Rocket Extreme Ultraviolet Grating Spectrometer (EGS): calibrations and results of the solar irradiance on February 8, 2002

Abstract

The rocket Extreme Ultraviolet Grating Spectrograph (EGS) instrument is flown onboard a sounding rocket as an underflight calibration for the Solar Extreme Ultraviolet Experiment (SEE) onboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics satellite. The first calibration flight took place from the White Sands Missile Range in New Mexico on February 8, 2002. Both preflight and postflight calibrations are performed in the extreme ultraviolet (EUV) range from 26.5 to $117.2nm$ and the far ultraviolet (FUV) range from 120 to $196nm$ to determine an accurate quantum throughput (QT) for the EGS instrument. These calibrations are performed using Beam Line 2 at the National Institute of Standards and Technology Synchrotron Ultraviolet Radiation Facility III. This QT determination has an uncertainty of about 10% for the EUV region and around 4.2% 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 12%. The rocket EGS is planned for an annual calibration flight to track the long-term changes of SEE EGS.