DatesObs

Overview

The DATESOBS files are not official Planck products but have been made available for the convenience of the community. They contain timing information split by survey, gridded by HEALPIX pixel, and sampled by UTC day for investigation of inter-survey source variability, comparison with external observations, and understanding of the survey strategy.

File Format

There are 27 files for all combinations of the 9 instrument bands and 3 surveys. The files themselves are:

• FITS format, with data in the first extension
• RING-ordered HEALPIX
• NSIDE 1024 for LFI, and 2048 for HFI

They contain two fields:

• DATESOBS - string - Comma-separated list of UTC days in YYMMDD format on which the pixel was observed
• NUMOBS - integer - The number of UTC days on which the pixel was observed

Unobserved pixels have been left blank.

Generation

The DATESOBS files were generated by projecting the line-of-sight of each detector on the sky for each observing ring starting on a ring-by-ring basis. Inputs were the satellite spin-axis and the opening angle of each detector. Position is thus accurate to nearest pixel center and timing to the start of each ring - integrations over midnight are only counted for the day in which they begin.

Note no beam information was used, just closest line-of-sight. The list of dates within a beam width is thus the union of all DATESOBS pixels with the appropriate area.

Pixels were counted observed if hit by a single detector within each instrument band; there is no consideration of intra-band coverage.

Finally the data has been masked by the per-survey frequency hit-map in order to mask unobserved data (mainly planet crossings). The survey_3_partial DATESOBS files are unmasked as no survey_3 maps are available.