BY SPACEFLIGHT NOW

March 18, 2001 -- Follow the countdown and flight of the Sea Launch Zenit 3SL rocket with the first XM Satellite Radio broadcasting spacecraft. Reload this page for the very latest on the mission.

SUNDAY, MARCH 18, 2001

American motorists seeking something new from their car radios received a boost Sunday when a rocket launched from a platform in the middle of the Pacific Ocean and delivered a digital audio broadcasting satellite into orbit. full story.

2342 GMT (6:42 p.m. EST)

Ground controllers have received signals from the XM-2 spacecraft via a tracking site in Perth, Australia confirming the satellite is alive following its successful ride into space by Sea Launch.

Check back later tonight for a complete wrap-up story.

The next mission for Sea Launch will carry the XM-1 "Roll" craft in early May to complete XM Satellite Radio's orbiting network to provide coast-to-coast music, news, sports and entertainment digital audio programming directly to the cars of subscribers across America.

2339 GMT (6:39 p.m. EST)

T+plus 66 minutes. SPACECRAFT SEPARATION! XM Satellite Radio's XM-2 "Rock" satellite has been released from the Block DM-SL upper stage to complete this sixth flight for Sea Launch and the first of 2001. Contact with the craft through a ground station in Perth, Australia is expected in about five minutes to verify the satellite's health following its journey into orbit.

2333:30 GMT (6:33:30 p.m. EST)

T+plus 60 minutes. One hour since the Sea Launch Zenit 3SL rocket blasted off from the Odyssey platform in the equatorial waters of the Pacific Ocean about 1,400 miles southeast of Hawaii. Spacecraft separation is about five minutes away. The deployment will occur high above the Central Indian Ocean.

2328:30 GMT (6:28:30 p.m. EST)

T+plus 55 minutes. Cutoff of the Block DM-SL's 11D58M main engine has been confirmed. This completes the powered phase of today's launch. The stage will now coast for another 10 minutes before deploying the XM-2 satellite.

2327:30 GMT (6:27:30 p.m. EST)

T+plus 54 minutes. The Block DM-SL firing continues as planned, Sea Launch says. No problems reported. This burn is occurring high above Central Africa.

2325:30 GMT (6:25:30 p.m. EST)

T+plus 52 minutes. About 2.5 minutes remaining in this second burn of the upper stage.

2322:15 GMT (6:22:15 p.m. EST)

T+plus 48 minutes, 45 seconds. The Block DM-SL upper stage is firing again for a six-and-a-half-minute burn to accelerate XM-2 into the intended geosynchronous transfer orbit.

2321:30 GMT (6:21:30 p.m. EST)

T+plus 48 minutes. The coast period is nearing an end as the upper stage is about to reignite.

2259:30 GMT (5:59:30 p.m. EST)

T+plus 26 minutes. No problems are being reported by Sea Launch as the vehicle continues its quiet coast period above the equator.

2251:30 GMT (5:51:30 p.m. EST)

T+plus 18 minutes. The first of two firings by the Block DM-SL upper stage should have been completed to deliver the XM-2 "Rock" spacecraft into geosynchronous transfer orbit, though Sea Launch has not yet confirmed that. The mission commentator is playing PR videos at present.

The stage and attached will coast in a preliminary parking orbit around Earth for the next 30 minutes before the next firing to complete the powered phase of launch. The stage restart is due to occur at T+plus 48 minutes, 26 seconds into flight for a six-minute, six-second burn. Spacecraft deployment is scheduled for T+plus 65 minutes, 12 seconds after launch.

2246:30 GMT (5:43:30 p.m. EST)

T+plus 13 minutes. Flight of the upper stage is reported normal. Standing by for confirmation of engine shut down in the next half-minute.

2243:30 GMT (5:43:30 p.m. EST)

T+plus 10 minutes. The Russian-made Block DM-SL upper stage will fire for another three minutes or so to inject the XM-2 satellite into a preliminary parking orbit. The targeted orbit should have a low point of 180 km and high point of 990 km with an inclination of 1.25 degrees to the equator.

2242:30 GMT (5:42:30 p.m. EST)

T+plus 9 minutes. The second stage has been jettisoned and the Block DM-SL upper stage is now firing for the first of two burns.

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

T+plus 7 minutes, 30 seconds. The second stage RD-120 main engine has cut off. The vehicle is now coasting before separation of the stage in about a minute.

2239:30 GMT (5:39:30 p.m. EST)

T+plus 6 minutes. No problems have been reported in today's climb to orbit for the Sea Launch Zenit 3SL rocket with the XM-2 satellite cargo.

