ABSTRACT
The grating prism (grism), slitless spectrometer aboard the Wide Field Infrared Survey Telescope enables a survey of emission-line galaxies. To facilitate its opto-mechanical alignment, a six-degree-of-freedom element was fabricated using alignment fiducials and integral flats and used to measure a wavefront by using an infrared interferometer placed at various field points over a 20×14 deg field of view in the grism coordinate frame. Modeling identified E2 to be the most sensitive element to the grism wavefront error and was used to efficiently align the system. The merit function regression method for a wide field of view was further used to verify the higher efficiency and accuracy of the proposed alignment technique compared with the conventional sensitivity table method.
ABSTRACT
The presence of a bright (Poisson) spot in the geometrical shadow of circular/spherical shapes has been known for the past two centuries. A broad class of telescopes that involve simultaneous transmit and receive require suppression of the reflected light from the secondary mirror on the detector. For instance, the on-axis design of optical telescope for the evolved Laser Interferometric Space Antenna (eLISA), a re-scoped version of the baseline LISA mission concept, requires suppression of reflected laser light from the secondary mirror on the detector. In the past few years, the hypergaussian functions with petal-shaped realization have been shown to significantly suppress intensity along the optical axis. This work reports on fabrication of a series of petal-shaped masks using a variety of techniques such as 3D printing, photolithography, and wire Electro Discharge Machining. These masks are designed and fabricated to operate in the range of Fresnel numbers between 4 and 120. This paper discusses the challenges, successes, and failures of each fabrication technique and the optical performance of typical masks with suggestions for potential follow up work.
