RPC-MAG The Fluxgate Magnetometer in the ROSETTA Plasma Consortium

The fluxgate magnetometer experiment onboard the ROSETTA spacecraft aims to measure the magnetic field in the interaction region of the solar wind plasma with comet 67P/Churyumov-Gerasimenko. It consists of a system of two ultra light (about 28 g each ) triaxial fluxgate magnetometer sensors, mounted on the 1.5 m long spacecraft boom. The measurement range of each sensor is ±16384 nT with quantization steps of 31 pT. The magnetometer sensors are operated with a time resolution of up to 0.05 s, corresponding to a bandwidth of 0–10 Hz. This performance of the RPC-MAG sensors allows detailed analyses of magnetic field variations in the cometary environment. RPC-MAG furthermore is designed to study possible remnant magnetic fields of the nucleus, measurements which will be done in close cooperation with the ROSETTA lander magnetometer experiment ROMAP.     

Gravitaxis and graviperception in Euglena gracilis.

Gravitactic orientation in the flagellate Euglena gracilis is mediated by an active physiological receptor rather than a passive alignment of the cells. During a recent space flight on the American shuttle Columbia the cells were subjected to different accelerations between 0 and 1.5 x g and tracked by computerized real-time image analysis. The dependence of orientation on acceleration followed a sigmoidal curve with a threshold at < or = 0.16 x g and a saturation at about 0.32 x g. No adaptation of the cells to the conditions of weightlessness was observed over the duration of the space mission (12 days). Under terrestrial conditions graviorientation was eliminated when the cells were suspended in a medium the density of which (Ficoll) equaled that of the cell body (1.04 g/ml) and was reversed at higher densities indicating that the whole cytoplasm exerts a pressure on the respective lower membrane. There it probably activates stretch-sensitive calcium specific ion channels since gravitaxis can be affected by gadolinium which is a specific inhibitor of calcium transport in these structures. The sensory transduction chain could involve modulation of the membrane potential since ion channel blockers, ionophores and ATPase inhibitors impair graviperception.     

Physical interpretation of interdisciplinary solar/interplanetary observations relevant to the 27–29 June 1980 SMY/STIP event no. 5

A sequence of six well defined interplanetary structures (magnetic clouds) was identified in the solar wind and magnetic field measurements of Helios-1 from 29 June-01 July, 1980. (location 0.64–0.67 AU, C. Long. ～165°, C. Lat. ～5.8°). These structures were characterized by a large northward directed solar wind flow; by well defined directional discontinuities of mainly the ‘tangential-type’ at their beginnings and ends; by some increase in proton and by very pronounced increases in alpha particle number densities - each accompanied by sudden temperature decreases (or in one case by an increase); by some times an increase in magnetic field strength and by values of Nα/Np typical of the inner solar atmosphere. These structures are suggested to have been ejections from a succession (27–29 June, 1980) of Type II producing flares in Hale Region 16923 which coronagraph and X-ray (GOES) data indicate constituted a family of transient producing events. Only two interplanetary shocks were identified in the relevant Helios-1 records. It is suggested on the basis of observations of the directionality of certain of the flare related Type II bursts that some of these shocks could have been missed by the spacecraft. This implies that, in the absence of directional information, correlation of an observed interplanetary shock wave with a solar Type II burst may not always lead to a unique result.     

Vanguard--a European robotic astrobiology-focussed Mars sub-surface mission proposal

We present a new European Mars mission proposal to build on the UK-led Beagle2 Mars mission and continue its astrobiology-focussed investigation of Mars. The small surface element to be delivered to the Martian surface--Vanguard--is designed to be carried by a Mars Express-type spacecraft bus to Mars and adopts a similar entry, descent and landing system as Beagle2. The surface element comprises a triad of robotic devices--a lander, a micro-rover of the Sojourner class for surface mobility, and three ground-penetrating moles mounted onto the rover for sub-surface penetration to 5 m depth. The major onboard instruments on the rover include a Raman spectrometer/imager, a laser plasma spectrometer, an infrared spectrometer--these laser instruments provide the basis for in situ "remote" sensing of the sub-surface Martian environment within a powerful scientific package. The moles carry the instruments' sensor head array to the sub-surface. The moles are thus required to undergo a one-way trip down the boreholes without the need for recovery of moles or samples, eliminating much of the robotic complexity invoked by such operations.     

