Rosina – Rosetta Orbiter Spectrometer for Ion and Neutral Analysis

The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) will answer important questions posed by the mission’s main objectives. After Giotto, this will be the first time the volatile part of a comet will be analyzed in situ. This is a very important investigation, as comets, in contrast to meteorites, have maintained most of the volatiles of the solar nebula. To accomplish the very demanding objectives through all the different phases of the comet’s activity, ROSINA has unprecedented capabilities including very wide mass range (1 to >300 amu), very high mass resolution (m/Δ m > 3000, i.e. the ability to resolve CO from N₂ and ¹³C from ¹²CH), very wide dynamic range and high sensitivity, as well as the ability to determine cometary gas velocities, and temperature. ROSINA consists of two mass spectrometers for neutrals and primary ions with complementary capabilities and a pressure sensor. To ensure that absolute gas densities can be determined, each mass spectrometer carries a reservoir of a calibrated gas mixture allowing in-flight calibration. Furthermore, identical flight-spares of all three sensors will serve for detailed analysis of all relevant parameters, in particular the sensitivities for complex organic molecules and their fragmentation patterns in our electron bombardment ion sources.     

Cratering Records in the Inner Solar System in Relation to the Lunar Reference System

The well investigated size-frequency distributions (SFD) for lunar craters is used to estimate the SFD for projectiles which formed craters on terrestrial planets and on asteroids. The result shows the relative stability of these distributions during the past 4 Gyr. The derived projectile size-frequency distribution is found to be very close to the size-frequency distribution of Main-Belt asteroids as compared with the recent Spacewatch asteroid data and astronomical observations (Palomar-Leiden survey, IRAS data) as well as data from close-up imagery by space missions. It means that asteroids (or, more generally, collisionally evolved bodies) are the main component of the impactor family. Lunar crater chronology models of the authors published elsewhere are reviewed and refined by making use of refinements in the interpretation of radiometric ages and the improved lunar SFD. In this way, a unified cratering chronology model is established which can be used as a safe basis for modeling the impact chronology of other terrestrial planets, especially Mars.     

Optical moving target detection with 3-D matched filtering

Three-dimensional (3-D) matched filtering has been suggested as a powerful processing technique for detecting weak, moving optical targets immersed in a background noise field. The procedure requires the processing of entire sequences of frames of optical scenes containing the moving targets. The 3-D processor must be properly matched to the target signature and its velocity vector, but will simultaneously detect all targets to which it is matched. The results of a study to evaluate the 3-D processor are presented. Simulation results are reported which show the ability of the processor to detect targets well below the background level. These results demonstrate the capability and robustness of the processor, and show that the algorithms, although somewhat complicated, can be implemented readily. Some effects on the number of frames processed, target flight scenarios, and velocity and signature mismatch are also presented. The ability to detect multiple targets is demonstrated     

A study of the polar current systems using the IMS meridian chains of magnetometers

Magnetic field data from a meridian chain of observatories and the recently developed computer codes constitute a powerful tool in studying substorm current systems in the polar region. In this paper, we summarize some of the results obtained from the IMS Alaska meridian chain of observatories. The basic data are the average daily magnetic field variations for 50 successive days (March 9–April 27, 28) which represent a moderately disturbed period. With the aid of the two computer codes, we obtained the distribution of the following quantities in the polar ionosphere in invariant-MLT coordinates: (1) the total ionospheric current; (2) the Pedersen current; (3) the Hall current; (4) the field-aligned currents; (5) the Pedersen-associated field-aligned currents; (6) the Hall-associated field-aligned currents; (7) the electric potential; (8) the Joule heat production rate; (9) the auroral particle energy injection rate; (10) the total energy dissipation rate. All these quantities are related to each other self-consistently at every point under the initial assumptions used in the computation. By using a model of the magnetosphere, the following quantities in the polar ionosphere are projected onto the equatorial plane and the Y — Z plane at X = -20 R _E: (11) the Pedersen current counterpart; (12) the Hall current counterpart; (13) the electric potential; (14) the Pedersen-associated field-aligned currents; (15) the Hall-associated field-aligned currents. These distribution patterns serve as an important basis for studying the generation mechanisms of substorm current systems and the magnetosphere-ionosphere coupling process.     

Probability Density of the Maximum Likelihood Elevation Estimate of Radar Targets

The probability density of the maximum likelihood estimate of elevation angle of a radar target in the presence of multipath is calculated. For detectable signals that have low signal-to-noise ratios, the density is a mixture of a Gaussian density and a delta function at the horizon.     

