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ExoMars Trace Gas Orbiter Instruments

Investigating the Martian atmosphere

The ExoMars Trace Gas Orbiter is an ESA and Roscosmos mission to Mars, launched on 14 March 2016. It will investigate trace gases – gases which are present in small concentrations in the atmosphere, making up less than 1 per cent of it. There will be particular focus on hydrocarbons or sulphur species which could be signatures of active biological or geological processes, at present or in the past.

The Trace Gas Orbiter carries scientific instruments for the detection of trace gases with an improved accuracy - 1000 better - compared to previous measurements from orbit and ground-based measurements. It will also provide new data for the study of the temporal and spatial evolution of trace gases in the Martian atmosphere, and for the location of their source regions.

Artist's impression of the Trace Gas Orbiter showing where the science intruments are located. Credit: ESA/ATG medialab

The scientific payload operations of the Orbiter will start in 2017 and are planned to last for a minimum of one Martian year (687 Earth days).

Science objectives

The Orbiter will be used to investigate trace gases with the following scientific objectives:

Deliver a detailed characterisation of the Martian atmosphere's composition.
This includes mapping the distribution of trace gases, identifying their sources and sinks, and studying geographical and temporal variability.

The first scientific goal will be to detect a broad suite of atmospheric trace gases, and key isotopologues (molecules that have at least one atom with a different number of neutrons than the parent molecules), to establish the atmospheric inventory.

Following a positive detection of key species, geographical (location and altitude) and seasonal mapping will be carried out. Mapping of the Deuterium/Hydrogen ratio will also be performed, to provide new information on water reservoirs and atmospheric escape.

A third goal is characterising the state of the atmosphere, in particular temperatures, aerosols, water vapour, and ozone. The data assimilation technique adopted by the science team will allow them to model the atmospheric circulation. This will help determine whether particular gases are emanating from specific areas on Mars and to provide insights into the nature of the trace gas source.

Imaging of surface features

Another important objective is to image and to characterise features on the Martian surface which may be related to trace gas sources. The data should provide information on the geological and dynamical context (such as volcanism) for any sources detected.

Mapping of subsurface hydrogen

The final objective is to map the subsurface hydrogen to a depth of one metre, with a resolution ten times better than previous measurements.

Instruments in brief

The Trace Gas Orbiter, manufactured in Europe, will carry a science payload of four instruments: 

NOMADNadir and Occultation for MArs Discovery
NOMAD combines three spectrometers, two infrared and one ultraviolet, to perform high-sensitivity orbital identification of atmospheric components, including methane and many other species, via both solar occultation and direct reflected-light nadir observations.
Principal Investigator: Ann Carine Vandaele, Belgian Institute for Space Aeronomy, Belgium
Co-Principal Investigator: José Lopez Moreno, Instituto de Astrofísica de Andalucía, Spain
Co-Principal Investigator: Giancarlo Bellucci, Istituto Nazionale di Astrofisica, Italy
Co-Principal Investigator: Manish Patel, The Open University, United Kingdom
Participating countries: Belgium, Spain, Italy, United Kingdom, United States of America, Canada.


ACSAtmospheric Chemistry Suite
This suite of three infrared instruments will help scientists to investigate the chemistry and structure of the Martian atmosphere. ACS will complement NOMAD by extending the coverage at infrared wavelengths, and by taking images of the Sun to better analyse the solar occultation data.
Principal Investigator: Oleg Korablev, Space Research Institute (IKI), Moscow, Russia


CaSSIS – Colour and Stereo Surface Imaging System
A high resolution camera (5 metres per pixel) capable of obtaining colour and stereo images over a wide swathe. CaSSIS will provide the geological and dynamical context for sources or sinks of trace gases detected by NOMAD and ACS.
Principal Investigator: Nicolas Thomas, University of Bern, Switzerland
Co-Principal Investigator: Gabriele Cremonese, Istituto Nazionale di Astrofisica, Italy
Participating countries: Switzerland, Italy, Poland


FREND – Fine Resolution Epithermal Neutron Detector
This neutron detector will map hydrogen on the surface down to a metre deep, revealing deposits of water-ice near the surface. FREND’s mapping of shallow subsurface water ice will be up to 10 times better than existing measurements.
Principal Investigator: Igor Mitrofanov, Space Research Institute (IKI), Moscow, Russia


Last Update: 04 November 2016

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