But the outlook for tomorrow predicts only a 40 percent chance of acceptable weather due to thick clouds and disturbed conditions from a passing cold front.
The launch window outlook calls for a scattered clouds at 2,000 feet, broken decks at 4,500 and 9,000 feet, overcast skies at 23,000 feet, rain showers in the area, good visibility, easterly winds of 9 to 14 knots and a temperature of 70 degrees F.
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"This capability is critical to the U.S. military because they depend on reliable, targeted communication to complete missions and to protect service members worldwide. MUOS is designed to support those requirements by providing users narrowband communications with greater mobility, higher data rates and improved operational availability," said Mark Pasquale, Lockheed Martin vice president and MUOS program manager.
"This capability translates into higher mission success rates and greater levels of personnel safety and awareness. MUOS is imperative in equipping warfighters with the technology they need to perform their day-to-day activities, and we are working diligently to deliver MUOS to our customer. MUOS will provide initial on-orbit capability in 2012 and will achieve full operational capability in 2015, extending UHF narrowband communications availability well past 2025."
"MUOS is a next-generation narrowband military satellite communications system that supports a worldwide, multi-service population of users in the Ultra High Frequency band. As a next-generation system, MUOS offers significantly enhanced capabilities, such as increased capacity, link availability and, for the first time, UHF (satellite-based) communications on-the-move capability," said Mark Pasquale, Lockheed Martin vice president and MUOS program manager.
"In the current (with Navy's Ultra High Frequency Follow-On satellite fleet) environment, ground users must be stationary with an antenna positioned directly toward the satellites to send out information. With MUOS, not only will users be able to connect with the satellites while on-the-move, the satellites will be connected to ground-based receiving stations that provide connectivity to the Global Information Grid, enabling users to send and receive data, calls and video worldwide.
"The system transitions from a circuit switch to an all-IP dynamic network which supports on demand, ad-hoc and priority based planning. MUOS also provides users with predetermined priority which allows bandwidth to be shared efficiently."
Still calling for a few clouds at 3,000 feet, scattered clouds at 12,000 feet and broken high cirrus at 22,000 feet, possibly some isolated rain showers, good visibility, southerly winds of 10 to 15 knots and a temperature of 73 degrees F.
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The Common Core Booster stage's liquid oxygen tank is the largest tank to be filled today. It holds 48,745 gallons of cryogenic oxidizer for the RD-180 main engine.
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 perform three firings to propel the payload -- initially into a parking orbit, then into a highly elliptical intermediate orbit and eventually to the targeted geosynchronous transfer orbit this evening.
Clocks have one more built-in hold planned at T-minus 4 minutes. That pause will last 10 minutes during which time the final "go" for launch will be given. All remains targeted for liftoff at 5:46 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.
Loading of cryogenic liquid oxygen and liquid hydrogen into the Atlas 5 rocket will be getting underway a short time from now.
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Air Force meteorologists are calling for a few clouds at 3,000 feet, scattered clouds at 12,000 feet and broken high cirrus at 22,000 feet, possibly some isolated rain showers, good visibility, southerly winds of 10 to 15 knots and a temperature of 73 degrees F.
Also, testing is being conducted of the C-band system used to track the rocket as it flies downrange, the S-band system for telemetry relay from vehicle and the vehicle's internal batteries.
Depending on a payload's weight and desired orbit, mission planners add strap-on solid boosters to the United Launch Alliance-made rocket to incrementally increase the vehicle's performance.
Atlas 5 vehicles are capable of flying with as many as five boosters, an option that was employed to generate as much thrust as possible to launch NASA's New Horizons space probe bound for Pluto in 2006 and NASA's Juno to Jupiter last August. For this particular mission, the weight of MUOS drove the selection of the 551 and the plan to fire the Centaur upper stage three times instead of the usual two burns.
"Weighing nearly 15,000 pounds, MUOS 1 is the heaviest satellite launched to date by an Atlas launch vehicle. Our customers for this mission asked for a mission design that would launch this very heavy and capable satellite in a manner that would minimize the amount of energy (and propellant) that the satellite would have to consume to position itself into the final geosynchronous orbit," said Jim Sponnick, United Launch Alliance's vice president of mission operations.
