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The probe beam deflection technique, based on the mirage effect, has been applied to monitor laser processing of polymer and metal films and to measure damage thresholds of optical coatings. The technique is described and it will be shown that its sensitivity permits distinguishing between surface effects like heating and cracking, causing normal sound waves, and plasma formation outside the surface, giving rise to shockwaves. Examples are presented for single-shot ablation with 14 ns laser pulses of 248 nm wavelength. In particular, ablation studies of Ni films of varying thicknesses disclose a quantitative correlation between threshold fluences and thermal properties like heat diffusion, melting, and evaporation. In contrast, for Cr films a simple thermodynamic model fails because the films crack before melting and vaporizing.

The BREM-STAR/TIGER-STAR satellite represents a dedicated low-cost concept for 3D monitoring of the thermosphere/ionosphere (T/I) to be conducted during an overlapping period of the ISS SOLAR mission. The primary goal is to execute precise radiometric measurements of the variable solar and terrestrial extreme ultraviolet/ultraviolet (EUV/UV) radiation and their impact on the T/I system. In combination with high-frequency measurements of the Earth's magnetic field over a period of two years the interaction of the solar wind with the upper atmospheric region will be investigated. Additional two-frequency GPS measurements allow to derive Total Electron Content (TEC). The TEC values will be correlated with the solar EUV/UV and solar wind inputs to improve the correction algorithms for a broad range of applications in the fields of space communication and navigation. In the frame of the TIGER program the development of more accurate models of the thermosphere/ionosphere shall be supported by this proposed project. The scientific payload and its implications on the satellite system are described.

Long-term radiometric accuracy is a fundamental requirement for future measurement of solar and terrestrial atmospheric EUV emissions from space. Since remote sensing of EUV radiation will become an important measuring technique to explore the thermosphere, new methods have to be established to trace calibration changes of EUV instrumentation, too. With the proposed satellite ATON (Egyptian god of the sun) the solar energy input and other important thermospheric/ionospheric parameters (O2, O, O+, N2, N+, NO, H, He, Ne, Tn, X-rays, solar EUV energy, polar energies) shall be measured based on absolute in-flight calibration of solar and airglow instrumentation. The model payload consists of (1) auto-calibrating solar EUV spectrometers, (2) airglow-solar spectrometer, (3) airglow spectrometer (high spectral resolution), (4) EUV photometers (high data statistics), (5) radio beacon experiment and (6) photocathode arrangement (the latter to detect short-lived solar phenomena of aeronomic interest). The basic measuring concept and instrumental details are presented.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Single-shot ablation thresholds of nickel and gold films in the thickness range from 50 nm to 7 μm have been measured for 14 ns laser pulses at 248 nm, using photoacoustic shock wave detection in air. The metal films were deposited on fused silica substrates. The ablation threshold was found to increase linearly with film thickness up to the thermal diffusion length of the film. Beyond this point it remains independent of film thickness. The proportionality between threshold fluence and thickness allows the prediction of ablation thresholds of metal films from the knowledge of their optical properties, evaporation enthalpies and thermal diffusivities. Physically it proves that ablation is driven by the energy density determined by the thermal diffusion length. A simple thermodynamic model describes the data well. Thermal diffusivities, an essential input for this model, were measured using the technique of transient thermal gratings. In addition, the substrate dependence of the ablation threshold was investigated for 150 nm Ni films.

Using photoacoustic shock wave detection and transient thermal gratings, ablation thresholds (at 248 nm) and thermal diffusivities of nickel and gold films on fused silica have been measured in air for thicknesses ranging from 50 nm to 7 μm. In addition, for a given film thickness, the substrate dependence of the ablation threshold was investigated. For films on fused silica, the ablation thresholds vary linearly with film thickness up to a certain value, determined by the thermal diffusion length of the metal. Beyond this point the thresholds are independent of film thickness. This proves that ablation is driven by the thermal energy deposited per volume, where the latter is made up by irradiated area times thermal diffusion length. A simple thermodynamic model describes the data and allows the prediction of ablation thresholds for bulk metals and metal films. Thermal diffusivity measurements show no distinct dependence on film thickness and reproduce within a certain margin the bulk values of the metal.

