MDI “Quirks”

Observations:

· Changing noise floor in low-l spectra

· 52.125 μHz peaks

· Elliptical image

· Center is not center

· Radius varies

· Wave power depends on direction and focus

· Focus changes with time

· Image not in a plane

· Throughput changes

· Magnetic noise not spatially uniform

· Magnetic field saturates in sunspots

· Spurious oscillations (analysis caused)

· MTF varies over image

· High Res has significant focus variation

· Tuning motors “hung” several times

· Shutter got noisy

· Fringes in cal mode

· Not able to explain detune image shapes

· Magnetic field calibration wrong by about factor of 2

· Doppler calibration wrong by ??

· Cross equator flows

· Michelson tuning changes with time

· Annual variation in center position

· 5-min vs. 1-min magnetic field average zero offset

· noise in large scale magnetic field too large

· IP errors in some frame-lists

· Telemetry of image sometimes fails to finish

· Truncation errors in onboard calculations

· Window temperature increases with time

· Flat field procedure fails – fingerprints

· Doppler offsets with frame list changes

· 96min contamination of 12min averages

· a few instances of incorrect time

Likely or certain causes:

Shutter

· Repeatability was good, now not so good

· Beat with major frame pulse or ISS beats with major frame pulse

Focal Plane

· Distortion uncertainty

· CCD tipped

· Some other distortion so center not center

· Astigmatism

Radiation damage to window and Michelsons likely source of throughput changes

Roll angle offset hard to measure