1. COBRAT project: LONG DURATION FLIGHTS OF STRATOSPHERIC BALLOONS FOR THE STUDY OF HIGH ENERGY PHENOMENA Jean-Baptiste RENARDElena SERAN Gwenaël BERTHETMichel GODEFROY Valéry CATOIREFrancis VIVAT Nathalie HURET Dominique LAGOUTTE Pierre-Louis BLELLY François LEFEUVRE Jean-André SAUVAUD Aurélie MARCHAUDON François FORME Jean-Louis PINCON Claude ROBERT Torsten NEUBERT Michel TAGGER Serge SOULA

2. This is a starting project, linked with TARANIS satellite (CNES) and ASIM instrument onboard ISS (ESA) High energy phenomena in the middle and upper stratosphere above thunderstorms Discharges above thunderstorms

3. t=1.66 mst=2.06 mst=2.26 mst=2.46 mst=2.66 ms t=3.06 ms t=3.46 ms t=3.66 ms t=7.86 mst=6.26 ms t=4.66 mst=4.06 ms 40 km 45 km 50 km 55 km 60 km 65 km 70 km 75 km 80 km 40 km 45 km 50 km 55 km 60 km 65 km 70 km 75 km 80 km Fast camera imaging of a sprite

4. TARANIS and ASIM : Instruments for the measurements of Transient Luminous Events (TEL) and of Terrestrial Gamma-ray Flashes (TGF) Launch around 2012...

5. TARANIS: - cameras and photometers - X and Gamma rays detectors - measurements of high-energy electrons - measurements of electric and magnetic fieldsASIM: - observations from the lowest available orbit (350-450 km) - spectroscopic imaging mission - cameras and photometers - X and Gamma Ray detectors

6. Production of NOx (NO+NO 2 ) in the upper stratosphere by high energy phenomena, for ex. after strong solar eruption (high energy protons) Detection using satellite instruments over polar cap GOMOS onboard Envisat Nighttime measurements

7. Smaller enhancements expected during TLE/TGF events Satellite data are difficult to use for detection of such « local » NOx enhancements - Line of sight of several hundreds of km in the stratosphere (=> dilution of the absolute values of the enhancements) - Need of daytime and nighttime measurements (long persistence of the enhancements due to the absence of photochemistry)

8. Best solution : Use of instruments onboard stratospheric balloons up to altitude of 40 km Remote sensing and in-situ measurements Gondolas of ~200 kg ? Need of “long duration flights” (at least several days) to stay close to thunderstorm areas BSO (zero pressure) balloons COBRAT Project (Coupled Observations from Balloon Related to ASIM and Taranis): Measurements of stratospheric chemistry and of TLE and TGF (+ imaging measurements from ground)

9. Several gondolas with different instruments coming from different European teams - Measurements of stratospheric species by in-situ and remote sensing techniques - Detection of terrestrial gamma rays flashes - Electric fields measurements - Detection of TLE by fast cameras

10. Terrestrial Gamma-ray Flashes - Balloons can allow to perform in situ measurements - Between 20 and 40 km, good probability of detecting TGF - Use of an already existing balloon-borne instrument (that needs to be improved …) ? Electric fields measurements - Instrument needs to be defined … Detection of TLE ATLEC - Use of fast cameras ATLEC (Atmospheric Transient Luminous Event Camera) …