SUNDAY, DECEMBER 6, 2015
Bound for an orbital rendezvous with the International Space Station on Wednesday, a commercial Cygnus freighter was successfully launched by an Atlas 5 rocket this afternoon to restart American cargo deliveries to the research outpost.
Read our launch story.
2351 GMT (6:51 p.m. EST)
VIDEO REPLAY of today's Atlas 5 rocket launch with Cygnus.
2304 GMT (6:04 p.m. EST)
Solar array deployment confirmed aboard the Cygnus vessel. The arrays are new for this mission and circular in shape to replace the previous retangular ones.
"This is a little bit lighter, same power generation. They don't articulate. They'll be the Mickey Mouse ears. That's probably the big moment in this mission for everybody is watching those things come out," Dan Tani, former astronaut and senior director of mission and cargo operations, Orbital ATK, said before launch.
"The power is the same. The motivation was mass."
2300 GMT (6:00 p.m. EST)
Wing No. 1 is fully unfurled.
2252 GMT (5:52 p.m. EST)
Both power-generating solar wings are in the deployment process.
2246 GMT (5:46 p.m. EST)
Commanding for solar array deploy has occurred.
2235 GMT (5:35 p.m. EST)
The next Atlas 5 rocket launch from Cape Canaveral is planned for Feb. 3 at 8:49 a.m. EST (1349 GMT) to deploy the GPS 2F-12 navigation satellite.
2032 GMT (5:32 p.m. EST)
"In the 12 months since this launch was ordered, the ULA and Orbital ATK teams worked very closely together to integrate the Cygnus with the Atlas launch system, including development of a new structural adapter and also a mission design that includes a 30-minute launch window for this ISS rendezvous mission, ” said Jim Sponnick, ULA vice president, Atlas and Delta Programs.
2030 GMT (5:30 p.m. EST)
“Congratulations to the team on today’s successful launch! Partnering with Orbital ATK to launch the Cygnus resupply vehicle to the ISS for NASA, a first for ULA, marks a great achievement for the team, and has provided a critical service to the nation and to the crew on the ISS,” said Jim Sponnick, ULA vice president, Atlas and Delta Programs. “This mission is delivering more than 7,000 pounds of cargo including supplies for the crew and critical materials supporting science and research investigations.”
2210 GMT (5:10 p.m. EST)
This was the 131st successful Atlas program launch in a row spanning more than two decades and the 60th for an Atlas 5.
2208 GMT (5:08 p.m. EST)
It was a "magnificent ride to orbit", says Frank Culbertson, former space shuttle and station astronaut and now Orbital ATK's Space Systems Group president.
2206 GMT (5:06 p.m. EST)
T+plus 21 minutes, 5 seconds. SPACECRAFT SEPARATION! The Centaur upper stage has deployed the Orbital ATK's commercial Cygnus resupply ship destined to deliver over 7,000 pounds of cargo to the International Space Station some 60 hours from now.
2204 GMT (5:04 p.m. EST)
T+plus 20 minutes. Good performance from the vehicle has resulted in a nominal orbit being achieved.
2203 GMT (5:03 p.m. EST)
T+plus 18 minutes, 17 seconds. MECO. Centaur's main engine has shut down following the prime burn today, achieving orbit for Cygnus to intercept the International Space Station on Wednesday morning.
2202 GMT (5:02 p.m. EST)
T+plus 17 minutes, 15 seconds. Everything looking normal with one minute to go in this burn.
2201 GMT (5:01 p.m. EST)
T+plus 16 minutes. Speed now over 16,000 mph.
2159 GMT (4:59 p.m. EST)
T+plus 15 minutes, 30 seconds. RL10 engine parameters still look good.
2157 GMT (4:57 p.m. EST)
T+plus 13 minutes. Centaur remains on course and looking good.
2156 GMT (4:56 p.m. EST)
T+plus 12 minutes, 15 seconds. About six minutes are left in this burn of Centaur.
