Data compression for helioseismology

Efficient data compression will play an important role for several upcoming and planned space missions involving helioseismology, such as the upcoming Solar Orbiter mission, to be launched in 2018. Solar Orbiter will host several instruments, including the Polarimetric and Helioseismic Imager (PHI) that will provide the Doppler velocity images used for helioseismology. Major constraints for helioseismology with Solar Orbiter are the low telemetry rate and the probably short observing time. This thesis gives a first estimate of the impact of lossy data compression on helioseismology, putting special emphasis on the Solar Orbiter mission. In the first part of the thesis, simulations of solar surface convection and a model of the PHI instrument are used to evaluate the performance of PHI for helioseismology. The derived power spectra of solar oscillations suggest that PHI will be suitable for helioseismology. The low telemetry rate of Solar Orbiter requires extensive compression of the helioseismic data obtained by PHI. The performance of data compression is tested in the second part of this thesis using data provided by the Helioseismic and Magnetic Imager (HMI). Both the signal-to-noise ratio of supergranulation in time-distance helioseismology and the accuracy and precision of probing differential rotation with local correlation tracking of granulation are robust regarding lossy data compression. This indicates that the low telemetry rate of Solar Orbiter may not be a major challenge for helioseismology.