"Considering all of the commodities and capabilities of the Centaur, our mission design team developed this three-burn mission profile to provide an optimal solution for the MUOS customer. The third burn accomplishes both perigee raising and a substantial reduction in the orbit inclination at an altitude of 15,000 nautical miles above the earth, which provides substantial performance benefits to the mission. The three burn mission design for MUOS provides 1,000 lbs greater lift capability than a conventional 2-burn geosynchronous transfer orbit."
The Russian RD-180 first stage main engine will ignite at T-minus 2.7 seconds, shooting a giant cloud of steam from the pad's main exhaust duct while undergoing a check to ensure its vital signs are healthy. The five strap-on solid rocket boosters are lit at T+plus 0.8 seconds, leading to liftoff at T+plus 1.1 seconds.
The combined power will send the 20-story Atlas vehicle thundering into the sky in a hurry. Its fast speed off the launch pad will be remarkably different than other Atlas 5 missions without solid boosters that appear majestically slow.
The Aerojet-made solid boosters will burn for about 90 seconds to assist the RD-180 in propelling the rocket. The SRB casings remain attached to the first stage for a few additional seconds before separating.
Once out of the discernible atmosphere, the bulbous nose cone encapsulating the MUOS payload can be shed at T+plus 3 minutes, 22 seconds. The fairing was made by Ruag Space of Switzerland.
The kerosene-fueled first stage will continue to fire until T+plus 4 minutes, 24 seconds. The bronze stage separates about six seconds later, leaving the hydrogen-fueled Centaur upper stage to ignite for a burn lasting nearly 8 minutes that will inject itself into a preliminary orbit of 90 by 337 nautical miles high, tiled 28 degrees to the equator.
Centaur completes its first burn over the central Atlantic Ocean and enters an 8-minute coast. The Pratt & Whitney Rocketdyne RL10 cryogenic engine then restarts for a firing to propel the spacecraft to the second step on its way to the planned orbit. This six-minute burn put the rocket into a 104 by 18,600 nautical mile orbit inclined 26 degrees.
Then begins a lengthy coast away from the planet for two-and-a-half hours, flying to a point about 15,000 nautical miles above the far eastern Indian Ocean where the final burn will occur.
One final push nearly two hours and 57 minutes into flight will raise the orbit's low point and reduce the inclination closer to the equator. The burn, lasting less than a minute, places the payload into a 1,870 by 19,323 nautical mile orbit at 19 degrees inclination.
The satellite separation from Centaur is expected at 8:47 p.m. EST (0147 GMT), given an on-time launch, to complete the ascent sequence.
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The thickness of the clouds and any violations to the cumulus cloud rules pose the only concerns for the weather team today.
The countdown clocks are starting to tick right now, beginning a seven-hour sequence of work that will prepare the rocket, payload and ground systems for today's blastoff at 5:46 p.m. EST (2246 GMT).
Soon the launch team will 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 C-band system used to track the rocket as it flies downrange, plus a test of the S-band telemetry relay system. The Complex 41 site will be cleared of all personnel at 2:51 p.m.
A planned half-hour hold begins at 3:06 p.m. when the count reaches T-minus 120 minutes. Near the end of the hold, the team will be polled at 3:33 p.m. to verify all is in readiness to start fueling the rocket for launch.
Supercold liquid oxygen begins flowing into the Centaur upper stage around 3:53 p.m., followed by the first stage filling around 4:06 p.m. Liquid hydrogen fuel loading for Centaur will be completed a short time later.
A final hold is scheduled at the T-minus 4 minute mark starting at 5:32 p.m. That 10-minute 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.
Today's launch window extends from 5:46 to 6:30 p.m. EST (2246-2330 GMT).
"Whether it's in vehicles, on ships, in submarines and aircraft, or simply carried by service members who are dismounted from vehicles and on the move, this system was designed to bring them voice and data communications," said Capt. Paul Ghyzel, program manager of the Navy's Communications Satellite Program Office.
"As we bring MUOS online, we'll bring up a capability that allows (users) to move around the battlespace and be able to continue to communicate over the horizon. The top requirements for the MUOS system have to with capacity, coverage and link availabilities. So we'll be providing 24-hour-a-day, 7-day-a-week global coverage."
The two mobile trailers connected to the launching platform, which were part of the convoy during this morning's rollout, soon will be hooked up to power and communications systems at the pad. These trailers provide conditioned air to the payload and communications with the rocket during the rollout and the countdown. They are protected from the blast of launch by a concrete structure on the north-side of the platform.
