Follow the preparations and launch of the Orbital Sciences Pegasus rocket with NASA's HESSI solar flare research spacecraft. Reload this page for the very latest on the mission.


Solar explorer successfully launched by Pegasus rocket
After a 19-month delay, NASA's HESSI spacecraft was finally lofted into orbit Tuesday aboard an air-launched Pegasus rocket, but not without a hiccup in the countdown that forced officials to abort one attempt before succeeding a second time around. Read our full launch story.

2330 GMT (6:30 p.m. EST)

The HESSI team says the spacecraft is alive and well following its launch into orbit today. The power-generating solar arrays have been deployed and contact was established through the Berkeley ground site during a pass about an hour ago.

2109 GMT (4:09 p.m. EST)

The initial look at the orbit data shows an apogee of 600.24 km, perigee of 586.85 km and inclination of 38.023 degrees. The orbit achieved is well within the acceptable range. The pre-flight prediction was 600 km circular.

Check back a little later for an update once the status of HESSI is confirmed and a complete wrap-up story on today's launch.

2108 GMT (4:08 p.m. EST)

T+plus 9 minutes, 45 seconds. SPACECRAFT SEPARATION! NASA's High Energy Solar Spectroscopic Imager satellite has been deployed from the Orbital Sciences Pegasus rocket's third stage to complete today's launch.

The spacecraft's four solar arrays will be deployed in pairs of two over the next few minutes. First contact with HESSI is expected in about 90 minutes when the satellite passes over its prime control station at the University of California-Berkeley.

2107 GMT (4:07 p.m. EST)

T+plus 9 minutes, 30 seconds. Attitude of the rocket and performance to orbit all reported normal.

2106 GMT (4:06 p.m. EST)

T+plus 8 minutes, 45 seconds. The third stage has burned out, completed the powered phase of HESSI's launch. Orbit has been achieved. Coming up on payload deployment in about a minute.

2106 GMT (4:06 p.m. EST)

T+plus 7 minutes, 45 seconds. The solid-fueled third stage motor of Pegasus is now firing, accelerating the HESSI spacecraft to its orbit.

2105 GMT (4:05 p.m. EST)

T+plus 7 minutes, 30 seconds. The spent second stage has separated. Standing by for ignition of the upper stage.

2105 GMT (4:05 p.m. EST)

T+plus 7 minutes. Pegasus has completed the reorientation maneuver using its cold-gas thrusters.

2104 GMT (4:04 p.m. EST)

T+plus 6 minutes, 40 seconds. No problems reported as the Pegasus continues its coast phase. The vehicle is now reorienting in preparation for stage separation and third stage burn.

2103 GMT (4:03 p.m. EST)

T+plus 5 minutes. All vehicle systems are reported normal to this point in the flight. The vehicle heading on an east-northeast course above the Atlantic Ocean.

2102 GMT (4:02 p.m. EST)

T+plus 4 minutes, 30 seconds. The Pegasus rocket's onboard computer has determined the coast period will last until 7 minutes, 32.7 seconds based upon the performance of the vehicle's first two stages.

2101 GMT (4:01 p.m. EST)

T+plus 2 minutes, 50 seconds. The solid-fueled second stage has burned out. The Pegasus rocket is now in a coast period for the next four and a half minutes or so. During this time the rocket will compute the performance of the flight thus far and adjust the third stage ignition time if necessary.

2100 GMT (4:00 p.m. EST)

T+plus 2 minute, 12 seconds. The two halves of the payload fairing enclosing the HESSI satellite on the end of the Pegasus rocket has been jettisoned. Second stage continues to burn.

2059 GMT (3:59 p.m. EST)

T+plus 1 minute, 36 seconds. The first stage has separated and ignition of the Pegasus' second stage has occurred.

2059 GMT (3:59 p.m. EST)

T+plus 1 minute, 20 seconds. The solid-fueled first stage has burned out. The vehicle is now in a ballistic coast for a few seconds before the spent stage is jettisoned and the second stage ignites.

2058 GMT (3:58 p.m. EST)

T+plus 40 seconds. The Pegasus rocket is passing through maximum dynamic pressure. Attitude of the vehicle is reported normal.

2058:17 GMT (3:58:17 p.m. EST)

IGNITION. Solid motor ignition and NASA's HESSI spacecraft is finally en route to orbit to study solar flares -- the most powerful explosions in the solar system.

