Engineering topics

Goldberg, R. A.

Publications and source records attributed to Goldberg, R. A..

At least 37 records · Page 2

NASA NTRS2000

Noctilucent Clouds and Corresponding Meteorological Conditions

Temperature measurements obtained using the passive falling sphere technique in 1991, 1993, and again in 1999 are being used to study the relationship between the neutral atmosphere and Noctilucent Clouds (NLC) The earlier NLC studies provided useful information on the behavior of the neutral atmosphere. The recent study program, the Distribution and Role of Particles in the Polar Summer Mesosphere (DROPPS) produced additional significant information of the neutral atmosphere and Noctilucent Cloud (NLC) association. Temperature lapse rates from seven rocket observations that were generally monatonic indicated changes at the mesopause during the NLC event of 5 July. Between 5 July, 2313 UTC and 6 July 0209 UTC, the temperature lapse rate between about 85 and 92 km was different and the altitude of the minimum temperature changed by 5 km. Furthermore, change in wind direction and speed, although not yet fully analyzed, may be associated with the change of the temperature structure, possibly due to advection. Comparisons are made between the meteorological conditions during the NLC events of 1991, 1993, and 1999.

Schmidlin, F. J.↗

NASA NTRS2000

A Study of Meteorological Conditions Associated With Noctilucent Clouds

Temperature measurements were obtained in the upper stratosphere and mesosphere between 50 and 95 km with passive inflatable falling spheres launched on small meteorological rockets as part of the DROPPS (Distribution and Role of Particles in the Polar Summer Mesosphere) program. Temperatures of the neutral atmosphere have been combined with similar measurements obtained during 1991 and 1993. Temperatures were found to change monatonically with altitude except during the Nocticulent Clouds (NLC) occurrences during DROPPS. The temperature lapse rate changed between 5 July 1999, 2313 UTC and 6 July 1999, 0209 UTC; this included a lowering of the altitude of minimum temperature by about 5 km. Furthermore, winds backed from a northeasterly direction to a northwesterly direction. Whether the change in temperature observed is a result of advection related to the changes of the wind field due to advection. Comparisons will also concentrate on the meteorological conditions during the NLC event during DROPPS and earlier 1991 and 1993 NLC'S.

Schmidlin, F. J.↗

NASA NTRS1999

The Importance of Meteorological Measurement for the Scientific Study of the Mesosphere

The rocket-borne falling sphere technique has been providing temperature and wind measurements to 90 km. For example, the High Resolution Doppler Imager (HRDI) experiment on the Upper Atmosphere Research Satellite (UARS) and during the GUARA Campaign. The measurement of temperature and wind using the falling sphere method is well known, but will be briefly reviewed. The vertical resolution of the data is examined at different geographical locations and seasons. Time/height sections characterizing the temperature and wind structure will be presented for low (Alcantara, Brazil), middle (Wallops Island and Barking Sands, Hawaii), and high latitudes (ARR and ESRANGE). We address radar quality required, data smoothing, and expected measurement accuracy. Special emphasis will be given to the data gathered during the GUARA campaign, especially small- and large-scale motions including transports of momentum and heat. In the GUARA campaign, the combined Use of small meteorological payloads to measure large scale temperature and wind variations coupled with measurements of small scale turbulence from the larger rockets provided clear cut evidence of gravity wave breaking in the 85 to 90 km region.

Schmidlin, F. J.↗

NASA NTRS1999

The Importance of Meteorological Measurements for the Scientific Study of the Mesosphere

The rocket-borne falling sphere technique has been providing temperature and wind measurements to 90 km. For example, the HRDI experiment on the Upper Atmosphere Research Satellite (UARS) and during the GUARA Campaign. The measurement of temperature and wind using the falling sphere method is well known, but will be briefly reviewed. The vertical resolution of the data is examined at different geographical locations and seasons. Time/height sections characterizing the temperature and wind structure will be presented for low (Alcantara, Brazil), middle (Wallops Island and Barking Sands, Hawaii), and high latitudes (ARR and ESRANGE). We address radar quality required, data smoothing, and expected measurement accuracy. Special emphasis will be given to the data gathered during the GUARA campaign, especially small- and large-scale motions including transports of momentum and heat. In the GUARA campaign, the combined use of small meteorological payloads to measure large scale temperature and wind variations coupled with measurements of small scale turbulence from the larger rockets provided clear cut evidence of gravity wave breaking in the 85 to 90 km region.

