Engineering topics

Voss, H. D.

Publications and source records attributed to Voss, H. D..

At least 19 records

NASA NTRS2006

The Polar Summer MLT Plasma Environment as Seen by the DROPPS Sounding Rockets

During early July, 1999, the DROPPS (Distribution and Role of Particles in the Polar Summer Mesosphere) campaign launched two rocket payloads whose purpose was to study the polar summer MLT (mesosphere and lower thermosphere), particularly PMSEs (polar mesospheric summer echoes) and PMCs (polar mesospheric clouds). The rockets were launched from the Anderya Rocket Range in Norway the nights of the 5th and 14th of July. Both payloads included a front-mounted PID (Particle Impact Detector) consisting of charge and mass telescopes to measure aerosol and dust mass distributions. Ice particles of nanometer size are believed to be responsible for PMSEs through the process of electron scavenging. Evidence for this process is suggested, for example, by the presence of an electron "biteout" simultaneously measured by several instruments at an altitude of approx. 82 - 87km during the first DROPPS launch. This presentation will characterize similarities and differences between both flights as seen by the charge and mass telescopes, starting at launch until the loss of data on the downleg of each flight. Various stages of the flights will be considered in detail, such as the PMSE layer and the apogee at 117 km, as well as the calibration of the data before launch.

Assis, Michael P.↗

NASA NTRS2001

In-Situ Detections of a Satellite Breakup by the SPADUS Experiment

For the first time, a particle detector in Earth orbit has provided evidence to directly link sub-millimeter orbital debris to a specific satellite breakup. The University of Chicago's Space Dust instrument (SPADUS), on the U.S. Air Force's Advanced Research and Global Observation Satellite (ARGOS), has been operating in a nearly polar orbit at an altitude of about 830 km since soon after its launch on 23 February 1999. The experiment was designed primarily to detect small natural and man-made particles less than 100 microns in diameter. Using a dual-plane Polyvinylidene Fluoride (PVDF)-based detection system, SPADUS can measure dust particle flux, mass distribution, velocity, and trajectory. During its first year in orbit, SPADUS recorded 195 impacts, about one impact every two days. In late March 2000 the instrument detection rate soared by approximately an order of magnitude, suggesting a potential encounter with a cloud or stream of debris. A review of the impact times and ARGOS orbital characteristics indicated that most of the detections occurred at multiples of half-revolution intervals deep in the northern and southern hemispheres, with a clear majority of impacts found in the latter. Orbital analyses linked these impact events to the orbital plane intersections of ARGOS and the debris cloud of a Chinese orbital stage (International Designator 1999-057C, US Satellite Number 25942) which had undergone a severe fragmentation on 11 March 2000 at an altitude 100 km below that of ARGOS. Approximately 40 of the SPADUS detections during the period 25 March 1 April could be associated with the postulated Chinese debris cloud. Other periods of high impact flux on SPADUS may be related to debris clouds from different sources.

Tuzzolino, A. J.↗

NASA NTRS1999

The DROPPS Program: A Rocket/Lidar/Radar Study of the Polar Summer Mesosphere

During July of 1999, two sequences of rockets were launched from the Norwegian rocket range in Andoya, Norway. The purpose of these studies was to investigate the properties of the polar summer mesosphere, particularly relating to polar mesospheric summer echoes (PMSE) and their possible relationship to noctilucent clouds (NLC). Each of two sequences was anchored with a DROPPS Black Brant payload, consisting of 20 instruments to measure the electrodynamic and optical structure of the mesosphere and lower thermosphere. These were provided by participants from five American and two European scientific laboratories. The DROPPS (Distribution and Role of Particles in the Polar Summer) payloads were each accompanied by a sequence of meteorological rockets, and by several European payloads designed to study electrodynamics structure of the same region. ALOMAR (Arctic Lidar Observatory for Middle Atmosphere Research) Lidars, and MF (Medium Frequency) and MST (Mesosphere, Stratosphere, and Troposphere) Radars were used to continuously monitor the mesosphere for NLCs and PMSEs respectively. EISCAT VHF (European Incoherent Scatter Radar Very High Frequency) radar provided similar information about PMSEs downstream from the launch site. Sequence 1 was launched on the night of 5-6 July into a strong PMSE display coupled with a weak NLC at the low end of the PMSE. Sequence 2 was launched on the early morning of 14 July into a strong NLC with no PMSE evident. Here we describe the details of the program along with preliminary results.

