Ray Boucarut

Optical stimulus for the calibration of the Ultraviolet and Optical Telescope (UVOT) for SWIFT

The Ultraviolet and Optical Telescope (UVOT) is one of the three astronomical instruments onboard the SWIFT spacecraft. The optical calibration of this instrument, which was done prior to integration to the SWIFT spacecraft optical bench, is key to determine if UVOT will meet its science objectives. In this paper, we describe the optical ground support equipment (GSE) used for the calibration of UVOT. These tests, which were carried out in the Diffraction Grating Evaluation Facility (DGEF), at NASA Goddard Space Flight Center, required building an optical stimulus. We report the radiometric measurements of all the optical components used in putting together this stimulus. This includes a vacuum collimator with a Cassegrain design, a Pt/Cr-Ne light source, a complete set of neutral density filters spanning 6 orders of magnitude in transmission levels, a set of narrow-band filters matching the center of each of the six bands of UVOT, a set of pinholes of various sizes, flat fielding diffusers, and a set of parabolic mirrors.

HgCdTe Detectors for the Hubble Space Telescope Wide Field Camera 3 IR Channel

Detector performance has been characterized for the HST WFC3 IR channel. This will be the first TEC cooled IR instrument on the Hubble Space Telescope (HST), which is made possible because of recent progress in HgCdTe technology. The original detector requirements are compared with the performance of the delivered devices. Achievements in quantum efficiency and dark current are described, as well as difficulties in meeting requirements for noise and dark stability. A special technique developed to illuminate a single pixel, which has demonstrated the excellent spatial resolution of the detectors is described.

Design, construction and testing of lateral transfer retroreflectors for space-based applications

The function of a Lateral Transfer Retroreflector is to accurately shift a beam of light laterally, while changing its direction 180 degrees. It uses three optically-flat, reflective surfaces located in mutually perpendicular planes to return an output beam parallel, but laterally separated from the input beam. The device maintains parallelism of the two beams regardless of its own orientation. From mid-2011 to late 2015, two types of LTR were designed, developed, produced and tested at Goddard Space Flight Center in Greenbelt Maryland. Information about the development process, along with performance results is given.

Pass-band filter performance for space-flight dark energy missions

The nature of Dark Energy can by constrained by the precise determination of super-novae distance moduli in ultraviolet to near IR pass-bands. Space-based observations are required for these moduli to be measured with the scientifically required photometric accuracies. Consequently, robust pass-band filters operable at cryogenic temperatures (120-140K) are needed that have challenging performance attributes including high in-band transmission, low ripple, good out-ofband rejection, and moderate band-edge slope. We describe the requirements and performance of dielectric multi-layer filters with spectral profiles that are suitable for both achieving the science and for accurate calibration using plausible on-orbit measurement systems.

The Hubble Space Telescope Wide Field Camera 3 Instrument Charge-Coupled Device Detectors

The Hubble Space Telescope Wide Field Camera 3 (WFC3) is a new instrument planned for deployment during Servicing Mission 4 in 2004. One of its key scientific goals is to provide panchromatic coverage from the near-UV through the near-IR. This is accomplished using two detector technologies, Marconi Applied Technologies back-thinned CCDs and Rockwell Scientific Mercury-Cadmium-Telluride (HgCdTe) IR focal planes. The Marconi CCDs have been delivered and characterized. The performance of these devices is exceptionally good, and will provide a new wide-field, near-UV capability for the observatory. Several notable advances are described.