Loading of more than 20,000 gallons of RP-1 kerosene fuel into the Antares Ukrainian-built first stage is complete. Liquid oxygen continues flowing into the rocket until the final few minutes.

Engineers will soon do final checks of the rocket's flight termination system and configure that device for launch.

T-minus 29 minutes and counting. Loading of kerosene into the rocket is going well. The first stage's helium pressurant bottles are now submerged.

Chilldown is underway and all systems are reported to be in good shape for an on-time launch at 6:22 p.m. EDT (2122 GMT).

T-minus 35 minutes and counting. The team is "go" for low-flow chilldown of the main engines beginning in about five minutes.

The Wallops range is relocating personnel on nearby Assateague island to comply with safety rules regarding the rocket's debris footprint should something go wrong during launch.

The Cygnus spacecraft on this flight is carrying 2,215 kilograms, or 4,883 pounds, of supplies to the International Space Station. It measures about 16.8 feet tall, and the pressurized cargo module has a volume of about 18 cubic meters, or 635 cubic feet.

Here are some statistics on today's launch:

• 5th Antares rocket launch
• 11th orbital launch from the Mid-Atlantic Regional Spaceport
• 4th launch of a Cygnus spacecraft
• 3rd space launch from Wallops in 2014
• 20th U.S. space launch in 2014
• 68th global space launch attempt in 2014

T-minus 40 minutes and counting. The launch team will polled in a few minutes to begin low-flow chilldown of the first stage's AJ26 engines. The chilldown procedure ensures the propellant lines leading to the engines are conditioned for the shock of super-cold liquid oxygen stored at minus 298 degrees Fahrenheit.

The launch team has verified good telemetry links between the rocket and ground controllers.

T-minus 43 minutes and counting. The launch team is loading the flight trajectory file into the Antares flight computer.

The transporter-erector-launcher system, essentially a mobile launch tower next to the rocket, is being configured to pull back from the launch vehicle, the launch team reports. Gripper arms on the tower have opened from around the rocket.

The tower will retract a few degrees away from the rocket in the final seconds of the countdown.

Liquid oxygen is flowing into the Antares rocket's Ukrainian-built first stage in high-flow mode now at a rate of 150 gallons per minute.

Today's launch is carrying Orbital's fourth Cygnus spacecraft to orbit on its third operational mission.

The unmanned cargo hauler is comprised of two modules - a service and propulsion module built by Orbital Sciences and a pressurized logistics module built by Thales Alenia Space in Italy. It measures nearly 17 feet long and 10 feet in diameter.

The spacecraft features 32 thrusters built by Aerojet Rocketdyne and solar panels provided by Dutch Space, a subsidiary of EADS Astrium based in the Netherlands.

Cygnus will extend its solar panels moments after deploying from the Antares second stage about 10 minutes after liftoff. Engineers expect to get a signal from the spacecraft a moments after separation confirming that the panels have deployed.

T-minus 60 minutes and counting.

Fueling operations continue for today's liftoff at 6:22:38 p.m. EDT (2222:38 GMT). The launch window extends for 10 minutes.

Wallops regularly launches suborbital sounding rockets for scientific and engineering research purposes, and the facility has occasionally launched small satellites with Orbital Sciences Minotaur rockets.

The Virginia Commercial Space Flight Authority owns the Mid-Atlantic Regional Spaceport, which oversaw development of the launch pad used by Antares. The Commonwealth of Virginia paid for about $80 million of the $120 million cost of the launch pad, with most of the rest of the funding coming from the federal government.

Combined with the cost of the Antares hangar and a Minotaur rocket launch pad just south of the Antares facility, the MARS complex cost about $150 million.

The countdown has resumed after pre-planned hold, and liquid oxygen is now being pumped into the Antares rocket in low-flow mode.

Propellant is being pumped into the Antares rocket's first stage. About 21,000 gallons of RP-1, a high-refined rocket-grade kerosene, and about 41,000 gallons of liquid oxygen will be loaded into the first stage over the next half-hour.

The kerosene is stored at roughly room temperature and the liquid oxygen is chilled to minus 383 degrees Fahrenheit. The oxygen will slowly boil off during the countdown, and liquid oxygen continue flowing into the rocket until shortly before liftoff.

The first stage tanks are designed by Yuzhnoye and built by Yuzhmash in Ukraine based on heritage from the Zenit rocket. The liquid oxygen tank is positioned in the upper part of the 12.8-foot-diameter stage and the RP-1 tank is in the lower part of the stage.

