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.

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太阳动力学观测站日震和磁成像仪的在轨性能

日震和磁成像仪 (HMI) 仪器是 NASA 太阳动力学观测站 (SDO) 航天器的主要组成部分。自 2010 年 5 月 1 日开始全面定期科学运行以来，HMI 的运行具有显着的连续性，例如，在 2015 年 9 月 30 日结束的 SDO 主要任务的五年多期间，HMI 收集了所有可能的 45 秒速度图的 98.4%；最小化这些全盘多普勒图的间隙对于日震学至关重要。HMI 速度、强度和磁场测量用于众多调查中，因此了解数据的质量非常重要。本文介绍了用于跟踪 HMI 仪器性能的校准测量，并详细介绍了主要任务期间重要仪器参数的趋势。定期校准序列提供用于改进和更新 HMI 数据校准的信息。定期调整仪器前窗和光具座的设定点温度以保持仪器焦点，并改变温度控制方案以提高可观测量的稳定性。曝光时间已更改，以补偿仪器吞吐量 20% 的下降。对快门和调谐机构性能的测量表明，它们按预期老化并继续按照规格运行。定期调整可调谐光学滤波器元件的参数以解决中心波长的漂移。频繁测量不断变化的 CCD 相机特性（例如增益和平场）可用于校准观测结果。日食、凌日和航天器偏离点等不常见的预期事件会中断常规仪器操作，并提供执行额外校准的机会。机载仪器异常现象很少见，而且出现的时间似乎相当一致。该仪器继续表现良好。