Once upon a time, scientific data was hard to find and took a lot of time to analyze. In astronomy, data was originally recorded on fragile photographic plates at telescopes spread out all over the world. You can imagine how hard it was to transport and share this data! In the late 20th century, most data collection (from both satellites and Earth-based telescopes) became computerized, but it required special software to analyze, and only the astronomers who built the equipment could easily analyze it.
Near the turn of the century, however, much of the data and software became standardized and placed into easily accessible computerized archives. Now many more astronomers can look at data originally acquired by satellites they hadn't directly worked on. Today, the data and software are becoming accessible to students.