Peter Falkner

Solar polar orbiter: a solar sail technology reference study

An assessment is presented of a Solar Polar Orbiter mission as a Technology Reference Study. The goal is to focus the development of strategically important technologies of potential relevance to future science missions. The technology is solar sailing, and so the use of solar sail propulsion is, thus, defined a priori. The primary mission architecture utilizes maximum Soyuz Fregat 2-1b launch energy, deploying the sail shortly after Fregat separation. The 153 × 153 m square sail then spirals into a circular 0.48-astronomical-unit orbit, where the orbit inclination is raised to 90 deg with respect to the solar equator in just over 5 years. Both the solar sail and spacecraft technology requirements have been addressed. The sail requires advanced boom and new thin-film technology. The spacecraft requirements were found to be minimal because the spacecraft environment is relatively benign in comparison with other currently envisaged missions, such as the Solar Orbiter mission and BepiColombo.

GeoSail: An Elegant Solar Sail Demonstration Mission

In this paper a solar sail magnetotail mission concept was examined. The 43-m square solar sail is used to providethe required propulsion for continuous sun-synchronous apse-line precession. The main driver in this mission was found to be the reduction of launch mass and mission cost while enabling a nominal duration of 2 years within the framework of a demonstration mission. It was found that the mission concept provided an excellent solar sail technology demonstration option. The baseline science objectives and engineering goals were addressed, and mission analysis for solar sail, electric, and chemical propulsion performed. Detailed subsystems were defined for each propulsion system and it was found that the optimum propulsion system is solar sailing. A detailed tradeoff as to the effect of spacecraft and sail technology levels, and requirements, on sail size is presented for the first time. The effect of, for example, data acquisition rate and RF output power on sail size is presented, in which it is found that neither have a significant effect. The key sail technology requirements have been identified through a parametric analysis.

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 µm 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 mm2 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 °C−1 MFA temperature, < ±0.2 nT within 250 h) are very satisfying and the linear gain drift of 60 ppm °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 cm2 mg−1.

Sample return from mercury and other terrestrial planets using solar sail propulsion

A conventional Mercury sample return mission requires significant launch mass due to the large AV required for the outbound and return trips and the large mass of a planetary lander and ascent vehicle. It is shown that solar sail spacecraft can be used to reduce lander mass allocation by delivering the lander to a low, thermally safe orbit close to the planetary terminator. In addition, the ascending node of the solar sail spacecraft parking orbit plane can be artificially forced to avoid out-of-plane maneuvers during ascent from the planetary surface. Propellant mass is not an issue for spacecraft with solar sails, and so a sample can be returned relatively easily without resorting to lengthy, multiple gravity assists. A 275-m2 solar sail with a sail assembly loading of 5.9 g/m2 is used to deliver a lander, cruise stage, and science payload to a forced sun-synchronous orbit at Mercury in 2.85 years. The lander acquires samples and conducts limited surface exploration. An ascent vehicle delivers a small cold-gas rendezvous vehicle containing the samples for transfer to the solar sail spacecraft. The solar sail spacecraft then spirals back to Earth in 1 year. The total mission launch mass is 2353 kg, launched using a Japanese H2 class launch vehicle, C3 = 0. Extensive launch date scans have revealed an optimal launch date in April 2014 with sample return to Earth 4.4 years later. Solar sailing reduces launch mass by 60% and trip time by 40%, relative to conventional mission concepts. In comparison, mission analysis has demonstrated that solar-sail-powered Mars and Venus sample returns appear to have only modest benefits in terms of reduced launch mass, at the expense of longer mission durations, than do conventional propulsion systems.

A 92dB-DR 13mW /spl Delta//spl 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 plusmn2,000nT with 10pT resolution. The chip operates up to 260krad of total ionizing dose. The chip uses 20mm2 in a 0.35mum CMOS process.

The BepiColombo Mission

BepiColombo is an interdisciplinary mission to the planet Mercury which will provide the detailed information necessary to understand Mercury and its magnetospheric environment. The mission is envisaged to consist of three spacecrafts, the Mercury Planetary Orbiter (MPO), the Mercury Magnetospheric Orbiter (MMO) and the Mercury Surface Element (MSE). The mission went through a re-assessment with the aim of optimizing resources and and advancing the scientific return. Various mission scenarios were investigated and new pay load concepts were adopted. The newly defined mission will be presented focusing on the launch scenario and the MPO reference payload. 1. I n t r o d u c t i o n Mercury bears information, which unraveled might be the key to unders tanding the origin and early evolution of our solar system. The necessary details of its properties can, however, only be provided by a space mission. Nevertheless, only one spacecraft ever visited Mercury almost 30 years ago, when Mariner 10 performed three fly-byes in 1974-1975. Hence, precise characterization is still imminent. Drawing conclusions on the formation and evolution of Mercury requires a complete description of the planet and its environment. BepiColombo therefore is an interdisciplinary mission dedicated to a comprehensive investigation of the four basic components of the Mercury system: the planet s interior, surface, exosphere and magnetosphere. As such it will open a new frontier in the study of our solar system. The mission went through a re-assessment process to optimize resources and advance the scientific return. The new mission scenario is presented in a concise overview. 75 terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S1539299600015124 Downloaded from https://www.cambridge.org/core. IP address: 54.191.40.80, on 10 Sep 2017 at 04:18:44, subject to the Cambridge Core