Schmidlin, F. J.↗

NASA NTRS1999

Relativistic Electrons Observed at UARS and the Interpretation of their Storm-Associated Intensity Variations

The High Energy Particle Spectrometer (HEPS) instrument on the Upper Atmosphere Research Satellite (UARS) provides a database of electron intensities well resolved in energy and pitch-angle. Because of its 57 deg. orbital inclination, UARS encounters with magnetic shells L greater than 2 occur quite far off-equator (B/B (sub 0) greater than 9), corresponding to equatorial pitch angle alpha (sub 0) greater than 20 deg. Data acquired by HEPS (October 1991 through September 1994) span the declining phase of Solar Cycle 22. To reveal the storm-associated time dependence of relativistic electron intensities over the wide range of energies (50 keV to 5 MeV) covered by HEPS, we divide the daily average of the measured spectrum at a given L value (bin width = 0.25) by the corresponding 500-day average and plot the results with a color scale that spans only 2.5 decades. The data show that our off-equatorial electron intensities typically increase with time after the end of recovery phase (not during main phase or recovery phase) of each geomagnetic storm. The delay in off-equatorial energetic electron response and the subsequent lifetime of the corresponding electron flux enhancement seem to increase with particle energy above 300 keV. The trend below 300 keV seems to be opposite, such that the delay varies inversely with electron energy. Our working hypothesis for interpretation is that stormtime radial transport tends to increase the phase-space densities of trapped relativistic electrons but typically leads to a flux increases at specified energies only as the current (as indicated by Dst) decays. Flux enhancements in early recovery phase are greatest for equatorially mirroring electrons, and to pitch-angle anisotropies are initially large. Subsequent pitch-angle diffusion broadens the flux enhancement to particles that mirror off equator, thus gradually increasing low-altitude electron intensities (as detected by HEPS/UARS) on time scales equal to about 20% of corresponding lifetimes against diffusion into the loss cone. Alternative interpretations will also be examined.

Pesnell, W. D.↗

NASA NTRS1997

Comparison of plasma probes in the lower ionosphere

The instrumentation and the observations performed by four identically instrumented sounding rockets, designed to investigate the mesosphere and lower thermosphere, are reported. The four sounding rockets were launched from the Brazilian equatorial range Alcantara in August 1994. The instruments were capable of determining ion and electron densities. The results of data processing showed discrepancies hitherto unnoticed by other experiments.

Friedrich, M.↗

NASA NTRS1994

Energy deposition and middle atmosphere electrodynamic response to a highly relativistic electron precipitation event

Rocket data have been used to evaluate the characteristics of precipitating relativistic electrons and their effects on the electrodynamic structure of the middle atmosphere. These data were obtained at Poker Flat, Alaska, on May 13 and 14, 1990, during a midday, highly relativistic electron (HRE) precipitation event. Solid state detectors were used to measure the electron fluxes and their energy spectra. An X ray scintillator was included on each flight to measure bremsstrahlung X rays produced by energetic electrons impacting on the upper atmosphere. However, these were found the be of negligible importance for this particular event. The energy deposition by the electrons has been determined from the flux measurements and compared with in situ measurements of the atmospheric electrical response. The electrodynamic measurements were obtained by the same rockets and additionally on May 13, with an accompanying rocket. The impact flux was highly irregular, containing short-lived bursts of relativistic electrons, mainly with energies below 0.5 MeV and with fluxes most enhanced between pitch angles of 0 deg - 20 deg. Although the geostationary counterpart of this measured event was considered to be of relatively low intensity and hardness, energy deposition peaked near 75 km with fluxes approaching an ion pair production rate in excess of 100/cu cm s. This exceeds peak fluxes in relativistic electron precipitation (REP) events as observed by us in numerous rocket soundings since 1976. Conductivity measurements from a blunt probe showed that negative electrical conductivities exceeded positive conductivities down to 50 km or lower, consistent with steady ionization by precipitating electrons above 1 MeV. These findings imply that the electrons from the outer radiation zone can modulate the electrical properties of the middle atmosphere to altitudes below 50 km. During the decline and activity minimum of the current solar cycle, we anticipate the occurence of similar events but with fluxes 1-2 orders of magnitude above that reported here, based on studies of earlier solar cycles (e.g., Baker et al., 1993).

Goldberg, R. A.↗

NASA NTRS1994

NLC-91: An experimental study of the polar summer mesosphere

In the summer of 1991, a major scientific campaign (NLC-91) involving 31 rocket flights was conducted from ESRANGE, Kiruna, Sweden and from Heiss Island, Russia to investigate the chemical, dynamical, and electrodynamical properties of the polar summer mesosphere. The rocket flights were also coordinated with two coherent radar facilities, EISCAT (European Incoherent Scatter Scientific Association) and CUPRI (Cornell University Portable Radar Instrument), as well as other ground facilities, to provide continual monitoring of the mesosphere by remote sensing techniques. The primary objectives of the campaign were to study noctilucent clouds (NLC's) and polar mesospheric summer echoes (PMSE's), including their possible relationship to local aerosols and/or small scale turbulence. The program involved scientific participation from eight countries, and promises to produce many results during the next few years. This overview considers the scientific campaign and briefly discusses preliminary results. These results are provided in more detail in papers following this overview.

