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Launch vehicle effluent (LVE) monitoring is part of NASA's overall tropospheric and stratospheric environmental program. Following nine techniques are evaluated and developed in report: bubbler method, pH measurements, indicator tubes, microcoulometers, modified condensation nuclei counter, dual-isotope absorption, gas-filter correlation, chemiluminescent nitric oxide detection, chemiluminescent luminol-oxidation detection.
Densities for carbon dioxide measured by the upper-atmospheric mass spectrometers on Viking 1 and Viking 2 are analyzed to yield height profiles for the temperature of the Martian atmosphere between 120 and 200 kilometers. Densities for nitrogen and argon are used to derive vertical profiles for the eddy diffusion coefficient over the same height range. The upper atmosphere of Mars is surprisingly cold, with average temperatures for both Viking 1 and Viking 2 of less than 200 K, and there is significant vertical structure. Model calculations are presented and shown to be in good agreement with measured concentrations of carbon monoxide, oxygen, and nitric oxide.
Neutral mass spectrometers carried on the aeroshells of Viking 1 and Viking 2 indicate that carbon dioxide is the major constituent of the Martian atmosphere over the height range 120 to 200 kilometers. The atmosphere contains detectable concentrations of nitrogen, argon, carbon monoxide, molecular oxygen, atomic oxygen, and nitric oxide. The upper atmosphere exhibits a complex and variable thermal structure and is well mixed to heights in excess of 120 kilometers.
Models are developed for the photochemistry of a CO2-H2O-N2 atmosphere on Mars. Estimates are given for the concentrations of N, NO, NO2, NO3, N2O5, HNO2, HNO3, and N2O as a function of altitude. Nitric oxide is the most abundant form of odd nitrogen, present with a mixing ratio relative to CO2 of the order of 1 hundred-millionth. Deposition rates for nitrite and nitrate minerals could be as large as 300,000 N equivalent atoms per sq cm/sec under present conditions and may have been higher in the past.
The quantum yield or branching ratio of N(2D) atoms formed in the reaction e + NO(+) yields N + O was measured to be 76% plus or minus 6%. Photoionization of buffered nitric oxide by a flash lamp was studied using time-resolved atomic absorption. Atoms were produced both by direct photodissociation and by dissociative recombination, and these two effects were separated by means of SF6 as an electron scavenger.
Rocket observations of the lower ionosphere in the winter of 1971 at two locations show differences of electron density which are attributed to enhancements of nitric oxide and energetic electron fluxes precipitated into the mesosphere during the poststorm phase of a geomagnetic storm. Electron density distributions were observed above Wallops Island, Virginia, and Keweenaw, Michigan, larger values occurring at Keweenaw. Energetic electron fluxes were greater at Keweenaw (L = 3.9) than at Wallops Island (L = 2.5). While particle ionization was the dominant factor in establishing the electron density during one measurement at Keweenaw, particles were not present two days earlier, even though the electron density distribution was significantly larger than that observed at Wallops Island on both occasions. An accompanying ion composition profile measured at Keweenaw during the earlier flight showed NO(+) to be the dominant ion to 76 km, where the concentration of hydrated ions H3O(+).(H2O)n, exceeded that of NO(+).
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.
Special operating modes of the open source neutral mass spectrometer (OSS) on the Atmosphere Explorer C permit the measurement of odd nitrogen (N + NO) number densities between 180 and 450 km. By using optical measurements of NO concentrations from the ultraviolet nitric oxide experiment on AE-C, number densities of N are obtained. Altitude profiles for the midlatitude legs of three orbits in the late spring of 1974 are presented and compared with densities predicted by the AE-C (OSS) empirical N model at 375 km. Atomic nitrogen appeared to be in diffusive equilibrium at least above 200 km in each of the orbits studied. A typical number density of N at 200 km, 0900 LST, and 40 deg N latitude in late May 1974 is 30 million per cu cm.
We have investigated the possible reactions of chlorine atoms, chlorine monoxide, and hydrogen chloride with D region negative ions. The mesospheric concentrations of the neutral chlorine gases have been predicted with a diurnally varying one-dimensional model of the upper atmosphere. Despite the low abundances of chlorine compounds in air their high reactivity leads to the formation of substantial quantities of clorine negative ions at high altitudes. The concentration of chlorine ions is limited in daylight by rapid reactions with oxygen and hydrogen atoms and at night by the competitive production of other stable ions. The presence of chlorine negative ions in the upper atmosphere is consistent with in situ mass spectrometer observations of charged species. The abundance of chlorinated ions in the D region may be correlated with mesospheric nitric oxide and water vapor concentrations.
Installation of molybdenum nitric oxide (NO)-to-higher oxides of nitrogen (NOx) converter in chemiluminescent gas analyzer and use of air purge allow accurate measurements of NOx in exhaust gases containing as much as thirty percent carbon monoxide (CO). Measurements using conventional analyzer are highly inaccurate for NOx if as little as five percent CO is present. In modified analyzer, molybdenum has high tolerance to CO, and air purge substantially quenches NOx destruction. In test, modified chemiluminescent analyzer accurately measured NO and NOx concentrations for over 4 months with no denegration in performance.