2238:30 GMT (5:38:30 p.m. EST)

T+plus 5 minutes. The second stage engine continue to fire. This burn will last another 2.5 minutes. Also, the Sea Launch helicopter has made an aerial inspection of the Odyssey platform with no significant damage or fires reported.

2237:30 GMT (5:37:30 p.m. EST)

T+plus 4 minutes. The payload fairing, or nose cone, of the rocket has separated. Also, NASA's Tracking and Data Relay Satellite System has acquired signal from the Block DM-SL upper stage.

2236:45 GMT (5:36:45 p.m. EST)

T+plus 3 minutes, 15 seconds. The first stage RD-171 engine has shutdown as planned and the spent stage was jettisoned. It will impact the Pacific Ocean about 800 km downrange. Ignition of the second stage engine has been confirmed.

2235:30 GMT (5:35:30 p.m. EST)

T+plus 2 minutes. The first stage engine is being throttled to ease the dynamic loads on the rocket and XM-2 satellite.

2235 GMT (5:35 p.m. EST)

T+plus 90 seconds. Zenit continues to follow the proper flight path. Velocity now 2,100 miles per hour.

2234:30 GMT (5:34:30 p.m. EST)

T+plus 60 seconds. The Zenit is passing through maximum dynamic pressure. Engine pressures reported normal.

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

T+plus 30 seconds. The Zenit rocket is pitching over to the proper trajectory with a normal flight reported.

2233:30 GMT (5:33:30 p.m. EST)

LIFTOFF! The Sea Launch Zenit 3SL rocket ascends from the Odyssey platform with the first digital audio broadcasting spacecraft for XM Satellite Radio.

2232:30 GMT (5:32:30 p.m. EST)

T-minus 1 minute. Now 60 seconds away from liftoff.

2231:30 GMT (5:31:30 p.m. EST)

T-minus 2 minutes. The engine start preparations are beginning to ready the first stage RD-171 powerplant for ignition. The Russian-made engine has four nozzles and powers the rocket for the first two minutes, 24 seconds of flight.

2229 GMT (5:29 p.m. EST)

T-minus 4 minutes and counting. Initial readiness checks of managers indicates all systems are "go" for an on-time launch. The final clearance for liftoff will begin at T-minus 1 minute. Meanwhile, the transporter/erector arm is now fully retracted to the hangar and the doors have been sealed. Also, XM-2 has switched to internal power.

2228 GMT (5:28 p.m. EST)

T-minus 5 minutes and counting. Standing by for final readiness polls.

2227 GMT (5:27 p.m. EST)

T-minus 6 minutes and counting. Today's mission will be the sixth for Sea Launch and its first of 2001.

2225 GMT (5:25 p.m. EST)

T-minus 8 minutes and counting. The automated launch sequence continues smoothly. No technical problems are being reported as the countdown continues to today's scheduled launch at 2233:30 GMT.

2223 GMT (5:23 p.m. EST)

T-minus 10 minutes and counting. The weather conditions at the launch site along the equator are well within limits for liftoff just 10 minutes from now. The skies are clear and sunny, temperature is 78.4 degrees F, with a east-northeasterly wind of 7.8 knots and 7.5-foot waves.

2221 GMT (5:21 p.m. EST)

T-minus 12 minutes and counting. The final launch danger area sweep by the Sea Launch helicopter has been completed with the zone verified clear.

2219 GMT (5:19 p.m. EST)

T-minus 14 minutes and counting. Temperature and pressure measurements are now being verified.

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

T-minus 15 minutes and counting. The launch team confirms fueling of the Zenit rocket and its Block DM-SL upper stage has been completed. Also, thousands of gallons of sea water is being pumped into the Odyssey launch platform to keep the converted oil-drilling rig stable for today's liftoff.

2216 GMT (5:16 p.m. EST)

T-minus 17 minutes and counting. The countdown is reaching a major milestone as the transporter/erector arm is retracted from against the rocket. The arm was used earlier to roll the rocket out of the environmentally-controlled hangar atop the Odyssey platform and to lift the rocket upright. Once the arm is lowered to the platform deck, it will be rolled back into the hangar and the build doors closed for launch.

2215 GMT (5:15 p.m. EST)

Sea Launch is counting down the final 18 minutes to its flight of the Zenit 3SL rocket carrying the first spacecraft for XM Satellite Radio. Sea Launch officials aboard the command and control ship located at 154 degrees West longitude on the equator report all systems are go for liftoff at 2233:30 GMT.

2015 GMT (3:15 p.m. EST)

Fueling operations have commenced aboard the Odyssey platform stationed on the equator in the Pacific Ocean for today's launch of the Zenit 3SL rocket. The vehicle is being loaded with kerosene propellant and cryogenic liquid oxygen. The platform has been cleared off all workers for this hazardous operation, with all personnel now aboard the Sea Launch Commander ship safely positioned about 3.5 miles away.

