EUV Variability Experiment (EVE)

1. EUV Variability Experiment(EVE) Rick Kohnert EVE Systems Engineer kohnert@lasp.colorado.edu EVE Instrument Overview

2. OUTLINE • Science Overview • Requirements • Summary Overview • Design Implementation • Mitigation Efforts • Development Flow • Schedule • Risk Assessment

3. EVE Science Goal/SDO Role • Specify and understand the highly variable solar extreme ultraviolet (EUV) electromagnetic radiation and its impacts on the geospace environment and the societal consequences Solar Dynamics Observatory (NASA-GSFC) Space Weather Operations (NOAA, Air Force) Solar Images -> Flares, CMEs Thermosphere Models -> Satellite Tracking HMI AIA Ionosphere Models -> Communications Solar Irradiance -> Energy Input EUV Spectrum EVE SDO Connects the Sun to the Earth

4. EVE Science Questions/Objectives

5. Ionosphere Why EUV Measurements? • The solar extreme ultraviolet (EUV: l < 120 nm) radiation is the primary energy input for the thermosphere (where satellites reside) and the ionosphere (what affects communications) Primary atmospheric absorbers are N2, O, O2, and O3 Plot shows where the solar radiation is deposited in the atmosphere

6. What is the solar EUV ? • The solar EUV radiation consists of emissions from the solar chromosphere, transition region, and corona • EUV is < 0.01% of the total solar irradiance (TSI: >99% from photosphere) • But EUV variations are a factor of 2 - 100 (wavelength dependent), whereas TSI has only 0.1% variations • And EUV is completely absorbed in Earth’s atmosphere • And EUV photons are energetic enough to ionize the atmosphere (creates the ionosphere)

7. How does EVE measure the EUV? • Multiple EUV Grating Spectrograph (MEGS) • At 0.1 nm resolution • MEGS-A: 5-36 nm • MEGS-B: 35-105 nm • At 1 nm resolution • MEGS-SAM: 0-7 nm • At 20 nm resolution • MEGS-Photometers: @ 15, 25, 40, 60, 121.6 nm • Ly-a Proxy for other H I emissions at 80-102 nm • EUV Spectrophotometer (ESP) • At 4 nm resolution • 18.4, 25.6, 30.4, 36.8, 58.4 nm • At 7 nm resolution • 0-7 nm (zeroth order) Dl 0.1 1 4 7 20 nm

8. EVE Success Criteria (Level 1)

9. Driving Requirements

10. The EVE Team

11. EVE Summary Overview • EVE is currently on budget and on schedule • Developed detailed schedules • schedule slack remains intact and incorporates 2 months in subsystem development and 2 months in EVE I&T • EVE has successfully completed all major reviews to date • SDO SRR/SCR (April 8-11, 2003) • 9 EVE RFAs total, responses submitted, 3 remain open, all can be closed • All critical actions are closed • EVE PDR (December 17-18, 2003) • “The material presented provided a very good demonstration that the EVE team has, in general, met the design and analyses status requirements for a PDR and is prepared to move into more detailed design activity” - Thomas Cygnarowicz, Chair, Systems Review Office • 33 RFAs total, received March 1, 2004, no critical actions identified • EVE Review & Working Group Participation • Participated in 2Project peer reviews to date • Held 18instrument peer reviews to date (includes independent external reviewers) • Participated in 13 working group and technical interchange meetings to date • Includes 3 meetings with the project in the development of the ICDs

12. EVE Summary Overview Continued Program Plans • Detailed Schedules are in place • Tracked, updated and reported monthly • Flowed Requirements • Delivered EVE Product Assurance Implementation Plan (PAIP) • Flowed Program & LASP requirements to subcontractors • ICDs in formal review • Assembled system level requirements • Have written and are writing subsystem requirements • Implemented Performance Assurance • Performing FMEAs (draft in review at LASP) • Single point failure trade study completed December 2004 • Preliminary parts list submitted

13. Changes Since SCR Note: New configuration meets all SDO EVE science requirements

14. EVE Instrument EVE Optical package EEB (EVE Electronics Box) EVE on Instrument Module

15. MEGS Optical Overview

16. ESP Optical/Mechanical Layout

17. EVE Electrical Block Diagram • RedundantSpacecraft Interfaces • 1355 (High Speed Bus) • 1553 (Command and HK Telemetry) • Instrument power • Survival heater power • Decontamination heater power • Temperature monitors (5)

