ExoMars Trace Gas Orbiter (TGO)

Searching for signature gases in the Martian atmosphere

The 2016 ExoMars Trace Gas Orbiter is the first in a series of Mars missions to be undertaken jointly by the two space agencies, ESA and Roscosmos. A key goal of this mission is to gain a better understanding of methane and other atmospheric gases that are present in small concentrations (less than 1% of the atmosphere) but nevertheless could be evidence for possible biological or geological activity.

 
 

ExoMars Orbiter in cruise configuration. Credit: ESA

Investigations with space- and Earth-based observatories have demonstrated the presence of small amounts of methane in the Martian atmosphere that has been shown to vary with location and time. Since methane is short-lived on geological time scales, its presence implies the existence of an active, current source of methane. It is not clear, yet, whether the nature of that source is biological or chemical. Organisms on Earth release methane as they digest nutrients. However, other purely geological processes, such as the oxidation of iron, also release methane.

The Orbiter will carry a scientific payload capable of addressing this scientific question, namely the detection and characterisation of trace gases in the Martian atmosphere. From its ~400-km altitude science orbit, the instruments onboard the Orbiter will be deployed to detect a wide range of atmospheric trace gases (such as methane, water vapour, nitrogen dioxide, acetylene), with an improved accuracy of three orders of magnitude compared to previous measurements. The measurements carried out by the Orbiter will provide evidence about the location and sources of these gases; these locations could be targeted as prime landing sites for future missions.

 

Communicating on Mars

The Orbiter will carry the EDM on the journey from Earth towards Mars and, as it approaches the planet, deploy it for entering the Martian atmosphere on its way to land on a predefined area on the surface of the planet. After deployment, the Orbiter will monitor the UHF transmission from the EDM from its coasting to Mars till its landing on the Red Planet. It will also facilitate the real-time transmission to Earth of the most important data measured by the EDM.

Scientific investigations will take top priority until the second mission in the ExoMars programme begins, with the arrival of the ExoMars rover in 2018. At that stage the Orbiter will become a valuable Mars telecommunications asset, providing communication services to the Rover operating on the surface of Mars. The Orbiter will act as a data relay centre for sending commands to the rover and downloading data to Earth through the ESA space communications network.

 

The ExoMars Trace Gas Orbiter at a glance
During its operational lifetime the ExoMars Trace Gas Orbiter will perform three key roles:
  1. Support the deployment and part of the data transmission of the Entry, Descent and Landing Demonstrator Module, which is the other major element of the ExoMars 2016 mission;
  2. Host a scientific payload that will carry out investigations into the biological or geological origin of trace gases on Mars;
  3. Serve as a data relay to support communications for ESA’s ExoMars Rover during the ExoMars 2018 mission.

 

The ExoMars Trace Gas Orbiter Design

The Trace Gas Orbiter spacecraft, designed by ESA, builds on the heritage accumulated from earlier ExoMars mission scenarios. The main characteristics of the Orbiter are determined by the functions that it will perform and the launch vehicle, a Proton launcher, to be provided by Roscosmos.

 

Main technical characteristics of
the ExoMars Trace Gas Orbiter
Structure
1194 mm central tube interfacing with the launcher
Propulsion
Bi-propellant propulsion system with 424 N main engine; for Mars orbit insertion and manoeuvres
Power
20 m2 solar arrays fully populated with cells (GaAs triple junctions) providing ~ 2000 W power, with a 1 degree of freedom (rotational) mechanism
Power
2 modules of Lithium-Ion batteries with ~ 5100 Wh/ 180 Ah total capacity; to cover eclipses during the nominal lifetime of the Orbiter (until end 2022)
Communication
2200 mm X-Band High Gain Antenna with a 2 axes pointing mechanism and 65 W RF TWTA (Travelling Wave Tube Amplifier); for communication with Earth
Communication
Electra UHF-Band transceivers (NASA provided) with a single Helix antenna; for communication with surface assets (e.g. Rovers, Landers)
Thermal control
Yaw Steering strategy implemented during the science phase to ensure 3 cold faces for science payload instruments (+X, +Z and –Z)
Mass budget Up to 135.6 kg of science payload
EDM deployment
Spin-eject separation system for releasing the EDM before Mars orbit insertion

 

For further details, please contact:

Giacinto Gianfiglio, ExoMars System and Orbiter Module Manager
Email: giacinto.gianfiglioesa.int

 


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Last Update: 12 Jul 2012