2154 GMT (4:54 p.m. EST)
T+plus 10 minutes. All systems reported stable as the Centaur fires to reach an initial Earth orbit for Cygnus.
2153 GMT (4:53 p.m. EST)
T+plus 9 minutes. Centaur performance is reported right on target.
2151 GMT (4:51 p.m. EST)
T+plus 7 minutes. The rocket is tracking right down the planned flight path.
2149 GMT (4:49 p.m. EST)
T+plus 5 minutes. Centaur engine readings look good as this burn gets underway.
2149 GMT (4:49 p.m. EST)
T+plus 4 minutes, 50 seconds. The two halves of the four-meter-diameter Atlas 5 rocket nose cone encapsulating the spacecraft have separated.
2149 GMT (4:49 p.m. EST)
T+plus 4 minutes, 37 seconds. Centaur has ignited! The RL10C-1 engine is up and running at full thrust to power the vehicle into orbit.
2149 GMT (4:49 p.m. EST)
T+plus 4 minutes, 25 seconds. The Atlas 5's Common Core Booster has been jettisoned, completing the first stage of flight, and the Centaur upper stage's liquid hydrogen and liquid oxygen systems are being readied for engine start.
2149 GMT (4:49 p.m. EST)
T+plus 4 minutes, 18 seconds. BECO. Booster Engine Cutoff is confirmed as the RD-180 powerplant on the first stage completes its burn. Standing by to fire the retro thrusters and separate the spent stage.
2148 GMT (4:48 p.m. EST)
T+plus 3 minutes, 45 seconds. Atlas now weighs just a quarter of what it did at liftoff.
2147 GMT (4:47 p.m. EST)
T+plus 2 minutes, 45 seconds. Reaction control system has been activated.
2147 GMT (4:47 p.m. EST)
T+plus 2 minutes, 35 seconds. Atlas continues tracking on course.
2147 GMT (4:47 p.m. EST)
T+plus 2 minutes, 30 seconds. Atlas now weighs half of what it did at liftoff.
2147 GMT (4:47 p.m. EST)
T+plus 2 minutes, 15 seconds. Vehicle systems looking good.
2146 GMT (4:46 p.m. EST)
T+plus 1 minutes, 45 seconds. The RD-180 main engine continues to fire normally, burning a mixture of highly refined kerosene and liquid oxygen.
2146 GMT (4:46 p.m. EST)
T+plus 95 seconds. Now passing through the region of maximum aerodynamic pressure on the vehicle as its accelerates through the dense lower atmosphere.
2146 GMT (4:46 p.m. EST)
T+plus 85 seconds. All looks good aboard Atlas as it passes Mach 1.
2145 GMT (4:45 p.m. EST)
T+plus 60 seconds. Cygnus is racing to the International Space Station for rendezvous on Wednesday.
2145 GMT (4:45 p.m. EST)
T+plus 40 seconds. The Atlas 5 has maneuvered on course to take aim on the International Space Station.
2145 GMT (4:45 p.m. EST)
T+plus 15 seconds. The Atlas 5 rocket has cleared the tower on 860,000 pounds of thrust from the RD-180 main engine. Pitch, yaw and roll maneuvers are underway to put the rocket on the proper heading.
2144:57 GMT (4:44:57 p.m. EST)
LIFTOFF! Liftoff of Atlas 5 with the Cygnus cargo ship, restarting America's commercial resupply of the International Space Station!
2144 GMT (4:44 p.m. EST)
T-minus 20 seconds. "Go Atlas" and "Go Centaur" was just called by launch team during a final status check.
2144 GMT (4:44 p.m. EST)
T-minus 40 seconds. Centaur's liquid oxygen and liquid hydrogen tanks are stable at flight pressures.
2143:57 GMT (4:43:57 p.m. EST)
T-minus 1 minute. Now 60 seconds from liftoff. At the time of launch, the space station will be flying just off the east coast of the U.S.
