Artist's conception of the Helios 1B satellite in orbit. Photo: Matra Marconi Space

The primary passenger aboard Arianespace Flight 124 is Helios 1B, a European optical reconnaissance spy satellite built by Matra Marconi Space. The craft is the second to be launched under a joint defense program formed between France, Italy and Spain. The French Ministry of Defence is in charge of the Helios system, and has delegated responsibility for the space segment to French space agency CNES.

The French Missile and Space Directorate heads the overall $2 billion Helios program, the first military reconnaissance system developed in Europe. Program funding is divided with France providing 79 percent, Italy adding 14 percent and 7 percent from Spain.

The Helios 1A and 1B spacecraft are based upon Matra Marconi Space's Spot 4 Earth-observing satellite. They are 3-axis stabilized and nadir pointing. The optical reconnaissance satellites provide images with approximately one-meter resolution. Operations can be performed only during daylight and clear weather conditions.

Helios 1B facts
Service entry	Early 2000
Mass	2,500 kg
Power	2.1 kW
Design life	5 years
Orbit	Low sun-synchronous, near-polar
Resolution	Classified *
Imaging instrument	Pushbroom
Image telemetry	X band, encrypted
Telemetry/control	S band, encrypted
Attitude control/reference	Two gyros, star sensors
Control mechanisms	Hydrazine thrusters, momentum wheels, magnetic torquers
* Military observers believe the resolution is one-meter. Source: Matra Marconi Space press materials

Helios 1A was launched aboard Arianespace Flight 75 on July 7, 1995. The Ariane 40 rocket placed the satellite into a near-polar orbit with a perigee of 679 km, apogee of 682 km and inclination of 98.1 degrees to the equator. The spacecraft entered service three months later.

A follow-on pair of advanced Helios 2 satellites are under development by Matra Marconi Space, and will be based on the Spot 5 satellite design. They will feature an infrared capability to allow observations at night.

Arianespace Flight 124 will feature an Ariane Structure for Auxiliary Payloads, or ASAP, to carry a French military microsatellite into space. The upcoming mission will place the 50 kg Clementine satellite into orbit following deployment of Helios 1B.

Clementine's mission is to test technologies for military eavesdropping satellites of the future. The tiny craft was provided by Alcatel Space and Thomson to study the Earth's radioelectrical environment.

The satellite will be the second technology testbed to be launched as a precursor to the French Zenon signals intelligence satellite program. The first was Cerise, launched along with Helios 1A in 1995.