2058:12 GMT (3:58:12 p.m. EST)

DROP. The Orbital Sciences Pegasus rocket is away from the L-1011 aircraft.

2057:39 GMT (3:57:39 p.m. EST)

T-minus 30 seconds. The batteries for the first stage flight control fins have been activated, allowing the fins to undergo a sweep test prior to launch. The fins are used to steer the rocket during its initial climb to space.

With the batteries activated there is just 90 seconds to launch today or else an abort will be called. That is due to the limited life of the batteries.

In the final moments prior to release of Pegasus, the L-1011 carrier aircraft crew will oversee the last seconds of the countdown and flip the switch that will drop the three-stage vehicle, with the HESSI spacecraft aboard, from the belly of the jet.

2057:09 GMT (3:57:09 p.m. EST)

T-minus 1 minute and counting.

2056 GMT (3:56 p.m. EST)

T-minus 90 seconds. The carrier aircraft now achieving the proper launch heading. The Pegasus will be released in an east-northeasterly direction with a flight azimuth of 75 degrees.

2055 GMT (3:55 p.m. EST)

T-minus 2 minutes, 30 seconds. The L-1011 is in the launch box.

2055 GMT (3:55 p.m. EST)

T-minus 3 minutes. The transient power bus has gone internal and the rocket's guidance computer now in free inertial mode.

2054:09 GMT (3:54:09 p.m. EST)

T-minus 4 minutes and counting. The launch team now entering the final checklist for today's flight of the Pegasus rocket with NASA's High Energy Solar Spectroscopic Imager spacecraft.

Drop time now reset for 3:58:09 p.m. EST.

2052 GMT (3:52 p.m. EST)

NASA Launch Manager Omar Baez has completed his final pre-launch poll and all systems are "go."

2052 GMT (3:52 p.m. EST)

The Pegasus rocket's avionics are now switching from power provided by the L-1011 to internal battery power with no problems reported.

2049 GMT (3:49 p.m. EST)

T-minus 10 minutes and counting. HESSI has been verified back on internal power. Weather in drop box also confirmed "go" for launch.

2048 GMT (3:48 p.m. EST)

T-minus 11 minutes and counting. Range Safety reports the flight termination system checks are complete and good. Meanwhile, the L-1011 is now in the final sweeping turn to align with the proper flight pattern after the abort.

2046 GMT (3:46 p.m. EST)

T-minus 13 minutes and counting. The drop mechanism has been re-verifed armed and Pegasus' flight termination system is re-armed.

2044 GMT (3:44 p.m. EST)

T-minus 15 minutes and counting. The clocks have been restarted. The latest drop time projection is 3:59:06 p.m. EST.

2035 GMT (3:35 p.m. EST)

The Air Force-controlled Range, which provides communications, tracking and safety services to all Cape launches, believes the loss of communications was caused by something on the aircraft-side. The air crew reports they heard the calls from the ground. Their responses, however, were not heard on the ground.

Countdown clocks are being reset to T-minus 15 minutes and holding. Launch still targeted for 3:56 p.m.

The Pegasus and HESSI spacecraft are in good shape with no technical problems being worked.

2031 GMT (3:31 p.m. EST)

NEW LAUNCH TIME! The launch team has been polled and everyone gave a "go" to recycle the countdown and try again today. The tentative drop of Pegasus is now 3:56 p.m. EST (2056 GMT). Again, the first countdown was abort with just over two minutes to go when communications were lost with the aircraft crew. Although the communications link was restored, officials felt best to abort and try again as a precaution.

2029 GMT (3:29 p.m. EST)

The Stargazer carrier aircraft is now in the turn to begin the trek back to the drop point. There is no estimation yet on when the new drop time will be today.

2027 GMT (3:27 p.m. EST)

The Pegasus rocket has switched back to external power and is safed. The L-1011 aircraft will now go around and try again. Officials scrubbed this attempt due to the loss of communications between the ground-based launch management team and the controllers aboard the plane. Today's launch window extends to 5:21 p.m. EST.

2026:09 GMT (3:26:09 p.m. EST)

ABORT! The ground team has called the aircraft team to abort the countdown.

2024 GMT (3:24 p.m. EST)

The launch team on the ground has lost the communications link with the crew aboard the L-1011 aircraft.

2022:31 GMT (3:22:31 p.m. EST)

T-minus 6 minutes and counting. Clocks have been tweaked one more time to 3:28:31 p.m.