2143 GMT (4:43 p.m. EST)
T-minus 90 seconds. The safety system has been armed.
2143 GMT (4:43 p.m. EST)
T-minus 1 minute, 45 seconds. Liquid oxygen and liquid hydrogen propellant topping to the Centaur upper stage is being secured.
2143 GMT (4:43 p.m. EST)
T-minus 1 minute, 55 seconds. The launch sequencer has been commanded to start.
2142:57 GMT (4:42:57 p.m. EST)
T-minus 2 minutes. The Atlas first stage and Centaur upper stage are now switching from ground power to internal batteries.
2142 GMT (4:42 p.m. EST)
T-minus 2 minutes, 30 seconds. The first stage RP-1 kerosene fuel tank and the liquid oxygen have stepped up to proper flight pressure levels.
2141:57 GMT (4:41:57 p.m. EST)
T-minus 3 minutes. The Atlas first stage liquid oxygen replenishment is being secured so the tank can be pressurized for launch.
2141 GMT (4:41 p.m. EST)
T-minus 3 minutes, 50 seconds. The ground pyrotechnics have been enabled.
2140:57 GMT (4:40:57 p.m. EST)
T-minus 4 minutes and counting. Clocks have resumed for the final minutes of today's countdown to launch the Atlas 5 rocket carrying Cygnus resupply ship for the space station.
2139:57 GMT (4:39:57 p.m. EST)
Countdown clocks will resume in one minute.
2138 GMT (4:38 p.m. EST)
The ULA launch director has given the permission to fly today.
2138 GMT (4:38 p.m. EST)
Polling of the team by Atlas launch conductor has occurred. All systems are reported "go" to continue with the countdown for liftoff at 4:44:57 p.m. EST.
2134 GMT (4:34 p.m. EST)
Standing by for the launch team readiness polls.
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2129 GMT (4:29 p.m. EST)
Cygnus is on internal power and go for launch.
2123 GMT (4:23 p.m. EST)
The Cygnus freighter nestled inside the nose of the Atlas 5 rocket is switching to internal power for launch.
2120 GMT (4:20 p.m. EST)
No problems being reported by the launch team. Countdown continues to sit in the hold period at T-minus 4 minutes, waiting for the launch window to open at 4:44 p.m. EST.
2117 GMT (4:17 p.m. EST)
Weather remains GO for liftoff based on the current conditions and expected to stay favorable for a 4:44 p.m. EST launch today.
2114:57 GMT (4:14:57 p.m. EST)
Thirty minutes from liftoff of the Atlas 5 rocket on its first mission for the International Space Station.
2110:57 GMT (4:10:57 p.m. EST)
T-minus 4 minutes and holding. The countdown has entered the planned 30-minute hold to give the launch team a chance to review all systems and assess the weather before pressing ahead with liftoff.
2109 GMT (4:09 p.m. EST)
T-minus 5 minutes. Standing by to go into the final built-in hold.
2104:57 GMT (4:04:57 p.m. EST)
Now 40 minutes till launch. Rumbling away from the planet on nearly a million pounds of thrust, the Atlas 5 rocket will be flying in a basic, two-stage configuration without any added strap-on solid motors. The vehicle sports an aluminum, 14-foot-diameter nose cone that encapsulates the Cygnus spacecraft during the atmospheric ascent before being shed.
With the liftoff thrust not considerably more than the rocket's weight, this Atlas will display a slow and majestic rise trailing only a flickering golden flame from its RD-180 main engine.
Once above the launch pad, the rocket sets sail for the trek over the Atlantic Ocean, constantly gaining speed as its double-nozzle engine gulps 25,000 gallons of kerosene fuel and 50,000 gallons of superchilled liquid oxygen in just four-and-a-half minutes.
The bronze first stage, its propellants depleted and job now completed, then jettisons with the help of tiny thrusters. Some 106.5 feet long and 12.5 feet around, the stage is discarded to fall back into the open sea.
