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Tondello, G.

Publications and source records attributed to Tondello, G..

10 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

The quiescent corona and slow solar wind

The observations of the ultraviolet coronagraph spectrometer (UVCS), operating onboard the Solar and Heliospheric Observatory (SOHO) spacecraft, are discussed. The purpose of the UVCS is the study of the quiescent coronal streamer and the slow solar wind. The observations started in January 1996. Polarized radiance data in the visible continuum were obtained. Some characteristics of the coronal streamer from the UVCS recorded data are discussed. A model for the source of the slow solar wind in the inner corona is proposed.

Noci, G.↗
NASA NTRS1994

UVCS/SOHO capability for determining coronal conditions before, during, and after CME's

The ultraviolet coronal spectrometer (UVCS)/SOHO instrument will provide spectroscopic determinations of plasma parameters describing the evolution of coronal conditions at the site of coronal mass ejections (CME's). Prior to a CME event, UVCS can provide an empirical model of the coronal region where the event originates. The model would include values for the proton density, temperature, and outflow velocity; the electron density and temperature; and minor ion densities, temperatures, and outflow velocities. This information would be determined for heliocentric heights from about 1.5 to 3.5 of the solar radius with a subset of the parameters determined up to heights of 12 of the solar radius. During the event, UVCS would repeatedly sample one or more heights between 1.5 and 3.5 of the solar radius with a time resolution of about 1 min. The goal would be to determine the mass and energy content of the CME as it moves outward. After the event, the conditions in the region would be determined as before. Information about the instrument optical specifications and sensitivity is provided.

Strachan, Leonard↗
NASA NTRS1992

The development and test of a deformable diffraction grating for a stigmatic EUV spectroheliometer

The objectives were to address currently unanswered fundamental questions concerning the fine scale structure of the chromosphere, transition region, and corona. The unique characteristics of the spectroheliometer was used in combination with plasma diagnostic techniques to study the temperature, density, and velocity structures of specific features in the solar outer atmosphere. A unified understanding was sought of the interplay between the time dependent geometry of the magnetic field structure and the associated flows of mass and energy, the key to which lies in the smallest spatial scales that are unobservable with current EUV instruments. Toroidal diffraction gratings were fabricated and tested by a new technique using an elastically deformable substrate. The toroidal diffraction gratings was procured and tested to be used for the evaluation of the Multi-Anode Microchannel Array (MAMA) detector systems for the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) and UV Coronagraph Spectrometer (UVCS) instruments on the SOHO mission.

Timothy, J. Gethyn↗
NASA NTRS1988

Imaging extreme ultraviolet spectrometer employing a single toroidal diffraction grating - The initial evaluation

The design and test results of a high-efficiency EUV imaging spectrometer employing a concave toroidal grating which is illuminated at normal incidence in a Rowland circle mounting and has only one reflecting surface are discussed. Photographic tests and initial photoelectric tests with a two-dimensional pulse-counting detector system demonstrate the excellent image quality of the grating at wavelengths near 600 A. Applications of the spectrometer for the study of nonsolar objects and solar regions (including the chromosphere, transition region, and corona) are considered.

Huber, M. C. E.↗
NASA NTRS1986

An imaging extreme ultraviolet spectrometer for astrophysical investigations in space

A high-efficiency, extreme ultraviolet (EUV) imaging spectrometer has been constructed and tested. The spectrometer employs a concave toroidal grating illuminated at normal incidence in a Rowland circle mounting and has only one reflecting surface. The toroidal grating has been fabricated by a new technique employing an elastically deformable submaster grating which is replicated in a spherical form and then mechanically distorted to produce the desired aspect ratio of the toroidal surface for stigmatic imaging over the selected wavelength range. The fixed toroidal grating used in the spectrometer is then replicated from this surface. Photographic tests and initial photoelectric tests with a two-dimensional, pulse-counting detector system have verified the image quality of the toroidal grating at wavelengths near 600 A. The basic designs of two instruments employing the spectrometer for astrophysical investigations in space are described, namely, a high-resolution EUV spectroheliometer for studies of the solar chromosphere, transition region, and corona; and an EUV spectroscopic telescope for studies of nonsolar objects.

Huber, M. C. E.↗
NASA NTRS1976

The absorption spectrum of neutral boron, B I

The absorption spectrum of B I has been studied in the 900-2000 A wavelength range by the flash pyrolysis technique. Transitions were observed from both the 2s(2)2p 2P ground state and the 2s2p2 4P metastable state. Five new quartet terms have been identified, with improved values obtained for two previously identified terms. A method of focusing has been developed, allowing the Ballofet-Romand-Vodar (1961) source to be used as a source of single-shot continuum in the lower wavelengths (300-1200 A) of the normal incidence region.

Roig, R. A.↗
NASA NTRS1975

Extensions to the spectrum of singly ionized barium /Ba II/

The spectrum of singly ionized barium has been studied in absorption by flash pyrolysis. Corrected wavelengths and energy levels have been obtained. Fifteen new levels have been established and 24 new lines have been observed. Photoionization is shown to be the dominant ionization mechanism in this technique.

Roig, R. A.↗
NASA NTRS1975

Experimental observation of the absorption spectrum of Fe I in the region 1600-900 A

Laboratory observations of the absorption spectrum of Fe I in the vacuum UV region between 900 and 1600 A are reported. The spectrum was obtained by applying the flash pyrolysis technique to iron foils of 1-micron thickness; the continuum was provided by a Garton source used in series with a spark gap. Plots which show several strong autoionized lines superimposed on a smooth continuum are presented along with a table of narrow lines between 904.900 and 1380.208 A. It is noted that the present spectrum is in agreement with others that have been obtained with the flash pyrolysis technique.

Tondello, G.↗
NASA NTRS1974

Refractive index of He in the region 920-1910 A

The refractive index of He has been determined in the region 920-1910 A by measurements of wavelength shifts in a 3-m spectrograph alternately filled with He and evacuated. Differential pumping systems were used to allow operation of the light source at conveniently low pressures. Several plates were measured and analyzed in order to reduce statistical errors. The results at 919 A agree with the theory within 1%, i.e., less than the experimental error.

Huber, M. C. E.↗