Description of the payload

HASI is a multisensor package which has been designed to measure the physical quantities characterizing Titan's atmosphere during the descent of the HUYGENS probe in the framework of the NASA/ESA CASSINI/HUYGENS mission in November 2004.

The Comas Sola balloon campaign was conducted, in order to test the HASI hardware and software in the terrestrial atmosphere and investigate the influence of the HUYGENS probe on the electrical measurements in a real environment, and to obtain experience of the data acquisition and handling.

The gondola was named Comas Solá in honour of the Spanish astronomer who discovered the atmosphere of Titan in 1908 and consisted of a 1:1 mock-up of the HUYGENS probe carriying the HASI instrument.

The payload was suspended from the balloon by a cable with a minimum distance between balloon and gondola of 110 m. The craft had a diameter of 1.5 m and a height of 0.8 m, including the damping system, with a total weight of 137 kg. The instruments controlling the flight, GPS, temperature sensor and radar, were in a box of 2 m cube and 50 kg weight between the balloon and the gondola.

The electronic boxes and sensors were mounted to conserve the equilibrium of Comas Solá, with the Accelerometer at the centre of gravity. The temperature sensors, the pressure probe, two PWA booms and two RADAR sensors, were located outside the gondola, in the same positions as that for HUYGENS. The platform was covered by a thermal insulating medium to preserve the electronic against the extreme temperature conditions of the Earth's stratosphere.

Details of the balloon flight and scientific outcome

Launch site: Virgen del Camino Airport, León, Spain  
Balloon launched by: Centre National d'Etudes Spatiales (CNES)
Balloon manufacturer/size/composition: Zero Pressure Balloon model 35SF 35.000 m3
Balloon serial number: 35 SF Nº 67
Campaign: COMAS SOLA  
Payload weight: 545 kgs
Gondola weight: 144 kgs

The balloon was launched by dynamic method with help of an auxiliar balloon, at 10:25 on December 12, 1995.

Turning eastwards it ascended at 6 m per second up to reach the float altitude of 30174 m, at 11:57.

From there it slowly descended to 19525 m, at 13h 16m, when the balloon was cut-down and the payload descended by parachute.

After a flight of 340 km, the touch down place was in Navarra at coordinates 42º27'11N, 1º28'47W, around 4 hours after launch.

The Huygens mission at Titan was simulated by a drop test; the probe was separated from the balloon in order to descent to ground dragged by a parachute.

Measurements have been performed both in the ascending and descending phases.

The results obtained during this balloon flight not only validated the HASI performance but they also provided a reference for direct comparison with the measurements performed with the same instrument in the atmosphere of Titan.

External references and bibliographical sources

Images of the mission

Mock Up of the HUYGENS vehicle. Launch of the HUYGENS mock up with an auxiliary balloon holding the payload. Another launch phase