The first stage's two AJ26 engines will consume the liquid propellant during a 3-minute, 55-second burn.

The Antares second stage, a Castor 30XL motor built by ATK, is propelled by solid fuel already loaded into the rocket.

Filling of the Ukrainian-built first stage with kerosene fuel has switched to high-flow mode. The start of liquid oxygen loading will come in the next few minutes.

Low-flow loading of RP-1 kerosene into the Antares rocket's first stage is underway.

The Antares launch team has been polled and is "go" to begin filling the rocket's first stage with liquid propellants.

Two hours until liftoff. Chilldown of the Antares rocket's liquid oxygen loading system continues to condition ground plumbing for loading of the super-cold propellant aboard the launcher's first stage later in the countdown.

With excellent conditions and a sun-splashed sky over NASA's Wallops Flight Facility, the launch weather officer predicts a 100 percent chance of acceptable weather for liftoff of the Antares rocket at 6:22:38 p.m. EDT (2222:38 GMT).

The weather team predicts broken clouds at 25,000 feet, southerly winds at 12 knots and a temperature of 67 degrees Fahrenheit at launch time.

All systems with the Antares rocket, the Cygnus spacecraft, the Wallops range, and weather are currently green.

Here's the launch timeline the Antares rocket will follow during launch.

If you will be away from your computer but would like to receive occasional launch updates, sign up for our Twitter feed to get text message updates sent to your cellphone. U.S. readers can also sign up from their phone by texting "follow spaceflightnow" to 40404. (Standard text messaging charges apply.)

The launch team has completed testing of the rocket's flight termination system, and the countdown is now moving into activating the vehicle's pyrotechnic ordnance systems in a few minutes.

The subcooler at launch pad 0A is being filled with liquid nitrogen for chilldown of the liquid oxygen loading system. This procedure conditions the launch facility's pipes for the flow of liquid oxygen, which is chilled to approximately minus 298 degrees Fahrenheit.

Testing of the rocket's telemetry links is complete, and next comes testing of the flight termination system, which would be used to destroy the launcher if it flew off course.

A poll of the launch team indicates all stations are go for chilldown of launch pad 0A's liquid oxygen loading system.

The launch countdown has resumed after officials extended a pre-planned 15-minute hold. Launch remains set for 6:22:38 p.m. EDT (2222:38 GMT) .

The launch team is powering up telemetry transmitters at this point in the countdown ahead of testing of the rocket's communications and flight termination systems.

Four hours until launch of the Antares rocket on its fourth flight in 15 months.

Cygnus time synchronization has been completed, and the launch management team has arrived on console to begin the final countdown procedures.

The launch team will soon begin the process of priming the plumbing on the launch facility for loading of super-cold liquid oxygen, which begins at about 4:52 p.m. EDT (2052 GMT).

An alignment of the rocket's guidance and navigation system has been completed.

The weather outlook for tonight's 10-minute launch window calls for a 97 percent chance of favorable conditions.

A poll of the launch team indicates all consoles are ready for prelaunch processing.

The Antares rocket's first stage thrust vector control system is being activated and checked out for flight. The steering system gimbals the first stage's two AJ26 engines to guide the rocket during the first 3 minutes, 54 seconds of flight.

Engineers confirm they are receiving telemetry from the Antares rocket and Cygnus spacecraft following power-up.

The Antares rocket's systems are now being powered up.

Ethernet testing on the Antares rocket's avionics system has been completed.

The launch team reports all battery voltages on the rocket are as expected as testing of the Antares flight computer continues in the early stages of the countdown.

The countdown began on time to begin final preps for today's 6:22 p.m. EDT (2222 GMT). blastoff of the 14-story Antares rocket from the Mid-Atlantic Regional Spaceport at NASA's Wallops Flight Facility in Virginia.

The Antares rocket will be powered up shortly around 12:30 p.m. EDT (1630 GMT), and the launch team is going through a checklist of testing to ensure all systems are in good shape. The launch pad is also scheduled to be evacuated of all personnel around 11:52 a.m. EDT (1552 GMT).

The call-to-stations for the engineers on the launch team occurred at 10:22 a.m. EDT (1422 GMT), with voice checks and opening of the prelaunch checklist at 10:37 a.m. EDT (1437 GMT).

