The PROBA2 PI-team welcomes research proposals for the sixth round of its Guest Investigator program for research based on SWAP and LYRA data analysis by scientists outside the SWAP and LYRA PI-teams. We encourage in particular early-career post-docs and PhD students to apply, although more senior guest investigators' proposals are also welcome. In this round we anticipate funding for around six guest investigators or teams who will visit the PROBA2 Science Center at the Royal Observatory of Belgium, in Brussels, between August 2015 and April 2016. Please note that the deadline for applications has now passed.