4 research outputs found
Design and Lessons Learned on the Development of a Cryogenic Pupil Select Mechanism Used in the Testing and Calibration of the Integrated Science Instrument Module (ISIM) on the James Webb Space Telescope (JWST)
Calibration and testing of the instruments on the Integrated Science Instrument Module (ISIM) of the James Webb Space Telescope (JWST) is being performed by the use of a cryogenic, full-field, optical simulator that was constructed for this purpose. The Pupil Select Mechanism (PSM) assembly is one of several mechanisms and optical elements that compose the Optical Telescope Element SIMulator, or OSIM. The PSM allows for several optical elements to be inserted into the optical plane of OSIM, introducing a variety of aberrations, distortions, obscurations, and other calibration states into the pupil plane. The following discussion focuses on the details of the design evolution, analysis, build, and test of this mechanism along with the challenges associated with creating a sub arc-minute positioning mechanism operating in an extreme cryogenic environment. In addition, difficult challenges in the control system design will be discussed including the incorporation of closed-loop feedback control into a system that was designed to operate in an open-loop fashion
Design and Lessons Learned on the Development of a Cryogenic Pupil Select Mechanism (PSM)
Calibration and testing of the instruments on the Integrated Science Instrument Module (ISIM) of the James Webb Space Telescope (JWST) is being performed by the use of a cryogenic, full-field, optical simulator that was constructed for this purpose. The Pupil Select Mechanism (PSM) assembly is one of several mechanisms and optical elements that compose the Optical Telescope Element SIMulator, or OSIM. The PSM allows for several optical elements to be inserted into the optical plane of OSIM, introducing a variety of aberrations, distortions, obscurations, and other calibration states into the pupil plane. The following discussion focuses on the details of the design evolution, analysis, build, and test of this mechanism along with the challenges associated with creating a sub arc-minute positioning mechanism operating in an extreme cryogenic environment. In addition, difficult challenges in the control system design will be discussed including the incorporation of closed-loop feedback control into a system that was designed to operate in an open-loop fashion
iLocater: a diffraction-limited Doppler spectrometer for the Large Binocular Telescope
We are developing a stable and precise spectrograph for the Large Binocular
Telescope (LBT) named "iLocater." The instrument comprises three principal
components: a cross-dispersed echelle spectrograph that operates in the
YJ-bands (0.97-1.30 microns), a fiber-injection acquisition camera system, and
a wavelength calibration unit. iLocater will deliver high spectral resolution
(R~150,000-240,000) measurements that permit novel studies of stellar and
substellar objects in the solar neighborhood including extrasolar planets.
Unlike previous planet-finding instruments, which are seeing-limited, iLocater
operates at the diffraction limit and uses single mode fibers to eliminate the
effects of modal noise entirely. By receiving starlight from two 8.4m diameter
telescopes that each use "extreme" adaptive optics (AO), iLocater shows promise
to overcome the limitations that prevent existing instruments from generating
sub-meter-per-second radial velocity (RV) precision. Although optimized for the
characterization of low-mass planets using the Doppler technique, iLocater will
also advance areas of research that involve crowded fields, line-blanketing,
and weak absorption lines.Comment: 13 pages, 11 figure