BY SPACEFLIGHT NOW

February 7, 2001 -- Follow the preparations and launch of the Sicral 1 and Skynet 4F military communications satellites aboard an Arianespace Ariane 4 rocket. Reload this page for the very latest on the mission.

WEDNESDAY, FEBRUARY 7, 2001

Arianespace launched its first double military payload Wednesday, lofting a pair of communications relay satellites for the British and Italian defense ministries. Read our full launch story.

2331 GMT (6:31 p.m. EST)

MISSION SUCCESS! The Ariane 4 rocket has successfully delivered the Sicral 1 and Skynet 4F military communications satellites into orbit tonight. This marks the 61st straight success for the workhorse European launcher.

Check back later tonight for a wrap up story. Please note that our Ariane coverage was less than normal because of the launch of space shuttle Atlantis tonight.

2327 GMT (6:27 p.m. EST)

T+plus 21 minutes. The Ariane 4 rocket has achieved orbit tonight following a delayed liftoff from French Guiana. The Sicral 1 spacecraft has been released, and now the third stage is reorienting for deployment of Skynet 4F.

2311 GMT (6:11 p.m. EST)

T+plus 5 minutes. The first stage has dropped away and second stage engine is firing. The fairing has also separated.

2308 GMT (6:08 p.m. EST)

T+plus 2 minutes, 30 seconds. Liquid strap-on boosters have separated. We will update later this evening with more after the shuttle launches.

2306 GMT (6:06 p.m. EST)

LIFTOFF! Liftoff of the Ariane 4 rocket on an all-military mission for Europe.

2305 GMT (6:05 p.m. EST)

Minus-1 minute. Equipment aboard the Ariane 44L rocket is being switched off ground-supplied power and to onboard batteries for launch.

In the final seconds of the countdown, activities will include releasing the inertial platform at minus 9 seconds, and the release command to the retraction system for the two cryogenic arms will be given at Minus-5 seconds.

2304 GMT (6:04 p.m. EST)

Minus-2 minutes and counting. The third stage liquid oxygen tank has been pressurized for the launch.

2302 GMT (6:02 p.m. EST)

Minus-4 minutes and counting. The launch team is monitoring the final topping off of liquid oxygen and liquid hydrogen supplies aboard the rocket's third stage.

2300 GMT (6:00 p.m. EST)

Minus-6 minutes. The synchronized launch sequence has started, the problems are resolved. Computers are now in control of this final segment of the launch countdown.

During the next six minutes, the Ariane 44L rocket, satellite payload and ground systems will be configured for launch. There are two master computers running the countdown. One is responsible for fluids and propellants and the other for final preparation of the electrical systems such as initiating the flight program, activation of the engine steering systems and power transfer from ground supplies to onboard batteries. The computers will control until minus 5 seconds when a majority logic sequencer takes over for first stage engine start at zero seconds. Engine performance checks are done in parallel by the two computers starting at plus 2.8 seconds. Finally, the command will be issued to open the launch table clamps for liftoff between ignition +plus 4.1 and 4.6 seconds.

2254 GMT (5:54 p.m. EST)

Skynet 4F is now "go" for launch. However, Sicral needs some more time to update its onboard timing before resuming the countdown.

2251 GMT (5:51 p.m. EST)

The hold continues at Minus-6 minutes -- the point prior to starting the computer-controlled launch sequence. The count cannot be held once entering the sequence.

2241 GMT (5:41 p.m. EST)

Authorization to resume the countdown is still to come. Today's window extends until 2328 GMT (6:28 p.m. EST).

2234 GMT (5:34 p.m. EST)

Some tests have proved successful and plans call for the countdown to resume in about 15 minutes.

2226 GMT (5:26 p.m. EST)

The countdown continues to hold. There is no estimation on when the issue with Skynet 4F will be resolved.

2222 GMT (5:22 p.m. EST)

Minus-6 minutes and holding. The countdown has been stopped while engineers address a last-minute concern with the British Skynet 4F satellite payload. Today's launch window extends one hour to 2328 GMT (6:28 p.m. EST).

Meanwhile, officials have confirmed weather conditions in Kourou will be acceptable for all of today's window.

