David A. Dorn

2Kx2K molecular beam epitaxy HgCdTe detectors for the James Webb Space Telescope NIRCam instrument

The NIRCam instrument will fly ten of Rockwell Scientific’s infrared molecular beam epitaxy HgCdTe 2048x2048 element detector arrays, each the largest available with current technology, for a total of 40 Megapixels. The instrument will have two varieties of MBE HgCdTe, a SWIR detector with λco = 2.5 μm, for the shortwave channel of NIRCam (0.6-2.3 μm); and a MWIR detector with λco = 5.3 μm, for the longwave channel of NIRCam (2.4-5.0 μm). Demonstrated mean detector dark currents less than 0.01 electrons per second per pixel at operating temperatures below 42 K for the MWIR and below 80 K for the SWIR, combined with quantum efficiency in excess of 80 percent and read noise below 6 electrons rms, make these detector arrays by far the most sensitive SWIR and MWIR devices in the world today. The unique advantages of molecular beam epitaxy as well as FPA data on noise, dark current, quantum efficiency, and other performance metrics will be discussed. In addition, the focal plane assembly package designs will be presented and discussed.

Inline phosphoric acid thickness & uniformity measurement system

Increasingly, manufacturers of silicon solar cells are doping wafers by misting, spraying, or rolling on phosphoric acid. No inline system exists for measuring the mass and uniformity of the deposited film to provide process control feedback in real-time. We show that an optical infrared measurement system can calculate film mass and uniformity inline. Using a parametric optical model, we calculate the expected amount of reflected infrared light as a function of film thickness, acid concentration, incidence angle, and different material optical properties. The model results suggest that the technique is applicable over a wide range of process conditions. Measurements taken of a 20% concentration film for varying film thickness correlate well with the model. We believe this confirms the overall utility of this in-line system for a range of differing process variables.

Space telescope focal planes: history and future technology directions

The capabilities and performance of focal plane subsystems used in astronomical space telescopes have increased significantly over the last 45 years. Significant gains have been made in format size, sensitivity, and spectral range coverage. This paper outlines the history of UV, visible, and IR astronomy missions occurring over this time period and describes the focal planes used. We also discuss the progression of the associated detector and focal plane technology during this timeframe. Although there have been significant gains over the last 45 years, there is still both the promise and need for continued improvement. Several missions over the next few years will use new and innovative technologies. In this paper, we describe upcoming missions and how technological breakthroughs in detectors, focal plane packaging, and readout electronics will extend the reach of science. Finally, we conclude by describing how these technologies will mature over the next 10 years.

First results from the Space Telescope Imaging Spectrograph

The STIS instrument was installed into HST in February 1997 during the Servicing Mission 2. It has almost completed checkout and is beginning its science program, and is working well. Several scientific demonstration observations were taken to illustrate some of the range of scientific uses and modes of observation of STIS.