Optimizing Science with the Hubble Space Telescope

Brad Whitmore, whitmore@stsci.edu

One of the primary goals of the Space Telescope Science Institute (STScI) is to optimize science with the Hubble Space Telescope. This mantra has been with me since I joined the Institute some 27 years ago. It infuses everything we do at the Institute, from organizing the telescope allocation process, to scheduling the telescope, to calibrating and characterizing the instruments, to making the data available through the archives. I was recently reminded of this by a presentation given by Riccardo Giacconi at the 20th anniversary Hubble Fellowship Symposium. (See accompanying transcript of Giacconi’s remarks.) He talked about the early days when he was the Institute’s Director, and about the “science system engineering” view we took to optimizing science from Hubble. He has expanded on this topic in his book, Secrets of the Hoary Deep: A Personal History of Modern Astronomy. In the context of the symposium, Giacconi explained that this “system” approach even included the creation of the Hubble Fellowship program.

I recently became the Institute’s Project Scientist for Hubble. I was not expecting to apply for this position, but when the job advertisement came out and included statements like “explore potential science-driven enhancements that STScI can make to increase the impact of Hubble,” I found that it resonated. I felt it was a description of all the positions I have held over the years while at the Institute. In preparing for the job interview I started thinking about the various facets of optimizing science, not realizing that this was simply following the system-engineering approach that had been ingrained in me since arriving at the Institute.

I found myself thinking about a metric called “discovery efficiency,” which I first heard used by Holland Ford to characterize the improvement in science that the planned Advanced Camera for Surveys (ACS) would have over the existing Wide Field Planetary Camera 2 (WFPC2). The discovery efficiency is the product of the quantum efficiency (QE) times the field of view (FOV) of a detector. Unless a proposed new instrument improves the discovery efficiency by at least an order of magnitude over its predecessor, it is hard to generate the enthusiasm needed to win over a review committee. In a recent example, the discovery efficiency in the ultraviolet for Wide Field Camera 3 (WFC3) is about 50 times better than WFPC2 (primarily due to the better QE) and better by a similar margin over the ACS (primarily due to the smaller FOV of the High Resolution Camera on ACS). The discovery efficiency of WFC3 in the infrared is also about 30 times better than NICMOS, due to a combination of both QE and FOV.

This concept of a science metric led me to develop the following framework for optimizing science with Hubble, based on three categories of performance: telescope capabilities, project turnaround time, and user bandwidth.