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NASA NTRS1994

The cosmic-ray oxygen and helium spectra measured at Pioneer 10 over the time of the 1987 modulation minimum, and implications for the He/O source ratio

At the time of the recent sunspot minimum in 1987 when the cosmic-ray intensity within the heliosphere was a maximum, Pioneer 10(P10) was at a radial distance of approximately 42 AU. The solar modulation parameter Phi is estimated to have reached a minimum value of approximately 150 MV at P10 at that time, as compared with a minimum value of approximately 500 MV at the Earth. Thus P10 is in a sense effectively approximately 0.7 of the way to the heliospheric modulation boundary whatever its physical distance in astronomical units. Accordingly, the spectra of the various cosmic-ray species are much nearer to the interstellar spectra than any spectra ever before measured. We have therefore examined the penetrating high energy telescope (HET) data from P10 for a 2.5 yr period around 1987 to obtain a statistically accurate spectrum of oxygen nuclei over the energy range from 90 to 450 MeV/nucleon for comparison with a 'reference' interstellar spectrum. A similar spectrum is derived for helium nuclei. These two spectra and their ratios constitute important 'reference' spectra for all of the heavier cosmic-ray nuclei. The cosmic-ray source ratio required to explain the observed He/O ratio, when a full Galactic propagation calculation is carried out including secondary He-4 and He-3 production, is 15.9. The implications of this very low ratio and a comparison with the He/O ratio measured at high energies are discussed.

Webber, W. R.↗

NASA NTRS1987

Solar activity and heliosphere-wide cosmic ray modulation in mid-1982

A plausible candidate flare is identified for each of the four major Forbush-like decrease events that were observed in the outer heliosphere in mid-1982. The associations are as follows: (1) FD 1 at P10 - backside flare at W152 deg on June 3; (2) FD 1 at P11 - 2B flare at E25 deg on June 6; (3) FD2 at P11 - 3B flare at E36 deg on July 12; and (4) FD 2 at P10 - 1N limb flare at W100 deg on July 22. In each case, the identified flare was 35 deg or less in ecliptic longitude from the affected satellite. There is no compelling evidence from near-sun spacecraft observations that the shocks from any of the four identified flares encompassed both P10 and P11. A significant fraction of the major near-sun interplanetary disturbances during June and July of 1982 arose in the relatively narrow range of Carrington longitude from 275-320 deg.

Cliver, E. W.↗

NASA NTRS2002

Effects of Hypergravity Exposure on Plasma Oxytocin (OT) Concentrations in Pregnant and Lactating Rat Dams

From pregnancy to weaning there is a progressive elevation of plasma oxytocin (OT) levels associated with nursing activity, irrespective of litter size. In the present study, we analyzed the effects of continuous 1.5G, 1.75G and 2.0G hypergravity exposure on OT plasma concentration in prepartum (Gestation Day 20) (G20) and lactating (Postnatal day) (P10) rat dams. For this study, litter size was controlled with a yoking procedure established in our lab where individual control litters were yoked-matched to individual hypergravity litters. We reviewed all data at hypergravity irrespective of gravitational level and compared the values with the controls in both G20 (HG, n=15;SC, n=9) and P10 (HG, n=21;SC, n=16). Results showed that over time, we did observe the expected OT increase in both groups. In G20 dams, measurement of OT concentrations showed no significance. However, at P10, measurements of OT concentrations suggest a reduction of about 20% compared to established controls in our laboratory, 0.9+/-0.09 ng/ml for the controls and 0.7+/-0.06 ng/ml for centrifuged animals (p<0.02). These data suggest that exposure to centrifugation may reduce OT levels during lactation. When these plasma samples were obtained, the dams were removed from the litters, and values were not adjusted for the size of the litters. The reduction in OT with centrifugation may reflect a decrease in nursing activity or a decreased responsiveness of the mammary hypothalamic axis. In addition, we have analyzed data on plasma prolactin concentrations and mammary gland development, which may give additional insight to the results of our OT measurements.

