A 92dB-DR 13mW Delta/Sigma modulator for spaceborn fluxgate sensors

A 2-2 cascaded DeltaSigma modulator is adapted for near sensor digitization of the magnetic field measured by a fluxgate sensor. The chip contains three fluxgate channels (13mW each) and one voltage channel (10mW). The fluxgate channels achieve a DR of 92dB for field ranges greater than ± 2,000nT with 10pT resolution. The chip operates up to 260krad of total ionizing dose. The chip uses 20mm(sup 2) in a 0.35µm CMOS process

Highly integrated front-end electronics for spaceborne fluxgate sensors

Scientific instruments for challenging and cost-optimized space missions have to reduce their resource requirements while keeping the high performance levels of conventional instruments. In this context the development of an instrument front-end ASIC (0.35 mu m CMOS from austriamicrosystems) for magnetic field sensors based on the fluxgate principle was undertaken. It is based on the combination of the conventional readout electronics of a fluxgate magnetometer with the control loop of a sigma-delta modulator for a direct digitization of the magnetic field. The analogue part is based on a modified 2-2 cascaded sigma-delta modulator. The digital part includes a primary (128 Hz output) and secondary decimation filter (2, 4, 8,..., 64 Hz output) as well as a serial synchronous interface. The chip area is 20 mm(2) and the total power consumption is 60 mW. It has been demonstrated that the overall functionality and performance of the magnetometer front-end ASIC (MFA) is sufficient for scientific applications in space. Noise performance (SNR of 89 dB with a bandwidth of 30 Hz) and offset stability (< 5 pT degrees C-1 MFA temperature, < +/- 0.2 nT within 250 h) are very satisfying and the linear gain drift of 60 ppm degrees C-1 is acceptable. Only a cross-tone phenomenon must be avoided in future designs even though it is possible to mitigate the effect to a level that is tolerable. The MFA stays within its parameters up to 170 krad of total ionizing dose and it keeps full functionality up to more than 300 krad. The threshold for latch-ups is 14 MeV cm(2) mg(-1)

An experiment to study and control the Langmuir sheath around INTERBALL-2

The satellite INTERBALL-2 has an orbit with high inclination (62.8°), covering the altitude range between a few hundred and about 20000 km. The ambient plasma conditions along this orbit are highly variable, and the interactions of this plasma with the spacecraft body as well as the photo-electron sheath around it are considered to be interesting topics for detailed studies. The electric potential of the spacecraft with respect to the ambient plasma that develops as a result of the current equilibrium reacts sensitively to variations of the boundary conditions. The measurement and eventual control of this potential is a prerequisite for accurate measurements of the thermal plasma. We describe the purpose and technical implementation of an ion emitter instrument on-board INTERBALL-2 utilising ion beams at energies of several thousand electron volts in order to reduce and stabilise the positive spacecraft potential. First results of the active ion beam experiments, and other measures taken on INTERBALL-2 to reduce charging are presented. Furthermore, the approach and initial steps of modelling efforts of the sheath in the vicinity of the INTERBALL-2 spacecraft are described together with some estimates on the resulting spacecraft potential, and effects on thermal ion measurements. It is concluded that even moderate spacecraft potentials as are commonly observed on-board INTERBALL-2 can significantly distort the measurements of ion distribution functions, especially in the presence of strongly anisotropic distributions.Key words. Space plasma physics (active perturbation experiments; spacecraft sheaths · wakes · charging; instruments and techniques).</p

An experiment to study and control the Langmuir sheath around INTERBALL-2

International audienceThe satellite INTERBALL-2 has an orbit with high inclination (62.8°), covering the altitude range between a few hundred and about 20000 km. The ambient plasma conditions along this orbit are highly variable, and the interactions of this plasma with the spacecraft body as well as the photo-electron sheath around it are considered to be interesting topics for detailed studies. The electric potential of the spacecraft with respect to the ambient plasma that develops as a result of the current equilibrium reacts sensitively to variations of the boundary conditions. The measurement and eventual control of this potential is a prerequisite for accurate measurements of the thermal plasma. We describe the purpose and technical implementation of an ion emitter instrument on-board INTERBALL-2 utilising ion beams at energies of several thousand electron volts in order to reduce and stabilise the positive spacecraft potential. First results of the active ion beam experiments, and other measures taken on INTERBALL-2 to reduce charging are presented. Furthermore, the approach and initial steps of modelling efforts of the sheath in the vicinity of the INTERBALL-2 spacecraft are described together with some estimates on the resulting spacecraft potential, and effects on thermal ion measurements. It is concluded that even moderate spacecraft potentials as are commonly observed on-board INTERBALL-2 can significantly distort the measurements of ion distribution functions, especially in the presence of strongly anisotropic distributions

Project M3—a study for a manned Mars mission in 2031

This study deals with a manned mission which focuses on building an orbital station around Mars. The advantages in comparison to direct-landing scenarios are outlined and the necessary technology is described. The orbiting station prohibits contamination of and from the Red Planet and houses six astronauts in a 1100 days journey to Mars providing three pressurized modules: two of them will remain in a Low Mars Orbit for further human missions while the third module is used as an Earth Return Vehicle. A Bimodal Nuclear Thermal Propulsion System is used also for electrical power production. An advanced Environment Control and Life Support System, the necessary radiation shielding, human factors and crew selection criteria have been studied. The described partly reusable Mars Landing Module allows highest possible flexibility in the choice of landing scenario. The overall mission budgets in the fields of mass, power and costs have been estimated