The scientific payload of the space-based Solar and Heliospheric Observatory (SOHO)

The space-based Solar and Heliospheric Observatory (SOHO) is a joint venture of ESA and NASA within the frame of the Solar Terrestrial Science Programme (STSP), the first Cornerstone of ESA's long-term programme Space Science — Horizon 2000. The principal scientific objectives of the SOHO mission are: a) a better understanding of the structure and dynamics of the solar interior using techniques of helioseismology, and b) a better insight into the physical processes that form and heat the Sun's corona, maintain it and give rise to its acceleration into the solar wind. To achieve these goals, SOHO carries a payload consisting of 12 sets of complementary instruments which are briefly described here.     

WHISPER, A RESONANCE SOUNDER AND WAVE ANALYSER: PERFORMANCES AND PERSPECTIVES FOR THE CLUSTER MISSION

The WHISPER sounder on the Cluster spacecraft is primarily designed to provide an absolute measurement of the total plasma density within the range 0.2–80 cm^-3. This is achieved by means of a resonance sounding technique which has already proved successful in the regions to be explored. The wave analysis function of the instrument is provided by FFT calculation. Compared with the swept frequency wave analysis of previous sounders, this technique has several new capabilities. In particular, when used for natural wave measurements (which cover here the 2–80 kHz range), it offers a flexible trade-off between time and frequency resolutions. In the basic nominal operational mode, the density is measured every 28 s, the frequency and time resolution for the wave measurements are about 600 Hz and 2.2 s, respectively. Better resolutions can be obtained, especially when the spacecraft telemetry is in burst mode. Special attention has been paid to the coordination of WHISPER operations with the wave instruments, as well as with the low-energy particle counters. When operated from the multi-spacecraft Cluster, the WHISPER instrument is expected to contribute in particular to the study of plasma waves in the electron foreshock and solar wind, to investigations about small-scale structures via density and high-frequency emission signatures, and to the analysis of the non-thermal continuum in the magnetosphere.     

The magnetopause erosion and the magnetosheath magnetic field penetration into the dayside magnetosphere

The earthward displacement of the magnetopause observed during a southward IMF (or the magnetopause erosion) and its dependence on the solar wind plasma and magnetic field parameters is studied by investigating data of about 30 magnetopause crossings by the ISEE 1 and 2 spacecraft. It is shown that the magnetopause erosion may be explained by a depression of the magnetic field intensity in the dayside magnetosphere caused by the penetration of the magnetosheath magnetic field (component perpendicular to the reconnection line) into the magnetosphere. The penetration coefficient (the ratio of the intensity of the penetrated field to the intensity of the magnetosheath magnetic field) is estimated and found to equal approximately 1.     

Cold resistance and metabolic activity of lichens below 0°C

Laboratory measurements show that lichens are extremely tolerant of freezing stress and of low-temperature exposure. Metabolic activity recovered quickly after severe and extended cold treatment. Experimental results demonstrate also that CO₂ exchange is already active at around −20°C. The psychrophilic character of polar lichen species is demonstrated by optimum temperatures for net photosynthesis between 0 and 15°C. In situ measurements show that lichens begin photosynthesizing below 0°C if the dry thalli receive fresh snow. The lowest temperature measured in active lichens was −17°C at a continental Antarctic site. The fine structure and the hydration state of photobiont and mycobiont cells were studied by low-temperature scanning electron microscopy (LTSEM) of frozen hydrated specimens. Water potentials of the frozen system are in the range of or even higher than those allowing dry lichens to start photosynthesis by water vapor uptake at +10°C. The great success of lichens in polar and high alpine regions gives evidence of their physiological adaptation to low temperatures. In general lichens are able to persist through glacial periods, but extended snow cover and glaciation are limiting factors.     

Experimental investigations of quasistable radiation belts formed after solar proton events in September–October 1989 and March 1991 based on measurements made by “Liulin” dosimeter-radiometer on board the “MIR” space station

Since 1988 high sensitivity dosimeter-radiometer “Liulin” has been installed on board the MIR space station. Device measured absorbed dose rate and flux of penetrating particles. Results of measurements showed that after powerful solar proton events (SPE) September–October, 1989 and March, 1991 additional quasistable radiation belts were formed in the near earth space within the interval L=1.8−3.0. These “new” belts were observed as an additional maximums in flux (and sometimes dose) channels when crossing the SAA region. “New” belts were quasi stable and existed at least several months, decaying slightly after SPE. Dose to flux ratio analysis showed that major components of these belts were energetic electrons and protons arising in connection with preceding SPEs.