of the presentations are provided below. In addition to these reports, members of the Space Environments and Effects Analysis Section (TEC-EES) will briefly present other complementary activities, including future activities.

These final presentation days follow on from the Space Environments and Effects final presentation days held in September 1998.

The times given here are subject to change and a final detailed timetable will be established nearer the event.


SPENVIS

D. Heynderickx, B. Quaghebeur, E. Speelman; BIRA-IASB, Belgium

The SPace ENVironment Information System (SPENVIS), developed under the GSTP, provides standardized access to models of the hazardous space environment through a WWW interface. The interface includes parameter input with extensive defaulting, definition of user environments, streamlined production of results (both in graphical and textual form), background information, and extensive on-line help and background information. Intranet and single-user implementations are availabe in addition to the main Internet site.

SPENVIS is designed to help spacecraft engineers perform rapid analyses of environmental problems and, with extensive documentation and tutorial information, allows engineers with relatively little familiarity to produce reliable results. It is based on internationally recognised standard models and methods in many domains. It uses an orbit generator to produce orbital files for many different aspects of mission analysis, and can also generate maps and profiles to study the distribution of model parameters.

SPENVIS is a highly valuable advance for hardness assurance and system engineering, allowing reliable, authoritative and streamlined access to standard methods and models, alongside an active environment standard document. The results of this type of initiative are increased efficiency, reduced cost and faster assessment of environmental hazards.

SPENVIS includes models for:

  •  
    • Radiation environments
    • Radiation Effects
    • Spacecraft Surface Charging
    • Spacecraft Internal Charging
    • Atmosphere and ionosphere (including atomic oxygen)
    • Microparticles (small debris and meteoroids)
    • Geomagnetic Fields
    • Access to data from space environment measurements
    • The ECSS Space Environment Standard

The ESABASE Software - Current status and new User Interface

F. Liard; ABB ALSTOM/ETC, UK (Contract 10920, Work Order 21, CCN2)

 

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. What is unique about ESABASE is that it allows geometry modelling including kinematics and pointing derived from orbital data. These facilities are important when the effects of the environment are affected by the spacecraft geometry and/or its movement. The main applications areas are: atomic oxygen impingement, micro-particle (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 new user interface which has been developed using Java technology will be presented.


Engineering Tools for Internal Charging

D.J. Rodgers, K.A. Ryden, P.M. Latham, G.L.Wrenn, L. Levy, G. Panabiere; DERA, Farnborough, UK, T.S. Space Systems, Farnborough, UK, DESP/ONERA, Toulouse, France (Contract 12115 Work Order 1)

 

Internal dielectric charging remains a persistent cause of anomalies on modern spacecraft. This process causes charging within lightly shielded dielectric materials on spacecraft in the electron radiation belt. This presentation describes work aimed at developing a self-consistent procedure for assessing the susceptibility of dielectric structures to this hazard. A previous study resulted in the development of DICTAT, an engineering tool to calculate the maximum electric field within a dielectric and to compare this with a threshold for electrostatic discharge. Where the threshold is exceeded, DICTAT calculates changes to the structure required to reduced the threat to an acceptable level. The current study results from a number of issues that arose during this earlier work.

 

A good knowledge of the electrical properties of the dielectric is crucial to a DICTAT simulation but, in practice, accurate information is rarely available from existing literature. The current study has resulted in the definition of a standard set of laboratory irradiations and the development of a fitting tool that will enable the material properties to be found. This tool has been successfully applied to laboratory data. A programme of laboratory irradiations has provided data to validate DICTAT and the fitting tool. This work included tests to separate time-dependent and electric field effects on conductivity and has highlighted the dangers in using material parameters from literature where the experimental procedure is not known in detail. Work was carried out to measure temperature and radiation effects on conductivity without expensive, electron beam tests. This has resulted in better knowledge of the associated material parameters and an assessment of the importance of delayed conductivity effects.