The Pegasus rocket's avionics are now switching from power provided by the L-1011 to internal battery power with no problems reported.

2021 GMT (3:21 p.m. EST)

Another adjust to the launch time! Drop is now planned for 3:28:45 p.m. EST based on the latest check of the L-1011 aircraft's flight path.

2018:35 GMT (3:18:35 p.m. EST)

T-minus 8 minutes and counting. The final launch readiness poll by NASA Launch Manager Omar Baez has been performed and all systems remain "go" for drop the Pegasus rocket.

2017:35 GMT (3:17:35 p.m. EST)

T-minus 9 minutes and counting. Weather conditions have been verified "go" for today's launch.

2016:35 GMT (3:16:35 p.m. EST)

T-minus 10 minutes. Checks of the flight termination system have been completed without any problems noted. The FTS would be used to destroy the Pegasus rocket should a problem arise during the launch.

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

T-minus 11 minutes. The launch time has been adjusted again. Now shooting for a 3:26:35 p.m. drop of Pegasus.

Meanwhile, the rocket's flight termination system has gone to internal power. Also, the HESSI spacecraft has switched to internal power for launch.

2014 GMT (3:14 p.m. EST)

T-minus 13 minutes and counting. The release mechanism is confirmed armed. And Pilot Rodney Boone reports the "arm" light is illuminated in the cockpit.

2012 GMT (3:12 p.m. EST)

T-minus 15 minutes and counting. The release mechanism that will drop the Pegasus rocket from the L-1011 carrier jet is now being armed. This hydraulic system involves four main hooks holding the Pegasus to the aircraft as well as a nose hook.

2010 GMT (3:10 p.m. EST)

T-minus 17 minutes and counting. One of the spacecraft ground stations -- in Goldstone, California -- is reporting it is currently down. However, there are several other stations ready to support today, so this won't be a constraint to launch.

2007 GMT (3:07 p.m. EST)

Based on the flight time of the carrier jet, the planned drop time has been adjusted to 3:27:12 p.m. EST. So the countdown has been reset, with clocks now passing the T-minus 20 minute mark.

2006 GMT (3:06 p.m. EST)

The "P-turn" point is now occurring for the L-1011. The aircraft is banking to the right, heading northwesterly for the start of a loop to turn around and head back to the drop point.

2004 GMT (3:04 p.m. EST)

A T-38 jet from Langley, Virginia, has intercepted the L-1011 over the Atlantic. The T-38 will serve as a chase plane, providing live video of Pegasus being dropped and its initial climb to space.

2002 GMT (3:02 p.m. EST)

T-minus 24 minutes and counting. The carrier aircraft has passed by the planned drop point for the Pegasus rocket today at an altitude of about 38,000 feet.

The flight crew reported smooth conditions, westerly winds from 265 degrees at 78 knots and clear skies. The plane will continue on its current westerly heading for the next few minutes before looping around and heading back to the drop point on an easterly track.

2000 GMT (3:00 p.m. EST)

The Stargazer carrier aircraft has completed the 180-degree U-turn and is now headed westerly to the drop box for today's launch. The plane will actually fly through the box before making another looping turn to head back and drop the Pegasus. See a map of the flight path.

The spacecraft team reports the battery temperature issue with HESSI, reported earlier, is not a constraint to launch.

1956 GMT (2:56 p.m. EST)

Now 30 minutes away from the scheduled drop time when the three-stage Orbital Sciences Pegasus rocket is released from L-1011 carrier aircraft above the Atlantic Ocean off the coast of Florida. Release is targeted to occur at 3:26 p.m. EST.

During an interview yesterday, Capt. Bill Weaver, the man flying the L-1011 aircraft today, described what is like to be aboard the Stargazer jet during the launch of a Pegasus rocket.

Although the countdown is controlled from the ground, the aircraft crew actually pushes the button to drop Pegasus after receiving the final "go" from the Orbital Sciences Launch Conductor.

The circuitry for the release system is armed approximately 15 minutes before the drop by the Launch Panel Operator aboard the aircraft, Weaver said. Later a switch will be flipped in the cockpit by Pilot Rodney Boone. This switch, located on the right-hand portion of the center console between the captain and pilot, "enables" the release to be become active.

In the final seconds of the countdown the Launch Conductor on the ground will call out "Drop on my mark...3, 2, 1, drop." At that point, Boone will push a button next to the enable switch, releasing the Pegasus rocket and HESSI to fall away from the L-1011 aircraft. See a photo of the drop button taken yesterday during our tour of the L-1011.

