header image 2  

University of Southern California

 
Instruments
ESP SEM HDIC RGIC OFS I OFS II XUV FFES

Filter Free EUV Spectrometer

The dual-grating filter-free spectrometer is based on the same freestanding transmission gratings and silicon photodiodes used on the successful Solar EUV Monitor (SEM) aboard SOHO and the EUV Solar Photometer (ESP) part of the EVE instrument suite to be flown on SDO. Its two gratings, placed in series, along with a simple baffle structure provide excellent out of band “white” light rejection.
Because the instrument does not use any thin film filters or reflective optics it is not susceptible to the degradation and instability associated with such optical elements. The spectrometer’s (laboratory shown in panel above prototype) transmission efficiency at 58.4nm has been measured in the llaboratory to be 1.2x10-3 while its solar “white” light transmission (when tuned to observe 58.4nm) is less than 1x10-9.  The figure in the left panel shows the response of the spectrometer to a monochromatic 58.4nm source (blue line) and to solar “white” light (orange line) viewed through the 60’ Solar telescope at Mt. Wilson Observatory.

 

 

  
    website last updated 5/31/2007