Official mission poster. Photo: Arianespace.

A pair of European miliary reconnaissance satellites are awaiting launch from South America on Friday aboard an Arianespace Ariane 4 rocket.

Liftoff is planned for 1622 GMT (11:22 a.m. EST) from the ELA-2 launch complex in Kourou, French Guiana along South America's northeastern coastline. A 20-minute launch window will be available to get the rocket airborne.

The primary payload for Arianespace Flight 124 is the Helios 1B surveillance spacecraft built under a cooperative program between France, Italy and Spain.

The launch of Helios 1B comes four years after Helios 1A was carried into space aboard an Ariane 4.

The French Ministry of Defence is in charge of the $2 billion Helios program, with the French space agency CNES responsible for the satellites and their launches.

Matra Marconi Space built both Helios optical reconnaissance satellites, which are believed to have one-meter resolution.

The Ariane 40 rocket, the least powerful of the Ariane 4 family with no strap-on boosters, will deliver Helios 1B into a polar sunsynchronous orbit. Spacecraft separation is expected about 18 minutes and 20 seconds after liftoff.

A secondary passenger for Friday's launch is Clementine, a small experimental satellite designed to test signals intelligence technologies.

Clementine was built by Alcatel Space and Thomson, and should be released into space about 21 minutes and 53 seconds into flight.

The launch will be the 123rd for an Ariane rocket, the 8th of 1999, the 92nd Ariane 4 to be flown and the 7th for an Ariane 40 configuration vehicle.

If all goes according to plan, it will mark the 50th consecutive successful launch of an Ariane 4 rocket, establishing a new commercial record.

The current record of 49 straight successes was set in 1995 by the McDonnell Douglas Delta 2. Ariane 4 tied that record in November with the launch of GE-4.