EUV Variability Experiment (EVE)

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EUV Variability Experiment(EVE)
EVE Instrument Overview

• Rick Kohnert
• EVE Systems Engineer
• kohnert_at_lasp.colorado.edu

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OUTLINE

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

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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

Space Weather Operations (NOAA, Air Force)
Solar Dynamics Observatory (NASA-GSFC)
Solar Images -gt Flares, CMEs
Thermosphere Models -gt Satellite Tracking
HMI
AIA
Ionosphere Models -gt Communications
Solar Irradiance -gt Energy Input
EUV Spectrum
EVE
SDO Connects the Sun to the Earth
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EVE Science Questions/Objectives
What questions will EVE answer? EVE Objective The EVE Plan
1 What is the solar EUV spectral irradiance and how much does it vary? Specify the solar EUV spectral irradiance and its variability on multiple time scales Measure the EUV 0-105 nm with 0.1 nm resolution H I Lyman-a at 121.6 nm Measurement Time Scales 20sec cadence, continuous sequence
2 Why does the solar EUV spectral irradiance vary? Advance current understanding of how and why the solar EUV spectral irradiance varies Use AIA and HMI solar images to understand the interactions of the solar magnetic fields and the evolution of the solar features (e.g., plage, active network) and how these affect the solar variations
3 How well can we predict the absolute value and variability of the solar EUV spectral irradiance? Improve the capability to predict the EUV spectral irradiance variability Develop new forecast and nowcast models of the solar EUV irradiance for use in the NOAA space weather operations
4 How does the geospace environment respond to variations in the solar EUV spectral irradiance and what are the societal impacts? Understand the response of the geospace environment to variations in the solar EUV spectral irradiance and the impact on human endeavors Use solar EUV irradiances with thermosphere and ionosphere models to better define the solar influences on Earths atmosphere Input EVE solar data near real-time into NOAA operational atmospheric models to improve accuracy of solar storm warnings and satellite drag calculations and to predict communications disruptions
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Why EUV Measurements?

• The solar extreme ultraviolet (EUV l lt 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
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What is the solar EUV ?

• The solar EUV radiation consists of emissions
  from the solar chromosphere, transition region,
  and corona
• EUV is lt 0.01 of the total solar irradiance
  (TSI gt99 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 Earths
  atmosphere
• And EUV photons are energetic enough to ionize
  the atmosphere (creates the ionosphere)

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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 _at_ 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
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EVE Success Criteria (Level 1)
Level 1 Reference PERFORMANCE REQUIREMENTS FOR FULL SUCCESS Measurement Objectives
A-2.1.1.1.1.1 The EVE shall perform solar spectral irradiance measurements in the range of 0.1 to 105 nanometers with a time period of no longer than 20 seconds between successive measurements 0.1 to 105 nm with a 10 second cadence
A-2.1.1.1.1.2 The EVE shall measure at least 18 emission lines at a spectral resolution of 0.1 nanometers with a minimum absolute accuracy of 25 percent for each emission line 18 or more emission lines at ?? 0.1 nm, 20 accuracy (brighter lines)
PERFORMANCE REQUIREMENTS FOR MINIMUM SUCCESS
A-2.1.1.1.2.1 The EVE shall perform hourly solar spectral irradiance measurements in n less than six emission lines at a spectral resolution of 0.2 nanometers and an absolute accuracy of 40 percent to specify the chromosphere, transition region, and corona
A-2.1.1.1.2.2 The EVE shall perform a measurement of the Helium-II emission line at 30.4 nanometers at a spectral resolution of at least 5 nanometers and an absolute accuracy of 40 percent
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Driving Requirements
Parameter Requirement
? Range 0.1-105.0 nm
?? Resolution 0.1 nm for 18 or more emissions
Time Cadence 20 seconds
Accuracy 25 over mission life
Signal to Noise Ratio 15 over mission life
Pointing Accuracy lt15 arc-minutes
Visible Light Rejection gt 1010
Contamination lt 400 Angstroms NVR distributed over the optical path
CCD Gain 2e-/dn
CCD Operating Temperature -100 C
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The EVE Team
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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 IT
• 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 2 Project peer reviews to date
• Held 18 instrument 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

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EVE Summary Overview Continued
Program Plans
Program Management Plan v Safety and Handling Plan v
Configuration Management Plan v Risk Assessment and Management Plan v
Instrument Calibration Plan v Software Development Plan v
Descope Plan v Performance Verification Plan ?

