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Witt, G.

Publications and source records attributed to Witt, G..

17 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

A comparison of PMSE and other ground-based observations during the NLC-91 campaign

During the period July-August 1991, observations were made of Polar Mesospheric Summer Echoes (PMSE) at 46.9 MHz and 224 MHz by the CUPRI and EISCAT radars, respectively, at two sites in northern Scandinavia. Those observations are compared here with observations of noctilucent clouds, nergetic particle precipitation and magnetic disturbances. The appearance and morphology of PMSE are found to be closely correlated at the two frequencies and the two sites, 200 km apart. No correlation is found between PMSE and noctilucent clouds or magnetic disturbance. No correlation is found between energetic particle precipitation and the appearance of PMSE at 46.9 MHz for the whole time period. At 224 MHz, there is no evidence for a correlation before the beginning of August and only one event suggesting a possible correlation after the beginning of August. A minimum in occurrence for PMSE is found between 16 and 21 UT (17-22 LST) which may be related to an expected minimum in background wind strength in that time interval.

Kirkwood, S.↗
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 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 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 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 NTRS1984

Temperature measurements during the CAMP program

The Cold Arctic Mesopause Program (CAMP) was conducted at ESRANGE, Sweden, in July/August 1982. During the time period of several weeks, the temperature was monitored by ground-based OH emission spectrometers and by satellite radiance measurements. Rocket launchings occurred on the nights of 3/4 and 11/12 August. On 3/4 August, seven rocket payloads were launched during a period of noctilucent cloud sighting over ESRANGE. The presence of the NLC was confirmed by several rocket-borne photometer profiles. The temperature measurements showed that the temperature profiles in the stratosphere and lower mesosphere were near the expected values of high latitude summer models. A large amplitude wave structure with three temperature minima of 139K, 114K and 111K were observed at altitudes between 83 and 94 km. The temperature minimum at 83 km was the location of the observed NLC. The temperature minima caused by the growth of the gravity wave amplitude in the highly stable mesosphere provide the regions for the growth of particles by nucleation to optical scattering size, as well as regions where the nuclei for condensation can be formed through ion chemistry paths.

Philbrick, C. R.↗
NASA NTRS1982

A rocket-borne photometric measurement of O3 and NO2 in the equatorial stratosphere

A determination of the NO2 and O3 mixing ratios has been made by measuring the attenuation of sunlight at 409 nm and 254, 288, 316 nm from an ascending rocket launched from Kourou, French Guiana (5 N) during the morning twilight of March 21, 1974. A peak NO2 volume mixing ratio of 4.4 x 10 to the -9th + 40%, -50% was measured at 30 km altitude.

Schlyter, P.↗
NASA NTRS1977

Ion composition in a noctilucent cloud region

Ion composition at mesospheric altitudes was measured at high-latitude (Kiruna, Sweden) and mid-latitude (Wallops Island, Virginia) sites under summer daytime conditions, using two sets of rocket measurements both made with pumped quadrupole ion mass spectrometers. Cluster ions of hydronium and of nitric oxide were observed at midlatitudes, while, in addition to these cluster ions, a preponderance of heavy ions between 90 and 145 amu, was observed at high latitudes. These latter results may suggest the presence of metallic particles and ions which form hydrated cluster ions within the noctilucent cloud region.

Goldberg, R. A.↗
NASA NTRS1976

Ion composition in a noctilucent cloud

Ion composition at mesospheric altitudes was measured and compared between high and mid-latitude sites under summer daytime conditions. Rocket-borne measurements were made with pumped quadrupole ion mass spectrometers. The mid-latitude data were obtained at Wallops Island, Virginia on June 30, 1973, at 1510 LMT. Large quantities of hydronium cluster ions were observed through 109+, with maximum concentrations at 55+ and 73+. Also, cluster ions of nitric oxide were observed through 84+. The high latitude launch occurred at Kiruna, Sweden on August 2, 1973, at 0700 LMT following visual sighting of a noctilucent cloud on the prior evening. The data near mesopause shows cluster ions, but also a preponderance of heavy ions between 90 and 145 AMU, with groupings 18 AMU apart but unrelated to the more typical cluster ions. One possible set of consistent identifications leads to iron and iron oxide hydrates. These results may suggest the presence of metallic particulates and ions which form hydrated clusters ions.

Goldberg, R. A.↗