The atmospheric cosmic- and solar energetic particle radiation environment at aircraft altitudes

Galactic cosmic rays interact with the solar wind, the earth's magnetic field and its atmosphere to produce hadron, lepton and photon fields at aircraft altitudes. In addition to cosmic rays, energetic particles generated by solar activity bombard the earth from time to time. These particles, while less energetic than cosmic rays, also produce radiation fields at aircraft altitudes which have qualitatively the same properties as atmospheric cosmic rays. We have used a code based on transport theory to calculate atmospheric cosmic-ray quantities and compared them with experimental data. Agreement with these data is seen to be good. We have then used this code to calculate equivalent doses to aircraft crews. We have also used the code to calculate radiation doses from several large solar energetic particle events which took place in 1989, including the very large event that occurred on September 29^th and 30^th of that year. The spectra incident on the atmosphere were determined assuming diffusive shock theory.     

Optical oxygen sensor instrumentation based on the detection of luminescence lifetime.

Optical oxygen sensors are mainly based on the principle of luminescence quenching. In contrast to arready existing intensity-based systems, the measurement of the luminescence lifetime provides certain advantages, such as insensitivity to photobleaching or leaching of the dye, or changes in the intensity of excitation light. This facilitates the use of simple optical systems or optical fibres. A new family of oxygen-sensitive dyes, the porphyrin-ketones, has been introduced, which exhibits favorable spectral properties and decay times in the order of tens and hundreds of microseconds. This allows the use of simple optoelectronic circuitry and low-cost processing electronics. An optical oxygen sensor module has been developed with the dimensions of only 120 x 60 x 30 mm. The prototype is based on the measurement of the decay time of the luminophore by measuring the phase shift between the square-wave excitation and the detected square-wave of the emission coming from the sensor. The instrument is based on semiconductor devices (light-emitting diodes, photodiodes) and may be used for the detection of oxygen in gaseous or liquid samples. The measurement range of the device is from 0 to 200 hPa oxygen partial pressure with a resolution of < 1 hPa over the whole measurement range. The overall measurement accuracy of < +/- 1 hPa has been obtained for periods of 24 h of continuous measurement in a thermostatted environment. The sensor response times t90 are typically < 1 s for gases and 0.5 to 5 min for liquid samples.     

Dosimetry during the first IBIS facility flight.

The dosimetry of cosmic rays was performed during the first experimental flight of the IBIS facility. Different thermoluminescent detectors (TLD) have been used to measure the contribution of the low linear energy transfer component (LET < 10 keV/micrometer) and plastic nuclear track detectors (PNTD) for the high linear energy tranfer (LET) component. Several parameters of tracks have been measured to determine the LET spectra of primary and secondary charged particles. The total absorbed dose rate (TLD+PNTD) during the flight was 0.23 mGy/day and the dose equivalent rate using the ICRP 60 was 0.52 mSv/day. The corresponding mean quality factor was 2.4. These results are in agreement with those obtained aboard the MIR station with a tissue equivalent proportional counter.     

Study of microaccelerations onboard the <Emphasis Type="Italic">International Space Station</Emphasis> with the DAKON-M convection sensor

The results of experiments with the DAKON-M convection sensor onboard the Russian orbital segment of the International Space Station are described. A comparison of the sensor measurements with the results of calculation of the quasistatic microacceleration component at the point of installation is made. For this comparison we have used three measurement intervals of the experiments in 2009, during which spacecraft were docked with the station, undocked from it, and actuation of jet engines of the attitude control system took place. When calculating microacceleration, we use the measurement data of the low-frequency MAMS accelerometer, installed on the American segment, and the telemetry data on the ISS rotational motion. This information allowed one to convert the MAMS measurements to the point of installation of the DAKON-M convection sensor. A comparison of sensor measurements with calculated microaccelerations showed sufficiently accurate coincidence between the calculated and measured data.     

A procedure for calculating the damping in multi-element space structures

A procedure is outlined for estimating the damping in a multi-element space structure by incorporating distributed material damping and discrete nonlinear joint properties into a linear analysis. Tests have been conducted in which the transient response of a truss member is measured in free fall in a vacuum in order to obtain precise material damping characteristics. The force-state mapping technique is then used to identify the localized nonlinearities in joints by mapping the force transmitted through the joint as a function of the full mechanical state of the joint. The identified nonlinear joint parameters are then linearized using an equivalent energy approach which finds the equivalent linear stiffness and linear viscous damping by equating the integrated work done and energy dissipated by the nonlinearity to those of a spring and damper undergoing sinusoidal motion. The distributed material damping and localized nonlinear effects are then incorporated to form a linearized damped finite element model. Finally, an eigenvalue perturbation analysis is developed to explore the effect of introducing damping at the joints on the overall dynamics of the truss, and to obtain design guidance on where supplemental joint damping might optimally be added.     

Kalman Filter Design for Target Tracking

The problem of solving the matrix Riccati differential equation in the design of Kalman filters for the target tracking problem is considered. An algebraic transformation method is used to reduce the order of the Riccati differential equation and to obtain explicit expressions for the filter gains (in terms of the interceptor /target separation range) which results in a substantial reduction of the computer burden involved in estimating the target states. The applicability of the transform technique is demonstrated for the receiver thermal noise and the target glint noise cases.     

Possibilities for the detection of microbial life on extrasolar planets

We consider possibilities for the remote detection of microbial life on extrasolar planets. The Darwin/Terrestrial Planet Finder (TPF) telescope concepts for observations of terrestrial planets focus on indirect searches for life through the detection of atmospheric gases related to life processes. Direct detection of extraterrestrial life may also be possible through well-designed searches for microbial life forms. Satellites in Earth orbit routinely monitor colonies of terrestrial algae in oceans and lakes by analysis of reflected ocean light in the visible region of the spectrum. These remote sensing techniques suggest strategies for extrasolar searches for signatures of chlorophylls and related photosynthetic compounds associated with life. However, identification of such life-related compounds on extrasolar planets would require observations through strong, interfering absorptions and scattering radiances from the remote atmospheres and landmasses. Techniques for removal of interfering radiances have been extensively developed for remote sensing from Earth orbit. Comparable techniques would have to be developed for extrasolar planet observations also, but doing so would be challenging for a remote planet. Darwin/TPF coronagraph concepts operating in the visible seem to be best suited for searches for extrasolar microbial life forms with instruments that can be projected for the 2010-2020 decades, although resolution and signal-to-noise ratio constraints severely limit detection possibilities on terrestrial-type planets. The generation of telescopes with large apertures and extremely high spatial resolutions that will follow Darwin/TPF could offer striking possibilities for the direct detection of extrasolar microbial life.