The  variability of the solar Magnesium II index at 279.9 nm as measured by the NRL SUSIM aboard UARS over 14 years. The Mg II solar ultraviolet absorption line core-to-wing ratio index is one of the important metrics of solar activity and is used in connection with applied upper atmospheric models as well as basic solar and atmospheric research.
The variability of the solar Magnesium II index at 279.9 nm as measured by the NRL SUSIM aboard UARS over 14 years. The Mg II solar ultraviolet absorption line core-to-wing ratio index is one of the important metrics of solar activity and is used in connection with applied upper atmospheric models as well as basic solar and atmospheric research.

Objective
Reduce existing major (~30%) absolute and relative 1 hr -11 year solar ultraviolet (115-440 nm) spectro-radiometric measurement discrepancies to the 0.3-3% level in order to achieve sufficient precision of irradiance data for input to models of Earth’s upper atmosphere, including the ionosphere and thermosphere.
Highly variable solar ultraviolet radiation, absorbed by Earth’s upper atmosphere, modulates formation of the ionosphere and heating of the thermosphere thus affecting space based radars, communications, and orbital tracking. SUSIM (and Hinode) data are used to validate solar EUV forecasting models.

Approach
SUSIM: an advanced, high-precision solar ultraviolet spectral irradiance monitor on the NASA UARS (Upper Atmosphere Research Satellite) Mission

  • NRL was SUSIM PI institution for NASA
  • NRL conceived and developed the SUSIM with its onboard dual precision self calibration capability
  • Built on successful NRL Skylab slit spectrograph (SO82B), Calroc calibration sounding rocket, and SUSIM Spacelab-2

UARS Mission: September 1991 (Launch) - June 2005

  • Provided a long term orbital platform for SUSIM to measure the solar spectral irradiance to the required precision of 0.3-3% for 14 years and for longer than a full 11 year solar cycle

Deliverable/Value/Accomplishment

  • The NRL UARS/SUSIM met the solar spectro-radiometric measurement requirements over the entirety of the UARS mission operations
  • The NRL SUSIM spectral solar irradiance measurement precision has not been surpassed
  • NRL is currently developing a laboratory capability to more accurately calibrate future spectro-radiometric space instruments that will be required for future climate change research