GIOVE-A 3 rd Euro Space Weather Meeting, 13-17 Nov 2006 ©SSTL/University of Surrey GIOVE-A Radiation Environment Study Regime and Instrument Description

GIOVE-A ©SSTL/University of Surrey 3rd Euro Space Weather Meeting, 13-17 Nov 2006

GIOVE-A Radiation Environment Study Regime and Instrument Description

B Taylor, C Underwood (University of Surrey)S Jason, S Fellows, E Rooney (SSTL)

K Ryden, D Rodgers, P Morris (QinetiQ)G Gatti, G Mandorlo, H Evans, E Daly (ESA)

©SSTL/University of Surrey 3rd Euro Space Weather Meeting, 13-17 Nov 20062

Outline

• The MEO Radiation Environment• Galileo & the GIOVE-A Spacecraft• GIOVE MEO Environment Goals• Radiation Monitors onboard GIOVE• Timeline


The MEO Radiation Environment

• Cosmic Rays– Constant background flux of

protons and heavy ions– Well defined energy spectrum

up to ~1020eV

• Solar Proton Events– Predominantly encountered

at solar maximum, few at solar minimum

– Geomagnetic field provides varying protection



• Outer radiation belt– Significant proton fluxes

confined below ~4 RE– Outer Belt composed of

Electrons – Extends between 3 - 7RE– >1 MeV flux peaks at

around ~4-5 RE at ~106-107 electrons cm-2s-1

GIOVE-AOrbit



• Environment Models– AE-8

• Standard for engineering use

• Mostly empirical, little physics

• Based on data from satellites from 60’s & 70’s

• Static, long term average model

• Covers entire range of belt

• Versions for Solar Max & Solar Min

– CRRESELE• Based on 2 years of data from GTO at Solar max

Electron Belt model comparison

1.00E+00

1.00E+01

1.00E+02

1.00E+03

1.00E+04

1.00E+05

1.00E+06

1.00E+07

0 1 2 3 4 5 6 7

Altitude/ Earth Radii>1

MeV

Ele

ctro

n Fl

ux

CRRESELE

AE-8 MAX

AE-8 MIN



• Environment Variability– Distribution varies greatly

due to solar cycle– Spatial distribution varies

due to geomagnetic field variation at higher altitudes

– Injection events due to geomagnetic storms can enhance environment by orders of magnitude

– Closely linked to Solar activity

GOES >2MeV Electron Flux

0.00E+00

1.00E+09

2.00E+09

3.00E+09

4.00E+09

5.00E+09

6.00E+09

7.00E+09

8.00E+09

9.00E+09

1.00E+10

0-Jan-00 14-May-01 26-Sep-02 8-Feb-04 22-Jun-05

Date

Flu

x/cm

^-2

s^-1



• Environment dangers and effects– Total Ionising Dose (TID) caused by energetic particles

(electrons, protons and heavy ions)– Single Event Effects (SEE) caused by energetic heavy

ions and protons– Electrostatic Discharge (ESD) – caused by penetrating

electrons



• Previous MEO Spacecraft– Combined Release and Radiation Effects Satellite

(CRRES)• Launched into Geostationary Transfer Orbit (GTO) in 1990• ~1 year mission

– Space Technology Research Vehicles (STRV)• Two satellites launched into GTO in 1994• ~2.5 year mission

– GPS• Multiple spacecraft carry radiation detectors• Data is property of US DoE - limited access



• Solar Cycle Coverage– GIOVE-A lifetime is

over solar minimum– GIOVE combined with

STRV gives data on two consecutive solar minima

– CRRES data at solar maximum

1985 1990 1995 2000 2005 2010

Year

Sunspot Number

STRV

CRRES

GIOVE-A


Galileo

• Galileo- The European Global Navigation Satellite System (GNSS)– Independent, commercial

system– Two test bed spacecraft –

GIOVE -A & -B– Four In Orbit Validation

(IOV) spacecraft– Final constellation to consist of

30 satellites, 27 active, 3 spare in 3 orbital planes

– Total cost of system: ~€3-4 billion


GIOVE-A Spacecraft

• GIOVE-A– Precursor to Galileo Programme– Objectives

• Secure frequency filing• Demonstrate key payload

technologies• Provide Signal-in-Space for

Experimentation• Measure MEO environment

– Requirements • Two year mission lifetime• Low cost, rapid schedule• Kick-Off - July 2003 and Launch – 29th December 2005


MEO Environment Goals

• Optimise the design of the Galileo satellites– Confirm requirements are correct, modify if necessary

• Are existing models a good enough description of the environment?– LET spectrum– Electron Fluxes– Total Ionising Dose– Dose rates


Radiation Monitors on GIOVE-A

• MERLIN – QinetiQ– Cosmic-Ray LET Spectra– Proton Flux– Total Ionising Dose– Electrons/ Deep Charging

Currents

• CEDEX – UniS/SSTL– Cosmic-Ray LET Spectra– Proton Flux– Dose-Rate Induced

Photocurrents

Proton fluxHeavy ion LETspectrum

Total dose B

Total dose AElectrons &deep charging

MerlinSpace Weather Monitor



CEDEX

Merlin



Radiation Monitors


Radiation Monitors onboard GIOVE-B

• SREM- ESA – Due for Launch late 2007 on

GIOVE-B– Three precision particle detectors

• Electrons & Protons

– Internal total dose measurement


Timeline – Initial Operations

• CEDEX & Merlin turned on - 29th December 2005– Second contact after launch– Operated near continuously since first switch-on

• Environmental Readiness Review (ERR) 06/04/2006

• Environmental Payloads Commissioning Phase– Setup of download and processing chain

• Initial Operations Phase– Initial analysis of data with simplified shielding models


Timeline – Main Operations

• Main Operations Phase – Part 1– Simplified 1D Mulassis, and 3D GEANT-4 model of the

payloads/ spacecraft. – Results compared to AE8/CRRESELE

• Main Operations Phase – Part 2 – Electron response of Merlin using Geant4, SREM data

expected (but now delayed)– Data compared with static and quasi-static models (AE8,

FLUMIC, CRRESELE, ESAMEA, etc). – Results used to validate modelling performed in MOP-1– Pile-up induced responses to electrons in Proton Flux

measurements from Merlin investigated to derive further data on electron environment


Conclusions

• Merlin and CEDEX have been operating since December 2005

• Initial commissioning activities are complete• Data analyses continue to be refined• The following two papers will describe the units in

more detail and present the in-orbit results


Thank you foryour attention

For further information contact :Dr Elizabeth Rooney

Surrey Satellite Technology Limited

Tycho House, 20 Stephenson Road,

Surrey Research Park, Guildford, Surrey, GU2 7YE, UK

Tel: +44 1483 803803, FAX: +44 1483 803804

Email: [email protected] Web: www.sstl.co.uk

Documents

GIOVE-A 3 rd Euro Space Weather Meeting, 13-17 Nov 2006 ©SSTL/University of Surrey GIOVE-A Radiation Environment Study Regime and Instrument Description