2218 GMT (5:18 p.m. EST)

Minus-10 minutes. Countdown clocks will be halted at Minus-6 minutes until the unspecified problem with Skynet 4F is resolved. There isn't any details on what the problem is, however.

2208 GMT (5:08 p.m. EST)

Minus-20 minutes. Launch team members are watching systems on the Ariane 4 rocket, spacecraft and ground support equipment. There is a problem with the Skynet 4F satellite, however.

The rocket is now fully fueled at the ELA-2 launch pad. The first and second stages and four liquid strap-on motors were loaded with storable propellants earlier this week. The third stage was filled with cryogenic liquid oxygen and liquid hydrogen over the last three hours.

2030 GMT (3:30 p.m. EST)

The Arianespace Ariane 4 rocket has entered the final hours of the countdown to launch today in French Guiana. Launch remains scheduled for 2228 GMT (5:28 p.m. EST) and extends for an hour.

We will have live updates on the final countdown and flight as best as possible today while also covering the the space shuttle launch.

0501 GMT (12:01 a.m. EST)

Two European military communications satellites are stacked atop the most powerful version of Arianespace's Ariane 4 rocket for liftoff today from the jungle launch pad in Kourou, French Guiana.

Flight 139 will have exactly one hour to get off the ground or else wait at least another 24 hours. The launch window opens at 2228 GMT (5:28 p.m. EST).

The workhorse Ariane 4 rocket will fly in the "44L" version with four liquid-fueled strap-on boosters attached to a basic three-stage core vehicle.

Final preparations are underway at the Ariane's launch site in Kourou. The Ariane 44L's first stage, second stage and four liquid-fueled boosters were filled with their storable propellant combination on Tuesday.

Positioned inside the rocket's nose cone are the two satellite payloads -- separated by the Spelda dual attach fitting -- destined for geostationary transfer orbit.

The Sicral 1 spacecraft will, for the first time, provide fully Italian-controlled space-based communications for the country's Ministry of Defense. The 5,711-pound satellite was built by an industry consortium in Italy. Alenia Spazio provided the satellite bus, FiatAvio manufactured the propulsion system and will handle launch operations, while Telespazio worked with the ground segment.

Sicral 1 is fitted with nine SHF, UHF, and EHF band transponders and, from its perch 22,300 miles above a point on the equator at 16.2 degrees East (over Congo), will have the capability to reach armed forces in Italy, the rest of Europe and the Middle East. The spacecraft is designed to operate for at least a decade. Its power-generating solar arrays will span almost 75 feet tip-to-tip.

Skynet 4F will be the sixth spacecraft in a venerable decade-old communications satellite series in place at the British Ministry of Defence. Built by Astrium, it will offer secure communications for the United Kingdom's military forces for at least 8 years through its 8 transponders. The Skynet satellites are widely used throughout the Balkans by peacekeeping forces.

The spacecraft features a mass of 3,276 pounds and will be positioned at either 1 degrees West or 6 degrees East. That point hovers above the Gulf of Guinea.

For launch, the Sicral 1 satellite will be positioned on top of the dual payload adapter and will be deployed first. On the bottom and deployed second will be Skynet 4F.

Looking ahead, the final countdown for Flight 139 will commence at 0758 GMT (2:58 a.m. EST). The service gantry surrounding the rocket will begin retracting at 1633 GMT (11:33 a.m. EST). Liquid hydrogen and liquid oxygen will begin flowing into the Ariane 4's cryogenic third stage at 1853 GMT (1:53 p.m. EST). The launcher's telemetry, radar transponder and telecommand systems will be activated and checked out at 2123 GMT (4:23 p.m. EST). If all systems are deemed "go" for launch, then the authorization for the start of the synchronized launch sequence will be given at 2222 GMT (5:22 p.m. EST). Following that milestone are a series of fast-paced events that culminate with the ignition of the liquid-fueled Viking engines on the Ariane 4's first stage and four strap-on boosters. That mark will be followed four seconds later by lift-off.

