The Extreme Ultraviolet and X-Ray Irradiance Sensors (EXIS) on GOES-R: Measurements, Calibration, Validation, and Data Products
F.G. Eparvier ([email protected]), T.N. Woods, A.R. Jones, M. Snow, D.L. Woodraska, E.M.B. Thiemann, W.E. McClintock, M. Anfinson, R.A. Viereck, J.L. Machol, M. Todirita, G.J. Comeyne, and S.K. Tadikonda The Solar EUV and Soft X-Rays (XUV)
n The solar EUV and XUV radiation consists of emissions from the solar chromosphere, transition region, and corona q EUV/XUV is < 0.01% of the total solar irradiance (TSI: >99% from photosphere) q But EUV/XUV variations are a factor of 2 - 1000 (wavelength dependent), whereas TSI variations are typically only 0.1% q And EUV/XUV is completely absorbed in Earth’s upper atmosphere q And EUV/XUV photons are energetic enough to ionize the atmosphere (creates the ionosphere)
AMS, Seattle, January 2017 2 EUV and X-Ray Irradiance Sensors (EXIS)
• EXIS instruments measure the absolute brightness of the integrated disk of the Sun
• X-Ray Sensor (XRS) Purpose: Monitor solar flares (and help predict proton events) that can disrupt communications and degrade navigational accuracy
• Extreme Ultraviolet Sensor (EUVS) Purpose: Monitor solar variations that directly affect satellite drag/tracking and ionospheric changes, which impact communication EXIS shares the Solar Pointing Platform and navigation operations on the solar array yoke with SUVI. 3 AMS, Seattle, January 2017 3 EXIS Glamour Shots
EUVS
XRS
4 AMS, Seattle, January 2017 4 EXIS Nursery at LASP (GOES-R, S, T, and U)
5 AMS, Seattle, January 2017 5 GOES-R XRS Overview n Each XRS channel (A & B) has: q Two photometers with different sized apertures for solar minimum and solar maximum/ A2: A1: flaring conditions (Large Solar max/flare Solar min overlap in both dynamic ranges λ = 0.05-0.4nm adds redundancy in λ = 0.05-0.4 nm measurements) B1: q Silicon photodiodes with Be Solar min filters (thicknesses of filters and λ = 0.1-0.8 nm B2: Solar max/flare diodes scaled to match λ = 0.1-0.8nm previous XRS bandpasses) Dark q Low-power, low-noise electrometers Dark n XRS also has:
q Dark channel for simultaneous Flare Location with XRS: background corrections XRS-A and XRS-B solar max q Improved calibration detectors are quadrant photodiodes methodology giving the location of bright X-Ray q Improved measurement to irradiance conversion flares AMS, Seattle, January 2017 6 XRS Data Products n Measurements (in 30-sec groups): q Irradiances: 0.05-0.4 and 0.1-0.8 nm bands at 1-sec n Note: requirements met with 3-sec median q Raw counts for each diode (1-sec) q Data flags q Pointing information (to pass on to higher level products) n Higher Level Products: q Flare classes (A, B, C, M, X) and magnitude q Flare event alerts (start, max, duration, magnitude) q Flare locations q Proton event alerts
AMS, Seattle, January 2017 7 Extreme Ultraviolet Sensor (EUVS) n Three channels to provide proxies for the emissions from the chromosphere (CH), transition region (TR), and corona (COR) n Measured proxies are used to model the full EUV range (5-115 nm and 121.6 nm) n MgII C/W key to internal EUVS degradation tracking method (and a NOAA required measurement)
λ Δλ Integration Chan. measured Optical Design (nm) Time (sec) (nm) A 25.6, 28.4, 0.6 1.0 Spectrograph (grazing incidence) with foil 30.4 filter and 24-element custom photodiode array B 117.5, 1.0 1.0 Spectrograph with interference filter and 24- 121.6, element custom photodiode array 133.5, 140.5 C 275-285 0.1 3.0 Spectrograph with interference filter and 512-element photodiode array (MASCS)
AMS, Seattle, January 2017 8 EUVS Measurements
n Chromosphere: q Primary: MgII C/W (EUVS-C)
q Redundant: CIII 117.5 nm and CII 133.5 nm (EUVS-B) n Transition Region: q Primary: Ly-alpha 121.6 nm (EUVS-B) q Redundant: SiIV/OIV 140.5 nm (EUVS-B), HeII 30.4 nm and HeII 25.6 nm (EUVS-A) n Corona: q Primary; FeXV 28.4 nm (EUVS-A) Note: All measurements can be used in the EUVS model, but the “primary” ones are n Hot Coronal: the minimum necessary to meet q Primary: 0.1-0.8 nm (XRS) requirements. q Redundant: 0.05-0.4 nm (XRS)