Goldberg, Richard A.↗

NASA NTRS1996

Magnetospheric Atmospheric X-ray Imaging Experiment (MAXIE)

This report summarizes the activities sponsored by the Office of Naval Research for the Magnetospheric Atmospheric X-ray Imaging Experiment (MAXIE). The MAXIE instrument was developed as a joint activity of Lockheed, The Aerospace Corporation, and the University of Bergen, Norway. Lockheed was responsible for the overall management of the program, interfacing with the appropriate government agencies, the overall electrical and mechanical design, flight software, environmental testing, spacecraft integration activities, on orbit checkout, and data processing activities. The Magnetospheric Atmospheric X-ray Imaging Experiment (MAXIE), the ONR 401 experiment, is the first in a new class of satellite-borne remote sensing instruments. The primary innovation is the ability to obtain rapid, sequential, images with high sensitivity of the earth's X ray aurora from a low altitude polar orbiting satellite. These images can be used to identify dynamic temporal variations in the three-dimensional (energy and position) distribution of electron precipitation into the atmosphere. MAXIE was launched on the TIROS NOAA-13 satellite on 9 August 1993. The experiment performed well during its turn-on sequence; however, the spacecraft bus failed on 21 August 1993. New spacebased technologies successfully used in MAXIE were mixed-mode ASIC microcircuits, a zero torque scanning system with associated viscoelastic damping, a paraffin stow release mechanism, a parallel integrating PHA processor, a low noise Si(Li) sensor telescope, and an advanced thermal cooling system. MAXIE's on orbit operation, control of penetrating particle backgrounds, and scientific data indicated good overall performance.

Imhof, W. L.↗

NASA NTRS1993

An LDEF 2 dust instrument for discrimination between orbital debris and natural particles in near-Earth space

The characteristics of a space dust instrument which would be ideally suited to carry out near-Earth dust measurements on a possible Long Duraction Exposure Facility reflight mission (LDEF 2) is discussed. As a model for the trajectory portion of the instrument proposed for LDEF 2, the characteristics of a SPAce DUSt instrument (SPADUS) currently under development for flight on the USA ARGOS mission to measure the flux, mass, velocity, and trajectory of near-Earth dust is summarized. Since natural (cosmic) dust and man-made dust particles (orbital debris) have different velocity and trajectory distributions, they are distinguished by means of the SPADUS velocity/trajectory information. The SPADUS measurements will cover the dust mass range approximately 5 x 10(exp -12) g (2 microns diameter) to approximately 1 x 10(exp -5) g (200 microns diameter), with an expected mean error in particle trajectory of approximately 7 deg (isotropic flux). Arrays of capture cell devices positioned behind the trajectory instrumentation would provide for Earth-based chemical and isotopic analysis of captured dust. The SPADUS measurement principles, characteristics, its role in the ARGOS mission, and its application to an LDEF 2 mission are summarized.

Tuzzolino, A. J.↗

NASA NTRS1991

Relativistic electron enhancements - Simultaneous measurements from synchronous and low altitude satellites

This paper presents, for the first time, simultaneous measurements of trapped relativistic electron enhancements at synchronous altitude and precipitating electrons in the bounce loss cone at low altitudes. The measurements show that the daily variations in the precipitation flux for L greater than 5 correlated well with the daily variations in the total flux at high altitude, both with respect to sudden enhancements as well as flux depletions. The daily averaged precipitating flux (E greater than 1 MeV) at L = 6.1 to 7.1 was about 0.3 percent of the daily averaged directional flux (E not less than 1.5 MeV) observed at synchronous altitude, whereas within narrow spikes the precipitating directional fluxes were often within a factor of 10 of the daily averaged trapped fluxes. Strong depletions in the synchronous altitude not less than 1.5 MeV electron intensities are shown to be associated with low-altitude measurements of the equatorward movement of precipitating spikes to lower L shells.

Imhof, W. L.↗

NASA NTRS1983

Electron density and energetic particle precipitation observed during the eclipse of 26 February 1979

Electron density profiles and energetic particle fluxes are obtained based on data collected by two rockets launched from Red Lake, Ontario, respectively, at the beginning and end of totality during the solar eclipse of February 26, 1979. Data obtained by a rocket launched on February 24, 1979 showed that the electron density was normal (at 10,000 cu cm) above 110 km, to rocket apogee (130.5 km). Below 110 km, the electron density was found to be enhanced compared with data from Wallops Island at the same solar zenith angle (63 deg). It is proposed that this enhancement was due to the large flux of field-aligned energetic particles observed on the same rocket. The electron density above 110 km to rocket apogee (132.6 and 132. 3 km) was found to be reduced during totality by a factor of about three. However, below 110 km, the electron density was found to be much greater than observed during previous eclipses, probably due to the additional ionization resulting from energetic particles. The particle flux measured on February 26 was found to be an order of magnitude less than on February 24 but showed greater variability, particularly at the higher energies (100 keV).