The cryogenic Centaur upper stage ignites moments after shedding the lower booster, lighting the RL10 engine to continue clawing toward orbit.
Covered with insulating foam, this stage stretches 41.5 feet in length and 10 feet in diameter. Centaur must perform a lengthy burn to loft Cygnus into the proper orbit around the planet.
2054:57 GMT (3:54:57 p.m. EST)
Today marks the 60th flight for Atlas 5, born of the Air Force's competition to develop next-generation Evolved Expendable Launch Vehicles. In its previous 59 missions since debuting in August 2002, the Atlas 5 has flown 23 flights dedicated to the Defense Department, 12 for NASA, 12 with spy satellites for the National Reconnaissance Office and 12 commercial missions with communications and Earth-observing spacecraft.
2051 GMT (3:51 p.m. EST)
The weather officer has amended his forecast with some low clouds drifting into the area. The outlook predicts broken decks of clouds at 1,900 and 30,000 feet, isolated coastal showers, good visibility, northerly winds of 18 gusting to 22 knots and a temperature of 71 degrees F.
The wind limit today is 23 knots.
2044:57 GMT (3:44:57 p.m. EST)
Now 60 minutes from liftoff. Fueling of the Atlas rocket with cryogenic liquid oxygen and liquid hydrogen is complete as the countdown continues as planned for a liftoff at 4:44:57 p.m. EST.
2040 GMT (3:40 p.m. EST)
Fast-filling of the first stage liquid oxygen tank has been completed. Topping mode is now underway.
2036 GMT (3:36 p.m. EST)
The liquid hydrogen tank in the Centaur upper stage just reached the 96 percent level. Topping is now beginning.
2030 GMT (3:30 p.m. EST)
The first stage liquid oxygen has reached the 80 percent level.
2026 GMT (3:26 p.m. EST)
Centaur's liquid hydrogen tank is 30 percent full. The cryogenic propellant will be consumed with liquid oxygen by the stage's Aerojet Rocketdyne-made RL10 engine.
2017 GMT (3:17 p.m. EST)
Chilldown of the liquid hydrogen system has been accomplished. The launch team has received the "go" to begin filling the Centaur upper stage with the supercold fuel.
2015 GMT (3:15 p.m. EST)
Half of the Atlas liquid oxygen tank has been filled so far.
2007 GMT (3:07 p.m. EST)
First stage liquid oxygen tank is 30 percent full thus far. Chilled to Minus-298 degrees F, the liquid oxygen will be used with RP-1 kerosene by the RD-180 main engine on the first stage during the initial four minutes of flight today. The 25,000 gallons of RP-1 were loaded into the rocket Wednesday.
2004 GMT (3:04 p.m. EST)
Upper stage liquid oxygen has reached flight level.
1958 GMT (2:58 p.m. EST)
The Centaur liquid oxygen tank reached the 96 percent level. The topping off process is starting now.
1957 GMT (2:57 p.m. EST)
The first stage liquid oxygen flow rate is switching from slow-fill to fast-fill mode.
1954 GMT (2:54 p.m. EST)
The chilldown conditioning of liquid hydrogen propellant lines at Complex 41 is starting to prepare the plumbing for transferring the Minus-423 degree F fuel into the rocket. The Centaur holds about 12,700 gallons of the cryogenic propellant.
1953 GMT (2:53 p.m. EST)
Three-quarters of the Centaur liquid oxygen tank has been filled so far.
1948 GMT (2:48 p.m. EST)
The chilldown conditioning of the systems for the first stage liquid oxygen tank have been completed. And a "go" has been given to begin pumping supercold liquid oxygen into the Atlas 5's first stage.
The Common Core Booster stage's liquid oxygen tank is the largest tank to be filled today. It holds 49,000 gallons of cryogenic oxidizer for the RD-180 main engine.
1945 GMT (2:45 p.m. EST)
Learn more about the process United Launch Alliance uses to fuel Atlas 5 rockets.
