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Nier, A. O.

Publications and source records attributed to Nier, A. O..

At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Composition and structure of the Martian atmosphere - Preliminary results from Viking 1

Results from the aeroshell-mounted neutral mass spectrometer on Viking 1 indicate that the upper atmosphere of Mars is composed mainly of CO2 with trace quantities of N2, Ar, O, O2, and CO. The mixing ratios by volume relative to CO2 for N2, Ar, and O2 are about 0.06, 0.015, and 0.003, respectively, at an altitude near 135 kilometers. Molecular oxygen is a major component of the ionosphere according to results from the retarding potential analyzer. The atmosphere between 140 and 200 kilometers has an average temperature of about 180 plus or minus 20 deg K. Atmospheric pressure at the landing site for Viking 1 was 7.3 millibars at an air temperature of 241 deg K. The descent data are consistent with the view that CO2 should be the major constituent of the lower Martian atmosphere.

Nier, A. O.↗
NASA NTRS1976

Double-focusing mass spectrometer

Device uses lighter, easily alined, magnet assembly to provide field required to interact with ion beam. It has no separate duct; instead, evacuated duct is formed by pole pieces which support vacuum pump. Magnetic gap and magnet assembly are reduced from 4.64 to 2.54 mm and from 2.4 to 1.5 kg, respectively.

Giffin, C. E.↗
NASA NTRS1976

Determination of exospheric neutral gas temperatures

The Atmosphere Explorer satellites (AE-C, -D, and -E) were initially placed into highly elliptical orbits with perigees around 140 km and apogees of 4000 km. As a result of such an orbital geometry, measurements of neutral constituents at high altitudes represent mainly vertical changes in densities. The influence of horizontal density gradients on measurements above 400 km is small. Under geomagnetically quiet conditions, the density profiles can be used to derive scale-height temperatures of the exosphere. The open-source neutral mass spectrometer (OSS) flown on all three AE-satellites measured neutral constituents such as N2, O, and N well above 400 km. The temperatures derived from scale heights show a good agreement among the constituents and the expected close correlation with the F10.7-cm solar flux. Satellites with highly elliptical orbits provide the opportunity to measure simultaneously both densities and temperatures.

Mauersberger, K.↗
NASA NTRS1976

Recombination of NO/+/ in the ionosphere

Simultaneous nighttime measurements of ion and neutral concentrations and temperatures made by the Atmosphere Explorer-C satellite were used to determine the recombination rate coefficient of NO(+) as a function of electron temperature. The results agree in shape and absolute magnitude to within one standard deviation with those of Walls and Dunn (1974), indicating that NO(+) ions in the ionosphere may be in the ground vibrational state.

Torr, D. G.↗
NASA NTRS1976

Seasonal variation of neutral thermospheric constituents in the Northern Hemisphere

The Atmosphere Explorer-C satellite carries a large number of experiments including an open source neutral mass spectrometer. Among the measurements obtained with this instrument were ones of particle densities of N2, O, and He at northern latitudes in early February and late June 1974. The orbital geometry of the satellite was such that comparisons could be made between the winter and summer values at the same altitudes and latitudes and at similar local solar times. The helium density shows in midmorning a winter to summer enhancement of a factor of 29 at 400 km. The enhancement at other altitudes, both higher and lower, is less. At 250 km the winter/summer oxygen ratio is 1.7, whereas the winter/summer nitrogen ratio is 0.6. Both ratios decrease with increasing altitudes. The analysis identifies an oxygen enhancement at low altitudes in winter and at high altitudes in summer.

Mauersberger, K.↗
NASA NTRS1976

Atomic and molecular oxygen densities in the lower thermosphere

The Atmospheric Explorer-C satellite used a neutral mass spectrometer containing a quasi-open ion source operating either in normal mode or in one that utilizes the satellite velocity to distinguish between incoming ambient particles and ambient particles which have struck instrument surfaces and become accommodated. An analysis was made of data from the mass spectrometer for those orbits when the open ion source operated either partially or entirely in the fly-through mode. A comparison of N2 density, total O density and O2/N2 density values at 200 km was made. The average N2 and O2 density values agree well with previous rocket soundings and other studies. It is believed that the individual absolute number densities obtained in the normal mode of operation are accurate to within 20% while those deduced from fly-through data may be accurate to only 30%.

Nier, A. O.↗
NASA NTRS1975

Rarefied gas dynamic effects on mass spectrometric studies of upper planetary atmospheres

Results are presented of measurements obtained with an open-source mass spectrometer both in earth orbit and in a laboratory molecular beam facility. The mass spectrometer/ion source combination was developed in the laboratory to be operable in either of two modes by altering ion extraction potential on ground command, i.e., as a stagnation cavity or to respond only to the incoming molecules of the unperturbed atmosphere. Results indicate that the use of this open-source configuration and dual-mode capability, allied with both standard static calibration and dynamic calibration using high-speed molecular beam techniques in the laboratory, allows collection of useful data on aeronomy of the upper atmosphere of planets and comet tails.

French, J. B.↗
NASA NTRS1975

Atomic nitrogen measurements in the upper atmosphere

The open-source neutral mass spectrometer (OSS) on the Atmosphere Explorer-C satellite (AE-C) measures the neutral constituents of the upper atmosphere. It has been found that atomic nitrogen densities can be determined at altitudes above 380 km. Most of the nitrogen atoms combine with oxygen adsorbed on the walls of the ion source to form NO. The measured net peaks at 14 amu and 30 amu show the scale height expected for atomic nitrogen; both peaks have a pronounced diurnal variation. Absolute number densities at 400 km are computed for a time period between February and April 1974 when measurements were taken in the northern hemisphere. Minimum and maximum densities of atomic nitrogen occur between 4 and 6 hr LST in the morning and around 16 hr LST in the afternoon, respectively. At 400 km, the minimum particle density is 100,000/cu cm and the maximum density 1.5 million/cu cm. In contrast to the response of N2 to geomagnetic activity, atomic N shows no appreciable effect.

