Engineering topics

Wells, C.

Publications and source records attributed to Wells, C..

4 records

NASA NTRS2016

Characterization of the JWST Pathfinder Mirror Dynamics Using the Center of Curvature Optical Assembly (CoCOA)

The JWST (James Webb Space Telescope) Optical Telescope Element (OTE) consists of a 6.6 meter clear aperture, 18-segment primary mirror, all-reflective, three-mirror anastigmat operating at cryogenic temperatures. To verify performance of the primary mirror, a full aperture center of curvature optical null test is performed under cryogenic conditions in Chamber A at NASA Johnson Space Center using an instantaneous phase measuring interferometer. After phasing the mirrors during the JWST Pathfinder testing, the interferometer is utilized to characterize the mirror relative piston and tilt dynamics under different facility configurations. The correlation between the motions seen on detectors at the focal plane and the interferometer validates the use of the interferometer for dynamic investigations. The success of planned test hardware improvements will be characterized by the multi-wavelength interferometer (MWIF) at the Center of Curvature Optical Assembly (CoCOA).

Wells, C.↗

NASA NTRS2016

Alignment Test Results of the JWST Pathfinder Telescope Mirrors in the Cryogenic Environment

After integration of the Optical Telescope Element (OTE) to the Integrated Science Instrument Module (ISIM) to become the OTIS, the James Webb Space Telescope OTIS is tested at NASAs Johnson Space Center (JSC) in the cryogenic vacuum Chamber A for alignment and optical performance. The alignment of the mirrors comprises a sequence of steps as follows: The mirrors are coarsely aligned using photogrammetry cameras with reflective targets attached to the sides of the mirrors. Then a multi-wavelength interferometer is aligned to the 18-segment primary mirror using cameras at the center of curvature to align reflected light from the segments and using fiducials at the edge of the primary mirror. Once the interferometer is aligned, the 18 primary mirror segments are then adjusted to optimize wavefront error of the aggregate mirror. This process phases the piston and tilt positions of all the mirror segments. An optical fiber placed at the Cassegrain focus of the telescope then emits light towards the secondary mirror to create a collimated beam emitting from the primary mirror. Portions of the collimated beam are retro-reflected from flat mirrors at the top of the chamber to pass through the telescope to the SI detector. The image on the detector is used for fine alignment of the secondary mirror and a check of the primary mirror alignment using many of the same analysis techniques used in the on-orbit alignment. The entire process was practiced and evaluated in 2015 at cryogenic temperature with the Pathfinder telescope.

OTIS↗

NASA NTRS1974

Ultraviolet stellar spectrophotometry from a balloon platform

A 40 centimeter diameter aperture, balloon-borne telescope and ultraviolet spectrometer is described and selected scientific results are briefly reviewed. The general configuration of the 0.4 angstrom resolution instrument is shown and the utilization of servo-controlled secondary mirror, image dissector detector, and special mirror coatings are discussed. An outlook for astronomical research in the mid-ultraviolet from balloon-borne telescopes is presented together with future development plans for JSC's balloon-borne payload.

Kondo, Y.↗

NASA NTRS1971

Detailed Skylab ECS consumables analysis for the interim revision flight plan (November, 1972, SL-1 launch)

The consumables analysis was performed for the Skylab 2, 3, and 4 Preliminary Reference Interim Revision Flight Plan. The analysis and the results are based on the mission requirements as specified in the flight plan and on other available data. The results indicate that the consumables requirements for the Skylab missions allow for remaining margins (percent) of oxygen, nitrogen, and water nominal as follows: 83.5, 90.8, and 88.7 for mission SL-2; 57.1, 64.1, and 67.3 for SL-3; and 30.8, 44.3, and 46.5 for SL-4. Performance of experiment M509 as scheduled in the flight plan results in venting overboard the cluster atmosphere. This is due to the addition of nitrogen for propulsion and to the additional oxygen introduced into the cabin when the experiment is performed with the crewman suited.

Wells, C.↗