Forty of Years ACIS: What’s Left to Learn?

The Advanced CCD Imaging Spectrometer (ACIS) instrument aboard the Chandra X-ray Observatory was conceived some 40 years ago, completed about 15 years later, and is now in its 24th year of operation on orbit. In this talk we attempt to highlight from the long and rich saga of the instrument some of the key innovations and innovators that brought ACIS into being and/or sustained it over the years. We recount some of the challenges encountered in ACIS development and operations, and consider whether these still offer any guidance for people and organizations aspiring to build instruments for future large X-ray observatories.