From wikipedia -
"All Hubble data are eventually made available via a public archive at
http://archive.stsci.edu/hst. Data are usually proprietary?available only to the principal investigator (PI) and astronomers designated by the PI?for one year after being taken. The PI can apply to the director of the STScI to extend or reduce the proprietary period in some circumstances.
Observations made on Director's Discretionary Time are exempt from the proprietary period, and are released to the public immediately. Calibration data such as flat fields and dark frames are also publicly available straight away. All data in the archive are in the FITS format, which is suitable for astronomical analysis but not for public use. The Hubble Heritage Project processes and releases to the public a small selection of the most striking images in JPEG and TIFF formats."