Baer, Lisa A.↗

NASA NTRS1975

Real time telemetry and data compression

The generation of telemetry and data compression by the flight program was verified. The adequacy of flight program telemetry control and timing is proven by the analysis of simulation laboratory runs of past programs through the use of telemetry. The telemetry data are correctly issued using specific tags called process input/output (P10) tags. Verification is accomplished by ensuring that a specific P10 tag and mode register setting identifies the correct parameter and that the data are properly scaled for subsequent ground station reduction. It was checked that the LVDC telemetry correctly adheres to the general requirements specified by the EDD. Data compression specifications are verified using compressed data from nominal flight simulations and from a series of perturbations designed to test data table overflows, data dump rates, and compression of data for occurrence events.

Source record↗

NASA NTRS1993

Giant transient decreases of cosmic rays in the outer heliosphere in September 1991

Large transient decreases over 20 percent were observed above 70 MeV cosmic ray intensity in September 1991, at the three spacecraft, V1, V2, and P10, in the outer heliosphere between 35 and 53 AU. These decreases appear to be related to the intense solar activity occurring in late May and early June, which was responsible for a series of rapid transient decreases at the earth that probably reduced the over 70-MeV intensity by more than 50 percent to the 1owest level ever recorded. Average transit speeds of about 600 to 800 km/s are deduced for the propagation of these transients between the earth and the outer heliosphere. The overall picture of the propagation of these transients is consistent with a massive, almost spherical modulating region moving outward in the heliosphere. The smooth almost exponential recovery of intensities at all three spacecraft for over 160 days after the decrease, and the large total modulation beyond P10 at the time of the decrease, suggest that the modulation boundary is well beyond 53 AU and probably beyond 100 AU.

Webber, W. R.↗

NASA NTRS1997

A Durable Reduction of Cosmic Ray Intensity in the Outer Heliosphere

This paper reports Pioneer 10 (P10) and Pioneer 11 (P11) observations of the intensity J(E(sub p) greater than 80 MeV) of galactic cosmic rays in the heliosphere near the heliographic equator during the 24-year period 1972-1996 and out to a heliocentric radial distance of 65 AU. It updates previous P10/P11 determinations of the time dependence of the radial gradient of intensity and emphasizes the recent 10-year period, especially the consequences of the great Forbush decrease in 1991. A fresh analysis compares P10 and P11 data with comparable data from IMP 8 at 1.0 AU. For this purpose, we have made a critical study of the data from three different instruments on IMP 8 and have developed a new time-dependent reference level of intensity at 1.0 AU for the period 1974-1996. Using this reference, we find that as of late 1996, recovery of intensity following the 1991 Forbush decrease has been markedly less complete in the outer heliosphere than at 1.0 AU. As a consequence, the mean radial gradient between 4 and 65 AU is now only about +0.3% 1/AU. Our findings favor the latitudinal wedge model of the heliosphere (Van Allen and Mihalov, 1990) and suggest that the modulation boundary of the heliosphere is far beyond 65 AU. Generally concordant, but less decisive, evidence of a similar nature has been reported previously by Van Allen (1993), Van Allen (1996), and Webber and Lockwood (1995b).

VanAllen, James A.↗

NASA NTRS2001

Effects of Hypergravity Exposure on Prolactin Levels in Pre-parturient , Parturient and Lactating Rat Dams