 

DICTAT includes a novel electron environment model, called FLUMIC, which is customised to the internal charging problem. This has been given greater functionality and improved accuracy by introducing new data sets.


Spacecraft-Plasma Interactions -Status Report

A. Hilgers; ESA/ESTEC Space Environments and Effects section

A brief review will be made of some activities relating to spacecraft and their interactions with the plasma environment, including:

  •  
    • particle in cell simulation toolkit research and developments
    • simulation of interactions between Rosetta and its plasma environment
    • analysis of plasma and charging data
    • plasma environment monitoring needs and outlook

Contamination Modelling - Outgassing / Vent Analysis Tool

C. Lemcke and J.-F. Roussel; HTS, Wallisellen, CH and DESP/ONERA, Toulouse, France (Contract 12867)

The new ESA contamination analysis tool has been developed in response to: (i) the increasing concern of contamination related to payloads on the international space station and other LEO observation missions and (ii) the development of improved models and algorithms to simulate outgassing and contamination. The main physical modelling enhancements are:

  • Inclusion of the gaseous environment in the form of a volume mesh, which permits to simulate back scatter and self scatter.
  • Inclusion of temperature dependence for emission and sticking in the characterisation of outgassing species.
  • Result processing to obtain column densities.
  • Modelling of vents: Vents can be defined as ON/OFF or exponentially decaying.

In addition to providing enhanced physical modelling capabilities, the development of the new tool was used as the vehicle for technology R&D for establishment of an open software environment making use of external tools for the discrete model generation and result visualisation. With UNIX and PC as the target platforms, the tool is available to the widest possible community. The presentation will include examples also showing the reference commercial modelling tools (model generation / result visualisation).


Impact craters on HST solar cells

G.A.Graham and A.T.Kearsley; Space Sciences Research Unit, School Of BMS, Oxford Brookes University, Oxford OX3 0BP. United Kingdom (Contract 13308)

Prior to the retrieval in 1993 from low Earth orbit, the "-V2" solar array wing of the Hubble Space Telescope was susceptible to hypervelocity impact damage (micrometre to millimetre scale) from both space debris and micrometeoroids. Although little of the original projectile is deposited in the impact crater as intact material, complex impact-derived melt residues that mix the host and the projectile often are preserved. Analytical scanning electron microscopy has been employed to investigate impact craters within the 10-100 micrometre diameter size range and associated residue chemistry where retained. A number of micrometeoroid residues of interplanetary origin have been identified along with one residue which maybe of an interstellar origin. The most common chemistry identified is space debris, with Aluminium and Aluminium Oxide (remnants of solid rocket motor operation) particularly in craters below 30 micrometres diameter being the dominant impactor.


Martian Environment Model Development - Status Report

J.-P. Huot; ESA/ESTEC Space Environments and Effects section

Direct or indirect observations of the environmental conditions in the atmosphere of Mars are too sparse to allow the compilation of a global spatial and temporal database of the conditions prevailing at a given location, at a given season and time of day. Such a database is nonetheless useful for the analysis of re-entry or aerobreaking, the design of surface landers and of remote sensing instruments aboard orbiters in the context of the future Mars missions. A database was  constructed with the help of a general circulation model (GCM) of the Martian atmosphere constructed by merging two GCM’s previously developed separately at LMD and AOPP. The data generated by numerical simulations have been validated with the available observations (Mariner 9, Viking and Pathfinder). The database has been installed at numerous centers and is currently used by CNES for feasibility studies of aero-assistance in the frame of the Mars Sample Return mission and for the preparation of the entry phase of the Netlander mission. The database has also been installed at the Geophysical Research Division of the Finnish Meteorological Institute, to assist the design of the surface module of the Netlander network, at the Cosmic Physics Group of the Astronomical Observatory of Capodimonte, for the preparation of the analysis of PFS data and of other Martian observations and at the Rutherford Appleton Laboratory for the design of the thermal protection of the Beagle 2 Lander.


