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Laboratory for Atmospheric and Space Physics

Intro to MinXSS Instruments

Introduction to MinXSS and its Science Instruments

MinXSS is a 3U CubeSat designed, built, tested, and operated from the University of Colorado at Boulder (CU) and the Laboratory for Atmospheric and Space Physics (LASP). Its size is determined by the standard 3U form factor: 34 cm x 10 cm x 10 cm, though the dimensions change slightly when the two solar arrays deploy. It weighs only 3.5 kg.

Figure 1: MinXSS mechanical block diagram. Left: stowed configuration. Right: deployed configuration. ADCS = attitude determination and control system; EPS = electrical power system; CDH = command and data handling; UHF COMM = ultra high frequency communications; X123 = primary science instrument; SPS = sun position sensor; XS or XP = X-ray sensor or X-ray photometer.

Two flight MinXSS CubeSats were built. The first one deployed from the International Space Station on 2016 May 16 (captured on camera as shown on title page). Routine science data collection began on 2016 June 8. The expected lifetime from this orbit is anywhere between 4-18 months depending on solar-influenced Earth atmospheric drag. MinXSS-2 will be launched in early 2017 into a higher orbit expected to last about 5 years. For more description of the MinXSS spacecraft, see Mason, et al. 2016 (doi: 10.2514/1.A33351).

The science instruments on MinXSS are the X123, SPS, and XP. The X123 is the primary instrument – a modified commercial-off-the-shelf silicon drift detector soft x-ray spectrometer from Amptek. MinXSS-1 (the first of the two MinXSS CubeSats) is designed to measure the solar spectrum from about 0.8 – 30 keV, but due to the relatively small size of the MinXSS aperture, the effective count rate lies between 0.8 – 10 keV, with the high energy end dictated by the solar conditions (flares vs. non-large-flaring Sun). The spectral resolution varies between 0.15 – ~0.3 keV FWHM across the spectral range 5.9 -> ~ 30 keV. Resolution between 0.8 and 5.9 is still being determined. Photons are counted and put into one of the 1024  nergy bins. The SPS provides fine pointing knowledge relative to the sun with about 2 arcsec precision. The P measures approximately the same spectral range as the X123 but is spectrally integrated to provide a single number for the band.  All of these instruments have been calibrated at the National Institute of Standards and Technology (NIST) Synchrotron Ultraviolet Radiation Facility (SURF). For more details on the instrument and calibration, see Moore, et al. 2016 (doi: 10.1117/12.2231945).