Within the next hour, the auto couplers between the pad and platform will be engaged to route umbilical connections from the ground to the rocket for tomorrow's fueling of the booster with cryogenic propellants.
Later today, the undercarriages used to move the mobile platform will be disconnected and the "trackmobiles" pulled free.
Ground crews will secure the rocket for a quiet evening leading into tomorrow's launch opportunity. Countdown clocks will start ticking seven hours before liftoff time.
The day's 44-minute launch window opens at 5:46 p.m. and closes at 6:30 p.m. EST.
Here's a timeline of the countdown's key events:
HR:MM..Eastern...Event T-6:20..10:46am...Countdown begins with rocket power up T-5:30..11:36am...Weather briefing T-4:55..12:11pm...Start clearing assembly building area T-4:20..12:46pm...C-band tracking beacon testing T-3:40...1:26pm...S-band telemetry link checks T-2:55...2:11pm...Establish blast danger area roadblocks T-2:20...2:46pm...Weather briefing T-2:15...2:51pm...Clear the pad T-2:00...3:06pm...T-120 minutes and holding (for 30min) T-2:00...3:31pm...Launch conductor briefing to team T-2:00...3:33pm...Readiness poll for fueling T-2:00...3:36pm...Resume countdown T-1:50...3:46pm...Centaur LOX transfer line chilldown T-1:43...3:53pm...Begin Centaur liquid oxygen loading T-1:30...4:06pm...Begin Atlas first stage LOX loading T-1:25...4:11pm...Centaur LH2 transfer line chilldown T-1:10...4:26pm...Centaur RL10 engine chilldown T-1:02...4:34pm...Begin Centaur liquid hydrogen loading T-0:40...4:56pm...FLight termination system final test T-0:16...5:20pm...RD-180 engine fuel fill sequence T-0:10...5:26pm...Weather briefing T-0:04...5:32pm...T-4 minutes and holding (for 10min) T-0:04...5:39pm...Readiness poll for launch T-0:04...5:42pm...Resume countdown T-0:00...5:46pm..LAUNCH
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Riding atop a mobile launching platform, the 206-foot-tall satellite booster is moving to Cape Canaveral's Complex 41 for the first of five launches to deploy the U.S. Navy's Mobile User Objective System. The Air Force is overseeing the launch operations for the Defense Department.
"On behalf of 3,600 employees, United Launch Alliance is very proud to be supporting our United States Air Force customer and also the U.S. Navy in the launch of the MUOS 1 satellite. The ULA team is singularly focused on ensuring critical satellites, such as MUOS 1, are safely delivered, providing critical communications capabilities to the women and men protecting our freedoms around the world," said Jim Sponnick, United Launch Alliance vice president for mission operations.
This slow half-hour drive from the 30-story Vertical Integration Facility to Cape Canaveral's Complex 41 pad uses a pair of specially-made "trackmobiles" to carry the rocket's 1.4-million pound mobile launching platform along rail tracks for the 1,800-foot trip.
The two-stage rocket and the MUOS 1 spacecraft were put together inside the assembly building in preparation for this rollout event. The Atlas 5 is designed to spend minimal time at the launch pad, which does not include a service gantry like other sites.
First motion for the rollout is targeted for 10 a.m. EST (1500 GMT). Watch this page for updates and photos!
Meanwhile, weather forecasters continue to call for an 80 percent chance of favorable conditions during Thursday's launch window that opens at 5:46 p.m. EST. The possibility of a cumulus cloud constraint poses the only concern.
The outlook at launch time includes scattered low- and mid-level clouds, some broken high cirrus, a chance of isolated showers in the area, good visibility, southerly winds of 12 to 18 knots and a temperature around 73 degrees F.
"High pressure will continue to dominate the area today through Thursday. For MLP roll this morning, south-southwest winds are expected with gusts in the low-mid teens. No lightning is expected. A cold front continues to weaken in Northern Florida bringing only a slight chance for isolated showers mainly northwest of the Cape Wednesday afternoon/evening," Air Force meteorologists report.
