TARANIS is a low altitude satellite dedicated to the study of the impulsive transfers of energy between the Earth atmosphere and the space environment occurring above thunderstorms.

In Celtic mythology Taranis is the god of thunder. The mission TARANIS (Tool for the Analysis of RAdiation from lightNIng and Sprites) is funded and operated by the French space agency CNES. LPC2E is in charge of the scientific coordination of the project and the technical coordination of the scientific payload. TARANIS is a low altitude satellite project to be launched by 2020 and dedicated to the study of impulsive transfers of energy between the Earth atmosphere and the space environment.

Such impulsive transfers, discovered by the observation at ground and on satellite (FORMOSAT-2) of Transient Luminous Events (TLEs) and the detection on satellites (CGRO, RHESSI, FERMI, and AGILE) of Terrestrial Gamma ray Flashes (TGFs), are observed above active thunderstorms and appear to be correlated to lightning activity.

Vue d'artiste de TARANIS. Crédit image CNES.
Artist’s impression of TARANIS. Credit image CNES.

To answer the numerous remaining questions about the physics of TLEs and TGFs, the TARANIS mission will provide a set of unprecedented and complementary measurements. Specific examples include:

Combined images of TLEs and TGFs (through fast micro-cameras and photometers, nadir-viewing and X-ray and Gamma-ray measurements) and the associated measurements of relativistic electrons and wave fields;

High resolution measurement of energetic electrons in energy, pitch angle and time allowing to detect high-energy electron beams associated with TGFs as well as Lightning-induced Electron Precipitation (LEP) and to track natural and man-made controlled variability of the radiation belts;

Onboard wave field measurements in a frequency range running from DC to 30 MHz allowing to record radio signatures of optical and particle transient phenomena and to detect the presence of quasi-electrostatic thundercloud fields.

TARANIS science

TARANIS mission profile

TARANIS belongs to the CNES Myriade satellite family. It is a three axis stabilized satellite. The dimension of the platform is about 1 m3. The total weight is around 180 kg, including about 36 kg for the scientific payload. The satellite subsystems include a mass memory of 16 Gbits capacity, a high rate X band telemetry (16.8 Mbits/s) for the transmission of the scientific data. TARANIS will be a two-year mission with a four-year mission as an objective. It will fly in a quasi-polar sun-synchronous orbit with an inclination of 98° and an altitude close to 700 km. TARANIS is scheduled to be launched in 2020 from Kourou as a piggyback on a Vega rocket. Due to limitations in the power budget, in particular for the nighttime orbits, the scientific experiments will be switched off at high geographical latitudes (below −60° and above 60°) during the nominal operation modes. However, this will allow coverage for most regions where lightning activity is strong and therefore where the probability of observations of TLEs or/and TGFs is high. The TARANIS mission Centre will be operated by LPC2E.

Scientific objectives

Representation of upper atmosphere lightning and transient luminous events (from Sato et al. 2008)

The observations of red sprites, blue jets, elves, sprite halos, gigantic jets, etc., named Transient Luminous Events (TLEs) and the observations of Terrestrial Gamma ray Flashes (TGFs) have pointed out the existence of impulsive transfers of energy between the Earth atmosphere and the space environment. Measurements performed by the ISUAL experiment onboard the FORMOSAT-2 satellite have shown that TLEs are fairly common in most regions of the globe.

Global distribution of elves, sprites and halos from ISUAL observations (from Chen et al., 2008).

RHESSI and FERMI observations show that TGFs involve very high energies, reaching 30 MeV. Processes that contribute to these phenomena and potential consequences on the Earth’s electrical and chemical environment are far from being fully understood. However, it is clear that the source of TGFs is itself a fundamentally new physical process that could have much broader implications and manifestations throughout the universe.