We analyzed the effects of 2.0-g, 1.75-g and 1.5-g hypergravity exposure on plasma concentrations of the lactotrophic hormone, prolactin (PRL), in female rats on pre-parturient (Gestation Day 20), parturient (Post-natal day 0) and lactating (P10) days. PRL levels have been found to be reduced in rat dams around the time of birth following exposure to gravitational loads varying from 2.16 to 3.14-g (Megory et. al., Aviation, Space and Environs 1129-1135, 1984). It has also been reported that at these high gravitational loads, neonatal mortality has been extremely high, suggesting a possible interaction between dam PRL concentration and neonatal outcome. We have previously reported no significant differences in PRL levels of parturient (PO) and lactating (P6 & P 15) dams when exposed to 1.5-g hypergravity, but did observe a slight elevation of PRL on PO and P 15, with a decrease on P6. In the present study, time-bred pregnant dams were exposed to either continuous 2.0-g, 1.75-g or 1.5-g centrifugation, beginning on Gestational day (G) 11 of the rats' 22-day pregnancy. We observed no significant differences in PRL concentrations between SC and any of the HG conditions. On G20 and PO, PRL concentrations of the 2.0-g and 1.5-g groups were slightly elevated as compared to SC. Similar to what we previously reported. PRL secretion was elevated in both HG and SC conditions on the day of birth relative to later during lactation, but on P10 it appeared to be reduced in HG relative to SC dams. These findings suggests that hypergravity slightly elevates plasma concentration of PRL in pre-parturient and lactating rat dams, with effects most pronounced during the periparturitional period and in a direction opposite to that observed following microgravity exposure.

Baer. Lisa A.↗

NASA NTRS1977

Analysis and design of a high power laser adaptive phased array transmitter

The feasibility of delivering substantial quantities of optical power to a satellite in low earth orbit from a ground based high energy laser (HEL) coupled to an adaptive antenna was investigated. Diffraction effects, atmospheric transmission efficiency, adaptive compensation for atmospheric turbulence effects, including the servo bandwidth requirements for this correction, and the adaptive compensation for thermal blooming were examined. To evaluate possible HEL sources, atmospheric investigations were performed for the CO2, (C-12)(O-18)2 isotope, CO and DF wavelengths using output antenna locations of both sea level and mountain top. Results indicate that both excellent atmospheric and adaption efficiency can be obtained for mountain top operation with a micron isotope laser operating at 9.1 um, or a CO laser operating single line (P10) at about 5.0 (C-12)(O-18)2um, which was a close second in the evaluation. Four adaptive power transmitter system concepts were generated and evaluated, based on overall system efficiency, reliability, size and weight, advanced technology requirements and potential cost. A multiple source phased array was selected for detailed conceptual design. The system uses a unique adaption technique of phase locking independent laser oscillators which allows it to be both relatively inexpensive and most reliable with a predicted overall power transfer efficiency of 53%.

Mevers, G. E.↗

NASA NTRS1981

Jovian magnetic models and the polarization angle of Jovian decimetric radiation

A comparative study of the direction of linear polarization of Jovian decimetric (synchrotron) radiation as measured astronomically and as determined from a model of the inner Jovian magnetosphere is discussed. It is noted that the model depicts the radiation as coming from rings of relativistic electrons in the Jovimagnetic equator at varying radial distances from the center of the planet. The equator is determined through each of two magnetic representations - the O4 model of Acuna and Ness (1976) and the P10-11 model of Smith et al. (1976) - derived from in situ Pioneer magnetometer measurements. Deviations from a (planar) dipole equator are found to occur at nearly all longitudes in both models; no evidence is found for a longitudinally localized magnetic anomaly.

Birmingham, T. J.↗

NASA NTRS1985

The cosmic ray interplanetary radial gradient from 1972 - 1985

It is now established that the solar modulation of cosmic rays is produced by turbulent magnetic fields propagated outward by the solar wind. Changes in cosmic ray intensity are not simultaneous throughout the modulation region, thus requiring time dependent theories for the cosmic ray modulation. Fundamental to an overall understanding of this observed time dependent cosmic ray modulation is the behavior of the radial intensity gradient with time and heliocentric distance over the course of a solar modulation cycle. The period from 1977 to 1985 when data are available from the cosmic ray telescopes on Pioneer (P) 10, Voyager (V) 1 and 2, and IMP 8 spacecraft is studied. Additional data from P10 and other IMP satellites for 1972 to 1977 can be used to determine the gradient at the minimum in the solar modulation cycle and as a function of heliocentric distance. All of these telescopes have thresholds for protons and helium nuclei of E 60 MeV/nucleon.