REM data analysis and SREM preparation

P. Buehler, W. Hajdas, L. Desorgher, A. Zehnder, M. Kruglanski,; Paul Scherrer Institute, CH-5232 Villigen PSI and Belgian Institute for Space Aeronomy, B-1180 Brussels (Contract 11108)

The two Radiation Environment Monitors, REM aboard Strv-1b and Mir have shown that the concept of using rather simple, light-weight, low power consuming instruments for monitoring the space particle radiation environment can be very valuable. Therefore ESA initiated the development of the Standard Radiation Environment Monitor, SREM, which will fly on several future missions. The first will be launched in 2000 on board STRV-1c. In this presentation we report on recent REM results and the preparation of the SREM data analysis.

 

REM aboard Strv-1b has provided a four year database of relativistic electron fluxes in the outer radiation belt. One of the most prominent features of these electron fluxes is their large temporal variations. In order to better understand the causes of these variations and to find a simple model describing them we studied correlations with various geomagnetic and solar wind parameters. The results show that the characteristic time scales are L-dependent and that substorm activity is one of the major drivers for the build up of the relativistic electron population.

 

LEO orbits are important for manned space missions, like Mir, Space Shuttle, ISS. In such an orbit most of the radiation dose occurs in the South Atlantic Anomaly and is caused by high energetic trapped protons of the inner radiation belt. At low altitudes, this proton population is controlled by the Earth's atmospheric density and its altitude gradient, which leads to an anisotropy of the proton fluxes. With the REM on board Mir it was possible to measure the ratio between east and west fluxes and to specify the energy dependence of this ratio.

 

In order to ensure good quality and timely data from the SREMs, preparation of the SREM data analysis environment was undertaken. An important input for the data analysis is the precise specification of the detector response to different particle species as function of energy. For SREM this information was obtained by calibration measurements with protons in the Proton Irradiation Facility, PIF and Monte Carlo simulations. A Data Management and Analysis System, DMAS, was developed which allows processing of all future SREM data in a uniform way. It includes tools for data retrieval, data pre-/processing, a quick-look facility, and a web publishing tool.


Space Environment Database and Analysis Tools (SEDAT) - Status Report

A. Hilgers; ESA Space Environments and Effects section

The Space Environment Database and Analysis Tools (SEDAT) project is intended to develop a new approach to the analysis of spacecraft charged-particle environments for engineering purposes. Energetic charged particles and plasma environments can cause a number of serious problems for spacecraft. Particles can come from the sun (solar energetic particle events), can be encountered in the radiation belts, or can be injected into the near-Earth regions during geomagnetic sub-storms.

 

The innovative approach of this activity is that rather than use of pre-constructed, static models of the environments, data sets are employed together with analysis modules and user-defined tools to extract data of practical use directly from the source data sets as they are needed. The project is assembling a database containing a large and comprehensive set of data about that environment as measured in-situ by a number of   missions. The user will be able to select a set of space environment data appropriate to the engineering problem under study. A set of software tools is being developed which can operate on the data in the SEDAT database. These tools will allow the user to carry out a wide range of engineering analyses. The SEDAT approach offers several advantages to the space environments and effects analyst, which will be discussed.



Energetic Particle Shielding and Interaction Tools

P. Truscott, F. Lei, R. Guerrian, S. Gianni and P. Nieminen; DERA UK, University of Southampton UK, CERN, Switzerland, ESA Space Environments and Effects section (Contract 12115 Work Order 3)

The need to assess the effects of radiation on spacecraft is becoming increasingly important due to the increased sensitivity of microelectronics and sensors and the reduced availability of radiation hard alternatives. Monte Carlo simulation offers the ability to model in detail the physics of space radiation to assess and optimise hardening strategies. Geant4 is a new-generation toolkit for Monte Carlo simulation, intended for a wide range of applications, including space. The current version of this code provides in a single tool comprehensive treatment of the physical processes from PeV energies of hadronic interactions, to <1 keV for electromagnetic interactions and ~eV energies for neutron transport. The European Space Agency as part of the Geant4 international collaboration has supported the development of Geant4 with the objective of making the code the basis of a general space radiation shielding and effects tool (SPARSET). This final presentation will review the physical processes modelled by Geant4 in the context of the user requirements for space radiation effects analysis, and will give an overview of the developments in Geant4 funded by ESA within the Technology Research Programme.


