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/m<sup>2</sup>/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 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 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.
Understanding both the absolute value and time variability of the solar extreme ultraviolet (EUV) spectral irradiance is necessary for understanding the structure and variability of the Earth’s thermosphere and ionosphere. Long-term measurement of the solar EUV irradiance requires a calibration scheme that addresses the following issues: (1) the calibration must be referenced to repeatable radiometric standards; (2) changes in calibration throughout the duration of the measurements must be tracked; and (3) the measurements must be validated with independent instruments and models. The calibration and performance of the TIMED Solar EUV Experiment (SEE), which has been measuring the solar EUV irradiance since early 2002, will be discussed in relation to these calibration objectives. The pre-flight calibrations of SEE are based on calibrated synchrotron sources at the National Institute for Standards and Technology (NIST) Synchrotron Ultraviolet Radiation Facility (SURF). The in-flight calibrations for SEE are based on redundant channels used weekly and annual suborbital rocket flights with the prototype SEE instruments that are calibrated before and after each launch at NIST SURF.
The Solar EUV Experiment (SEE) on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite will make measurements of the spectral irradiance of the Sun in the soft x-ray, extreme ultraviolet (EUV), and far ultraviolet (FUV) wavelength range. The EUV Grating Spectrograph (EGS) component of SEE is a 1/4 meter Rowland circle spectrograph with a mechanically-ruled concave grating and a microchannel plate detector with a two-dimensional 1024 x 64 coded anode (CODACON) readout. The EGS covers the wavelength range from approximately 26 to 197 nm. The primary calibration of the instrument was done at the NIST Synchrotron Ultraviolet Radiation Facility (SURF) III on their beam line #2. We will detail the calibration methods and results for the EGS, paying attention to the quantification of sensitivity variations over the instrument's large field of view (12.5 degree(s) x 5.3 degree(s)), plus scattered light, second-order, and linearity corrections.