1940 GMT (2:40 p.m. EST)
The Centaur liquid oxygen tank has reached the 20 percent mark.
1932 GMT (2:32 p.m. EST)
Filling of the Centaur upper stage with about 4,150 gallons of liquid oxygen has begun at Cape Canaveral's Complex 41 following the thermal conditioning of the transfer pipes.
The liquid oxygen -- chilled to Minus-298 degrees F -- will be consumed during the launch by the Centaur's single RL10 engine along with liquid hydrogen to be pumped into the stage a little later in the countdown. The Centaur will provide the thrust to put Cygnus into orbit.
1925 GMT (2:25 p.m. EST)
The Centaur liquid oxygen pad storage area has been prepped. The next step is conditioning the transfer lines, which is now beginning to prepare the plumbing for flowing the cryogenic oxidizer.
1914:57 GMT (2:14:57 p.m. EST)
T-minus 2 hours and counting! The launch countdown is continuing on schedule for today's flight of the Atlas 5 rocket to deploy the Cygnus cargo freighter for Orbital ATK.
Clocks have one more built-in hold planned at T-minus 4 minutes. During that pause the final "go" for launch will be given. All remains targeted for liftoff at 4:44:57 p.m. EST from Cape Canaveral's Complex 41.
In the next couple of minutes, chilldown thermal conditioning of the mobile launch platform upon which the rocket stands will begin. This is meant to ease the shock on equipment when supercold cryogenic propellants start flowing into the rocket.
1912 GMT (2:12 p.m. EST)
After briefing his team on procedures before entering into the final two hours of the countdown, the launch conductor at the Atlas Spaceflight Operations Center just held a pre-fueling readiness poll.
All console operators reported a "ready" status.
The ULA launch director also voiced approval for proceeding with the countdown.
Loading of cryogenic liquid oxygen and liquid hydrogen into the Atlas 5 rocket will be getting underway a short time from now.
1905 GMT (2:05 p.m. EST)
Man stations for cryogenic tanking. That's the word to the launch team.
1900 GMT (2:00 p.m. EST)
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1844:57 GMT (1:44:57 p.m. EST)
T-minus 2 hours and holding. The countdown has just entered the first of two planned holds over the course of the day that will lead to the 4:44:57 p.m. EST launch of the Atlas rocket. The holds give the team some margin in the countdown timeline to deal with technical issues or any work that is running behind. The final hold is scheduled to occur at T-minus 4 minutes.
1830 GMT (1:30 p.m. EST)
The weather outlook at Cape Canaveral continues to improve after days of cloudy, windy conditions. There's now a 70 percent chance of acceptable launch weather today.
Skies are partly cloudy, the radar is free of showers and winds have dropped off.
The outlook predicts a scattered clouds at 2,500 and 30,000 feet, isolated coastal showers, good visibility, north-northeasterly winds of 16 gusting to 20 knots and a temperature of 73 degrees F.
1829 GMT (1:29 p.m. EST)
Crews are departing the launch pad following completion of all hands-on work today. Fueling operations for the launch vehicle will be starting in about an hour.
1700 GMT (12:00 p.m. EST)
The early portion of the countdown has been going very well today. There's no issues being reported in the count and activities are on schedule.
1523 GMT (10:23 a.m. EST)
In today's first weather briefing to mission managers, the odds for the launch window stand at 40 percent favorable. Winds have eased to an acceptable range so far this morning. Meteorologists will be watching ground winds and cumulus clouds coming off the ocean during the launch window.
The outlook predicts a broken decks of clouds at 2,500 and 30,000 feet, isolated coastal showers, good visibility, northeasterly winds of 18 gusting to 22 knots and a temperature of 73 degrees F.
In summary, things look much improved today.
1424:57 GMT (9:24:57 a.m. EST)
The fourth countdown just began for the United Launch Alliance Atlas 5 rocket and the commercial Orbital ATK Cygnus cargo freighter to intercept the International Space Station from Cape Canaveral.