Mauersberger, K.↗
NASA NTRS1974

The measurement of chemically reactive atmospheric constituents by mass spectrometers carried on high-speed spacecraft

The quasi-open-source mass spectrometer carried on the Atmospheric Explorer-C satellite has a mode of operation which utilizes the velocity of the vehicle to distinguish between incoming ambient particles and ambient particles which have struck instrument surfaces and become accommodated. Utilization of this mode has made possible the simultaneous measurement of atomic and molecular ambient oxygen without the ambiguity which usually arises due to surface reactions in the instrument. The method appears promising as a means for analyzing planetary atmospheres or the gas surrounding comets.

Nier, A. O.↗
NASA NTRS1973

Loss of atomic oxygen in mass spectrometer ion sources.

A gas beam consisting of a mixture of atomic and molecular oxygen has been directed at the ion source of a mass spectrometer like those used in sounding rockets for determining the neutral composition of the lower thermosphere. The loss of atomic oxygen on mass spectrometer surfaces was evaluated by flagging the beam in several ways and comparing the experimental results with predicted values. The results obtained suggest that in rocket flights using similar instruments the atomic oxygen densities computed assuming no-loss conditions may be low by a factor of 2.5. Studies made using a beam containing tracer O-18 indicate that carbon dioxide observed when atomic oxygen enters the source is formed in a reaction involving atomic oxygen from the beam and carbon monoxide from the surfaces bombarded.

Lake, L. R.↗
NASA NTRS1973

The open-source neutral-mass spectrometer on Atmosphere Explorer-C, -D, and -E.

The open-source mass spectrometer will be used to obtain the number densities of the neutral atmospheric gases in the mass range 1 to 48 amu at the satellite location. The ion source has been designed to allow gas particles to enter the ionizing region with the minimum practicable number of prior collisions with surfaces. This design minimizes the loss of atomic oxygen and other reactive species due to reactions with the walls of the ion source. The principal features of the open-source spectrometer and the laboratory calibration system are discussed.

Nier, A. O.↗
NASA NTRS1973

Proposed revision to the US standard atmosphere 86 to 200 km

The research activities are reported of the committee for the extension to the U.S. Standard Atmosphere in the region from 80 to 200 km. Discussions include: lower boundary condition, philosophy and constraints of the model, and atmospheric composition.

Minzner, R. A.↗
NASA NTRS1973

Study of neutral composition of lower thermosphere at Fort Churchill.

On Feb. 4 and 6, 1969, and May 11, 1970, Aerobee rockets carrying neutral mass spectrometers were flown at Fort Churchill, Canada during conditions of low geomagnetic activity. As in earlier flights at White Sands, New Mexico, each rocket carried both 'open' and 'closed' ion source instruments. Vertical profiles of N2, O2, O, Ar, and He were measured. Results obtained were essentially the same as those observed at White Sands except that for the winter flights helium appeared to be in diffusive equilibrium.

Nier, A. O.↗
NASA NTRS1972

Molecular beam simulation of planetary atmospheric entry - Some recent results.

Progress is reported in the development of molecular beam techniques to simulate entry into planetary atmospheres. Molecular beam sources for producing fast beams containing CO2 and atomic oxygen are discussed. Results pertinent to the design and calibration of a mass spectrometer ion source for measurement of the Martian atmosphere during the free molecule portion of the entry trajectory are also presented. The shortcomings and advantages of this simulation technique are discussed, and it is demonstrated that even with certain inadequacies much information useful to the ion source design was obtained. Particularly, it is shown that an open-cavity configuration retains sensitivity to atomic oxygen, provides reasonable signal enhancement from the stagnation effect, is not highly sensitive to pitch and yaw effects, and presents no unforeseen problems in measuring CO2 or atomic oxygen.

French, J. B.↗
NASA NTRS1972

Measurement of the neutral composition of the lower thermosphere above Fort Churchill by rocket-borne mass spectrometer.

Measurement of the neutral atmospheric composition above Fort Churchill, Canada (59 N, 94 W), by mass spectrometers in two rocket flights at 0835 CST on Feb. 4 and 6, 1969. A quantitative measure for the extent of agreement with static diffusive equilibrium is introduced, and substantial agreement with profiles predicted when static diffusive equilibrium was assumed is found for all constituents including helium. A sensitive search for atomic nitrogen yielded upper limits of a few per cent for one flight and of 0.2% for the other.

Hickman, D. R.↗
NASA NTRS1972

Entry science experiments for Viking 1975.

A review is given of our present knowledge of the Martian atmosphere with special emphasis on the results obtained by the Mariner 4, 6 and 7 fly-bys. The Viking Project offers the first opportunity for in situ measurements which should resolve many questions left open by previous work. A description is given of the neutral gas mass spectrometer and retarding potential analyzer experiments to be performed as the lander enters the upper atmosphere and the experiments planned for determining atmospheric structure as the lander approaches the surface of the planet.

Nier, A. O.↗
NASA NTRS1972

The composition of the upper atmosphere

Miniature mass spectrometers were developed and were carried on sounding rockets to determine the composition of the upper atmosphere. Techniques have been developed that accurately correct for the velocity and spin of the moving vehicle. Above 120 km N2, O2, and Ar appear to be in diffusive equilibrium. Most He concentration measurements show a more rapid decline with altitude than predicted by diffusive equilibrium. Because of the highly reactive nature of atomic oxygen, measurements of this species by mass spectrometry are low by an unknown factor.

Nier, A. O.↗