16 November 2009European Space Weather Week Galileo and Space Weather E.J. Daly, D.J. Rodgers, H.D.R. Evans, P.Nieminen and V. Alpe ESA-ESTEC, The Netherlands

16 November 2009European Space Weather Week GALILEO km altitude circular orbit 3 orbital planes at 56° inclination. 9 equally-spaced operational satellites per plane, plus 1 spare lifetime 12 years mass: 675 kg dimensions: 2.7 m x 1.2 m x 1.1 m solar arrays: 18.7 m power of solar arrays: 1500 W (end of life)

16 November 2009European Space Weather Week Radiation Environment – Main dose threat comes from outer belt energetic electrons Galileo orbit lies at and above the outer belt peak higher than GPS –Solar particle events –Cosmic rays –Little geomagnetic shielding against GCR & SPEs, Plasma Environment – Hot ring current/plasmasheet environment – Cold plasmasphere

16 November 2009European Space Weather Week >1MeV electron flux from AE-8 model

16 November 2009European Space Weather Week Radiation and Plasma Effects on Galileo Spacecraft Cumulative effects –Total component dose (e.g. 4 mm sphere dose ~ 1 Mrad over 12 year lifetime) –Solar array damage (displacement damage) –Surface material property changes Dynamic effects –Single event effects (SEU, SET, etc.) –Internal charging ESD –Surface charging ESD High availability requirement means –Failures and upsets have high impact –Core operations cannot be suspended during space weather events All spacecraft see nearly the same environment

16 November 2009European Space Weather Week Mitigation Thorough engineering –testing, analysis, hardness assurance (specifications, margins…) Testing –expensive and time consuming Analysis –deployment of sophisticated simulation techniques Shielding –mass penalty System Design –anticipate effects and cope with them (SEU error corrections, operations, etc.) Knowledge –ensure gathering of in-orbit experience

16 November 2009European Space Weather Week GIOVE Giove-A (Dec. ’05) and Giove-B (Apr. ’08) Secure International Telecommunications Union allocated frequencies; Verify critical technologies e.g. atomic clocks and signal generator; Provide a test signal for ground-based systems; Characterise the radiation environment of the Galileo orbit. Giove-A Giove-B

16 November 2009European Space Weather Week Environment Sensors Giove-A Launched 28th Dec CEDEX (SSTL) and MERLIN (QinetiQ) Giove-B Launched 26th April SREM (Oerlikon/Contraves & PSI). Galileo IOV Launch end 2010 EMU (RUAG/Contraves & QinetiQ).

16 November 2009European Space Weather Week Role of Sensors Support investigation of in-orbit behaviour (events, anomalies, etc.) Validate or enhance specifications, e.g. –solar cycle variations, –dose and shielding analyses –define other variabilities Develop underlying models (static, dynamic) Therefore efforts underway to improve sensors –e.g. highly miniaturised sensors for multipoint measurements Not currently used in operations loop

16 November 2009European Space Weather Week GIOVE-A MERLIN (~ >0.8MeV, >1.0MeV and >1.6MeV) GIOVE-B SREM (~ >0.8 MeV, >2 MeV and >2.8 MeV)

16 November 2009European Space Weather Week MERLIN currents [>0.8(black), >1.0 (blue) and >1.6MeV (red)] and doses [3mm (orange) and 6mm (yellow) Al equivalent]. Periodic enhancements of environment (coincident with interplanetary CIRs) Early 2006 GIOVE-A

16 November 2009European Space Weather Week Post-launch 2008: Recent quiet period GIOVE-B SREM data illustrate variability on short and longer timescales >0.7 MeV >~2 MeV >~3 MeV

16 November 2009European Space Weather Week GIOVE-BINTEGRAL SREM electron data (>2MeV) from GIOVE-B (red) and INTEGRAL (green)

16 November 2009European Space Weather Week Plate 1 (>0.8MeV) Plate 3 (>1.6MeV) FLUMIC v2 (part of environment specification) comparison

16 November 2009European Space Weather Week Solar Protons Little experience with SPEs; IOV and final constellation can expect much more

16 November 2009European Space Weather Week Specific Mitigation Measures Plasma environment resembles geostationary orbit –Long experience of grounding and shielding measures Radiation dose environment more intense than geostationary orbit, especially at high energies –Control of dose through shielding and associated analysis –Selection and testing of components –Engineering MARGINS applied Internal charging environment more intense than geostationary orbit –Control of current through shielding –Anti-static materials –Grounding Radiation LET environment resembles geostationary orbit –Selection and testing of components –EDAC

16 November 2009European Space Weather Week Improvements to Analysis and Mitigation Better understanding and updated specifications based on observation for: –Long-term environment (e.g. MEO-V2 and recently developed ESA MEO model; see poster by D. Lazaro et al.). Outer belt solar cycle variability not considered in AE-8 –Space Weather enhancements Detailed prediction of radiation effects –Improved modelling of dose due to electrons. New ESA TRP item “Energetic Electron Shielding, Charging and Radiation Effects and Margins” to address this from beginning of 2010 –3-D modelling of internal charging fields and potentials –Improved measurement of ELDRS effects in components and RadFET measurements

16 November 2009European Space Weather Week Galileo spacecraft as potential SSA/SWE assets

16 November 2009European Space Weather Week Galileo spacecraft as potential SSA/SWE assets

16 November 2009European Space Weather Week Galileo spacecraft as potential SSA/SWE assets Long mission lifetime (~ 1 solar cycle) Crossing outer belt from L=4 upwards Filling an orbital gap where very limited European measurements were previously available High availability Good time resolution of the monitors Near identical spacecraft

16 November 2009European Space Weather Week Conclusions Galileo operates in a very severe environment; Galileo project takes proactive measures in spacecraft engineering and data gathering for the future; Environment specifications not contradicted so far : –environment variability considerable ; –extended solar minimum leads to quiet outer belt; –“declining phase” of solar cycle was harsh; –little solar particle event activity; Returned data are an important asset; Engineering approaches continually re-evaluated –shielding analysis fidelity, margins, etc.; Future R&D being prepared.

16 November 2009European Space Weather Week END

16 November 2009European Space Weather Week Abstract  The medium Earth orbit of Galileo and other navigation satellite constellations passes through the most severe parts of the outer radiation belt where the electron population is highly sensitive to space weather activity and the spectrum harder than in the more familiar geostationary orbit. As a consequence the total ionizing radiation doses in Galileo spacecraft are much larger than those experienced by typical geostationary telecommunications spacecraft, particularly for well shielded components. There are also potential ESD hazards from hot plasma-induced electrostatic charging on the surface and internal charging from penetrating electrons. Special engineering measures are necessary to protect spacecraft systems. This contribution discusses the various effects due to energetic particle radiation and plasma that are taken into account in the development of Galileo, and some of the analysis and mitigation measures implemented. The on-board radiation monitoring approach will be presented and relationships with SSA will be discussed. The on-board measurements could be SSA assets and the system itself has potential needs with respect to space weather knowledge and warnings. These principally relate to energetic electron enhancements and solar particle events.