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Microwave emissions due to hypervelocity impacts have been detected by heterodyne receivers in the ground experiments using an accelerator. It is aimed to establish the detection system of space debris impacts on a space structure via microwave. The emitted powers at the impact velocity of 10 km/sec are estimated from the characteristics at the experimental impact velocity. Considering the emitted power, the receiving antenna and the microwave frequency, the maximum distances for detecting the microwave emission are 1,032 m at 2 GHz band and 26 m at 22 GHz. The type and location of receiving antennas which can detect the impact on all habitation and experiment modules on the International Space Station are discussed. The impact can be sufficiently detected via a low gain antenna at 2 GHz band.

For large-scale space structures such as Solar Power Satellite (SPS) and International Space Station, it is important to estimate effects of space debris impacts. In LEO there are more than 8,800 debris larger than 10 cm in diameter that have a relative velocity of about 10 km/sec. Space debris larger than 10 cm have been tracked by ground-based radio frequency radars and optical observations. These orbital data obtained by radar measurement are available to avoid hypervelocity impacts of space debris. However, there are no data on debris of diameter between 1 cm and 10 cm. These medium size debris could give catastrophic damages to large-scale space structures. As solar array of SPS becomes larger, the potential hazard of debris impacts becomes an ever more serious concern. In addition, in 2001 there have been large breakup events in LEO. Fragmentation debris smaller than 1 cm in diameter were created by the events, and the number of debris increases drastically in LEO. In order to research on debris impacts against solar array of SPS, impact experiments and analyses were reviewed. The purpose of this study is to clarify a new research field on hypervelocity debris impacts against solar array. From past investigations, the following results were found. As a result of impact experiments on a flexible a-Si solar array with 0.25 mm in thickness, it was recognized that hypervelocity impacts formed the same size hole as the projectile on a flexible solar array. After passing through the thin solar array, the projectile was divided into fragments smaller than 1 mm in diameter. On the other hand, analyses on solar array of the Eureca satellite after retrieval in 1993 showed that small debris impacts in LEO created millimeter sized craters, and fragments ejected during the impact process generated micrometer sized craters. And microwave emission and arc discharge phenomena have been observed during the hypervelocity impact process. From a viewpoint of electromagnetic effec

We use Planck HFI data combined with ancillary radio data to study the emissivity index of the interstellar dust emission in the frequency range 100-353 GHz, or 3-0.8 mm, in the Galactic plane. We analyse the region l = 20 degrees-44 degrees and vertical bar b vertical bar

Using both the Very Large Array (VLA) at 7 mm wavelength, and the Australia Telescope Compact Array (ATCA) at 3 mm, we have searched for microwave emission from cool dust in the extrasolar planetary system Gliese 876 (Gl 876). Having detected no emission above our 3 sigma detection threshold of 135 microJy, we rule out any dust disk with either a mass greater than 0.0006 Earth mass or less than < 250 AU across. This result improves on previous detection aperture thresholds by an order of magnitude, and it has some implications for the dynamical modeling of the system. It also is consistent with the Greaves et al. hypothesis that relates the presence of a debris disk to close-in planets. Due to the dust-planetesimal relationship, our null result may also provide a constraint on the population or composition of the dust and small bodies around this nearby M dwarf., Published in The Astronomical Journal, v135 n6 p2194-2198, Jun 2008.

An analytical algorithm for the determination of land surface temperature and soil moisture from the Tropical Rainfall Measuring Mission/Microwave Imager (TRMM/TMI) remote sensing data has been developed in this study. The error analyses indicate that the uncertainties of the enrolled parameters will not cause serious errors in the proposed algorithm. By applying the proposed algorithm to TRMM/TMI remote sensing data collected during the Global Energy and Water Experiment (GEWEX) Asian Monsoon Experiment (GAME)/Tibet Intensive Observation Period field campaign in 1998 (IOP'98), the temporal and regional distributions of land surface temperature and volumetric soil moisture are evaluated over the central Tibetan plateau area. To validate the proposed method, the ground-measured surface temperature and volumetric soil moisture are compared to TRMM/TMI-derived land surface temperature and soil Fresnel reflectivity respectively. The results show that the estimated surface temperature is in good agreement with ground measurements; their difference and correlation coefficient are 0.52 ± 2.41 K and 0.80, respectively. A quasi-linear relationship exists between estimated Fresnel reflectivity and ground-measured volumetric soil moisture with a correlation coefficient 0.82. The land surface thermal status can also be clearly identified from the regional distribution of the estimated land surface temperature; the mountainous area and water bodies have a very lower surface temperature, while the river basin shows a higher surface temperature compared to the mountainous area. The southeastern part of the selected area has lower soil moisture, while the river basin exhibits high soil moisture. It is therefore concluded that the proposed algorithm is successful for the retrieval of land surface temperature and soil moisture using TRMM/TMI data over the study area.

The possibility of using a three-level-A-scheme for the excitation of the clock hyperfine transition in Rb87 is analyzed. The physics involved opens up two distinct avenues useful for the implementation of an atomic frequency standard, avenues based on two distinct phenomena: the electro-magnetically induced transparency (EIT or Dark Line) and the coherent microwave emission (Maser without population inversion). In spite of the close connection between the two phenomena, which are generated by the coherence created in the ground state by means of two coherent laser radiation fields (Coherent Population Trapping), the characteristics of an atomic frequency standard based on either of these phenomena may be quite different. The paper discusses the possibility of implementing on the basis of these two phenomena, new Rb87 atomic frequency standards having an excellent frequency stability, and makes explicit their differences., See also ADM001481. Presented at the Precise Time and Time Interval (PTTI) Meeting (31st Annual) held in Dana Point, CA on 7-9 December 1999. Published in the Proceedings of the Precise Time and Time Interval (PTTI) Meeting (31st Annual), p605-614, 1999.

A free electron laser equipment is currently underway in which a 1kA, 2.1MeV electron beam is excited by a helical wiggler field of 2 cm periodicity to produce submillimeter radiation at wavelengths between 400 and 600 micrometers. This experiment will operate in the high gain Raman regime with a maximum calculated output power at saturation of approximately 50MW. This free electron is unique in two respects. First, the electron beam will be transported through the wiggler with the aid of two short solenoidal focussing lenses. This system obviates the need for strong uniform guiding magnetic field in the interaction region thereby insuring that the cyclotron maser quality is not excited. Secone, this FEL employs a very high quality electron beam. The beam is produced in a multielectrode electron gun which uses a cold field emission cathode. The gun consists of a planar cathode and anode grid followed by four accelerating stages. The accelerating electrodes are shaped to provide electrostatic focussing by balancing the self-electric and magnetic fields of the beam.

During the past year microwave and millimeter wave emission experiments on three systems were carried out. System one is a Rippled-Field Magnetron and represents a hybrid between a conventional magnetron and a free electron laser. System two is a Circular Free Electron Laser in which a rotating ring of relativistic electrons is subjected to an azimuthally periodic magnetic field. The third system concerns an inverted Relativistic Magnetron.