Global distribution of TGFs from RHESSI observations: March 2002 – June 2008. (from Smith et al., 2008)

Generated within the atmosphere, the TLEs and TGFs, as well as the physical mechanisms that produce them, may affect the chemical constitution and the dynamics of the atmosphere. TARANIS will complement ground-based, plane-based and balloon-based experiments: (i) by providing simultaneous observations at the nadir of lightning flashes, TLEs, and TGFs; (ii) by measuring the accelerated and precipitated electrons; (iii) by monitoring the electromagnetic environment.

Scientific questions to be addressed

TARANIS aims at providing a complete package of novel instrumentation to answer specific questions raised by the many ground-based campaigns to observe TLEs, and by the highly successful FORMOSAT-2, RHESSI, and FERMI missions. The science objectives of the TARANIS mission are into three broad categories:

Advanced physical understanding of the links between TLEs and TGFs, in their source regions, and the environmental conditions (lightning activity, variations in the thermal plasma, occurrence of extensive atmospheric showers, etc.);

Identify the generation mechanisms for TLEs and TGFs and, in particular, the particle and wave field events that are involved in the generation processes or produced by the generation processes;

Evaluate the potential effects of TLEs, TGFs, and bursts of precipitated and accelerated electrons (in particular lightning induced electron precipitation and terrestrial electron beams) on the Earth atmosphere or on the radiation belts.

TARANIS scientific payload

To achieve the scientific objectives of the TARANIS mission, the instruments of the scientific payload are:

• MCP including MC (MicroCameras), a set of two cameras (a sprite camera and a lightning camera), and their associated analyzer, and PH (Photometers), a set of four photometers and their associated analyzer;

• XGRE (X-ray, Gamma-ray, and Relativistic Electron experiment), a set of three X and γ detectors and their associated analyzer;

• IDEE (Instrument Détecteurs d’Electrons Energétiques), two electron detectors with one analyzer per detector;

• IME-BF (Instrument de Mesure du champ Electrique Basse Fréquence), a sensor to measure the electric field in the low frequency range and the low frequency wave analyzer (electric and magnetic); IME-BF also includes an Ion Probe (SI) to determine fluctuations of thermal plasma;

• IME-HF (Instrument de Mesure du champ Electrique Haute Fréquence), a sensor to measure the electric field in the high frequency range and the associated high frequency wave analyzer;

• IMM (Instrument de Mesure du champ Magnétique), a compound triaxial system of search-coil magnetometers to measure the magnetic field in the low and medium frequency ranges and the medium frequency wave analyzer (electric and magnetic); IMM also includes a 0+ whistler Detector (SD) to perform onboard characterization of whistlers;

• MEXIC (Multi Experiment Interface Controller), electronics equipment to power and to manage the whole scientific payload.

Scientific payload of TARANIS. Credit image CNES.
  Instruments PI, affiliation
MCP Lightning micro-camera
TLE micro-camera
Four Photometers
 PI: Th. Farges, CEA (F)
XGRE Three X and γ detectors:
Photons : [20 keV – 10 MeV]
Relativistic e: [1 MeV – 10 MeV]
PIs: P-L. Blelly, IRAP (F)
Ph. Laurent, APC (F)
IDEE Two e detectors: [70 keV – 4 MeV] PI: P-L. Blelly, IRAP (F)
+ Univ. Prague (Cz)
IMM Triaxial search coil: [5 Hz – 1 MHz]
0+ whistler detector
PI: J-L. Pinçon, LPC2E (F)
+ Univ. Stanford (USA)
IME-BF LF-E antenna: [DC – 1 MHz]
Ion probe
PI: E. Seran, LATMOS (F)
IME-HF HF-E antenna: [100 kHz – 35 MHz] PI: J-L. Rauch, LPC2E (F)
+ Univ. Prague, IAP (Cz)
MEXIC Power and management of the payload  PI: F. Colin, LPC2E (F)
+ SRC (Pl)

Contact LPC2E: jean-louis.pincon@cnrs-orleans.fr