Uncooperative weather has been the problem the last three straight days, forcing the repeated scrub of the mission to deliver supplies to the station.
Clocks are picking up the seven-hour sequence of work that will prepare the booster, payload and ground systems for blastoff.
The available launch opportunities today:
* 4:44:57 p.m. EST
* 4:52:27 p.m. EST
* 4:59:57 p.m. EST
* 5:07:27 p.m. EST
* 5:14:57 p.m. EST
There is a 40 percent chance of allowable weather. Ground winds and cumulus clouds are the worries yet again.
The launch team will soon begin powering up the rocket to commence standard pre-flight tests. Over the subsequent few hours, final preps for the Centaur's liquid oxygen and liquid hydrogen systems will be performed, along with a test of the rocket's guidance system and the first stage propulsion and hydraulic preps, internal battery checks and testing of the GPS metric tracking system used to follow the rocket as it flies downrange, plus a test of the S-band telemetry relay system.
A planned 30-minute hold begins when the count reaches T-minus 2 hours. Near the end of the hold, the team will be polled to verify all is in readiness to start fueling the rocket for launch.
Supercold liquid oxygen begins flowing into the Centaur upper stage, followed by the first stage filling. Liquid hydrogen fuel loading for Centaur will be completed a short time later.
A final 30-minute hold is scheduled at the T-minus 4 minute mark. That pause will give everyone a chance to finish any late work and assess the status of the rocket, payload, Range and weather before proceeding into the last moments of the countdown.
SATURDAY, DECEMBER 5, 2015
1851 GMT (1:51 p.m. EST)
SCRUB. Blustery winds buffeting Cape Canaveral, and little-to-no hope for improvement by launch time, will postpone liftoff of the United Launch Alliance Atlas 5 rocket with Orbital ATK's commercial Cygnus cargo ship for the International Space Station until Sunday.
The decision was just announced that today's countdown will be suspended. This is a continuation of uncooperative weather that had delayed the launch Thursday and Friday, too.
Liftoff is re-scheduled for Sunday at the opening of a 30-minute launch window at 4:44:56 p.m. EST (2144:56 GMT). That would propel Cygnus on a path to rendezvous with the International Space Station on Wednesday.
The weather for Sunday's launch opportunity calls for a 40 percent chance of allowable conditions, with broken decks of low- and high-level clouds, coastal showers and northeasterly winds of 18 gusting to 22 knots. Winds and cumulus clouds will be the concerns.
If the launch does not go on Sunday, a liftoff on Monday or later in the week would likely require the Cygnus freighter to loiter in orbit for some unspecified number of days before it could approach the station.
That is because the crew will be busy with the comings and goings of Russian Soyuz spacecraft. Part of the crew lands next Friday and another three-man team launches and docks on Dec. 15.
The weather outlook for a Monday's launch opportunity at 4:22 p.m. EST (2122 GMT) calls for a 70 percent chance of favorable conditions.
1827 GMT (1:27 p.m. EST)
To recap what has transpired today, there was a technical problem that delayed powerup of the first stage. That issue has now been resolved and the vehicle is powered and proceeding through standard countdown activities, but the time used to troubleshoot the problem has pushed the liftoff time to 5:33:09 p.m. EST (2233:09 GMT).
There will be just one opportunity to launch the Atlas 5 rocket today because a COLA, or collision avoidance period, has eliminated the other opportunity that had been available at the end of the launch window.
Meanwhile, the winds remain strong and the forecast calls for just a 20 percent chance of acceptable conditions for liftoff.
1822 GMT (1:22 p.m. EST)
Based on the adjusted countdown, the built-in holds will last for four minutes at T-minus 2 hours and six minutes at T-minus 4 minutes. The team reports it can manage those times and the launch director have given his permission to proceed as a result.
1810 GMT (1:10 p.m. EST)
NEW LAUNCH TIME. Given the delays in the countdown, liftoff is reset for 5:33:09 p.m. EST (2233:09 GMT).
