The Miniature X-ray Solar Spectrometer (MinXSS) CubeSats: spectrometer characterization techniques, spectrometer capabilities, and solar science objectives

TL;DR

MinXSS CubeSats utilize a commercial X-ray spectrometer to perform moderate-resolution solar soft X-ray measurements, enabling new insights into solar activity and Earth's ionosphere.

Contribution

This paper details the characterization techniques and capabilities of the MinXSS spectrometer, highlighting its unique role in solar X-ray observations.

Findings

Spectrometer spectral response characterized using radioactive sources and NIST SURF.

Achieved a spectral resolution of 0.15 keV at 5.9 keV.

Demonstrated spectrometer linearity and response stability.

Abstract

The Miniature X-ray Solar Spectrometer (MinXSS) are twin 3U CubeSats. The first of the twin CubeSats (MinXSS-1) launched in December 2015 to the International Space Station for deployment in mid-2016. Both MinXSS CubeSats utilize a commercial off the shelf (COTS) X-ray spectrometer from Amptek to measure the solar irradiance from 0.5 to 30 keV with a nominal 0.15 keV FWHM spectral resolution at 5.9 keV, and a LASP-developed X-ray broadband photometer with similar spectral sensitivity. MinXSS design and development has involved over 40 graduate students supervised by professors and professionals at the University of Colorado at Boulder. The majority of previous solar soft X-ray measurements have been either at high spectral resolution with a narrow bandpass or spectrally integrating (broadband) photometers. MinXSS will conduct unique soft X-ray measurements with moderate spectral resolution over a relatively large energy range to study solar active region evolution, solar flares, and the effects of solar soft X-ray emission on Earth's ionosphere. This paper focuses on the X-ray spectrometer instrument characterization techniques involving radioactive X-ray sources and the National Institute for Standards and Technology (NIST) Synchrotron Ultraviolet Radiation Facility (SURF). Spectrometer spectral response, spectral resolution, response linearity are discussed as well as future solar science objectives.