1900 GMT (2 p.m. EST)

The final hours of the countdown are underway as Sea Launch technicians ready the Zenit 3SL rocket for flight later today carrying the XM Satellite Radio "Rock" spacecraft. Sea Launch is not reporting any significant troubles and the weather forecast is favorable for the liftoff at precisely 2233:30 GMT (5:33:30 p.m. EST).

SATURDAY, MARCH 17, 2001

The Sea Launch Zenit 3SL rocket -- topped with the XM-2 radio broadcasting satellite enclosed with its nose cone -- is now pointing skyward. The Ukrainian/Russian rocket was rolled out of its horizontal hangar atop the Odyssey launch platform and erected upright today as the countdown continued to liftoff Sunday.

Odyssey and the Sea Launch Commander ship arrived on the equator at 154 degrees West in the Pacific Ocean, about 1,400 miles southeast of Hawaii, early Friday just hours after countdown clocks began ticking from the L-72 hour mark.

Sunday's available launch window extends from 2233:30 to 2318:00 GMT (5:33:30-6:18:00 p.m. EST).

We will have live reports throughout the final countdown and flight.

THURSDAY, MARCH 15, 2001

The countdown got underway Thursday for Sea Launch's planned Sunday mission to place the first digital audio relay spacecraft into orbit for XM Satellite Radio, a company that aims to broadcast music, news and entertainment programming directly to cars across America starting this summer.

The ocean-going launch platform and Commander control ship were steaming to the designed point on the equator in the Central Pacific late Thursday. Once at the site -- 154 degrees West longitude -- the vessels will begin final pre-flight preparations.

Liftoff of the Zenit 3SL rocket from the Odyssey platform with the XM-2 satellite known as "Rock" is slated for Sunday at 2233:30 GMT (5:33:30 p.m. EST). The available launch window extends to 2318:00 GMT (6:18 p.m. EST).

This mission comes two months after the XM-1 spacecraft ("Roll") was seconds from blastoff when controllers called an abort due to a minor technical concern with the craft.

The anomaly ended up being nothing significant, but the countdown was stopped at T-minus 11 seconds. The pre-ignition sequence that the first stage's Russian-built RD-171 engine goes through before launch had already started, forcing officials to refurbish the powerplant.

To do that, the rocket had to be returned from the Pacific Ocean to Sea Launch's home port in Long Beach, California, forcing at least a two-month delay. XM Satellite Radio and Boeing Satellite Systems, the manufacturer of the two craft, opted to keep the pre-launch processing for XM-2 on track for a launch in March, instead of pushing that launch back to accommodate launching the "Roll" satellite first.

With that decision to let XM-2 take priority, XM-1's launch was delayed until around May when a fresh Zenit rocket will be used.

XM-2 was delivered to Long Beach on February 14 to begin its preparations for launch at the Sea Launch home port. The spacecraft was transported from its carrier to the ground-bound Payload Processing Facility (PPF) to undergo final processing for launch and to be attached to its payload adapter and payload fairing.

The complete payload unit was then transferred on February 26 from the PPF to the Assembly and Command Ship (ACS), named the Sea Launch Commander. It was attached to the awaiting Zenit 3SL rocket in the vessel's hangar, completing the assembly of the launcher.

The Zenit 3SL was then offloaded from the Sea Launch Commander onto the Odyssey launch platform on March 3, where it will stay through launch. The rocket was lifted to the vertical position later the same day to conduct tests on the vehicle and Odyssey.

After the Zenit 3SL was stowed back into its launch platform hangar, Odyssey departed Long Beach for its equatorial launch site on the morning of March 5, followed by the Sea Launch Commander on the evening of March 7.

The 72-hour long launch countdown began at 5:33 p.m. EST Thursday evening, as the two seagoing vessels neared their destination.

Odyssey and the Sea Launch Commander were set to arrive at the oceanic launch site Thursday night. At that point, Odyssey will fill its ballast tanks with seawater to anchor the vessel and technicians will board the platform to begin final checks on the rocket and launch systems.

XM-2 is almost identical to XM-1 in weight, size, and purpose. Weighing in at 10,324 pounds at launch, the craft will feature a solar array span of 132.5 feet once fully deployed and in position in geostationary orbit at 115 degrees West longitude. From there, it will provide digital quality audio programming to cars and households using a S-band communications payload provided by Alcatel Space of France. The spacecraft bus is based on the Boeing 702 design by Boeing Satellite Systems.

Stay with Spaceflight Now for continuing updates on pre-flight preparations and live coverage of the launch. We will provide live play-by-play updates during the final countdown and mission.