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 gridded by HEALPIX pixel and sampled by UTC day for investigation of inter-survey source variability and comparison with external observations.

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 UTC day. Inputs were the satellite spin-axis, the opening angle of each detector, and the per-survey 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). Position is thus accurate to nearest pixel center and rings which cross midnight UTC are only counted the day in which they begin.