AMS, Seattle, January 2017 9 L1b EUVS Model
• Based on FISM (Chamberlin 2007, 2008) using TIMED-SEE, SORCE, and SDO-EVE data as empirical data set • Uses all EXIS measurements available • Run at 30-sec cadence (to filter noise from 1- and 3-sec data) • Captures slow and fast variability separately 10 10 mi ni E (λ5nm,t) = A(λ5nm ) +∑ ji (λ5nm )⋅ Pi (t) +∑ki (λ5nm )⋅Qi (t) i=1 i=1
Solar Slow Fast Minimum Variability Variability Reference
Ei t − Emin,i Ei (t) − Ei (t) ( ) Q t Pi (t) = i ( ) = Emin,i Ei (t)
AMS, Seattle, January 2017 10 EUVS Data Products n Measurements (at 30-sec cadence): q Irradiances: in all the lines (at instrument time and 30-sec average)
q Mg II Core-to-Wing Ratio (at instrument time and 30-sec average) n Measured Ratio n NOAA scaled Ratio n Wing values and core fit parameters q Raw counts for each diode on all channels q Data flags q Daily averages of Irradiances and Proxies n Model (at 30-sec cadence): q Model Irradiances: 5-115 nm in 5 nm bins, plus 5 nm bin around Ly-α q Proxies used (P’s and Q’s) n Higher Level Products: q Improved Flare Spectral Modeling q EUV event alerts
AMS, Seattle, January 2017 11 Ground Characterizations Performed
n Characterizations performed at NIST Synchrotron Ultraviolet Radiation Facility (SURF-III) in Gaithersburg (reference standard for EUV):
q Absolute responsivity determined (all channels)
q Field-of-View variations mapped (XRS, EUVS-A/B)
q Temperature dependence of gain and responsivity (all)
q Linearity of response (XRS, EUVS-A/B)
n Characterizations done at LASP using in-house sources (relative calibration sources):
q Wavelength scale (EUVS-A/B, EUVS-C)
q Linearity of response (EUVS-C)
q FOV variations (EUVS-C)
AMS, Seattle, January 2017 12 In-flight Activities (PLT and Beyond)
n Characterizations / Tracking:
q Gain Calibrations (All Channels)
q Flat fields using on board stim lamps (EUVS-A/B/C)
q Cruciforms and FOV maps (All Channels)
q Dark / Noise Calibrations (All Channels)
q Degradation of EUVS-A/B (Bootstrap from EUVS-C) n Validations:
q Comparisons / Continuity with GOES-13 & -15
q Comparisons to SDO-EVE, TIMED-SEE, SORCE, MinXSS, SDO-EVE sounding rocket
q Comparisons to other models (FISM, S2K, EUVAC,…)
AMS, Seattle, January 2017 13 Next Generation of GOES Data Users
AMS, Seattle, January 2017 14 Backup Slides
AMS, Seattle, January 2017 15 Some Definitions n Space Weather: conditions on the Sun, in interplanetary space, and in the near-Earth environment that can affect space- and ground-based human endeavors. n Irradiance: absolute measure of the total amount of sunlight incident on a unit area at a specific distance from the Sun (usually 1-AU) 2 2 q usually expressed as Watts/m or photons/m /sec q Spectral Irradiance is how this total is distributed by wavelength (Watts/m2/nm or photons/m2/sec/nm) n Extreme Ultraviolet (EUV): wavelengths of light in the range from 10-122 nm n Soft X-Rays (XUV): wavelengths of light in the range from 0.1-10 nm n EXIS: the EUV and X-Ray Irradiance Sensors for GOES-R q Consists of the EUV Sensor (EUVS) and the X-Ray Sensor (XRS)
AMS, Seattle, January 2017 16 Irradiance Varies on All Timescales
• Solar Cycle - months to years – Evolution of solar dynamo with 22-year magnetic cycle, 11-year intensity (sunspot) cycle
XUV 0-7 nm Solar Cycle (11-years) H I 121.5 nm
• Solar Rotation - days to months Solar Rotation (27-days) – Beacon effect of active regions rotating with the Sun (27-days)
Flares
• Flares - seconds to hours – Related to solar storms (such as CMEs) due to the interaction of magnetic fields on Sun
AMS, Seattle, January 2017 17 Space Weather Effects
n Solar EUV/XUV are completely absorbed in the Earth’s upper atmosphere. q Creates the ionosphere q Heats the thermosphere n Variability in solar EUV/XUV causes variability in: q Amount and height of ionization (Total Electron Content, height of critical ionospheric layers, transmitivity and reflectivity of ionospheric layers) q Temperature and density distribution of atmosphere (satellite drag) q Composition of upper atmosphere (minor species, O/ N2, scale heights)
AMS, Seattle, January 2017 18 Realtime Space Weather Data Users