"It takes a couple seconds and then it releases," Weaver explains. "There is no doubt about it that the rocket has released. There is a tremendous reaction throughout the airplane. It weighs 52,000 pounds, so we experience an instantaneous weight loss of 52,000 pounds and the center of gravity shifts aft 10 percent, so the nose comes up in a pretty pronounced fashion, which is good because we like that for separation.

"We drop it at 39,000 feet and after the drop we end up eventually around 41,000, we gain a couple thousand feet altitude or separation and also we do about a 10 degree heading change to get out of the rocket exhaust.

"Five seconds after we drop it, (Pegasus) is about 500 feet below drop altitude and the first stage lights off and it pulls up. In the meantime, we have turned 10 degrees off the heading. By the time we roll out we can see it. We can hear it. When that rocket motor lights off it sounds like a freight train roaring underneath the plane. It is a pretty impressive event."

"We don't really see till we get out of the bank, then we have a really good view. We can see it all the way through first stage burn out, second stage ignition. We can't normally see the stage 3. One time we did at Vandenberg. Conditions were just right -- perfect sun, perfect atmosphere."

Joining Weaver and Boone aboard Stargazer today is Flight Engineer Bob Taylor and Launch Panel Operators Gary Vyhnalek and Mike Lang. The LPOs sit at a console near the front of the plane -- where you envision First Class would be -- and oversee the Pegasus and HESSI systems. See a photo of the console taken yesterday during our tour of the L-1011.

1951 GMT (2:51 p.m. EST)

The L-1011, at altitude of 33,000 feet, is now making a sweeping U-turn to the right, heading for the drop box.

1941 GMT (2:41 p.m. EST)

T-minus 45 minutes and counting. The flight path of the L-1011 today takes the jet east away from the Cape, reaching a point about approximately 100 miles off the coast. Stargazer then will make a U-turn to head west, back toward Florida, allowing the aircraft to fly through the predetermined drop box where the Pegasus rocket will be released, albeit traveling in the wrong direction. The pass through the box, however, allows the aircraft crew to verify weather conditions in the area.

After flying through the box, the aircraft will make another looping turn to head back for the box. About 90 seconds before the drop the flight crew will turn the L-1011 to the proper heading for launch -- a 75-degree azimuth from true north.

See a map of the flight path.

1929:15 GMT (2:29:15 p.m. EST)

T-minus 56 minutes, 45 seconds and counting. The "Stargazer" carrier aircraft with the Orbital Sciences Pegasus XL rocket attached to its belly just took off from the Skid Strip at Cape Canaveral Air Force Station in Florida for today's launch to place NASA's HESSI solar flare research probe into orbit. Departure was on Runway 13 -- the west-to-east approach of the strip.

This will be a 57-minute flight of the L-1011, a minute shorter than originally planned, leading to an on-time drop at 3:26 p.m. EST.

1925 GMT (2:25 p.m. EST)

The ground launch team has been polled by the Orbital Sciences Launch Conductor in preparation for the L-1011 carrier jet to depart Cape Canaveral. Takeoff time has just been adjusted to 2:29 p.m. EST, one minute later than originally planned.

1915 GMT (2:15 p.m. EST)

Good day and welcome to the start of our live play-by-play coverage of today's countdown and launch of the Pegasus rocket and HESSI spacecraft. Our updates are now coming to you live from the Mission Directors Center inside Hangar AE at Cape Canaveral Air Force Station. We are positioned in the observation gallery directly behind the senior mission managers.

At this point the L-1011 carrier aircraft is positioned on the end of the 10,000 foot runway at the Cape. NASA Launch Manager Omar Baez has just polled his team and everying is "go" for takeoff at 2:28 p.m. EST.

Read our earlier status center coverage.

Flight data file
Vehicle: Pegasus XL
Payload: HESSI
Launch date: Feb. 5, 2002
Launch window: 3:21-5:21 p.m. EST (2021-2221 GMT)
Mission staging site: Cape Canaveral, Fla.

Pre-launch briefing
Mission preview - Our story detailing the saga of multiple delays to HESSI's launch.

Launch timeline - Chart with the key events to occur during the launch.

HESSI - Facts and info on the NASA satellite being launched.

Pegasus - Overview of the air-launched Orbital Sciences rocket.

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