Goldberg, R. A.↗

NASA NTRS1994

Modification of mesospheric OH and O3 during a measured highly relativistic electron precipitation event

Highly relativistic electron precipitation events (HRE's) can provide a major source of energy affecting mesospheric constituents and ionization. Based on satellite data, these events are most pronounced near the minimum of the solar sunspot cycle, increasing in intensity, spectral hardness, and frequency of occurrence as the solar cycle declines. Since such events can be sustained up to several days, their integrated effect in the mesosphere can dominate over those of other energy sources such as relativistic electron precipitation events (REP's) and auroral precipitation. The energy deposition data to be discussed and analyzed were obtained by rocket at Poker Flat, Alaska, in May 1990 during a modest HRE observed at midday near the peak of the sunspot cycle. Using a NASA two dimensional model, significant enhancement of OH and depletion of O3 at 75 +/- 10 km altitude from the measured radiation are found. Estimates of enhanced effects were made for more intense HRE events, as might be expected during solar minimum. By causing O3 depletion, the electron precipitation can also regulate the penetration of solar UV radiation, which could affect the thermal properties of the mesosphere.

Goldberg, R. A.↗

NASA NTRS1993

An overview of NLC-91: A rocket/radar study of the polar summer mesosphere

In late July and early August of 1991, a major suborbital scientific campaign (NLC-91) involving scientists from eight countries was conducted as ESRANGE, Kiruna, Sweden and at Heiss Island, Russia. The purpose of the program was to investigate the chemical, dynamical, and electrodynamical properties of the polar summer mesosphere. Thirty one rocket flights were coordinated with two coherent radar facilities, EISCAT and CUPRI, and with other ground-based observatories and facilities. This permitted direct comparison between the in situ measurements and those obtained by remote sensing of the mesosphere via continuous ground-based monitoring. The primary objectives of the campaign were to study noctilucent clouds (NLCs) and polar mesospheric summer echoes (PMSEs), including their possible relationship to local aerosols and/or small scale turbulence. This overview describes the scientific program, discusses the geophysical conditions during launch activities, and reviews some of the preliminary results. More detailed results can be found in the papers which follow.

Goldberg, R. A.↗

NASA NTRS1993

An overview of NLC-91: A rocket/radar study of the polar summer mesophere

In late July and early August of 1991, a major suborbital scientific campaign (NLC-91) involving scientists from eight countries was conducted at ESRANGE, Kiruna, Sweden and at Heiss Island, Russia. The purpose of the program was to investigate the chemical, dynamical, and electrodynamical properties of the polar summer mesosphere. Thirty one rocket flights were coordinated with two coherent radar facilities, European Incoherent Scatter (EISCAT) and Cornell Univesity Portable Radar Interferometer (CUPRI), and with other ground-based observatories and facilities. This permitted direct comparison between the in situ measurements and those obtained by remote sensing of the mesosphere via continuous ground-based monitoring. The primary objectives of the campaign were to study noctilucent clouds (NLCs) and polar mesospheric summer echoes (PMSEs), including their possible relationship to local aerosols and/or small scale turbulence. This overview describes the scientific program, discusses the geophysical conditions during launch activities, and reviews some of the preliminary results. More detailed results can be found in the papers which follow.

Goldberg, R. A.↗

NASA NTRS1992

Electrodynamics payloads for small rockets

Totally integrated design facilitates electrical cleanliness and light weight, which are necessary in subsonic parachute-borne payloads for electrodynamics investigations. 'Blunt' probes measure ion conductivity, as do Gerdien condensers. Recent finite-element computer analyses combining flow and electrodynamics have resolved problems in determining ion densities and mobilities from Gerdien data. Three-axis electric fields are measured with deployable boom-mounted electrodes from dc through VLF. Splitting the cylindrical payload with an insulator and measuring the current between halves has provided a vertical Maxwell current detector mechanically rigid enough to measure, at ELF, energy related to coupling. A nose tip 'Smith' probe turbulence measurement is usually performed on ascent. Other instrumentation, such as photo-ionization sources and X-ray detectors, can also be included. These electrodynamic measurement payloads are about one meter in length and have a mass of about 9 kg. They can be launched with an Orion-class or smaller vehicle.

