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At least 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Twilight airglow. I - Photoelectrons and forbidden O I 5577-angstrom radiation.

A payload consisting of a number of experiments to study the earth's atmosphere was launched from White Sands on Feb. 8, 1971. The differential photoelectron flux spectrum was measured as a function of altitude. The energy distribution revealed the N2 vibrational structure appearing at 2.8 V, rising to a maximum at 4 eV, decreasing to an 8-volt-wide plateau at 20 V, and then further decreasing. The ion and electron density distributions were measured simultaneously. An optical measurement of forbidden O I 5577-A radiation was made. Both electron impact on atomic oxygen and dissociative recombination of O2(+) were found to produce this emission above 150 km. The recombination rate for the O(1 S) found from a reported nightglow profile is 2.5 plus or minus 1.5 x 10 to the minus 9th cu cm/sec. Between 140 and 120 km, photodissociation is a source of 5577 radiation. Chapman three-body recombination is dominant below 120 km.

Hays, P. B.↗
NASA NTRS1973

Quiet time magnetospheric field depression at 2.3-3.6 earth radii.

Flux gate magnetometer data from OGO 5 are presented that establish the existence of large field depressions under conditions of varying degree of disturbance at distances ranging from 2.3 to 3.6 earth radii at all local times. For this study, flux gate data obtained near perigee during the period of approximately one year from Jan. 21, 1969, to Feb. 23, 1970, were used.

Sugiura, M.↗
NASA NTRS1973

Mesoscale history of a small patch of clear air turbulence.

Sequential analyses of data from a network of eight special rawinsonde stations 100 km apart demonstrate the important effects of mesoscale disturbances in a 2.5-hr episode of light-to-moderate clear air turbulence (CAT). The most significant feature was the development of two turbulent fields below and above a 2-km region of a wind minimum which passed over Wallops Island, Va., near 1530 GMT on Feb. 4, 1970. The small scale of these features precludes their detection in the standard 12-hr observation sequence. The rawinsonde network utilized, which incorporates fine-scale details in both space and time, is adequate to provide a very useful current CAT depiction and an excellent source for the preparation of a short-range forecast of CAT.

Boucher, R. J.↗
NASA NTRS1973

Thermal electron energy distribution measurements in the ionosphere.

A recoverable payload instrumented for twilight airglow studies was launched by an Aerobee 150 from the White Sands Test Range on Feb. 8, 1971 at 13.56 UT. The payload included a low energy electron spectrometer (HARP) and a cylindrical Langmuir probe. The HARP electron spectrometer is a new device designed to make high resolution differential electron flux measurements. Measurements of ionospheric electron energy distribution in the range from about 0.2 to 4.0 eV are presented.

Hays, P. B.↗
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 NTRS1973

Magnetospheric plasma motion during a sudden commencement.

A sudden commencement occurred at 2348 UT on Feb. 15, 1967, when the ATS-1 satellite was about 2 hr past local noon at a geocentric distance of 6.6 earth radii. Plasma was observed by the Suprathermal Ion Detector first to flow in the antisolar direction, as expected, but then to flow westward, for about 2 min, at about 50 km/sec. Analysis of ground magnetograms suggests that the surprising westward flow, which must have involved an electric field of about 10 mV/m at 6.6 earth radii, resulted from the ionosphere's reaction to the sudden commencement. Beginning about 2 min before the start of the westward flow at ATS-1, ground magnetometers near the foot of the ATS-1 field line typically recorded magnetic-field deflections of about 70 gamma, to the northeast. Taking the ground observations, assuming a height-integrated Hall conductivity of 1 mho, and a standoff distance of 7.2 earth radii inferred from Explorer 33 solar-wind data, a magnetospheric electric field is derived which agrees in magnitude and direction with that required to produce the observed flow at ATS-1.

Lin, C.-A.↗
NASA NTRS1973

Dynamics of midlatitude light ion trough and plasmatails

Light ion trough measurements near midnight made by the RF ion mass spectrometer on OGO-4 operating in the high resolution mode in Feb. 1968 reveal the existence of irregular structure on the low latitude side of the midlatitude trough. Using two different relations between the equatorial convection electric field, assumed spatially invariant and directed from dawn to dusk, and Kp (one based on plasmapause measurements, the other on polar cap E field measurements) a model development was made of the outer plasmasphere. The model calculations produced multiple plasmatail extensions of the plasmasphere which compare favorably with the observed irregularities. Due to magnetic local time differences between the Northern and Southern Hemisphere along OGO's orbit, the time dependent irregularity structure observed is not symmetrical about the equator. The model development produces an outer plasmasphere boundary location which varies similarly to the observed minimum density point of the light ion trough. However the measurements are not extensive enough to yield conclusive proof that one of the electric field models is better than the other.

