  This paper describes the implementation of polycomp, a open-sourced, publicly
available program for compressing one-dimensional data series in tabular
format. The program is particularly suited for compressing smooth, noiseless
streams of data like pointing information, as one of the algorithms it
implements applies a combination of least squares polynomial fitting and
discrete Chebyshev transforms that is able to achieve a compression ratio Cr up
to ~40 in the examples discussed in this work. This performance comes at the
expense of a loss of information, whose upper bound is configured by the user.
I show two areas in which the usage of polycomp is interesting. In the first
example, I compress the ephemeris table of an astronomical object (Ganymede),
obtaining Cr ~ 20, with a compression error on the x, y, z coordinates smaller
than 1 m. In the second example, I compress the publicly available timelines
recorded by the Low Frequency Instrument (LFI), an array of microwave
radiometers onboard the ESA Planck spacecraft. The compression reduces the
needed storage from ~6.5 TB to ~0.75 TB (C_r ~ 9), thus making them small
enough to be kept in a portable hard drive.
