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, ODell et al., 2006, 'Determining the Physical Processes, Origin, and Fate of Cometary Knots in the Helix Nebula', 1.0, European Space Agency, https://doi.org/10.5270/esa-kl2u1b7