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

Autor: Jesper Schou, Charles S. Baldner, P. H. Scherrer, J. T. Hoeksema, R. I. Bush
Jazyk: angličtina
Rok vydání: 2018
Předmět:
010504 meteorology & atmospheric sciences
FOS: Physical sciences
Instrumental effects
01 natural sciences
Article
Quality (physics)
Shutter
0103 physical sciences
Calibration
Astrophysics::Solar and Stellar Astrophysics
Helioseismology
Magnetic fields
photosphere
Instrumentation and Methods for Astrophysics (astro-ph.IM)
010303 astronomy & astrophysics
Solar and Stellar Astrophysics (astro-ph.SR)
Instrumentation and data management
0105 earth and related environmental sciences
Remote sensing
Physics
Spacecraft
business.industry
Astrophysics::Instrumentation and Methods for Astrophysics
Astronomy and Astrophysics
Velocity fields
photosphere
Astrophysics - Solar and Stellar Astrophysics
Space and Planetary Science
Physics::Space Physics
Orbit (dynamics)
Interrupt
Astrophysics - Instrumentation and Methods for Astrophysics
business
Focus (optics)
Zdroj: Solar Physics
ISSN: 1573-093X
0038-0938
Popis: The Helioseismic and Magnetic Imager (HMI) instrument is a major component of NASA's Solar Dynamics Observatory (SDO) spacecraft. Since beginning normal 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. We describe the calibration measurements used to track HMI performance and detail trends in important instrument parameters during the mission. Regular calibration sequences provide information used to improve and update the HMI data calibration. 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 15% 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.
Comment: 50 pages, 18 figures, 20 tables
Databáze: OpenAIRE
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