Webber, W. R.↗

NASA NTRS1990

The onset of the new solar modulation cycle in 1987-1988 as a function of heliocentric radius and latitude

The onset of a new solar modulation cycle were studied in 1987 and 1988, on the basis of data on counting rates of particles with E greater than 60 MeV, observed at the IMP, Voyager (V), and Pioneer (P) satellites. It was found that the decrease at earth was rapid after the intensity maximum in early 1987 and was closely correlated with the increase in the average tilt of the heliospheric current sheet. The initial rapid intensity decrease was found to be related to three small Forbush decreases which are superimposed on a more gradual decrease. By the end of 1988, the intensity decreased by about 40 percent at earth, 30 percent at V2, and 18 percent at P10. This overall decrease was accompanied by an increase in the average integral radial gradient as well as a decrease in the radial dependence of the gradient. The onset of the new solar modulation cycle seems to be related to the complete altering of the solar magnetic structure as observed on the surface of the sun.

Webber, W. R.↗

NASA NTRS1990

Low Be-10 and Al-26 contents of ureilites - Production at meteoroid surfaces

The Be-10 contents of 22 ureilites and the Al-26 contents of 18 ureilites are reported. When corrected for exposure age, where known, and for composition, the results give production rate, P that are on average 20 percent lower than values typical of other meteorite classes. This depression of production rates, the weak correlations of both P26 and P10 with Ne-22/Ne-21 and the generally high He-3/Ne-21 and Ne-22/Ne-21 ratios in urelities all suggest that many of the samples occupied near-surface locations in their parent meteoroids. A reduced flux of cosmic rays does not by itself explain the elevated Ne-22/Ne-21 ratios and appears inconsistent with a proposed source for ureilites in the inner asteroid belt. Cosmogenic radionuclide data do not support the tentative pairing of ALHA 78019 with ALHa 78262 proposed on the basis of mineralogical similarities. The high Al-26 content of LEW 85440 may be the result of irradiation by solar cosmic rays.

Aylmer, D.↗

NASA NTRS1992

Further analysis of LDEF FRECOPA micrometeroid remnants

Experiments dedicated to the detection of interplanetary dust particles (IDP's) were exposed within the FRECOPA payload, installed on the face of the LDEF directly opposed to the velocity vector (west facing direction, location B3). We were mainly interested in the analysis of hypervelocity impact features of sizes less than or = 10 microns, found in thick Al targets devoted to the research of impact features. In the 15 craters found in the scanned area (approximately 4 sq. cm), the chemical analysis suggests an extraterrestrial origin for the impacting particles. The main elements we identified are usually refered to as chondrite elements: Na, Mg, Si, S, Ca, and Fe are found in various proportions, intrinsic Al being masked by the Al target; we notice a strong depletion in Ni, never observed in our samples. Furthermore, C and O are present in 90 percent of the cases; the C/O peak height ratio varies from 0.1 to 3. Impactor simulations by light gas gun hypervelocity impact experiments have shown that meaningful biogenic element and compound information maybe obtained from IDP residues below impacts of critical velocities, that are less than or = 4 km/sec for particles larger than 100 microns in diameter. Our results obtained for the smaller size fraction IDP's suggest that at such sizes, the critical velocity could be higher by a factor of 2 or 3, as chemical analysis of the remnants were possible in all the identified impact craters, performed on targets possibly hit at velocities greater than or = 7.5 km/s, which is the spacecraft velocity. These samples are now subjected to an imagery and analytical protocol that includes FESEM (field emission scanning electron microscopy) and LIMS (laser ionization mass spectrometry). The LIMS analyses were performed using the LIMA-ZA instrument. Results are presented, clearly indicating that such small events show crater features analogous to what is observed at larger sizes; our first analytical results, obtained for 2 events (P6 and P10) suggest that N is present in the IDP's remnants in which C and O were identified by EDX analysis. In one case (P6), enrichment in K and P is observed. Surface contamination by NaCl is evident on the FRECOPA surfaces.

