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Orbiter Instruments

RPC: Rosetta Plasma Consortium

RPC, the Rosetta Plasma Consortium, is a set of five instruments sharing a common electrical and data interface with the Rosetta orbiter. The RPC instruments are designed to make complementary measurements of the plasma environment around comet 67P/Churyumov-Gerasimenko.

Science Objectives

RPC is intended to investigate the following scientific areas of interest:

  • The physical properties of the cometary nucleus and its surface.
    Emphasis will be given to determination of the electrical properties of the crust, its remnant magnetization, surface charging and surface modification due to solar wind interaction, and early detection of cometary activity

  • The inner coma structure, dynamics, and aeronomy.
    Charged particle observation will allow a detailed examination of the aeronomic processes in the coupled dust-neutral gas-plasma environment of the inner coma, its thermodynamics, and structure such as the inner shocks

  • The development of cometary activity, and the micro- and macroscopic structure of the solar-wind interaction region as well as the formation and development of the cometary tail

In order to realize these investigations extensive in-situ monitoring of the plasma electrons and ions, their composition, distribution, temperature, density, flow velocity, and the magnetic field will be necessary. These measurements will improve the understanding of the coupling processes of cometary dust, gas, and plasma as well as its interaction with the solar wind. The plasma and fields measurements thus provide complementary information to that of other Rosetta instruments for a deeper understanding of the overall physics and chemistry of an active comet.

The flybys of asteroid Steins and asteroid Lutetia have provided an opportunity to study in detail the physics of the solar wind - asteroid interaction. RPC has excellent capabilities for the investigation of this interaction. It has also been possible to study the magnetic and electric conductivity properties of the asteroids.

Instrument Description

RPC consists of five sensors:

  • Ion Composition Analyser (ICA)
  • Ion and Electron Sensor (IES)
  • Langmuir Probe (LAP)
  • Fluxgate Magnetometer (MAG)
  • Mutual Impedance Probe (MIP),

    as well as a joint
  • Plasma Interface Unit (PIU)

    acting as instrument control, spacecraft interface, and power management unit.

Ion Composition Analyser

The Ion Composition Analyser (ICA) measures the three-dimensional velocity distribution and mass distribution of positive ions. The mass resolution is sufficient to differentiate between the major particle species such as protons, helium, oxygen, molecular ions, and heavy ion clusters (dusty plasma). The ICA comprises an electrostatic arrival angle filter, a hemispherical electrostatic analyser employed as an energy filter, and a magnetic deflection momentum filter. Particles are detected using a large micro channel plate and a two-dimensional anode array.

RELATED LINK ICA at the Swedish Institute of Space Physics

Ion and Electron Sensor

The Ion and Electron Sensor (IES) will simultaneously measure the flux of electrons and ions in the plasma surrounding the comet over an energy range from around one electron volt, which approaches the limits of detectability, up to 22 keV. IES consists of two electrostatic analysers, one for electrons and one for ions, which share a common entrance aperture. The charged particle optics for IES employs a toroidal top-hat geometry along with electrostatic angle deflectors to achieve an electrostatically scanned field of view of 90 × 360 degrees.

Langmuir Probe

The Langmuir Probe (LAP) instrument will measure the density, temperature and flow velocity of the cometary plasma. It comprises two spherical sensors mounted at the tip of deployable booms, with the sensors capable of being swept in potential to measure the current-voltage characteristic of the intervening plasma, which provides information on the electron number density and temperature. The probes can be held at a fixed bias potential to measure plasma density fluctuations and by a time-of-flight analysis of the signals from the two probes the plasma flow velocity can be determined.

RELATED LINK LAP at the Swedish Institute of Space Physics

Fluxgate Magnetometer

The Magnetometer experiment (MAG) will measure the magnetic field in the region where the solar wind plasma interacts with the comet. It consists of two triaxial fluxgate magnetometer sensors mounted on a 1.5 metre deployable boom that points away from the comet nucleus. One sensor is mounted near the outboard tip of the boom and one is mounted part way along the boom. The use of two sensors allows the effects of the spacecraft's own magnetic field to be minimised.

MAG will also study any magnetic field possessed by the comet nucleus, in cooperation with the ROMAP magnetometer experiment on the Rosetta lander.

RELATED LINK MAG at the Technical University of Braunschweig

Mutual Impedance Probe

The Mutual Impedance Probe (MIP) will derive the electron gas density, temperature, and drift velocity in the inner coma of the comet by measuring the frequency response of the coupling impedance between two dipoles.

MIP will also investigate the spectral distribution of natural waves in the 7 kHz to 3.5 MHz frequency range and monitor the dust and gas activity of the nucleus.

RELATED LINK MIP at Laboratoire de Physique et Chimie de l'Environnement

Plasma Interface Unit

The Plasma Interface Unit (PIU) acts as an interface between the five instruments that make up RPC and the Rosetta spacecraft by providing a single path for the transmission of scientific and housekeeping data to the ground and for the receipt and processing of commands sent from the ground. The PIU also takes power from the spacecraft and converts, conditions and manages it for the RPC instruments.

PIU also performs on-board data processing for the MAG sensor unit, which has no data processing capability of its own.

RELATED LINK PIU at Imperial College


Rosetta Blog articles

29/09/2016 Living with a comet: RPC team perspective
29/09/2016 A comet's life - a new sonification of RPC data
28/09/2016 Science 'til the very end
27/09/2016 Rosetta measures production of water at comet over two years
26/09/2016 The surprising comet
25/08/2016 Rosetta captures comet outburst
11/03/2016 Rosetta finds magnetic field-free bubble at comet
19/08/2015 What made the comet sing?
11/08/2015 Comet's firework display ahead of perihelion
03/08/2015 First release of Rosetta comet phase data from four orbiter instruments
29/07/2015 Rosetta shows how comet interacts with the solar wind
14/04/2015 Rosetta and Philae find comet not magnetised
22/01/2015 Watching the birth of a comet magnetosphere
22/01/2015 Getting to know Rosetta's comet – Science special edition
11/11/2014 The singing comet
Rosetta's plasma experiments check out of commissioning


Last Update: 24 November 2016

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