1. On-Orbit Performance and Calibration of the HMI Instrument J
On-Orbit Performance and Calibration of the HMI Instrument J. Todd Hoeksema, Rock Bush, Charles Baldner, Jesper Schou, Phil Scherrer, and the HMI Calibration Team
Relative Change in Front-Camera Flat Field Between and
Instrument Throughput Front (solid) and Side Cameras; Typical exposure 135 ms of max 450 ms.
The Helioseismic and Magnetic Imager (HMI) on the Solar Dynamics Observatory (SDO) has observed the Sun almost continuously since the completion of commissioning in May 2010, returning more than 100,000,000 filtergrams from geosynchronous orbit. Diligent and exhaustive monitoring of the instrument’s performance ensures that HMI functions properly and allows proper calibration of the full-disk images and processing of the HMI observables. We constantly monitor trends in temperature, pointing, mechanism behavior, and software errors. Cosmic ray contamination is detected and bad pixels are removed from each image. Routine calibration sequences and occasional special observing programs are used to measure the instrument focus, distortion, scattered light, filter profiles, throughput, and detector characteristics. That information is used to optimize instrument performance and adjust calibration of filtergrams and observables.
CCD Linearity for HMI Front and Side Cameras.
Top: Intensity vs Exposure Time on
Bottom: Third Order Polynomial Fit to Residual
CCD Intensity Temperature Sensitivity
Caption KEY -- Green: Data Coverage. Blue: Trending. Orange: Calibration.
Daily Dopplergram Recovery During HMI Prime Mission; Note Semiannual
Eclipse Seasons and Planned Calibrations.
Five-Year HMI Data Recovery: –
Number
Percent
Total Images
84,023,655
Missing
47,059
0.056%
Partial
7137
0.008%
ISS Open
998942
1.188%
Dopplergrams
3,448,326
98.330%
Missing Doppler
57,594
Residual Position Offset During Venus Transit. Red - Before Applying Distortion Correction.
Cumulative Number of Corrupt Images During the HMI Prime Mission as a Function of Time for the Front and Side Cameras
Daily Mean (Top) and Maximum (Bottom) Number of Bad Pixels for the Front Camera as a Function of Time.
HMI Best Focus vs. Time – Front Camera (top) Focus Difference Between Front/Side (bottom)
Post-Eclipse Focus Recovery During Spring 2014
QUALITY Bits Indicate Non-ideal Conditions.
Measured Instrument Plate Scale (Top)
Optics Package Temperature (Second Panel)
Telescope and Front Window Temperatures
The Thermal Control Scheme Changed in 2013
Solar Radius Retuned by Limb Finder as a Function of Effective Wavelength
HMI Routine Calibration Observations
Twice Daily:
Darks, True Continuum, Calmode Images
Weekly:
Focus Sweeps, PZT Off-points
Bi-weekly:
Detunes
Quarterly and Less Regularly:
SDO Off-points, Roll Calibrations
Corrected Phase Maps of the Tunable Filter Elements.
Effect of SDO Orbital Velocity on Measured Magnetic Field.
Top, Middle, Bottom: Umbra, Penumbra, and Quiet-Sun.
Left, Center, Right: Longitudinal B, Transverse B, and LoS M.
Wavelength Drift of Tunable Filter Elements Expressed as Phase Angle (180 = FSR)
Temporal Drift in HMI Velocity Zero Point Due to Drift in All Filter Elements
Top: Reflects Tuning Changes;
Bottom: Corrected for Tuning.