Borg, J.↗

NASA NTRS1995

Anomalous cosmic ray oxygen gradients throughout the heliosphere

We have used data from the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX), Ulysses, Voyager 1, Voyager 2, and Pioneer 10 spacecraft to determine the radial and latitudinal gradients of anomalous cosmic ray oxygen at 10 MeV/nuc during the last half of 1993. These five spacecraft cover radial distances from 1 AU (SAMPEX) to 58 AU (P10) and latitudes to 41 deg S (Ulysses) and 32 deg N (V1). We find that the radial gradient is a decreasing function of radial distance, approximately r(exp -n), with n = 1.7 +/- 0.7. The large-scale radial gradient between the inner and outer heliosphere is much smaller than it was during the last solar minimum period in approximately 1987. The latitudinal gradient is small and positive, 1.3 +/- 0.4 %/deg, as opposed to the large and negative latitudinal gradients found during 1987, but similar to the small positive latitudinal gradient measured during 1976 for anomalous cosmic ray helium. These observations confirm that effects of curvature and gradient drift in the large scale magnetic field of the Sun are important for establishing the three-dimensional intensity distributions of these particles in the heliosphere during periods of solar minimum conditions.

Cummings, A. C.↗

NASA NTRS1995

Radial evolution of the high/low frequency breakpoint in magnetic field spectra

The spectra of magnetic field variations in the solar wind show different behavior in two frequency regions; a high frequency region in which the spectral exponent is about -5/3 and a low frequency region in which it is typically -1. The two types of variations must arise from different processes and a clue to the relationship between the spectral regions lies in understanding the behavior of the breakpoint between the spectral regions. Studies of the average behavior of spectra have shown that the break point occurs at about 3.5 hours at 1 AU. It is also known that, on average, the breakpoint occurs at lower frequencies with larger heliocentric distances. Ideally however, instead of the average properties of the spectra, we would like to know how the breakpoint evolves in particular samples of the solar wind as they propagate to larger heliocentric distances. In the study reported here we take advantage of the fact that, in 1974, Pioneer 10 (4.4 AU) and Pioneer 11 (5.6 AU) were close to being co-aligned and being aligned with the Earth. Solar wind observed at Earth can be closely matched with solar wind later observed at P10 and P11. We here compare the breakpoint observed at Earth with that observed at Pioneers 10 and 11 for matched samples of the wind.

Feynman, J.↗

NASA NTRS2002

Neither Milk Production, Milk Transfer Nor Pup Growth Hormone Account for Reduced Body Weights of Rat Pups Reared In Hypergravity

Studies spanning the gravity continuum from 0 to 2-g are revealing new insights into how mammalian reproduction and development may proceed in the microgravity of space. Rat pups reared from either conception or midgestation in hypergravity (hg) weigh 6-15% less than 1-g controls. In the present study we analyzed maternal and pup factors that may account for reduced body weight of hg reared pups. Beginning on Gestational day (G)11 of the rats' 22 day pregnancy, rat dams and their litters were continuously exposed to either 1.5-g, 1.75-g or 2.0-g. Prolaction (Prl) and oxytocin (OT) were measured in hg-exposed dams during either pregnancy (G20) or lactation (Postnatal day [P] 10). Gravity related differences in Prl were not observed whereas OT was depressed during lactation in hg dams relative to controls (p less than 0.05). Milk transfer measured during a discrete suckling episode was actually increased in hg-reared litters and comparable numbers of milk-letdowns were observed in the two conditions. Recent reports using dwarfing phenotypes in mouse mutants have provided evidence for postnatal dependence on growth hormone (GH) and insulin-like growth factors (IGFs). Plasma GH measured in P10 pups using enzyme immunoassay (EIA) was significantly elevated in hg pups relative to 1-g controls (mean +/- sd., ng/ml: 2.0-g, 10.6 [3.0], 1.5-g 8.9 [4.0], 1.0-g, 7.95 [3.1]). Together, these findings suggest that neither milk production, milk transfer nor pup GH play significant roles in reduced body weights of hg-reared pups. Studies underway are focused on insulin-like growth factors.

