BepiColombo Mercury Magnetospheric Orbiter Design

Paper number

IAC-05-A3.2.B.06

Author

Dr. Hiroshi Yamakawa, Kyoto University, Japan

Year

2005

Abstract

BepiColombo, an interdisciplinary mission to Mercury, is a joint space science project between Europe and Japan. This mission comprises two science elements, the Mercury Planetary Orbiter (MPO) to be procured by ESA (European Space Agency) and the Mercury Magnetospheric Orbiter (MMO) to be procured by JAXA (Japan Aerospace Exploration Agency). The system baseline assumes the launch of the MPO and the MMO on a single Soyuz-Fregat vehicle during the launch window in the 2012 time frame. The SEPM (Solar Electric Propulsion Module) and the CPM (Chemical Propulsion Module), both of which to be procured by ESA, are utilized in the interplanetary cruise and for the Mercury orbit insertion. The cruise configuration is called the Mercury Composite Spacecraft (MCS): MMO-MPO-CPM+SEPM. ESA is responsible for the whole BepiColombo project including the launch, cruising, and the Mercury orbit insertion. JAXA is responsible for the procurement of the MMO and its operation.

The MMO studies Mercury’s magnetic field, its exosphere, its magnetosphere, and inner interplanetary space. The MMO accommodates instruments dedicated to the study of the electric and magnetic field, plasma and radio waves, plasma and neutral particles, and dust particles in the environment of Mercury. This paper summarizes the current design status of the MMO spacecraft system, subsystems, and onboard science instruments selected through the process of the Announcement of Opportunity (AO) in 2004.

When the MMO is attached to the MCS behind its Sun shield during the cruise phase, the MMO works as a subsystem or as a dormant payload of the three-axis stabilized MCS. The MMO becomes a spin-stabilized spacecraft after it is separated from the MCS following the Mercury orbit insertion. The MMO has no orbit control function, but only attitude control capability with N2 cold gas jet system. The MMO Mercury orbit is polar and highly elliptic; its major axis lies close to the equatorial plane to permit a global exploration of the magnetosphere from an altitude of 400 km up to a planetocentric distance of nearly 6 planetary radii.

The nominal spin rate is 15 rpm (spin period of 4 seconds), which facilitates the azimuth-scan of the particle and imaging instruments (MEA, MSA, MIA, HEP-ele, HEP-ion, ENA, MSASI, and MDM) and the deployment of two pairs of wire electric dipole antennas (WPT/MEFISTO for PWI) and two masts (MGF and SC for PWI) normal to the spin axis. The spin axis is pointed nearly perpendicular to the Sun (and the orbital plane of Mercury), slightly (~2°) inclined so as to prevent the shadow onto the wire antenna tips. In the high-temperature case around the periapsis phase, the spin axis should be perfectly perpendicular to the Sun for thermal control reasons.

Abstract document

IAC-05-A3.2.B.06.pdf

Manuscript document

IAC-05-A3.2.B.06.pdf (🔒 authorized access only).

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