The scientific objective of the ROSE (Rocket and Scatter Experiments) project is outlined together with a description of the rocket payload. The launch conditions are explained. Highlights of the results from the in situ as well as from the ground-based experiments are discussed with respect to the E -region plasma instabilities which are investigated.

Between July 1974 and September 1975 aboard AEROS-B the electron temperature and the electron density have been measured by the Retarding Potential Analyses and the Impedance Probe respectively in the altitude range 200–870 km. Temperature and density fluctuations along satellite paths have been analysed by digital filtering. The large amount of data allows the mean fluctuations at different heights and latitude intervals to be evaluated. The resulting two-dimensional arrays are presented for some time periods. The global distributions show different patterns in the polar and equatorial regions, and seasonal variations. Mean temperature fluctuations and fluctuations of electron density in general occur simultaneously though with different amplitudes. At high latitudes a seasonal dependence in the strength of the fluctuations of both quantities was observed.

Four sounding rocket payloads were launched in early 1977 to measure heating parameters in the auroral oval. Geophysical conditions were different for the four flights: auroral arc substorm main phase diffuse aurora, and auroral arc with negative bay. The conductivity tensor and the heating rates of particle and Joule heating are determined. The heating rates range in the order of a few tens of mWm −2 . These magnitudes accord with those determined with the aid of backscatter facilities and other sounding rocket observations.

Locally measured electron densities by means of impedance probes aboard the two satellites TAIYO and AEROS-B have been compared. After identifying suitable encounters the measured altitude variations of the density during nighttime showed to fit reasonable well with calculated height profiles in some cases. But remaining discrepancies reveal the factors by which the actual density deviate even than from monthly medians. Other cases with still larger differences with respect to the shape of the height profile above the F2 layer and the peak density (NmF2) and altitude (hmF2) are observed as well.

The two plasma experiments aboard the AFROS-B satellite determined the main plasma quantities in the height range 220-880km. These complementary instruments, a Retarding Potential Analyser and an Impedance Probe, provided the electron and ion temperatures, the main ion constitutents, the suprathermal electron flux and the plasma density.This paper summarizes a selection of the obtained results. Comparisons of several quantities with other observations demonstrate the high reliability of the AFROS plasma data. As a contribution to sensor theory a dependence of RPA measurements on the magnetic field vector has been established. The ion temperature and composition turn out to undergo a strong latitudinal variation, the highest hydrogen concentration in the upper atmosphere being located at ±20° latitude. Concerning the longitudinal variation of electron density discrepancies between measured data and existing models have been revealed. The statistical relation between the position of the mid-latitude trough and magnetic activity was studied for a fixed local time. First results of a synoptic study of the high latitude day-side ionosphere using AFROS-B and ISIS-II data are presented.

The HEating ROcket project HERO comprised the first in situ experiments to measure artificial ionospheric modifications at F layer heights set up by radio waves transmitted from the Heating facility at Ramfjord near Tromso in Northern Norway. Four instrumented payloads were launched on sounding rockets from Andoya Rocket Range during the autumn of 1982 into a sunlit ionosphere with the sun close to the horizon. The payloads recorded modifications, in particular, the presence of electron plasma waves near the reflection level of the heating wave. The amplitude and phase of the three components of the electric and magnetic fields of the heating wave were measured simultaneously as a function of altitude. Coherent spectra of the three electric field components of the locally generated electron plasma waves were obtained in a 50-kHz-wide band. At the same time quasi-continuous measurements were made on several fixed frequencies from 4 kHz to 16 kHz below the heating frequency and in the VLF-range using linear dipole antennas. Moreover, measurements were made of electron temperature, suprathermal electrons and local electron density along the rocket trajectory. The experimental results will be presented and discussed.