n Users who need realtime, uninterrupted space weather data are those who care about:
q Satellite tracking
q Satellite operations
q Navigation
q GPS location
q Ground-space communications
q Ground-ground communications n Some specific users:
q NASA
q Military (all branches, but specifically AFWA, NORAD)
q Shipping industry
q Airlines
q Commercial satellite industry
q Power companies
AMS, Seattle, January 2017 19 GOES-R EXIS Challenges
n Long Duration Mission:
q 5 year ground storage, 5 year on-orbit storage, 10 year operational lifetime n GEO Orbit:
q harsh radiation environment n Spectral Bands/Range:
q XRS: duplicate previous XRS bands, out-of-band rejection, and wavelength responses
q EUVS: determination of solar spectral irradiance from 5-127 nm from measurement, model, or both n Dynamic Range:
q Solar EUV/XUV irradiance varies by many orders of magnitude as a function of wavelength and on all timescales n Irradiance Product Accuracy:
q Achieving strict requirements necessitates adequate pre-flight calibration, in- flight calibration tracking, and careful tracking of uncertainties.
AMS, Seattle, January 2017 20 GOES-R EXIS
n Very specific measurement requirements laid out by NOAA and NASA n Designs presented here are the result of four years of concept formulation, trade studies, risk reduction activities, and preliminary design work. n EXIS consists of EUVS, XRS, and a combined electronics box (EXEB) to control subsystems and do command and data handling interface with spacecraft
EXIS = EUV and X-ray Irradiance Sensors The Key Components of EXIS: • EUVS = Extreme Ultraviolet Sensor • XRS = X-Ray Sensor • EXEB = EUVS/XRS Electrical Box
AMS, Seattle, January 2017 21 XRS and EUVS Overview
n NOAA requires the realtime monitoring of the solar irradiance variability that controls the variability of the terrestrial upper atmosphere (ionosphere and thermosphere). This requirement supports NOAA’s space weather operations and is implemented with two instruments: n XRS = X-Ray Sensor q XRS measures the solar soft x-ray irradiance in two bandpasses at 0.05-0.4 nm and 0.1-0.8 nm q On GOES manifest from beginning of program (~1978 on SMS) q all past and present instruments are ionization chambers with Be filters q XRS Purpose: Monitor solar flares (and help predict proton events) that can disrupt communications and degrade navigational accuracy n EUVS = Extreme UltraViolet Sensors q Through a combination of measurements and modeling, EUVS determines the solar EUV spectral irradiance in the 5 - 127 nm range q first included on GOES in 2006 (GOES-13, in on-orbit storage) as transmission grating spectrographs measuring 5 broad bandpasses
q EUVS Purpose: Monitor solar variations that directly affect satellite drag / tracking and ionospheric changes, which impact communication and navigation operations
AMS, Seattle, January 2017 22 X-Ray Sensor (XRS)
n XRS: measure 0.05-0.4 nm and 0.1-0.8 nm (matching previous bandpasses) with ≤3-second cadence n Pre-GOES-R XRS: Ionization chamber instruments with limited dynamic range (solar min unresolved in noise and bright flares clipped) n XRS for GOES-R: Solid state detectors that capture full dynamic range of solar variability
Energetic Particles
AMS, Seattle, January 2017 23 EUVS Degradation Tracking
n Utilizes same modeling techniques as irradiance data product n First: measure something degradation independent:
q Measure (EUVS-C):
n Mg II C/W
n Second: measure things that vary like Mg II C/W with the same instrument that measures TR emissions.
q Measure (EUVS-B):
n C II (133.5 nm), C III (117 nm): Chromosphere
n Si IV (141.5 nm) and H I (121.6 nm): Transition Region
q Degradation tracked by comparing to Mg II C/W (EUVS-C) over long term.
n Third: measure things that vary like TR with the same instrument that measures a Coronal emission.
q Measure (EUVS-A):
n He II (30.4 nm), He II (25.6 nm): Transition Region
n Fe XV (28.4 nm): Corona
q Degradation tracked by comparing to HI and Si IV (EUVS-B) over long term.
n Note: All channels have flatfield lamps to track pixel-to-pixel changes
AMS, Seattle, January 2017 24