That will be the one and only launch attempt for today. The closure of the launch window is unavailable because a collision avoidance blackout period due to an object already in space.
1807 GMT (1:07 p.m. EST)
The technical issue appears to be resolved and the launch team is proceeding with power up.
1751 GMT (12:51 p.m. EST)
The countdown clocks have been stopped again.
1730 GMT (12:30 p.m. EST)
T-minus 4 hours, 25 minutes and counting. Clocks have resumed while troubleshooting the voltage problem continues.
1645 GMT (11:45 a.m. EST)
T-minus 4 hours, 25 minutes and holding. The countdown has been stopped while the launch team evaluates a technical issue. The two built-in holds later in the countdown will be shortened to make up the time and still meet the opening of the launch window.
1550 GMT (10:50 a.m. EST)
In today's first weather briefing to mission managers, the odds for the launch window stand at 20 percent favorable and there's not a lot of optimism conditions will get much better this afternoon. Meteorologists will be watching ground winds, which are forecast to be even stronger than last night, and cumulus clouds coming off the ocean during the launch window.
The outlook predicts a broken decks of clouds at 2,500 and 30,000 feet, coastal showers, good visibility, northeasterly winds of 26 gusting to 30 knots and a temperature of 72 degrees F.
1450:39 GMT (9:50:39 a.m. EST)
After two straight days of weather problems preventing liftoff from Cape Canaveral, the third countdown just started for today's rescheduled launch of the Atlas 5 rocket and the Cygnus cargo freighter bound for a Wednesday rendezvous with the International Space Station.
"Hard couple of days. Could not be more proud of our launch team. Consummate professionals," United Launch Alliance president Tory Bruno tweeted last night.
Clocks are picking up the seven-hour sequence of work that will prepare the booster, payload and ground systems for blastoff.
The available launch opportunities today:
* 5:10:39 p.m. EST
* 5:18:09 p.m. EST
* 5:25:39 p.m. EST
* 5:33:09 p.m. EST
* 5:40:39 p.m. EST
But there is only a 20 percent chance of allowable weather today, according to Air Force meteorologists' latest update this morning. Ground winds and cumulus clouds are the problem.
The launch team will soon begin powering up the rocket to commence standard pre-flight tests. Over the subsequent few hours, final preps for the Centaur's liquid oxygen and liquid hydrogen systems will be performed, along with a test of the rocket's guidance system and the first stage propulsion and hydraulic preps, internal battery checks and testing of the GPS metric tracking system used to follow the rocket as it flies downrange, plus a test of the S-band telemetry relay system.
A planned 30-minute hold begins when the count reaches T-minus 2 hours. Near the end of the hold, the team will be polled to verify all is in readiness to start fueling the rocket for launch.
Supercold liquid oxygen begins flowing into the Centaur upper stage, followed by the first stage filling. Liquid hydrogen fuel loading for Centaur will be completed a short time later.
A final 30-minute hold is scheduled at the T-minus 4 minute mark. That pause will give everyone a chance to finish any late work and assess the status of the rocket, payload, Range and weather before proceeding into the last moments of the countdown.
FRIDAY, DECEMBER 4, 2015
Here's a look at the updated odds of acceptable launch weather conditions at Cape Canaveral for the Atlas 5 rocket over the next few days. The Air Force meteorologists predict:
* 30 percent favorable conditions on Saturday, with 30-minute window opening at 5:10 p.m. EST (2210 GMT), due to ground winds and cumulus clouds.
* 40 percent favorable conditions on Sunday, with 30-minute window opening at 4:44 p.m. EST (2144 GMT), due to ground winds and cumulus clouds.
* 70 percent favorable conditions on Monday, with 30-minute window opening at 4:22 p.m. EST (2122 GMT), due to cumulus clouds.
Thursday evening's launch attempt was scrubbed by persistent rain and clouds. Friday's shot was thwarted by ground winds.