INFO 17-2005: Huygens Probe on Target
31 July 1995
The Cassini/Huygens mission is an intentional co-operative effort planned by NASA and ESA to explore the Saturnian System. The Cassini spacecraft consists of the Cassini Orbiter (provided by NASA) and the detachable Huygens probe (provided by ESA).In October 1997, a Titan/Centaur rocket lifting-off from Cape Canaveral will boost the spacecraft into a 6.7 year trajectory to reach Saturn. The trajectory will use two swing-bys of Venus in April 1998 and June 1999, followed by an Earth swing-by in August 1999 and a Jupiter swing-by in December 2000 to boost speed and reach Saturn in July 2004. A few months after going into orbit around Saturn, the Cassini spacecraft will release the Huygens probe for its descent through the atmosphere of Titan, the largest satellite of Saturn. The Huygens probe will measure the abundance of elements and compounds in Titan's atmosphere, the distribution of trace gases and aerosols, winds, temperature, pressure and surface state and its composition. A multi-spectral camera on the probe will provide images of the landscape of Titan.
Titan is a unique planetary body in the solar system. It has an atmosphere which is primarily nitrogen. but is also rich in hydrocarbons. Due to the vast distance of the Saturnian system from the Sun, this atmosphere is at a very low temperature, thus greatly slowing down all the chemical processes. A study of this atmosphere will throw light on the development of our own atmosphere and contribute to our understanding of the origins of life on Earth.
The Huygens probe is being developed by ESA with Aerospatiale (F) as the industrial prime contractor. Since the start of the programme in April 1990, very good progress has been made in design and hardware development.
The entry into the Titan atmosphere will result in a very high surface temperature on the probe, generated as it decelerates due to the friction of the upper atmospheric layers. After the probe has slowed down sufficiently, a system of parachutes ensures a slow descent to the surface of Titan in approximately two and a half hours. The scientific measurements can only begin after the heat shield, which is needed to protect the probe during the high temperature entry phase, has been ejected. This occurs at an altitude of around 170 km above Titan's surface.
In order to validate this complex sequence, a Balloon Drop Test was recently carried out on a full size model of the probe. The balloon carried the probe to an altitude of 36 km above the test range (ESRANGE) near Kiruna in Sweden. The probe was automatically released and all the descent control systems were operated. This test was completely successfully and the Descent Module was recovered on ground intact and functioning (pictures are available upon request).
In addition, all the environmental testing has been carried out on another model to prove the structural and thermal integrity of the probe. The Structure Thermal and Pyro Model (SIAM) of the Huygens probe was delivered to NASA's Jet Propulsion Laboratory (JPL) on 5 July, 1995 for combined testing with the Cassini spacecraft.
For the electrical systems, a special Engineering Model has been subjected to functional testing and the results to date are successful. This model will also be delivered to JPL for combined testing in the near future.
Currently, the Flight Model hardware is being delivered to Daimler Benz in Munich, by the industrial subcontractors, where integration of the Flight Probe will take place.
"The design and the production of this complex system in a relatively short time of four years has proceeded very smoothly thanks to the motivation of the European space industry", said Huygens ESA Project Manager Hamid Hassan.
The Flight Probe will be delivered to NASA/JPL in early 1997 for a launch of Cassini-Huygens on a Titan IV/Centaur rocket in October 1997.