Engineering topics

Blevins, V. A.

Publications and source records attributed to Blevins, V. A..

4 records

NASA NTRS1993

The UARS particle environment monitor

The overall objective of the particle environment monitor (PEM) is to provide comprehensive measurements of both local and global energy inputs into the earth's atmosphere by charged particles and Joule dissipation using a carefully integrated set of instruments. PEM consists of four instruments: the atmospheric X-ray imaging spectrometer (AXIS), the high-energy particle spectrometer (HEPS), the medium-energy particle spectrometer (MEPS), and the vector magnetometer (VMAG). AXIS provides global scale images and energy spectra of 3- to 100-keV bremsstrahlung X-rays produced by electron precipitation into the atmosphere. HEPS and MEPS provide in situ measurements of precipitating electrons in the energy range from 1 eV to 5 MeV and protons in the energy range from 1 eV to 150 MeV. Particles in this energy range deposit their energy in the atmosphere at altitudes extending from several hundred kilometers down to as low as about 30 km. VMAG provides the magnetic field direction needed to indicate and interpret the locations and intensities of ionospheric and field-aligned currents as well as providing a reference for the particle measurements. Examples of data acquired early in the Upper Atmosphere Research Satellite (UARS) mission are presented.

Winningham, J. D.↗

NASA NTRS1981

High-Altitude Plasma Instrument for Dynamics Explorer-A

The Dynamics Explorer A High-Altitude Plasma Instrument (HAPI) will make differential measurements of the velocity-space distributions of electrons and positive ions over the energy/charge range of 5 eV to 32 keV. Five identical analyzers, each making simultaneous measurements of electrons and positive ions at 64 possible energy levels, will have viewing angles of 45, 78, 90, 102, and 135 deg relative to the spacecraft spin axis. The HAPI data will contribute to the overall Dynamics Explorer science objectives, particularly by providing information on the hot-plasma effects of the coupling of energy, mass, and momentum within the earth's atmosphere, ionosphere, and magnetosphere.

Burch, J. L.↗

NASA NTRS1981

The Low Altitude Plasma Instrument /LAPI/

The Low Altitude Plasma Instrument on the Dynamics Explorer-B spacecraft provides high resolution velocity space measurements of positive ions and electrons from 5 eV to 32 keV and a monitor of electrons with energies above 35 keV. It consists of an array of 15 parabolic electrostatic analyzers spanning 180 deg in angle and two Geiger-Mueller counters mounted on a one-degree of freedom scan platform. The platform is controlled by a magnetometer that allows placement of the array to selected angles with respect to the magnetic field. Each parabolic analyzer simultaneously measures electrons and positive ions. The temporal resolution and energy range of the measurements and the detector complement to be sampled are programmable by ground command

Winningham, J. D.↗

NASA NTRS1980

Pioneer Venus Sounder Probe Neutral Gas Mass Spectrometer

A neutral gas mass spectrometer was flown to Venus as part of the Pioneer Venus Multiprobe to measure the composition of its lower atmosphere. The instrument, mounted in the Sounder Probe, was activated after the probe entered the top of the atmosphere, and it obtained data during the descent from 62 km to the surface. Atmospheric gases were sampled through a pair of microleaks, the effluent from which was pumped by a combination of ion and getter pumping. A pneumatically operated valve, controlled by the ambient atmospheric pressure, maintained the ion source pressure at a nearly constant value during descent while the atmospheric pressure varied by three orders of magnitude. A single focusing magnetic sector field mass spectrometer with mass resolution sufficient to reasonably separate argon from C3H4 at 40 amu provided the mass analysis and relative abundance measurements. A microprocessor controlled the operation of the mass spectrometer through a highly efficient peak-tip stepping routine and data compression algorithm that effected a scan of the mass spectrum from 1 to 208 amu in 64 sec while requiring an information rate of only 40 bits/sec to return the data to earth. A subscale height altitude resolution was thus obtained. Weight, size, and power requirements were minimized to be consistent with interplanetary flight contraints.

Hoffman, J. H.↗