2015 Healpix Rings

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General description[edit]

The "HealPix Rings", or HPRs, produced by HFI for the 2015 data release, are an intermediate product of the HFI mapmaking progress, as described briefly in Frequency maps. HPRs are produced by binning the TOI data of a pointing period onto a band of Healpix map pixels. As a result of this binning, the data volume is reduced by nearly a factor of ~20

Production process[edit]

For each valid bolometer, HPRs are build for the following quantities:

the actual signal, after the treatment described in Timelines TBD after removal of the total dipole and of the bandpass correction
this is the total dipole, i.e., solar + orbital. This is what is used for the flux calibration and then removed from the TOI signal.
hit count
the number of TOI samples binned into each ring pixel.
the one-dimensional phase along the ring.
φ, θ, and ψ coordinates
the three coordinates, corresponding to the mean coordinates of the TOI samples actually binned into that pixel, as opposed to the pixel coordinates given by the pixelation scheme, and including the position angle ψ.

File Names[edit]

Files are named:

HFI_HPR_353-4a-{signal, bandpass, dipole, hit, phase, phi, theta, psi}_R3.00.fits

FITS file structure[edit]

The full mission (thus rings 240-26050) are stored in a single file as an image of Nrings x Npixels (25811 x 27664). The image is stored into a single extension of type IMAGE. The coordinate HPRs are encoded as double precision floating point values in order to maintain the needed accuracy, the others are single precision. File sizes are 5.4 and 2.7 GB, respectively.


(Planck) High Frequency Instrument

To be defined / determined

Flexible Image Transfer Specification