• 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

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Changes Since SCR
SCR Now Effects Comments
OFS Single Channel (2 gases) OFS Descoped (10/2003) Loss of spectral resolution direct coverage at long wavelengths Risk reduction descope (considered high risk to cost and schedule) Replaced by enhanced ESP, MEGS-P photometer channels, 5 additional rocket underflights OFS - new technology development, insufficient technical maturity, continued development did not fit with available resources
ESP Single Channel ESP - Single Channel Enhanced Extend ESP spectral coverage Reduced risk approach to retaining inflight cal capabilities Rescope and enhance to cover loss of OFS measurements Custom diodes allow for respread of coverage to new desired range
MEGS 2 Channels MEGS - 2 Channels Enhanced Change MEGS zero order light traps to Si diode traps that provide 8 channels w/filter wheel utilization Reduced risk approach to retaining inflight cal capabilities Rescope and enhance to cover loss of OFS measurements TIMED SEE SOURCE XPS photometer heritage
Aperture Doors (1-Shot) Addition Slight increase in mass Address potential contamination concerns (reduce risk) Heritage from Messenger/MASCS design In Review/Approval process w/Project
5 Rocket Underflights 5 underflights required to meet 25 absolute accuracy requirement with descope of OFS Fabricate rocket instruments (MEGS/ESP prototypes) in Phase C instead of Phase E
Note New configuration meets all SDO EVE
science requirements
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EVE Instrument
EVE Optical package
EEB (EVE Electronics Box)
EVE on Instrument Module
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MEGS Optical Overview
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ESP Optical/Mechanical Layout
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EVE Electrical Block Diagram

• Redundant Spacecraft Interfaces
• 1355 (High Speed Bus)
• 1553 (Command and HK Telemetry)
• Instrument power
• Survival heater power
• Decontamination heater power
• Temperature monitors (5)

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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 Projects 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)
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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 Acoustic are 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 _at_ Ball Aerospace
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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

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Technical Mitigation Timeline
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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 Electro
nics 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 (_at_ LASP) Performance Tests Vibration,
Thermal Vac
ESP Mechanism Life-Cycle Photodio
de Calibration Slit Area Measurement Grating
Characterization Electronics Test
USC
ESP Integration Performance Tests
GSFC
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Mass Power Summary
EVE Optical Package
Note project holds additional 20 above
allocation margin
EEB
POWER POWER POWER POWER
Component Sunlit Ave (W) Eclipse Ave (W) Peak (W)
MEGS ( OP heaters) 36.3 37.3 67.0
ESP 1.5 1.5 1.5
EEB 29.7 29.7 31.4
Total 67.5 68.5 99.9
EVE Allocation 76.0 76.0 -
EVE Allocation Margin 11.2 9.9 -

Additional Services Additional Services Additional Services Additional Services
Survival Heater 35.6 36.6 98.5
CCD Decontam Heater 63.0 - 98.4
MASS MASS
Component Mass (kg)
MEGS 23.61
ESP 3.27
EEB 14.96
Structure 2.82
Harness 2.35
Miscellaneous 1.43
Total 48.44
EVE Allocation 52.00
EVE Allocation Margin 6.8
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Power Mass Trends
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EVE Summary Schedule
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Current Risks Status

• Current concerns that require further
  analysis/resolution

Concern Mitigation Status
MEGS CCD detector system susceptibility noise sources (e.g., Ka band and S-band antenna emissions, other) late delivery of CCD ETU to support design verification Analysis by MIT, LASP, and SDO spacecraft team perform test verification with EVE breadboard CCD assembly 1) General noise susceptibility evaluation currently in progress 2) Test verification November 2004 (delivery of CCD ETU is the schedule driver)
Filter Mechanism motor lubrication potential migration issues Analysis of current design implementation (LASP/Swales) study issues observed by Chandra Evaluation currently in progress - anticipated resolution May 2004
MEGS CCD cooling system functionality Early breadboard/ functional characterization testing Thermal testing with breadboard CCD mechanical assembly planned for June 2004
SDN Hardware and Software Delivery Schedules Develop optimum EVE schedule need dates 1) Submitted to GSFC development teams for review/feedback 2) Early deliveries on track
Low Concern Moderate Concern
High Concern
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Current Risks Status (Continued)

• Current concerns that require further
  analysis/resolution

Concern Mitigation Status
MEGS CCD passivation process selection Evaluate test unit that has passivation process applied 1) Test unit delivery from MIT in early May 2004 2) EUV sensitivity evaluation performed by LASP
ESP signal-to-noise level characterization for the long wavelength channels Analysis by USC/LASP Analysis currently in progress - anticipated conclusion March 2004
Filter mechanism filter robustness Build breadboard and perform environmental testing (vibration, thermal, acoustics) 1) Vibration and thermal testing have been completed 2) Perform acoustics testing May 2004
Low Concern Moderate Concern
High Concern
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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)

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Supplemental Information
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Summary of EVE Reviews Meetings
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EVE Reviews Meetings Continued