The Herschel Virgo Cluster Survey - V. Star-forming dwarf galaxies – dust in metal-poor environments

We present the dust properties of a small sample of Virgo cluster dwarf galaxies drawn from the science demonstration phase data set of the Herschel Virgo Cluster Survey. These galaxies have low metallicities (7.8 < 12 + log(O/H) < 8.3) and star-formation rates ≲10^(-1) M_☉ yr^(-1). We measure the spectral energy distribution (SED) from 100 to 500 μm and derive dust temperatures and dust masses. The SEDs are fitted by a cool component of temperature T ≲ 20 K, implying dust masses around 10^5 M_☉ and dust-to-gas ratios within the range 10^(-3)–10^(-2). The completion of the full survey will yield a larger set of galaxies, which will provide more stringent constraints on the dust content of star-forming dwarf galaxies

Research relative to the development of a cryogenic microwave cavity gradiometer for orbital use

The noncryogenic, single axis, gravity gradiometer which is characterized by a sensitivity of the order of 10 to the minus 2 power Eovos Units in a few sec integration time was investigated. The prototype of testing gradiometer on the earth surface by the free fall in vacuo method was expanded. An existing free fall tower facility and the possibility of adding inside the falling elevator cabin an air tight, sealed, cylindrical container with inside pressure or = -0.001 Torr were examined to test the gradiometer in free fall conditions inside this evacuated container. Earth's gravity anomalies are simulated with masses of suitable shape, weight, and location. The attitude of the falling gradiometer is monitored by a three axis gyro package mounted on the instrument package. It is concluded that the free fall testing of the gradiometer is both feasible and practical

Investigation of traveling ionospheric disturbances

Maximum entropy power spectra of the ionospheric electron density were constructed to enable PINY to compare them with the power independently obtained by PINY with in situ measurements of ionospheric electron density and neutral species performed with instrumentation carried by the Atmospheric Explorer (AE) satellite. This comparison corroborated evidence on the geophysical reality of the alleged electron density irregularities detected by the ASTP dual frequency Doppler link. Roughly half of the localized wave structures which are confined to dimensions of 1800 km or less (as seen by an orbiting Doppler baseline) were found to be associated with the larger crest of the geomagnetic anomaly in the Southern (winter) Hemisphere in the morning. The observed nighttime structures are also associated with local peaks in the electron density

Study of certain tether safety issues. Continuation of investigation of electrodynamic stabilization and control of long orbiting tethers, volume 1

The behavior of long tethers (10-100 km) in space are addressed under two failure situations with potential safety impact: instantaneous jamming of the reel controlling the tether during deployment and cutting of the tether due to a meteor strike or other similar phenomena. Dual and multiple mass point models were used in the SAO SKYHOOK program to determine this behavior. The results of the program runs were verified analytically or by comparison with previously verified results. The study included the effects of tether damping and air drag where appropriate. Most runs were done with the tether system undamped since we believe this best represents the true behavior of the tether. Means for controlling undesirable behavior of the tether, such as viscous dampers in the subsatellite, were also studied

Orbital transfer and release of tethered payloads. Continuation of investigation of electrodynamic stabilization and control of long orbiting tethers Martinez-Sanchez, Manuel

The effect of reeling operations on the orbital altitude of the tether system and the development of control laws to minimize tether rebound upon payload release were studied. The use of the tether for LEO/GEO payload orbital transfer was also investigated. It was concluded that (1) reeling operations can contribute a significant amount of energy to the orbit of the system and should be considered in orbit calculations and predictions, (2) deployment of payloads, even very large payloads, using tethers is a practical and fully stable operation, (3) tether augmented LEO/GEO transfer operations yield useful payload gains under the practical constraint of fixed size OTV's, and (4) orbit to orbit satellite retrieval is limited by useful revisit times to orbital inclinations of less than forty-five degrees

Doppler measurements of the ionosphere on the occasion of the Apollo-Soyuz test project. Part 2: Inversion of differential and rotating Doppler shifts

The preparation of the analytical approach and of the related software used in the inversion of the differential and rotating Doppler data obtained from the ionospheric experiment of the Apollo-Soyuz Test Project (ASTP) is discussed. These data were collected in space-to-space paths (between the ASTP Docking Module (DM) and the Apollo Command Service Module and in space-to-ground paths (between the DM and ground). The Doppler links operated at 162 and 324 MHz and have an accuracy better than 3 MHz over 10-sec integration time. The inversion approach was tested with dummy data obtained with a computer simulation. It was found that a measurement accuracy of 1 to 10% in the value of the horizontal electron density gradient at 221-km altitude can be achieved, in space-to-space paths. For space-to-ground paths near the orbital plane, possible effects of the horizontal gradients on the received differential Doppler shifts were identified. It was possible to reduce the gradient-associated errors in the inversion that leads to the columnar electron content by approximately one-half. Accuracies of 5 to 10% in columnar electron content are achievable, with this gradient-compensation technique

Investigation of electrodynamic stabilization and control of long orbiting tethers

The possibility of using electrodynamic forces to control pendular oscillations during the retrieval of a subsatellite is investigated. The use of the tether for transferring payloads between orbits is studied

Ultra High Energy Neutrino-Relic Neutrino Interactions In Dark Halos to Solve Infrared-Tev And GZK Cut-Off

Ultra High Energy Neutrino scattering on Relic Light Neutrinos in Dark Galactic or Local Group lead to Z and WW,ZZ showering: the nucleon component of the shower may overcome the GZK cut-off while the electro-magnetic tail at TeVs up to EeVs energy may solve the Infrared-TeV cut-off in a natural way. Different Gamma TeV puzzles may find a solution within this scenario: new predictions on UHECR spectra in future data are derived.Comment: 4 pages, 3 figures, 2 tables ICRC 2001 HE 3.6 Dark Matter - German

System engineering study of electrodynamic tether as a spaceborne generator and radiator of electromagnetic waves in the ULF/ELF frequency band

The transmission and generation by orbiting tethered satellite systems of information carrying electromagnetic waves in the ULF/ELF frequency band to the Earth at suitably high signal intensities was examined and the system maintaining these intensities in their orbits for long periods of time without excessive onboard power requirements was investigated. The injection quantity power into electromagnetic waves as a function of system parameters such as tether length and orbital height was estimated. The basic equations needed to evaluate alternataing current tethered systems for external energy requirements are presented. The energy equations to tethered systems with various lengths, tether resistances, and radiation resistances, operating at different current values are applied. Radiation resistance as a function of tether length and orbital height is discussed. It is found that ULF/ELF continuously radiating systems could be maintained in orbit with moderate power requirements. The effect of tether length on the power going into electromagnetic waves and whether a single or dual tether system is preferable for the self-driven mode is discussed. It is concluded that the single tether system is preferable over the dual system