Previous calculations by five different modeling groups of the effect of space shuttle operations on the ozone layer yielded an estimate of 0.2 percent ozone reduction for the Northern Hemisphere at 60 launches per year. Since these calculations were made, the accepted rate constant for the reaction between hydroperoxyl and nitric oxide to yield hydroxyl and nitrogen dioxide, HO2 + NO yields OH + NO2, was revised upward by more than an order of magnitude, with a resultant increase in the predicted ozone reduction for chlorofluoromethanes by a factor of approximately 2. New calculations of the shuttle effect were made with use of the new rate constant data, again by five different modeling groups. The new value of the shuttle effect on the ozone layer was found to be 0.25 percent. The increase resulting from the revised rate constant is considerably less for space shuttle operations than for chlorofluoromethane production, because the new rate constant also increases the calculated rate of downward transport of shuttle exhaust products out of the stratosphere.
Nitric oxide and ozone concentrations in the lower stratosphere have been measured from a high-altitude research aircraft using in situ measuring techniques. Results of several geographical surveys are presented along with predictions of two two-dimensional stratospheric models. Meridional and zonal data were obtained in June 1974 and in June, July, and August 1975. At longitudes 122-158 deg W the meridional data taken between 5 and 80 deg N latitude show an increasing NO concentration with latitude, by a factor of 4 at 21-km altitude and a less marked increase at 18 km. The minimum NO concentration at 21 km is observed at 5 deg N latitude and is about 6 x 10 to the 8th power/cu cm. Zonal data at latitudes 22-38 deg N taken from 55 to 176 deg N longitude show little variation of the NO and O3 concentrations with longitude.
A balloon-borne photoionization mass spectrometer used to measure stratospheric trace gases is described. Ions are created with photons from high-intensity krypton discharge lamps and a quadrupole mass analyzer is employed for ion identification. Differential pumping is achieved with liquid helium cryopumping. To insure measurement of unperturbed stratospheric air, the entire system is contained in a sealed gondola and the atmospheric sample is taken some distance away during descent. The photoionization technique allows the detection of a low ionization potential constituent, such as nitric oxide, at less than a part in one billion in the presence of the major atmospheric gases and their isotopes. Operation of the mass spectrometer system was demonstrated during a daytime flight from Palestine, Texas on 26 April 1977. The sensitivity achieved and the unique selectivity afforded by this technique offer a capability for trace constituent measurement not possible with the more conventional electron impact ionization approach.
The present knowledge of ion production and loss processes in the D- and lower E-regions is evaluated with reference to a series of equatorial ground-based radiowave absorption measurements. An equatorial noontime reference electron density profile, corresponding to a nonflaring sun at solar cycle maximum, is derived on the basis of multifrequency absorption and virtual height measurements and data from a rocket-borne investigation. It is found that the Meira (1971) nitric oxide profile does not agree with the Gnanalingan (1974) empirical expression relating absorption to solar flux. Meira's densities below 90 km must be reduced by a factor of about 5 in order to correspond. A wide disparity is observed between the effective recombination coefficient and the average dissociative recombination coefficient for the known ion composition in the lower ionosphere. A study of diurnal variations of radiowave absorption and virtual height shows a great disagreement between calculated and measured values.
Examination of the distribution of tropospheric ozone indicates that surface destruction in the Northern Hemisphere (NH) should be about three times larger than in the Southern Hemisphere (SH). If, according to the traditional understanding of ozone, this species were a passive tracer in the troposphere, a threefold larger flux out of the stratosphere should exist in the NH than in the SH. However, meteorological analyses fail to support such pronounced hemispheric differences in stratosphere-troposphere exchange. Alternatively, therefore, it is hypothesized that photochemical synthesis of ozone in the troposphere may be particularly important in the NH because of asymmetries in the sources and distribution of carbon monoxide, hydrocarbons and nitric oxide.
The impact of the degree of fuel vaporization upon emission from a flametube combustor was studied using an inlet air pressure of 3 x 10 to the 5th power pascals, inlet air temperatures of 600K and 700K, a reference velocity of 35 meters per second and equivalence ratios of .6 and .72 using Jet A fuel. Incoming air was preheated to temperatures from 600K to 700K by a nonvitiating preheater. Jet A fuel was injected into this airstream through two different fuel injectors manifolded together and mounted in series upstream of a watercooled preforated plate flameholder. The fuel-air mixture burned in a watercooled combustor section. Samples of the fuel-air mixture upstream of the flameholder were obtained for analysis to determine the local degree of fuel vaporization and the fuel-air ratio. Samples of the combustion products were analyzed to determine gaseous emissions. The effects of vaporization on carbon monoxide and nitric on carbon monoxide and nitric oxide emissions are presented.
As part of the Ames Research Center program to explore the nature of stratosphere-troposphere exchange processes occurring in the Intertropical Convergence Zone, simultaneous in situ measurements of nitric oxide and ozone mixing ratios were made with the Ames stratospheric air sampler SAS 2. The SAS 2 is a second-generation system; it employs four parallel sensors and was designed primarily for measurements at altitudes of 60,000 ft and above on the U-2 stratospheric research aircraft. The only modifications required for this study was the addition of an air sample flow restrictor. Data were obtained with the SAS 2 system on July 26, 27, 30 and 31, 1977. Generally, 30-min measurements were made at each of six altitudes ranging from 45,000 ft to 70,000 ft, and separated by 5,000 ft intervals.
Reactions between nitrogen and water in the air surrounding lightning discharges can provide an important source of nitric oxide even under conditions where oxygen is a minor atmospheric constituent. Estimates are given for the associated source of soluble nitrite and nitrate. It is shown that lightning and subsequent atmospheric chemistry can provide a source of nitrate for the primitive ocean as large as one million tons of nitrogen per year, sufficient to fill the ocean to its present level of nitrate in less than one million years.