Engineering topics

Firth, J. G.

Publications and source records attributed to Firth, J. G..

5 records

NASA NTRS1987

The dust distribution within the inner coma of comet P/Halley 1982i - Encounter by Giotto's impact detectors

Analyses are presented of Giotto's Dust Impact Detection System experiment measurements of dust grains incident on the Giotto dust shield along its trajectory through the coma of comet P/Halley on March 13 and 14, 1986. Ground-based CCD imagery of the inner coma dust continuum at the time of the encounter are used to derive the area of grains intercepted by Giotto. Data obtained at large masses show clear evidence of a decrease in the mass distribution index at these masses within the coma; it is shown that such a value of the mass index can furnish sufficient mass for consistency with an observed deceleration.

Mcdonnell, J. A. M.↗

NASA NTRS1986

The Giotto dust impact detection system

The Giotto Dust Impact Detection System (DIDSY) consists of six independent subsystems to register the impact of all particulates of significant mass incident on the probe during the post-perihelion encounter with Comet Halley. Mounted on Giotto's front dust shield, the detectors will determine the mass spectrum of the dust, with a limiting sensitivity of 10 to the minus 17th power f, increasing to the largest grain masses encountered along Giotto's trajectory throught the cometary environment with an ultimate spatial resolution of 70 km. An additional detector is located on the rear shield to monitor dust particles that penetrate the from dust shield. An ambient plasma monitor measures the impact plasma generated by dust and gass impacts on the spacecraft.

Mcdonnell, J. A. M.↗

NASA NTRS1981

Control of the Soft X-ray Polychromator on the Solar Maximum Mission Satellite

The Soft X-ray Polychromator on the Solar Maximum Mission Satellite consists of two largely independent instruments: the Flat Crystal Spectrometer, a highly collimated scanning spectrometer mounted on a raster platform, and the Bent Crystal Spectrometer, a broadly collimated spectrometer providing high time-resolution (128 ms) spectra for the study of rapidly evolving phenomena. Each instrument is controlled by a microcomputer system built around an RCA 1802 microprocessor. This paper presents a discussion of the motivation for using a microprocessor in this application, and the design concepts that were implemented. The effectiveness of the approach as seen after several months of operation will also be discussed.

Springer, L. A.↗

NASA NTRS1980

The soft X-ray polychromator for the Solar Maximum Mission

The paper considers the soft X-ray polychromator (XRP) operating in the 1.4-22.4 A range of the soft X-ray spectrum which includes many emission lines important for the diagnosis of plasmas in the 1.5-50 million deg temperature range. The flat crystal scanning spectrometer provides for a channel polychromatic mapping of flares and active regions in the resonance lines of O VIII, Ne IX, and Mg XI; in its spectral scanning mode it covers essentially the entire 1.4-22.5 A region.

Acton, L. W.↗

NASA NTRS1979

A two-axis pointing system for an orbiting astronomical instrument

The system described was built for incorporation into a solar flare X-ray instrument due to be orbited as one of a number of instruments on the NASA Solar Maximum Mission (SMM) satellite in late 1979. It enables the instrument to be rotated about 2 mutually perpendicular axes in 5 arc-second steps within a range of 7 arc-minutes, thus giving the instrument the capability to map areas of the sun.

Turner, R. F.↗