Hubble Space Telescope (1990–present)

Hubble remains the most productive space telescope ever built, with over 35 years of operations and 1.5 million observations. Its data directly measured the universe's expansion rate with 1% precision, revealed supermassive black holes at galaxy centers, and captured the iconic Pillars of Creation — transforming cosmic understanding more than any other instrument to date. Compared to #2 Webb, Hubble covers ultraviolet to near-infrared wavelengths, delivering continuous optical monitoring that Webb cannot match, and it has logged 10 times more total observation hours than Chandra.