Smith, L. G.↗

NASA NTRS1981

Energetic particle precipitation at middle and low latitudes

The results from rocket observations of the nighttime electron density profile in the upper E region (120 to 200 km) over Wallops Island, Virginia are discussed. The observations demonstrated the importance of atmospheric tides in the formation of the intermediate layer near 150 km. These observations also show that, except perhaps on geomagnetically quiet nights, energetic particles are the dominant ionization source in the layer. Using rocket, satellite, and ground-based observations it is possible to study the global morphology of particle precipitation. It is found that, just as there are northern and southern auroral zones, there are also mid-latitude, low-latitude, and equatorial zones of precipitation. The evidence for these zones and the properties of the precipitating particles are summarized.

Smith, L. G.↗

NASA NTRS1980

Global zones of energetic particle precipitation

The paper identifies global zones of energetic particle precipitation in the nighttime atmosphere during disturbed magnetic conditions in rocket, satellite, and ground-based measurements. The known equatorial zone of precipitated energetic ions and neutrals is found at altitudes above 170 km, with its origin in the double-charge-exchange process of hydrogen and helium with the ring current. The flux of electrons increases linearly with altitude in the region 100-300 km and correlates with the 391.4 nm radiation intensity and magnetic activity. Finally, it is shown that the South Atlantic magnetic anomaly provides additional support for the identification of distinct low and mid-latitude zones; poleward from the plasmapause the precipitation flux is nearly isotropic and variable, and it consists of electrons and ions with the maximum intensity of the proton auroral zone occurring about 5 deg equatorward of the maximum of the electron auroral zone.

Voss, H. D.↗

NASA NTRS1980

Rocket measurements of energetic particles in the midlatitude precipitation zone

Measurements of energetic ion and electron properties as a function of altitude in the midlatitude zone of nighttime energetic particle precipitation are reported. The measurements of particle fluxes, energy spectra and pitch angle distributions were obtained by a Langmuir probe, six energetic particle spectrometers and an electrostatic analyzer on board a Nike Apache rocket launched near the center of the midlatitude zone during disturbed conditions. It is found that the incident flux was primarily absorbed rather than backscattered, and consists of mainly energetic hydrogen together with some helium and a small energetic electron component. Observed differential energy spectra of protons having an exponential energy spectrum, and pitch angle distributions at various altitudes indicate that the energetic particle flux decreases rapidly for pitch angles less than 70 deg. An energetic particle energy flux of 0.002 ergs/sq cm per sec is calculated which indicates the significance of energetic particles as a primary nighttime ionization source for altitudes between 120 and 200 km in the midlatitude precipitation zone.

Voss, H. D.↗

NASA NTRS1980

Rocket observations of energetic ions in the nighttime equatorial precipitation zone

The paper deals with the first direct measurements of energetic particles at low altitudes in the equatorial zone. The measurements were carried out at Chilca, Peru (magnetic dip = -0.7 degrees) during the NASA launch operation Antarqui. The results illustrate how the incident energetic particle intensity, energy spectrum, and pitch-angle distribution vary with altitude in the presence of a horizontal magnetic field.

Voss, H. D.↗

NASA NTRS1979

A rocket-borne energy spectrometer using multiple solid-state detectors for particle identification

A rocket-borne experiment using energy spectrometers that allows particle identification by the use of multiple solid-state detectors is described. The instrumentation provides information regarding the energy spectrum, pitch-angle distribution, and the type of energetic particles present in the ionosphere. Particle identification was accomplished by considering detector loss mechanisms and their effects on various types of particles. Solid state detectors with gold and aluminum surfaces of several thicknesses were used. The ratios of measured energies for the various detectors were compared against known relationships during ground-based analysis. Pitch-angle information was obtained by using detectors with small geometrical factors mounted with several look angles. Particle flux was recorded as a function of rocket azimuth angle. By considering the rocket azimuth, the rocket precession, and the location of the detectors on the rocket, the pitched angle of the incident particles was derived.

Fries, K. L.↗

NASA NTRS1979

A rocket-borne data-manipulation experiment using a microprocessor

The development of a data-manipulation experiment using a Z-80 microprocessor is described. The instrumentation is included in the payloads of two Nike Apache sounding rockets used in an investigation of energetic particle fluxes. The data from an array of solid-state detectors and an electrostatic analyzer is processed to give the energy spectrum as a function of pitch angle. The experiment performed well in its first flight test: Nike Apache 14.543 was launched from Wallops Island at 2315 EST on 19 June 1978. The system was designed to be easily adaptable to other data-manipulation requirements and some suggestions for further development are included.

