On-Orbit Performance of the Helioseismic and Magnetic Imager Instrument onboard the Solar Dynamics Observatory

Abstract

The Helioseismic and Magnetic Imager (HMI) instrument is a major component of NASA's Solar Dynamics Observatory (SDO) spacecraft. Since commencement of full regular science operations on 1 May 2010, HMI has operated with remarkable continuity, e.g. during the more than five years of the SDO prime mission that ended 30 September 2015, HMI collected 98.4% of all possible 45-second velocity maps; minimizing gaps in these full-disk Dopplergrams is crucial for helioseismology. HMI velocity, intensity, and magnetic-field measurements are used in numerous investigations, so understanding the quality of the data is important. This article describes the calibration measurements used to track the performance of the HMI instrument, and it details trends in important instrument parameters during the prime mission. Regular calibration sequences provide information used to improve and update the calibration of HMI data. The set-point temperature of the instrument front window and optical bench is adjusted regularly to maintain instrument focus, and changes in the temperature-control scheme have been made to improve stability in the observable quantities. The exposure time has been changed to compensate for a 20% decrease in instrument throughput. Measurements of the performance of the shutter and tuning mechanisms show that they are aging as expected and continue to perform according to specification. Parameters of the tunable optical-filter elements are regularly adjusted to account for drifts in the central wavelength. Frequent measurements of changing CCD-camera characteristics, such as gain and flat field, are used to calibrate the observations. Infrequent expected events such as eclipses, transits, and spacecraft off-points interrupt regular instrument operations and provide the opportunity to perform additional calibration. Onboard instrument anomalies are rare and seem to occur quite uniformly in time. The instrument continues to perform very well.

HARPS-N Solar RVs Are Dominated by Large, Bright Magnetic Regions

“…We use six images each day, sampled evenly over the 2.5 year operational period of the solar telescope at HARPS-N. Note that all HMI observables have a strong 24-hour modulation related to an imperfect removal of the SDO spacecraft's orbit (Couvidat et al 2016); to mitigate the effects of these and other systematics (Löhner-Böttcher & Schlichenmaier 2013, Reiners et al 2016, Hoeksema et al 2018 we therefore reference all derived RVs to the quiet-sun velocity and take daily averages of the derived filling factors and activity-driven RVs (Meunier et al 2010b, Haywood et al 2016. (See Sec.…”

Data set for solar flare prediction using helioseismic and magnetic imager vector magnetic field data

“…The noise is presented in the quality attribute of the magnetic data when errors occur in the processing of SHARP data. We removed all samples that had a quality value higher than 65,536 (or 10,000 in hexadecimal) [ 4 , 8 ]. Filter of active regions in the SRS data set: This module filters the location of the active region associated with the event (Positive or Negative) in the SRS data set.…”

“…The noise is presented in the quality attribute of the magnetic data when errors occur in the processing of SHARP data. We removed all samples that had a quality value higher than 65,536 (or 10,000 in hexadecimal) [ 4 , 8 ].…”

“… QUALITY This attribute refers to a flag from the SHARP's data set showing whether records are noisy (This attribute holds values from a pre-defined table as disposed in [10] ). When errors occur during the SHARP's data processing, the quality attribute reports them by holding values higher than 65,536 (or 10,000 in hexadecimal) [1 , 3 , 4 , 8] . If attribute's values range between 0 and 65,536, their associated data are of good quality.…”

Solar structure and evolution

“…Also, the six-station GONG network (Harvey et al 1996) has yielded nearly continuous data for modes of degree up to around 150 since late 1995, whereas modes including even higher degrees were studied with the SOI/MDI instrument on SOHO (Scherrer et al 1995;Rhodes et al 1997). Since May 2010 these high-resolution observations have been taken over by the HMI instrument on the Solar Dynamics Observatory (Hoeksema et al 2018), with regular MDI observations ending in April 2011. Detailed analyses of the BiSON low-degree observations were carried out by Broomhall et al (2009) and Davies et al (2014), while Schou (2015, 2018) analysed the MDI and HMI observations for modes of degree up to l % 300.…”