Engineering topics

Gardner, Larry D.

Publications and source records attributed to Gardner, Larry D..

3 records

NASA NTRS1998

Far Ultraviolet and Visible Light Scatter Measurements for CVD Silicon Carbide Mirrors for SOHO

Chemically-vapor-deposited (CVD) silicon carbide (SiC) has become a popular mirror material for spaceborne solar instrumentation for the vacuum ultraviolet wavelength range due to its appreciable broadband reflectance and favorable thermal and opto-mechanical properties. Scatter from surfaces of mirrors operating in this wavelength range can destroy otherwise good image contrast especially for extended targets such as the sun. While visible light scatter measurements are relatively easy to conduct, far ultraviolet (FUV) scatter measurements are not so easy. Visible light (633 nm) scatter measurements were performed on CVD SiC telescope mirrors (from the same vendor) for two instruments on the Solar and Heliospheric Observatory (SOHO) -- Ultraviolet Coronagraph Spectrometer (UVCS) and Solar Ultraviolet Measurement of Emitted Radiation (SUMER). Additionally, extensive FUV scatter measurements were made for SUMER telescope mirrors. We attempt to correlate the results for those visible light scatter measurements and to explore the usefulness of visible scatter measurements to predictions of FUV scatter for this important material.

Leviton, Douglas B.↗

NASA NTRS1997

End-to-End System Test and Optical Performance Evaluation for the Solar and Heliosphere Observatory (SOHO) Ultraviolet Coronagraph Spectrometer (UVCS)

The UVCS is one of the instruments carried by the Solar and Heliospheric Observatory (SOHO), a joint NASA/ESA Spacecraft launched in November 1995. It is designed to perform ultraviolet spectroscopy and visible light polarimetry of the extended solar corona. The primary scientific objectives of the UVCS investigation are to study the physical processes occurring in the extended solar corona, such as: the mechanism of acceleration of the solar wind, the mechanism of coronal plasma heating, the identification of solar wind sources, and the investigation of the plasma properties of the solar wind. The UVCS End-to-End test activities included a comprehensive set of system level functional and optical tests. Although performed under severe schedule constraints, the End-to-End System Test was very successful and served to fully validate the UVCS optical design. All test results showed that the primary scientific objectives of the UVCS Mission were achievable.

Carosso, Paolo A.↗

NASA NTRS1993

Stray-light suppression in a reflecting white-light coronagraph

An analysis of stray-light suppression in the white-light channel of the Ultraviolet Coronagraph Spectrometer experiment for the Solar and Heliospheric Observatory is reported. The white-light channel consists of a reflecting telescope with external and internal occultation and a polarimeter section. Laboratory tests and analytical methods are used to perform the analysis. The various stray-light contributions are classified in two main categories: the contribution from sunlight that passes directly through the entrance aperture and the contribution of sunlight that is diffracted by the edges of the entrance aperture. Values of the stray-light contributions from various sources and the total stray-light level for observations at heliocentric heights from 1.4 to 5 solar radii are derived. Anticipated signal-to-stray-light ratios are presented together with the effective stray-light rejection by the polarimeter, demonstrating the efficacy of the stray-light suppression design.

Romoli, Marco↗