Davis, L. L.↗

NASA NTRS1979

A rocket-borne pulse-height analyzer for energetic particle measurements

The pulse-height analyzer basically resembles a time-sharing multiplexing data-acquisition system which acquires analog data (from energetic particle spectrometers) and converts them into digital code. The PHA simultaneously acquires pulse-height information from the analog signals of the four input channels and sequentially multiplexes the digitized data to a microprocessor. The PHA together with the microprocessor form an on-board real-time data-manipulation system. The system processes data obtained during the rocket flight and reduces the amount of data to be sent back to the ground station. Consequently the data-reduction process for the rocket experiments is speeded up. By using a time-sharing technique, the throughput rate of the microprocessor is increased. Moreover, data from several particle spectrometers are manipulated to share one information channel; consequently, the TM capacity is increased.

Leung, W.↗

NASA NTRS1979

A rocket-borne electrostatic analyzer for measurement of energetic particle flux

A rocket-borne electrostatic analyzer experiment is described. It is used to measure energetic particle flux (0.9 to 14 keV) in the nighttime midlatitude E region. Energetic particle precipitation is believed to be a significant nighttime ionization source, particularly during times of high geomagnetic activity. The experiment was designed for use in the payload of a Nike Apache sounding rocket. The electrostatic analyzer employs two cylindrical parallel plates subtending a central angle of 90 deg. The voltage waveform supplied to the plates is a series of steps synchronized to the spin of the payload during flight. Both positive and negative voltages are provided, extending the detection capabilities of the instrument to both electrons and protons (and positive ions). The development, construction and operation of the instrument is described together with a preliminary evaluation of its performance in a rocket flight.

Pozzi, M. A.↗

NASA NTRS1979

Nighttime ionization by energetic particles at Wallops Island in the altitude region 120 to 200 km

Five Nike Apache rockets, each including an energetic particle spectrometer and an electron density-electron temperature experiment, have been launched from Wallops Island (L = 2.6) near midnight under varying geomagnetic conditions. On the most recent of these (5 January 1978) an additional spectrometer with a broom magnet, and a 391.4 nm photometer were flown. The data from this flight indicate that the energetic particle flux consists predominantly of protons, neutral hydrogen and possibly other energetic nuclei. The energy spectrum becomes much softer and the flux more intense with increasing Kp for 10-100 keV. The pitch angle distribution at 180 km is asymmetrical with a peak at 90 deg indicating that the majority of particles are near their mirroring altitude. Ionization rates are calculated based on the measured energy spectrum and mirror height distribution. The resulting ionization rate profile is found to be nearly constant with altitude in the region 120 to 200 km. The measured energetic particle flux and calculated ionization rate from the five flights are found to vary with magnetic activity (based on the Kp and Dst indexes) in the same way as the independently derived ionization rates deduced from the electron density profile.

Voss, H. D.↗

NASA NTRS1977

Energetic particles and ionization in the nighttime middle and low latitude ionosphere

Seven Nike Apache rockets, each equipped with an energetic particle spectrometer (12 E 80 keV) and electron-density experiments, were launched from Wallops Island, Virginia and Chilca, Peru, under varying geomagnetic conditions near midnight. At Wallops Island the energetic particle flux (E 40 keV) is found to be strongly dependent on Kp. The pitch-angle distribution is asymmetrical about a peak at 90 D signifying a predominately quasi-trapped flux and explaining the linear increase of count rate with altitute in the altitude region 120 to 200 km. The height-averaged ionization rates derived from the electron-density profiles are consistent with the rates calculated from the observed total particle flux for magnetic index Kp 3. In the region 90 to 110 km it is found that the nighttime ionization is primarily a result of Ly-beta radiation from the geocorona and interplanetary hydrogen for even very disturbed conditions. Below 90 km during rather disturbed conditions energetic electrons can be a significant ionization source. Two energetic particle precipitation zones have been identified at midlatitudes.

Voss, H. D.↗

NASA NTRS1976

Ionization by energetic electrons in the midlatitude nighttime E region

Observations of the electron density profile and flux of energetic electrons obtained in two rocket flights at Wallops Island near midnight are presented. The ionization rates of the upper E region deduced from the electron density profiles are found to support the dependence on Kp established in previous observation. Calculations of the ionization rates using the observed electron fluxes show agreement with the values derived from the electron density profiles.

Smith, L. G.↗