A feasibility study for the detection of the diurnal variation of tropospheric NO2 over Tokyo from a geostationary orbit

We have conducted a feasibility study for the geostationary monitoring of the diurnal variation of tropospheric NO₂ over Tokyo. Using NO₂ fields from a chemical transport model, synthetic spectra were created by a radiative transfer model, SCIATRAN, for summer and winter cases. We then performed a Differential Optical Absorption Spectroscopy (DOAS) analysis to retrieve NO₂ slant column densities (SCDs), and after converting SCDs into vertical column densities (VCDs), we estimated the precision of the retrieved VCDs. The simulation showed that signal-to-noise ratio (SNR) ? 500 is needed to detect the diurnal variation and that SNR ? 1000 is needed to observe the local minimum occurring in the early afternoon (LT13–14) in summer. In winter, the detection of the diurnal variation during LT08–15 needs SNR ? 500, and SNR ? 1000 is needed if early morning (LT07) and early evening (LT16) are included. The currently discussed sensor specification for the Japanese geostationary satellite project, GMAP-Asia, which has a horizontal resolution of 10 km and a temporal resolution of 1hr, has demonstrated the performance of a precision of several percent, which is approximately corresponding to SNR = 1000–2000 during daytime and SNR ? 500 in the morning and evening. We also discuss possible biases caused by the temperature dependence of the absorption cross section utilized in the DOAS retrieval, and the effect of uncertainties of surface albedo and clouds on the estimation of precisions.     

Beagle 2: a proposed exobiology lander for ESA's 2003 Mars Express mission.

The aim of the proposed Beagle 2 small lander for ESA's 2003 Mars Express mission is to search for organic material on and below the surface of Mars and to study the inorganic chemistry and mineralogy of the landing site. The lander will have a total mass of 60kg including entry, descent, and landing system. Experiments will be deployed on the surface using a robotic arm. It will use a mechanical mole and grinder to obtain samples from below the surface, under rocks, and inside rocks. Sample analysis by a mass spectrometer will include isotopic analysis. An optical microscope, an X-ray spectrometer and a Mossbauer spectrometer will conduct in-situ rock studies.     

Envelope Threshold Detection in a Class of Non-Gaussian Interference

This paper considers the detection of a sinusoidal or chirp signal imbedded in wideband FM interference (as might be generated by some types of active jamming), such that after pulse compression or other integration, the interference can be approximated by a sum of sinusoids of independent phase. The detection probability in such non-Gaussian noise is compared to that for Gaussian noise, with the Gaussian result approached, as required, in the limit that the number of sinusoids in the sum increases without bound. For detection using a comparison of the envelope with a threshold which yields a given false-alarm probability (CFAR detection), the detection probability is improved over the case of Gaussian noise, so that the usual approach basing the design on Gaussian noise would be conservative. Using a threshold determined from the envelope mean, the FM interference yields a lower false-alarm probability than for Gaussian noise, with detection probability only slightly degraded.     

The Magnetospheric Multiscale Magnetometers

The success of the Magnetospheric Multiscale mission depends on the accurate measurement of the magnetic field on all four spacecraft. To ensure this success, two independently designed and built fluxgate magnetometers were developed, avoiding single-point failures. The magnetometers were dubbed the digital fluxgate (DFG), which uses an ASIC implementation and was supplied by the Space Research Institute of the Austrian Academy of Sciences and the analogue magnetometer (AFG) with a more traditional circuit board design supplied by the University of California, Los Angeles. A stringent magnetic cleanliness program was executed under the supervision of the Johns Hopkins University’s Applied Physics Laboratory. To achieve mission objectives, the calibration determined on the ground will be refined in space to ensure all eight magnetometers are precisely inter-calibrated. Near real-time data plays a key role in the transmission of high-resolution observations stored on board so rapid processing of the low-resolution data is required. This article describes these instruments, the magnetic cleanliness program, and the instrument pre-launch calibrations, the planned in-flight calibration program, and the information flow that provides the data on the rapid time scale needed for mission success.     

Future Instrumentation for the Study of the Warm-Hot Intergalactic Medium

We briefly review capabilities and requirements for future instrumentation in UV- and X-ray astronomy that can contribute to advancing our understanding of the diffuse, highly ionised intergalactic medium.