18. Mitigation of Technical Challenges • CCD Technical Mitigation • Mechanical/Thermal Breadboard – vibration test completed, FEM correlated, and design refinements in process • Power Supply Breadboard – revealed that ripple requirements for CCD power cannot be met with DC/DC converters from the Project’s common buy • The subsequent trade study led to the incorporation of custom power supplies from Space Instruments for the CCD electronics • CCD Power and Grounding TIM – established ground and isolation requirements for the CCD subsystem (LASP, SI, MIT/LL, Ball) • Resulted in the change from chassis to analog grounds at the CCD header assembly • CCD Life Testing – planned life tests will verify in band sensitivity (QE) and total EUV fluence over mission life prior to the CDR • Engineering Models – engineering model CCD subsystems will verify noise performance prior to CDR CCD Mechanical System Vibration CCD Power Supply Breadboard Results (with filtering)

19. Mitigation Continued • The Filter Wheel breadboard has successfully demonstrated a sound design • Vibration (random) –tests have successfully demonstrated the integrity of filters and mounting scheme (and resulted in the identification of materials not suitable for use in unsupported filters: Sn) • Thermal Cycle –tests have successfully demonstrated filter wheel integrity over the survival temperature range • Filter Attenuation and Scatter –initial testing has verified that filters exceed the visible extinction requirement and the visible rejection requirements (light leaks/scatter) • Life Cycle and Acousticare planned prior to CDR (no current concerns) • Prototype filter transmissions are in measurement at SURF 10-6 req. 10-7 extinction 1 X 7 mm Foil Filter Red = After Env. Blue = Before Env. (=638.0nm) Filter Wheel Vibration @ Ball Aerospace

20. Mitigation Continued • EVE prototype structural mounts are complete • Testing planned for May 2004 • Vibration and thermal cycle • Use optic cube to verify alignments before and after tests • Grating Specification TIM • Reviewed the established grating specifications for scatter, optical parameters, and manufacturability • Gratings are on order • Swales under contract to perform Contamination Control engineering efforts • Contamination Control Plan • Mass transport models • Participate in SDO contamination control efforts

21. Technical Mitigation Timeline

22. EVE Instrument Development &Test Component Level Testing Instrument Level Testing Observatory Testing EEB Board level testing Flight code development EEB Functional testing w/ Instrument simulators EVE EEB Integration Performance Tests Alignments Pre-Environmental Cal Vibration Test Acoustic EMI/EMC Test Thermal/Vacuum Test Post-Env Cal SDO S/C integration Performance Tests Vibration Test Acoustic Test EMI/EMC Test Thermal/Vacuum Test MEGS Mechanism Life-Cycle Filter Transmission Slit Area Measurement Grating Characterization Detector Characterization Electronics Test MEGS Integration Performance Tests Vibration Thermal/Vacuum Tests CCD Detector & Logic Manufacture Performance Tests CCD System Assembly Integration Performance Tests Site Key: LASP MIT LL ESP (@ LASP) Performance Tests Vibration, Thermal Vac ESP Mechanism Life-Cycle Photodiode Calibration Slit Area Measurement Grating Characterization Electronics Test USC ESP Integration Performance Tests GSFC

23. Mass & Power Summary EVE Optical Package Note: project holds additional 20% above allocation margin EEB

24. Power & Mass Trends

25. EVE Summary Schedule

26. Current Risks Status • Current concerns that require further analysis/resolution Low ConcernModerate ConcernHigh Concern

27. Current Risks Status (Continued) • Current concerns that require further analysis/resolution Low ConcernModerate ConcernHigh Concern

28. Conclusion • The EVE Preliminary Design Review was successfully completed December 17-18, 2003 • Design requirements are met • Power and mass are within allocations • EVE is currently in the detailed design phase • Risks are identified, tracked, and mitigation strategies are in place (currently carrying only low to moderate risks)

29. Supplemental Information

30. Summary of EVE Reviews & Meetings

31. EVE Reviews & Meetings Continued