Chen, A. J.↗
NASA NTRS1974

Lightning damage to a general aviation aircraft: Description and analysis

The damage sustained by a Beechcraft King Air Model B90 aircraft by a single lightning discharge is presented and analyzed. The incident occurred during landing approach at Jackson, Michigan, on Feb. 19, 1971. In addition to the usual melted-metal damage at the lightning attachment points, there was severe implosion-type damage over a large area on the lower right side of the aircraft and impact- and crushing-type damage on the upper and lower surfaces on the left wingtip near the trailing edge. Analyses indicate that the implosion-type damage was probably caused by lightning-generated shock waves, that the impact-and crushing-type damage was caused by magnetic forces, and that the lightning discharge was a multiple strike with at least 11 strokes separated in time by about 4.5 milliseconds. The evidence indicates that the lightning discharge was rather different from the average in character severity.

Hacker, P. T.↗
NASA NTRS1973

Shock system of February 2, 1969

The shock system observed in the solar wind by Pioneer 9 and Ogo 5 on Feb. 2, 1969, consisted of the following major discontinuities: a forward slow shock; a forward fast shock; a tangential discontinuity at which the density dropped sharply and the flow direction changed; a tangential discontinuity at which the magnetic field strength jumped to an unusually high value; two closely spaced tangential discontinuities that bracketed a region of even greater field strength and that fronted a region of very cool, very dense, helium-enriched plasma; a reverse fast shock of low Mach number; and a second reverse fast shock of very low Mach number. The event had aspects of both corotating and flare-induced shock systems; it is suggested that the source of the disturbances was a flare occurring at or near an M region.

Unti, T.↗
NASA NTRS1973

Measurements of geomagnetically trapped alpha particles, 1968-1970. I - Quiet time distributions

Results of observations of geomagnetically trapped alpha particles over the energy range from 1.18 to 8 MeV performed with the aid of the Injun 5 polar-orbiting satellite during the period from September 1968 to May 1970. Following a presentation of a time history covering this entire period, a detailed analysis is made of the magnetically quiet period from Feb. 11 to 28, 1970. During this period the alpha particle fluxes and the intensity ratio of alpha particles to protons attained their lowest values in approximately 20 months; the alpha particle intensity versus L profile was most similar to the proton profile at the same energy per nucleon interval; the intensity ratio was nearly constant as a function of L in the same energy per nucleon representation, but rose sharply with L when computed in the same total energy interval; the variation of alpha particle intensity with B suggested a steep angular distribution at small equatorial pitch angles, while the intensity ratio showed little dependence on B; and the alpha particle spectral parameter showed a markedly different dependence on L from the equivalent one for protons.

Krimigis, S. M.↗
NASA NTRS1974

An observation of O/+/ 834 A nightglow emission

A 40-A resolution spectrometer was employed to measure the extreme ultraviolet nightglow emissions. The spectrometer was flown on a Black Brant V-C rocket, which was launched at 21:08 MST on Feb. 9, 1973, from White Sands Missile Range, New Mexico. The O(+) 834-A emission can be identified in the spectrum and has a brightness of 15 plus or minus 5 R. This emission is probably excited by the conjugate electrons. The data also indicate the presence of some nightglow emission in the 950- to 1050-A region that is still unidentified.

Kumar, S.↗
NASA NTRS1974

Electric and magnetic field observations during a substorm on February 24, 1970

Description of a series of electric field measurements obtained from the Injun 5 satellite and simultaneous magnetic disturbances observed in the interplanetary medium and on the ground during a magnetic substorm. The substorm analyzed took place on Feb. 24, 1970. Prior to the onset of the substorm, a greatly enhanced antisunward plasma flow was observed over the polar cap. The enhanced plasma flow occurred about 30 minutes after a switch in the direction of the interplanetary magnetic field from northward to southward. The electric fields across the polar cap immediately before and during the substorm were essentially unchanged, and it is thus indicated that an enhancement in the ionospheric conductivity rather than the electric field must be responsible for the large increase in the auroral electrojet current during the substorm.

