Overview of the whole Project

 

ABSTRACT

The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) will answer outstanding questions concerning the main objectives of the mission. To accomplish the very demanding objectives, ROSINA has unprecedented capabilities, including: very wide mass range from 1 amu to more than 300 amu; very high mass resolution (ability to resolve CO from N2 and 13C from 12CH); very wide dynamic range and high sensitivity; the ability to determine cometary gas and ion flow velocities and temperatures.

INTRODUCTION

The international Rosetta comet rendezvous mission represents an extraordinary opportunity to perform a detailed investigation of a primitive object in our solar system. As part of the core payload for this mission, the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) will answer outstanding questions concerning the main objectives of the mission. The primary measurement objective of the spectrometer is: To determine the elemental, isotopic and molecular composition of the atmospheres and ionospheres of comets as well as the temperature and bulk velocity of the gas and ions and the homogenous and inhomogenous reactions of gas and ions in the dusty cometary atmosphere and ionosphere. In determining the composition of the atmospheres and ionospheres of comets, the following prime scientific objectives, also defined by the Rosetta Science Definition Team will be achieved:

  • To determine the global molecular, elemental, and isotopic composition and the physical, chemical and morphological character of the cometary nucleus.
  • To determine the processes by which the dusty cometary atmosphere and ionosphere are formed and to characterize their dynamics as a function of time, heliocentric and cometocentric position.
  • To investigate the origin of comets, the relationship between cometary and interstellar material and the implications for the origin of the solar system.
  • To investigate possible asteroid outgassing and establish what possible relationship exists between comets and asteroids.

To accomplish these very demanding objectives, ROSINA has unprecedented capabilities, including:

  1. very wide mass range from 1 amu (Hydrogen) to more than 300 amu (organic molecules).
  2. very high mass resolution (ability to resolve CO from N2 and 13C from 12CH).
  3. very wide dynamic range and high sensitivity to accommodate very large differences in ion and neutral gas concentrations and large changes in the ion and gas flux as the comet approaches its perihelion.
  4. the ability to determine the outflowing cometary gas flow velocities and temperatures.

Correlated studies with optical observations, with, for example, the dust instruments, the magnetometer and the surface science package further augment the scientific return of the ROSINA instrument. The necessity for the unusual high capabilities of this experiment stems from the fact that it is one of the key instruments which is able to give meaningful data during the whole mission and thus by monitoring and characterizing the different phases of comet activity from apogee through perigee will lead to a full understanding of cometary behavior.

INSTRUMENT REQUIREMENTS

So far, no single instrument is able to answer all these questions. We have therefore adopted a three sensor approach: each sensor is optimized for part of the scientific objectives while at the same time complementing the other sensors. In view of the very long mission duration they also provide the necessary redundancy. Sensor I (DFMS) is a double focusing magnetic mass spectrometer with a mass range 1- 100 amu and a mass resolution of 3000 at 1% peak height. This sensor is optimized for very high mass resolution and large dynamic range. Sensor II (RTOF) is a reflectron type time of flight mass spectrometer with a mass range 1 to 300 amu and a high sensitivity. The mass resolution is better than 500 at 1% peak height. This sensor is optimized for high sensitivity over a very broad mass range. Sensor III (COPS) consists of two pressure gauges providing total pressure and ram pressure.

A full description of the ROSINA instrument is given in:

 Balsiger et al., 2007, ROSINA—Rosetta orbiter spectrometer for ion and neutral analysis, Space Science reviews, 128, 745-801.