Launched in 1990, the NASA/ESA Hubble Space Telescope remains the premier UV and visible light telescope in orbit. With well over 1.6 million observations from 10 different scientific instruments, the ESA Hubble Science Archive is a treasure trove of astronomical data to be exploited.
European Space Agency, Heida et al., 2018, 'Identifying the donor star of the most extreme ULX pulsar', 1.0, European Space Agency, https://doi.org/10.5270/esa-0n6l8uf