After launch, Flight 139 will take a normal ascent profile with a 2 minute, 28 second burn of the four boosters and a 3 minute, 32 second burn of the first stage. Once the first stage is jettisoned from the remaining parts of the rocket, the second stage Viking engine will come to life to continue to push to orbit. The protective payload fairing will be jettisoned just over the four-minute mark. The second stage will complete its job and the third stage will ignite just under 6 minutes into flight. Stage three will burn for over 13 minutes before shutting down and preparing for spacecraft separation. Sicral 1 will be separated at around 21 minutes after launch, followed 5 minutes later by Skynet 4F.

Flight 139 will be the 139th launch of the Ariane program. The flight will also mark the 103rd Ariane 4 launch and the 31st flight of the Ariane 44L.

Stay with Spaceflight Now throughout the day for unrivaled coverage of Flight 139 and the launch of shuttle Atlantis to the international space station.

TUESDAY, FEBRUARY 6, 2001

Arianespace officials have cleared Ariane 4 rocket with a pair of European military communications satellite for launch on Wednesday evening at 2228 GMT (5:28 p.m. EST), the opening of a one-hour window. Liftoff will take place from ELA-2 at the Guiana Space Center in Kourou, French Guiana.

Since our last update, launch preparations in Kourou have gone into full swing. On January 30, the Sicral 1 and Skynet 4F military payloads were sealed inside of the Ariane 4's payload fairing that protects the two craft during the first four minute of launch. That action was succeeded the following day by the transfer of the entire payload unit -- including the two satellites, payload fairing, and payload adapter.

Last Thursday, the composite was lowered onto and attached to the Ariane's third stage and vehicle equipment bay, which contains all the critical systems needed for a successful flight.

A final full-up launch rehearsal was conducted on Friday.

On Monday, after the launch readiness review, the Ariane 44L launcher was armed.

Looking ahead, the first stage, second stage, and the four liquid-fueled strap-on boosters will be filled with their storable hypergolic propellants, which are composed of unsymmetrical dimethyl hydrazine as the fuel and nitrogen tetroxide as the oxidizer.

The final launch countdown on Wednesday will see the cryogenic third stage being fueled with its super-cold propellant combination of liquid hydrogen and liquid oxygen.

Flight 139 is carrying two military communications satellites for the ministries of defense of Italy and the United Kingdom. Sicral 1 will serve Italy and Skynet 4F will operate for the UK.

Watch this page for continued updates on Flight 139 and live coverage of the final countdown and launch.

MONDAY, JANUARY 29, 2001

A pair of European military communications satellites are almost ready to take to the skies aboard an Ariane 4 launch vehicle that is currently undergoing final tests at its South American launch pad.

The Ariane 44L is being prepared to launch on February 7 from Guiana Space Center's ELA-2 complex in Kourou, French Guiana.

The most powerful version of the venerable European Ariane 4 launcher, the 44L features four liquid-fueled strap-on boosters.

Flight 139 is set to carry two military communications satellites for the United Kingdom and Italy.

Sicral 1 -- the first ever Italian military satellite -- will provide communications coverage for all aspects of the Italian Ministry of Defence. The spacecraft was built under an industry consortium that included such European aerospace industry giants as Alenia Spazio, FiatAvio and Telespazio.

Skynet 4F is the next satellite in a long-standing series to serve the British Ministry of Defence. The craft will relay tactical and strategic communications to and from the British military from its perch in geostationary orbit. Skynet 4F was manufactured by Astrium in Europe.

Payload processing for Flight 139 began back on October 25 when Skynet 4F arrived in Kourou to began preparations for launch. Sicral 1 arrived on December 8.

The launch campaign commenced on January 4 with the lifting of the first stage onto the mobile launch table. That action was followed by the integration of the second and third stages, as well as the four liquid-fueled boosters onto the launcher, virtually finishing the job of assembling the rocket by the third week of January.

Once testing in the launcher integration building was completed, the nearly complete Ariane 44L was rolled out to the ELA-2 launch pad along one kilometer of dual-rail tracks on January 25.

The two military satellite payloads are planned to be enclosed in their protective payload fairing and transferred to the launch pad in the next week or so, "topping off" the rocket.

Stay with Spaceflight Now throughout the remaining weeks in the launch campaign for continued reports on the status of Flight 139.