Neutral mass spectrometer measurements in the shuttle bay environment

A neutral mass spectrometer, flown as part of the Induced Environment Contamination Monitor (IECM), is briefly described. Results from STS-2, -3, -4, and Spacelab 1 are qualitatively summarized. The gases observed were, for the most part, those with molecular weights below 45 amu with sources attributable to instrument background, shuttle-induced environment, and the ambient atmosphere. The most abundant gases were H2O, N2, and He. Heavier gases consisted primarily of fluorocarbons

An acoustic wind measuring technique Scientific report no. 1

Technique for measuring winds using Saturn exhaust noise - acoustic technique, wind profile determined during Saturn SA-9 flight, and data reduction metho

Design study for electronic system for Jupiter Orbit Probe (JOP)

The conceptual design of the Jupiter probe spectrometer is presented. Block and circuit diagrams are presented along with tabulated parts lists. Problem areas are considered to be (1) the schedule, (2) weight limitations for the electronic systems, and (3) radiation hardness of the electronic devices

N2 temperature and density data for the 150 to 300 km region and their implications

Molecular nitrogen density and temperature measurements in thermosphere by thermosphere prob

Advanced Langmuir Probe (LP)

The dynamic response of the MK-2 version of the Langmuir probe amplifier was studied. The settling time of the step response is increased by: (1) stray node-to-ground capacitance at series connections between high value feedback resistors; and (2) input capacitance due to the input cable, FET switches, and input source follower. The stray node-to-ground capacitances can be reduced to tolerable levels by elevating the string of feedback resistors above the printing board. A new feedback network was considered, with promising results. The design uses resistances having much lower nominal values, thereby minimizing the effect of stray capacitances. Faster settling times can be achieved by using an operational amplifier having a higher gain-bandwidth product

Neutral gas mass spectrometer on the IECM

The neutral gas mass spectrometer on the Induced Environment Contamination Monitor is described. The results of the measurements are presented

Space shuttle molecular and wake vacuum measurements

The wake environment of the space shuttle is analyzed to determine whether it is feasible to perform ultrahigh vacuum experiments in or near the payload bay with the shuttle oriented such that the payload bay faces the antivelocity direction. Several mechanisms were considered by which molecules could approach the payload bay from this direction and their relative contributions to the wake environment are estimated. These mechanisms include ambient atmospheric molecules that have velocities in excess of the orbital velocity which can overtake the shuttle, ambient atmospheric molecules that are backscattered by collisions with the shuttle induced atmosphere, and self scattering from the induced atmosphere. These estimates are compared with the measurements made with the collimated mass spectrometer which was part of the Induced Environment Contamination Monitor flown on several of the early shuttle flights. Although the collimated mass spectrometer was not designed for this purpose and the instrument background for the species for which the collimator is effective is above the expected levels, upper limits can be established for these species in the wake environment which are consistent with the analysis. There was considerably more helium and argon observed in the wake direction than was predicted, however. Possible origins of these gases are discussed

HI studies of the Sculptor group galaxies. VIII. The background galaxies: NGC 24 and NGC 45

In order to complete our HI survey of galaxies in the Sculptor group area, VLA observations of NGC 24 and NGC 45 are presented. These two galaxies of similar magnitude M_B ~ -17.4 lie in the background of the Sculptor group and are low surface brightness galaxies, especially NGC 45. The HI distribution and kinematics are regular for NGC 24 while NGC 45 exhibits a kinematical twist of its major axis. A tilted-ring model shows that the position angle of the major axis changes by ~25 degrees. A best-fit model of their mass distribution gives mass-to-light ratios for the stellar disk of 2.5 and 5.2 for NGC 24 and NGC 45 respectively. These values are higher than the ones expected from stellar population synthesis models. Despite the large dark matter contribution, the galaxy mass is still dominated by the stellar component in their very inner regions. These high mass-to-light ratios are typical of what is seen in low surface brightness galaxies and may indicate that, in those galaxies, disks are far from the maximum disk case. The halo parameters derived from the best-fit models are thus lower limits.Comment: 23 pages, 10 figures, accepted for publication in The Astronomical Journa

Report from upper atmospheric science

Most of the understanding of the thermosphere resulted from the analysis of data accrued through the Atmosphere Explorer satellites, the Dynamics Explorer 2 satellite, and observations from rockets, balloons, and ground based instruments. However, new questions were posed by the data that have not yet been answered. The mesosphere and lower thermosphere have been less thoroughly studied because of the difficulty of accessibility on a global scale, and many rather fundamental characteristics of these regions are not well understood. A wide variety of measurement platforms can be used to implement various parts of a measurement strategy, but the major thrusts of the International Solar Terrestrial Physics Program would require Explorer-class missions. A remote sensing mission to explore the mesosphere and lower thermosphere and one and two Explorer-type spacecraft to enable a mission into the thermosphere itself would provide the essential components of a productive program of exploration of this important region of the upper atomsphere. Theoretical mission options are explored