HFI-bottom up

Like all experiments, Planck/HFI had a number of "issues" which it needed to track and verify were not compromising the data. While these are discussed in appropriate sections, here we gather them together to give brief summaries of the issues and refer the reader to the appropriate section for more details.

• Cosmic Rays - Unprotected by the atmosphere and more sensitive than previous bolometric experiment, HFI was subjected to many more cosmic ray hits than previous experiments. These were detected, the worst parts of the data flagged as unusable, and "tails" were modeled and removed. This is described in XXXXX
• Elephants - Cosmic rays also hit the 100 mK stage and cause the temperature to vary, inducing small temperature and thus noise variations in the detectors. This is described in XXXXX
• 1.6 K Stage Fluctuations
• 4 K Stage Fluctuations
• Popcorn Noise - Some channels were occasionally affected by what seems to be a "split-level" noise, which has been variously called popcorn noise or random telegraphic signal. These data are usually flagged. This is described in XXXXX
• Jumps - Similar to but distinct from popcorn noise, small jumps were occasionally found in the data streams. These data are usually corrected. This is described in XXXXX.
• 4 K Cooler-Induced EM Noise - The 4 K cooler induced noise in the detectors with very specific frequency signatures, which is filtered. This is described in XXXXX.
• 4 K Cooler-Induced Microphonics - The mechanical cooler was shown in XXXXX to cause very little microphonic parasites in the detector data.
• Pointing-Change Microphonics - The changes in pointing after each pointing period were shown in XXXXX to cause very little microphonic parasitic signal in the detector data.
• Compression - Onboard compression is used
• Noise Correlations
• Electrical Cross-Talk

• Pointing
• Focal Plane Geometry
• Main Beam
• Ruze Envelope
• Dimpling
• Far Sidelobes
• Planet Fluxes
• Point Source Fluxes

• Time Constants
• ADC Correction
• Gain changes with Temperature Changes
• Optical Cross-Talk
• Bandpass
• Saturation