HMI Configuration Changes

2013.07.16

Thermal control change

Thermal control scheme was changed from constant duty cycle to thermistor-controlled, resulting in more stable thermal control.

2015.01.28 19:36UTC

Crop radius change

The image crop radius was increased for limb flare observations. Some statistics keywords are affected.

2016.04.13 19:12UTC

Switch from mod C observations to mod L observations

The original observing scheme took circularly polarized filtergrams on the front camera (camera 2) for LOS observables computation, and all polarization states on the side camera (camera 1) for the vector magnetic field observations. After this date, the front camera and LOS observables computation is unchanged, but only linearly polarized filtergrams are taken on the side camera and the vector magnetic field products combine data from both cameras.

2018.08.17 04:52UTC

Lyot element crack

An anomalous dark streak in the upper-left of the instrument field appeared, which we attribute to a crack in one element of the Lyot filter. Updated flatfields largely correct this.

2018.10.16

Focus change

The best focus setting was changed, with increased front telescope tempratures. The plate scale of the instrument changed as a result.