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Planetary Orbiter

Planetary Orbiter

Summary

The Planetary Orbiter is dedicated to remote sensing. To ensure complete coverage of the planet it needs to have a polar orbit. The orbit's pericentre altitude of 400 km and apocentre altitude of 1500 km together with an orbital period of 2.3 hours, will provide an adequate shift of the ground track between successive orbits.

Orbit illustration

Low-resolution observations at the apocentre will identify areas of interest, while higher resolution imaging for details is performed at the pericentre. Nearly all of the instruments on the Planetary Orbiter are mounted on the nadir-pointing platform.

The Planetary Orbiter also carries an instrument complement dedicated to radio science. This requires an accuracy of the order of one arcsecond and one metre for the reconstitution of the attitude and orbit, which are derived from measurements provided by the accelerometer, star sensor and multiple-frequency Doppler tracking and ranging.


From pole to pole

To examine the planet from an orbit over the poles, the Planetary Orbiter will have a wide-angle and a narrow-angle camera working by visible and near-infrared light.

Infrared and ultraviolet spectrometers will ananlyse minerals at the surface and constituents of Mercury's tenuous atmosphere, while X-rays and gamma rays will reveal to other instruments the chemical composition of Mercury's soil. A neutron spectrometer will search for water-ice deposits beneath the surface. The Sun's activity, evident in its emissions of X-rays, will be recorded by a solar monitor.

Global mapping of Mercury's gravity by an accelerometer in the Planetary Orbiter forms part of a radio science experiment. This will follow up the link between gravity and Mercury's behaviour in orbit, first explained by Einstein. Provided the spacecraft's motions and attitude and the pressure of sunlight can be gauged with high precision, careful monitoring of radio signals from BepiColombo will provide new tests of the most fundamental aspects of the theory of general relativity.

Table of instruments

The scientific instruments onboard of the Planetary Orbiter.

Acronym

Instrument

Range

NAC

Narrow angle camera

350-1050 nm

WAC

Wide angle camera

350-1050 nm

IRS

Infrared spectrometer

0.8-2.8 µm

ALI

UV spectrometer

70-330 nm

MXS

Mercury X-ray spectrometer

0.5-10 keV

MGS

Mercury gamma-ray spectrometer

0.1-8 MeV

MNS

Mercury neutron spectrometer

0.01-5 MeV

RAD

Radioscience (two instruments)

- KAT

Ka/Ka band transponder

32-34 GHz

- ISA

Accelerometer

10-4-10 Hz

TOP

Laser altimeter

1064 ± 5 nm

NET

Near-Earth Objects Telescope

18 mag

Instrument objectives

 

NAC

WAC

IRS

ALI

MXS

MGS

MNS

RAD

TOP

NET

Morphology

X

X

 

 

 

 

 

X

X

 

Internal structure

 

 

 

 

 

 

 

X

 

X

Composition

 

 

 

X

X

X

X

 

 

 

Mineralogy

X

X

X

 

 

 

 

 

 

 

Exosphere

 

X

 

X

 

 

 

 

 

 

Fundamental science

 

 

 

 

 

 

 

X

 

 

Near-Earth Objects

 

 

 

 

 

 

 

 

 

X

RAD is the acronym for RADioscience that comprises the two instruments KAT and ISA.

Last Update: 1 September 2019
7-Nov-2024 15:52 UT

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