The NASA Solar Dynamics Observatory (SDO), scheduled for launch in 2009, incorporates a suite of instruments
including the EUV Variability Experiment (EVE). The EVE instrument package contains grating spectrographs that will
measure the solar extreme ultraviolet (EUV) irradiance from 0.1 to 105 nm. The Multiple EUV Grating Spectrograph
(MEGS) channels use concave reflection gratings to image solar spectra onto CCDs. MEGS will provide 0.1nm
spectral resolution between 5-105nm every 10 seconds with an absolute accuracy of better than 25% over the SDO 5-
year mission. MEGS-A utilizes a unique grazing-incidence, off-Rowland circle (RC) design to minimize angle of
incidence at the detector while providing ≥ 0.1nm resolution between 5-37 nm. MEGS-B utilizes a double-pass, cross-dispersed
double-Rowland circle design while providing ≥ 0.1nm resolution between 35-105 nm. We present the as-built
performance of the MEGS optical design, including spectral resolution, wavelength shift, focus and alignment.
The NASA Solar Dynamics Observatory (SDO), scheduled for launch in 2009, incorporates a suite of instruments
including the EUV Variability Experiment (EVE). The Multiple EUV Grating Spectrograph (MEGS) channels use
concave reflection gratings to image solar spectra onto CCDs that are operated at -100°C. MEGS provides 0.1nm
spectral resolution between 5-105nm every 10 seconds with an absolute accuracy of better than 25% over the SDO 5-
year mission. Characterizations and selection testing of the CCDs and the thin foil filters for SDO EVE have been
performed with both in-band and visible illumination. CCD selection was based on results from testing in LASP facility
Calibration and Test Equipment (CTE3) as well as results from at testingMIT. All CCDs meet the requirements for
electronics gain, flat field, Quantum Efficiency (QE), dark current, reverse clock, CTE, bad pixels and the -120°C
survival test. The thin foil filters selection was based on tests performed at LASP facilities and NIST. All filters provide
>106 attenuation of visible light with the proper EUV transmission needed for order sorting capabilities and are free of
critical pinholes.
The NASA Solar Dynamics Observatory (SDO), scheduled for launch in early 2009, incorporates a suite of instruments
including the EUV Variability Experiment (EVE). Two channels of EVE, the Multiple EUV Grating Spectrograph
(MEGS) A and B channels use concave reflection gratings to image solar spectra onto CCDs to measure the solar
extreme ultraviolet (EUV) irradiance from 5 to 105 nm. MEGS provides these spectra at 0.1nm spectral resolution every
10 seconds with an absolute accuracy of better than 25% over the SDO 5-year mission. The calibration of the MEGS
channels in order to convert the instrument counts in to physical units of W/m2/nm was performed at the National
Institute for Standards and Technology (NIST) Synchrotron Ultraviolet Radiation Facility III (SURF III) located in
Gaithersburg, Maryland. Although the final post-environmental calibrations have yet to be performed, preliminary
results from the pre-environmental calibrations show very good agreement with the theoretical optical design given by
Crotser et al. Further analysis is still needed in regards to the higher order contributions to determine the final first
order QT for all channels, but two techniques are currently being analyzed and show promising results.
The Solar Dynamics Observatory (SDO) Extreme ultraviolet Spectro-Photometer (ESP), as a part of the Extreme
ultraviolet Variability Experiment (EVE) suite of instruments, was calibrated at the National Institute
of Standards and Technology (NIST) on the Synchrotron Ultraviolet Radiation Facility (SURF) Beam Line 2
in February 2007. Precise ESP alignment to the SURF beam was achieved through successive scans in X, Y,
Pitch and Yaw, using a comparison of the four channels of the ESP quad photodiode as a measure of alignment.
The observed alignment between the ESP and the other instruments in the EVE package was found to be in
very good agreement with that measured at the Laboratory for Atmospheric and Space Physics (LASP) at the
University of Colorado during ESP/EVE integration. The radiometric calibration of the ESP photometers in
the spectral range around 4.4 nm (central zeroth order), and the four first order channels centered at about
18.9, 25.4, 29.8, and 36.1 nm was performed with SURF synchrotron radiation. The co-alignment of the SURF
beam and the ESP optical axis for each energy and injected current was determined based on quad diode (QD)
photometer responses (photodiode count-rate data). This determined beam position was later used to obtain
exact energy-wavelength-flux profiles for each of the calibration energies and to calculate the quantum efficiency
of the ESP channels. The results of this calibration (quantum efficiencies) are compared to the previous ESP
NIST calibration results at SURF Beam Line 9 and to SOHO/SEM efficiencies.
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