Gurnett, D. A.↗
NASA NTRS1974

X-rays from an auroral substorm at altitudes of 60-80 km and 15-20 km

A technique for the measurement of high altitude X-rays associated with auroral events is described. The instrument package is boosted to the lower D region by a rocket and descends slowly by parachute. This arrangement facilitates coordination with the launching of other rocket probes during events of interest. A flight on Feb. 2, 1973 from the Churchill Research Range provided 17 minutes of X-ray data above 28 km. The flight was made into an intense break-up event and X-ray fluxes were observed during two episodes of the explosive phase. The reduction of auroral absorption during the later phases of the event suggests precipitation of energetic electrons unaccompanied by the lower energy precipitation responsible for the absorption earlier in the substorm.

Sheldon, W. R.↗
NASA NTRS1974

Lyman-alpha imagery of Comet Kohoutek

Electrographic imagery of Comet Kohoutek in the 1100-1500 A wavelength range was obtained from a sounding rocket on Jan. 8, 1974, and from the Skylab space station on 13 occasions between Nov. 26, 1973 and Feb. 2, 1974. These images are predominantly due to Lyman-alpha (1216 A) emission from the hydrogen coma of the comet. The rocket pictures have been calibrated for absolute sensitivity and a hydrogen production rate has been determined. However, the Skylab camera suffered degradation of its sensitivity during the mission, and its absolute sensitivity for each observation can only be estimated by comparison of the comet images with those taken by the rocket camera, with imagery of the geocoronal Lyman-alpha glow, of the moon in reflected Lyman-alpha, and of ultraviolet-bright stars. The rocket and geocoronal comparisons are used to derive a preliminary, qualitative history of the development of the cometary hydrogen coma and the associated hydrogen production rate.

Carruthers, G. R.↗
NASA NTRS1975

The light curve of Comet Kohoutek

Visual estimates of total coma brightness define the light curve of Comet Kohoutek between Nov. 24, 1974 and Feb. 6, 1974. These data are well fitted by straight lines on the M-log r diagram. The preperihelion value of n is 2.2, and the post perihelion value is 3.8 up to January 16. A standstill in the decline is suspected between January 16 and 19. If the standstill is ignored the postperihelion data can be fitted less precisely by a single line with n equals 3.3. From photoelectric measures on four nights between January 5 and 13 after perihelion, n is found to be 4.1. The average B-V with a 32.4 arc sec diaphragm for those four nights is about 0.79; no clear systematic variation with time is noted.

Angione, R. J.↗
NASA NTRS1974

Three months in space

The third Skylab mission lasted from Nov. 16, 1973 until Feb. 8, 1974. The human and subjective aspects of long-term space flight are emphasized. Physiological questions are considered, taking into account the adaptation to zero-G and biological factors. Psychological problems are also investigated, giving attention to adaptation and adjustment, aspects of rest and recreation, and subjective factors and trivia. Working in zero-G was related to interior activities, observations regarding work station design, and extravehicular activity. A description is given of the various on-orbit operations on Skylab.

Pogue, W. R.↗
NASA NTRS1974

Initial results from the EUV spectroheliometer on ATM

The Harvard College Observatory photoelectric spectroheliometer on the Apollo Telescope Mount operated correctly in orbit from May 29, 1973 to Feb. 7, 1974. During this period many thousands of spatial and spectral scans at extreme ultraviolet wavelengths were recorded during observations of a variety of solar features. The construction and modes of operation of the instrument are outlined and the principal scientific results from a preliminary analysis of the data are described.

Reeves, E. M.↗
NASA NTRS1975

Simultaneous measurements of auroral particles and electric currents by a rocket-borne instrument system - Introductory remarks

A rocket-borne experiment package has been designed to obtain simultaneous in situ measurements of the pitch angle distributions and energy spectra of primary auroral particles, the flux of neutral hydrogen at auroral energies, the electric currents flowing in the vicinity of the auroral arc as determined from vector magnetic data, and the modulation of precipitating electrons in the frequency range 0.5-10 MHz. The experiment package was launched by a Nike-Tomahawk rocket from Poker Flat, Alaska, at 0722 UT on Feb. 25, 1972, over a bright auroral band. This paper is intended to serve as an introduction to the detailed discussion of results given in the companion papers. As such it includes a brief review of the general problem, a discussion of the rocket instrumentation, a delineation of the auroral and geomagnetic conditions at the time of launch, and comments on the overall payload performance.

Anderson, H. R.↗