"On launch day, a stronger cold front enters Northern Florida. Conditions over Eastern Florida should remain favorable at T-0; however, showers and clouds will move into the area during the late evening on Thursday. Southerly winds gusting into the upper teens are expected with only a slight chance of an isolated shower in the area during the launch window. The primary concern for launch is cumulus clouds developing as the area becomes gradually unstable in advance of the approaching front in Northern Florida."
The odds are just 40 percent favorable on the backup launch opportunity available Friday as that front over the launch site then.
"In the event of a 24-hour delay, a cold front will stall in Central Florida on Friday with showers and associated cloudiness expected throughout the day. A slight chance of an isolated thunderstorm also exists associated with the front on Friday. By launch time, winds will be southwesterly gusting in the mid teens. The primary concerns for a 24-hour delay are cumulus clouds, disturbed weather and thick clouds," the latest forecast says.
Scheduled for rollout to the Cape Canaveral launch pad Wednesday morning in preparation for blastoff Thursday evening, the first Mobile User Objective System satellite, dubbed MUOS 1, will be hauled into orbit for a 15-year mission to provide communications to U.S. and allied military forces on the move.
Towering 206 feet tall and generating two-and-a-half-million pounds of thrust at launch, the rocket will place the 15,000-pound satellite into its preliminary geosynchronous transfer orbit three hours into flight.
Liftoff is scheduled for 5:46 p.m. EST (2246 GMT) aboard a United Launch Alliance Atlas 5 from the Florida spaceport's Complex 41.
Read our background story to learn more about the Atlas 5 rocket.
Officials convened today's routine meeting to examine the status of the Atlas rocket, the MUOS spacecraft, the ground support network and weather forecast.
The review culminated with formal consensus to press ahead with countdown operations starting with Wednesday's rocket rollout to the Complex 41 pad.
Thursday's liftoff is targeted for 5:46 p.m. EST, the opening of a 44-minute launch opportunity extending to 6:30 p.m. EST.
The Air Force weather forecast team still predicts fine conditions for the rollout and during the launch window.
"For MLP roll Wednesday morning, south-southwest winds are expected with gusts in the mid teens. No lightning is expected. A weak cold front pushes through Northern Florida on Wednesday bringing only a slight chance for isolated showers mainly northwest of the Cape Wednesday afternoon/evening," meteorologists reported this morning.
"On launch day, a stronger cold front enters Northern Florida. Conditions over Eastern Florida should remain favorable at T-0, however showers and clouds will move into the area during the late evening on Thursday. Southerly winds gusting into the upper teens are expected with only a slight chance of an isolated shower in the area during the launch window. The primary concern for launch is cumulus clouds developing as the area becomes gradually unstable in advance of the approaching front in Northern Florida."
The latest prediction for launch time includes scattered low- and mid-level clouds, a broken deck of high cirrus, a chance of isolated showers in the area, good visibility, southerly winds of 12 to 18 knots and a temperature around 71 degrees F.
"The team has worked tremendously hard to get us to this point and we're ready to launch MUOS 1," Jim Sponnick, ULA's vice president of mission operations, told reporters during the pre-launch news briefing today.
The Launch Readiness Review will be held Tuesday to confirm all systems are "go" for rolling the rocket out to the pad on Wednesday and entering into the countdown operations on Thursday.
Weather forecasters continue to predict an 80 percent chance of good conditions for an on-time launch Thursday, but the outlook for the backup opportunity on Friday has deteriorated to just 40 percent favorable.
"On launch day, a stronger cold front enters the Florida panhandle but conditions over Eastern Florida should remain favorable. Southerly winds gusting into the upper teens are expected with only a slight chance of an isolated shower in the area. The primary concern for launch is cumulus clouds developing as the area becomes gradually unstable in advance of the approaching front in the panhandle," forecasters reported this morning.
The latest prediction for launch time includes scattered low- and mid-level clouds, a broken deck of high cirrus, a chance of isolated showers in the area, good visibility, southerly winds of 12 to 18 knots and a temperature around 74 degrees F.
"In the event of a 24-hour delay, a cold front will stall in Central to Southern Florida on Friday with showers and associated cloudiness expected throughout the day. A slight chance of an isolated thunderstorm also exists associated with the front on Friday. By launch time, winds will be northwesterly gusting in the upper teens/low 20s. The primary concerns for a 24-hour delay are cumulus clouds, disturbed weather and thick clouds."