Models of the Earths Radiation Belts

M. Kruglanski, D. Heynderickx, D. Boscher, P. Buehler; IASB-BIRA, Brussels, Belgium, Onera-DESP, Toulouse, France and PSI, Villigen, Switzerland

The standard models (AE-8 and AP-8) used for "Van-Allen" radiation belt environment assessment were constructed from data essentially acquired in the 1960's. Apart from the obvious need to enhance the models by using more up-to-date, higher quality data sets, the models were not able to address serious radiation issues for ESA and other current and future missions. In particular, radiation effects include transient processes (internal charging, radiation background, transients and SEU's in components, temporary enhancements to astronaut doses).

 

To address these transient processes, a completely new approach is needed for radiation belt modelling, involving details of the dynamics and the correlations with geophysical parameters. Attacking these issues is very difficult since it requires good data sets with long time and good spatial coverage. Exploitation of data sets for this purpose is often not straight-forward if it is to be done rigorously. The low altitude environment is also characterised by strong anisotropy, important for missions such as the International Space Station. A higher flux of energetic protons comes from the west than from the east when spacecraft are in the low altitude portion of the radiation belt known as the South Atlantic Anomaly. Models of this anisotropy were developed and were compared with data from the Radiation Environment Monitor on-board MIR. This data set is unique and provided very good validation of the model. The current phase of the project is addressing the main areas of concern:

  • the dynamics of the outer belt electrons, making use of new data sets and advances in radiation belt physical simulations, and examining appropriate "driving" geophysical parameters
  • the inner proton belt and its interactions with the atmosphere, including analysis of the anisotropy and contemporary data sets such as from the SAMPEX spacecraft.
  • model implementation and unification

The project has resulted in the development UNILIB, a well-engineered and documented subroutine library which is highly valuable in space physics and space environment studies.


In-situ impact detectors in space - development and data analysis - Status Report

G. Drolshagen; ESA/ESTEC Space Environments and Effects section

Status and results of the GORID and DEBIE impact detectors are presented. GORID continues to operate in GEO and the resulting data are being analysed in detail. An analytical debris model for GEO is under development. The development of the DEBIE impact detector is nearing completion. DEBIE-1 is scheduled for launch on PROBA in 2001, DEBIE-2 for the ISS in 2003.


Spacecraft Anomaly Analysis and Prediction System - SAAPS - Status Report

A. Hilgers; ESA/ESTEC Space Environments and Effects section

Space plasmas and radiation represent hazardous environments for Earth orbiting spacecraft. Problems are regularly experienced which in extreme cases can lead to failure or loss of spacecraft. It is important to be able to predict and analyse spacecraft anomalies that are caused by the space environment. The space environment is determined by the space weather, which ultimately is driven by the Sun. To be able to predict spacecraft anomalies it is necessary to compile the knowledge and observations of the space weather, which includes the Sun, the solar wind, and the Earth magnetosphere and relate it to the effects on spacecraft. 

 

The aim of the project is to develop an on-line service for spacecraft operators and environmental effect analysts.  The service is based on a software package called the Satellite Anomaly Analysis and Prediction System (SAAPS). There are three main modules of SAAPS: a database of spacecraft anomalies and environmental data, an analysis module, and a prediction module. The operation and the applicability of the different modules may depend heavily on historical data on spacecraft anomalies. Currently SAAPS contains anomaly data from several ESA satellite data sets. It must be pointed out that details of the anomaly data will never be made available to the users of the system other than in term of statistical information. Furthermore, the name of spacecraft and users will never be disclosed.