Croskey, C. L.↗

NASA NTRS1991

NLC-91

Noctilucent Clouds (NLC)-91 is a multinational rocket and radar program which will take place in Jul. - Aug. 1991 in northern Scandinavia and the Barents Sea. The main objective of the campaign is to determine with in situ experiments the dynamical, electrodynamical, physical, and chemical parameters of an NLC layer combined with ground based visible radar, lidar, and microwave experiments. The altitude resolution of ground based and in situ measurements in the cold mesopause region should be improved in NLC-91 compared to the previous campaigns below 100 m.

Kopp, E.↗

NASA NTRS1991

Rocket measurements of relativistic electrons - New features in fluxes, spectra and pitch angle distributions

Novel features are presented of precipitating relativistic electron fluxes measured on a spinning sounding rocket payload at midday between altitudes of 70 and 130 km in the auroral region. The sounding rocket was launched during a relativistic electron enhancement event of modest intensity. Electron fluxes were measured for a total of about 210 seconds at energies from 0.1 to 3.8 MeV, while pitch angle was sampled from 0 to 90 deg every spin cycle. Electrons with energies below about 0.2 MeV showed isotropic pitch angle distributions during most of the first 90 sec of data, while at higher energies the electrons had the highest fluxes near the mirroring angle (90 deg); when they occurred, the noted downward bursts were seen at all energies. The low-altitude fluxes are compared with those measured at geostationary orbit, and it is found that the low-altitude fluxes are much higher than expected from a simple mapping of a pancake distribution at high altitudes.

Herrero, F. A.↗

NASA NTRS1990

Electrodynamic response of the middle atmosphere to auroral pulsations

The MAC/EPSILON observational campaign encompassed the use of two Nike Orion rocket payloads which studied the effects of auroral energetics on the middle atmosphere. While one payload was launched during the recovery phase of a moderate magnetic substorm, during fairly stable auroral conditions, the other was launched during highly active postbreakup conditions during which Pc5 pulsations were in progress. The energetic radiation of the first event was composed almost entirely of relativistic electrons below 200 keV, while that of the second was dominated by much softer electrons whose high X-ray fluxes exceeded the cosmic ray background as an ionizing source down to below 30 km.

Goldberg, R. A.↗

NASA NTRS1990

Middle atmosphere electrical structure during MAC/EPSILON

Extensive use of rocket-launched probes during the the MAC/EPSILON campaign at the Andoya Rocket Range, Norway, has enabled the characterization of the region's electrical environment for all four flight series. The first rocket salvo was conducted during daylight (October 15, 1987) and the subsequent three occurred at night (October 21 and 28 and November 12, 1987), all of them during geomagnetically disturbed conditions. Measurements of polar electrical conductivity, ion mobility, and number density are presented, and their associated structure is investigated for local auroral ionization effects. This is believed to be the first time that Gerdien condenser mobility measurements have indicated a heavy-ion presence (positively charged aerosols) in the auroral mesopause region.

Mitchell, J. D.↗

NASA NTRS1989

Double-peaked sodium layers at high latitudes

Na lidar observations indicate that at high latitudes in summer the neutral Na layer frequently attains a double-peaked structure. The main layer with a maximum near 90 km altitude is supplemented by a secondary, narrow layer near 95 km altitude. Results are presented concerning secondary sodium layers. It appears likely that the formation of secondary Na layers observed frequently above the lidar site is not solely a 'sodium phenomenon', but part of a more comprehensive layering process for metal atoms and ions. Na(+)/Na density ratios close to 0.5 near the peaks of both the main and secondary layers are derived.

Von Zahn, U.↗

NASA NTRS1989

Middle Atmosphere Electrodynamics (MAE). Middle atmospheric electrodynamics during MAP

The recent revival and strong motivation for research in middle atmospheric electrodynamics can be attributed, in large part, to the discovery of large (V/m) electric fields within the lower mesosphere during the decade prior to MAP. Subsequent rocket soundings appeared to verify the preliminary findings. During the MAP era, more sophisticated techniques have been employed to obtain measurements which respond positively to criticisms of earlier results, and which provide more insight regarding the character of the fields. The occurrence of mesospheric V/m electric fields now seems to require the presence of aerosols, of local winds and related dynamics, and of an atmospheric electrical conductivity less than 10(-10)S/m. Furthermore, new theoretical ideas describing the origin of the V/m fields are consistent with the measurements. The current status of results regarding V/m fields in the middle atmosphere is reviewed in light of the more widely accepted electric field structure for this region from rocket, balloon and modeling results.

Goldberg, R. A.↗