The 44-minute-long launch window runs from 5:46 to 6:30 p.m. EST, and the only small concern for violating the weather rules during that period is the development of cumulus clouds over Cape Canaveral.
The forecast at launch time includes scattered low and high clouds, a chance of isolated showers in the area, good visibility, southerly winds of 10 to 15 knots and a temperature around 73 degrees F.
"Today, a strong arctic high pressure will continue to move through the central plains introducing gusty northwest winds and cold, dry conditions over Eastern Florida. On Monday, the high pressure will move east of the Carolinas and winds will begin to transition to a northeasterly direction by the afternoon/evening allowing temperatures to warm somewhat but remaining well below average. High pressure dominates the area on Tuesday along with a warmer southeasterly flow," Air Force meteorologists report.
"For MLP roll Wednesday morning, south-southwest winds are expected with gusts in the mid to upper teens. No lightning is expected. A weak cold front pushes through Northern Florida with only a slight chance for showers over the Cape Wednesday afternoon/evening.
"On launch day, a stronger cold front enters the Florida panhandle but conditions over Eastern Florida should remain favorable. Southerly winds gusting into the low teens are expected with only a slight chance of an isolated shower in the area. The primary concerns for launch are cumulus clouds developing as the area becomes slowly unstable in advance of the approaching front in the panhandle."
The odds of acceptable weather on the backup launch date of Friday falls to 60 percent due to the cloud cover from the passing cold front.
"In the event of a 24-hour delay, a cold front is expected to transit the peninsula through launch day with frontal passage expected in the afternoon on Friday," forecasters say. "A threat of showers exists in advance and along the front over Central Florida during the afternoon on Friday. A slight chance of an isolated thunderstorm also exists associated with the front as it transits the area. By launch time winds will be northwesterly gusting in the upper teens/low 20s. The primary concerns for a 24-hour delay are cumulus clouds and thick clouds."
An initial run at the final 4-minute phase of the countdown was halted mid-way through to simulate a hold and recycle prior to the pretend 12:20 p.m. launch time.
After demonstrating problem resolution and turning around the countdown for another attempt, clocks were reset for a 12:43 p.m. blastoff. The second run resulted in a successful mock launch.
Activities remain on track for launching the Atlas 5 rocket with MUOS 1 next Thursday from Cape Canaveral at 5:46 p.m. EST (2246 GMT).
Read our full story.
Read our full story.
And check out this photo gallery of MUOS 1 being nestled into the Atlas rocket's launch shroud last week.
The MUOS 1 spacecraft will be brought to the VIF next week for mounting atop its launcher in preparation for blastoff on Feb. 16 to begin the long-awaited upgrade to the U.S. military's mobile communications network with dramatically improved capacity over the Navy's previous satellite constellation.
The Wet Dress Rehearsal culminated with the vehicle fully fueled to rehearse the real launch day coming on Feb. 16 to deliver the U.S. Navy's next-generation mobile communications satellite into orbit.
The countdown was halted just before the T-0 time as planned, and the launch team began exercising its hold and recycle steps to safe the rocket.
The cryogenic fuels will be offloaded this afternoon and the vehicle allowed to warm up before it is transported back to the assembly building tomorrow.
Next up in the pre-flight campaign is mounting the MUOS 1 payload atop the rocket early next week.
The fully assembled rocket with the satellite aboard will be rolled out to the Complex 41 pad the day before launch.
Fueling of the first stage and the Centaur upper stage will be getting underway shortly as the count targets a mock liftoff time of 1:00 p.m. EST for this WDR -- or Wet Dress Rehearsal.
The giant booster consisting of its bronze-colored first stage, Centaur upper stage and five strap-on solid-fuel rockets was recently assembled together atop the mobile launching platform at the Vertical Integration Facility.
This morning's rollout, which took place just after 10 a.m. EST, is part of the Wet Dress Rehearsal activities that each Atlas undergoes prior to launch. The rocket will be fully fueled tomorrow for a realistic countdown simulation.
The event is designed to iron out any problems with the hardware and exercise the launch team.
Once the simulated launch day is completed, the rocket will be rolled back to the assembly building for final pre-flight work. Attachment of the MUOS 1 satellite payload will occur next week.
Liftoff remains targeted for sunset Feb. 16 during a window opening at 5:46 p.m. EST (2246 GMT).