Bear, L. A.↗

NASA NTRS2002

Hypergravity Effects on Rodent Pregnancy and Parturition

No mammal has yet undergone birth, or parturition, in the microgravity of space. Previous studies (Ronco & Alberts, 2000) have shown that mid-pregnant rat dams exposed to spaceflight (0-g) and landed 48-72 hrs before term successfully delivered robust, healthy offspring Microgravity-exposed dams exhibited twice the expected numbers of labor contractions whereas length of pregnancy, duration of labor, fetal wastage, number of neonates born and litter gender ratios were identical to controls. In the present study, we report the results of rodent pregnancy and parturition at the opposite end of the gravity spectrum, in hypergravity. Dams exposed to either: 1.0-g, 1.5-g, 1.75-g or 2.0-g from Gestational day (G) 11 and throughout the births of their litters had comparable pregnancy and labor durations, fetal wastage, numbers of neonates born and litter Tender ratios. During parturition, hypergravity-exposed dams exhibited significantly fewer labor contractions as compared to 1.0-g controls. Dams that underwent birth in hypergravity had significantly fewer offspring surviving the immediate postpartum period (P1: 1.0-g, 11.92 +/- 2.84; 1.5-g, 10.88 +/- 2.17; 1.75-g, 9.22 +/-1.99; 2.0-g, 8.83 +/- 3.31). Within 24 hrs postpartum, neonatal survival was further diminished in hypergravity [P2: 100% (1.0-g); 96% (1.5-g); 96% (1.75-g); 73% (2.0-g)] and continued to decline (P10: 100%(1.0-g.); 90%(1.5-g); 87%(1.75-g), 40%(2.0-g)]. Neonatal losses stabilized by P5 for the 1.5-g andl.75-g conditions but continued until P9 for the 2.0-g condition. Together, these findings show that postnatal, but not prenatal, survival is compromised following birth in hypergravity, Maternal and neonatal factors that contribute to peri-parturitional vulnerability to altered gravity environments will be discussed.

Ronca, A. E.↗

NASA NTRS2015

Self- and Air-Broadened Line Shapes in the 2v3 P and R Branches of 12CH4

In this paper we report line shape parameters of 12CH4 for several hundred 2V(sub 3) transitions in the spectral regions 5891-5996 cm( exp -1) (P branch) and 6015-6115 cm(exp -1) (R branch). Air- and self-broadening coefficients were measured as a function of temperature; line mixing via off-diagonal relaxation matrix element coefficients was also obtained for 47 transition pairs. In total, nearly 1517 positions and intensities were retrieved, but many transitions were too weak for the line shape study. For this analysis, we used 25 high-resolution (0.0056 and 0.0067 cm(ex[ -1) and high signal-to-noise (S/N) spectra of high-purity 12CH4 and the same high-purity 12CH4 broadened by dry air recorded at different sample temperatures between 130 K and 295 K with the Bruker IFS 125HR Fourier transform spectrometer at JPL. Three different absorption cells were used (1) a White cell set to a path length of 13.09 m for room temperature data, (2) a single-pass 0.2038 m long coolable cell (for self-broadening) and (3) a multipass cell with 20.941 m total path coolable Herriott cell (for air-broadening). In total there were 13 spectra with pure 12CH4 (0.27-599 Torr) and 12 air-broadened spectra with total sample pressures of 80-805 Torr and volume mixing ratios (VMR) of methane between 0.18 and 1.0. An interactive multispectrum nonlinear least-squares technique was employed to fit the individual P10-P1 and R0-R10 manifolds in all the spectra simultaneously. Results obtained from the present analysis are compared to other recent measurements.

Devi, V. Malathy↗