14 October 2004 Rocket Extreme ultraviolet Grating Spectrometer (EGS): calibrations and results of the solar irradiance on February 8, 2002
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The rocket Extreme ultraviolet Grating Spectrograph (EGS) instrument is flown onboard a sounding rocket as an underflight calibration for the Solar Extreme ultraviolet Experiment, or SEE, onboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite. The first calibration flight took place from the White Sands Missile Range in New Mexico on February 8, 2002. Both pre-flight and post-flight calibrations are performed in the extreme ultraviolet (EUV) range from 26.5 nm to 117.2 nm and the far ultraviolet (FUV) range from 120 nm to 196 nm in order to determine an accurate quantum throughput (QT) for the EGS instrument. These calibrations are performed using Beam Line 2 (BL2) at the National Institute of Standards and Technology (NIST) Synchrotron Ultraviolet Radiation Facility III (SURF-III). This QT determination has an uncertainty of about 6% for the EUV region and around 3.5% for the FUV region. Once the QT for the instrument is found from the calibrations, it is applied to the solar spectrum obtained during the flight in order to get the absolute spectral irradiance with an uncertainty of approximately 10%. This rocket spectrum is then applied to the SEE EGS to obtain absolute irradiance values for the satellite instrument and to calibrate it for changes, such as degradation, that have occurred since its own pre-flight calibrations. This calibration transfer is done by scaling the SEE EGS solar spectrum at the time of the rocket flight to the rocket spectrum to get the same irradiance values, which produces a scaling factor that can be applied to other SEE EGS measurements. The rocket EGS is planned for an annual calibration flight to track the long-term changes of SEE EGS.
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Phillip C. Chamberlin, Thomas N. Woods, Francis G. Eparvier, "Rocket Extreme ultraviolet Grating Spectrometer (EGS): calibrations and results of the solar irradiance on February 8, 2002", Proc. SPIE 5538, Optical Constants of Materials for UV to X-Ray Wavelengths, (14 October 2004); doi: 10.1117/12.559874; https://doi.org/10.1117/12.559874

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