Chilldown of the Antares liquid oxygen loading system begins at 3:07 p.m. EDT (1907 GMT) in preparation for propellant loading at 4:52 p.m. EDT (2052 GMT).

Officials scrubbed the launch of an Antares rocket with fresh supplies for the International Space Station on Monday after a boat sailed into restricted waters off Virginia's Eastern Shore, violating safety rules for a widely-anticipated launch that was expected to be visible to millions along the U.S. East Coast.

Read our full story.

Orbital now says Tuesday's launch window opens at 6:22:38 p.m. EDT (2222:38 GMT). Frank Culbertson, Orbital's executive vice president for advanced programs, said all systems were ready for liftoff tonight, except for the errant sailboat in restricted waters.

Launch time tomorrow would be at 6:19 p.m. EDT (2219 GMT).

The Antares team is now safing the rocket and backing out of countdown procedures. Later, the team will unload propellant from the rocket's liquid-fueled first stage.

SCRUB. Orbital Sciences has called off launch tonight due to a boat which strayed into restricted waters near the Antares launch site.

T-minus 12 minutes and counting. The countdown has resumed and all parameters are go for launch, except the range.

Officials are targeting liftoff at the end of tonight's launch window at 6:55:04 p.m. EDT (2255:04 GMT) if the boat is cleared in time.

T-minus 12 minutes and holding. The countdown clock has stopped to wait for the range to clear a sailboat in downrange waters.

T-minus 13 minutes and counting. The roughly five-ton Cygnus spacecraft, christened the "Deke Slayton" after the Mercury Seven astronaut, is running on internal power and is in good shape for launch.

T-minus 14 minutes and counting. The launch team is planning a hold at T-minus 12 minutes to wait for the Wallops range to clear sailboat downrange from the launch pad.

T-minus 16 minutes and counting. Another poll is coming up at T-minus 12 minutes to approve the start of a medium-flow chilldown, another step to condition the main engines for ignition.

Upper level winds are reported favorable for launch.

T-minus 20 minutes and counting.

Today's launch will fly southeast from Wallops Island, Va. Communications sites in Virginia, North Carolina and Bermuda will track the rocket during its 10-minute flight, along with support from NASA's Tracking and Data Relay Satellite System.

The Cygnus spacecraft will reach the International Space Station on Nov. 2 after launch tonight.

Loading of more than 20,000 gallons of RP-1 kerosene fuel into the Antares Ukrainian-built first stage is complete. Liquid oxygen continues flowing into the rocket until the final few minutes.

Engineers will soon do final checks of the rocket's flight termination system and configure that device for launch.

T-minus 30 minutes and counting. Loading of kerosene into the rocket is going well. The first stage's helium pressurant bottles are now submerged.

Chilldown is underway and all systems are reported to be in good shape for an on-time launch at 6:45 p.m. EDT.

T-minus 35 minutes and counting. The team is "go" for low-flow chilldown of the main engines beginning in about five minutes, pending resolution of a couple of issues, including a boat in the restricted waters downrange.

T-minus 40 minutes and counting. The launch team will polled in a few minutes to begin low-flow chilldown of the first stage's AJ26 engines. The chilldown procedure ensures the propellant lines leading to the engines are conditioned for the shock of super-cold liquid oxygen stored at minus 298 degrees Fahrenheit.

The launch team has verified good telemetry links between the rocket and ground controllers.

Liquid oxygen is flowing into the Antares rocket's Ukrainian-built first stage at a rate of 150 gallons per minute.

T-minus 45 minutes and counting. The launch team is loading the flight trajectory file into the Antares flight computer.

The Cygnus spacecraft on this flight is carrying 2,215 kilograms, or 4,883 pounds, of supplies to the International Space Station. It measures about 16.8 feet tall, and the pressurized cargo module has a volume of about 18 cubic meters, or 635 cubic feet.

Here are some statistics on today's launch:

• 5th Antares rocket launch
• 11th orbital launch from the Mid-Atlantic Regional Spaceport
• 4th launch of a Cygnus spacecraft
• 3rd space launch from Wallops in 2014
• 20th U.S. space launch in 2014
• 68th global space launch attempt in 2014

The transporter-erector-launcher system, essentially a mobile launch tower next to the rocket, is being configured to pull back from the launch vehicle, the launch team reports. Gripper arms on the tower have opened from around the rocket.

The tower will retract a few degrees away from the rocket in the final seconds of the countdown.

Today's launch is carrying Orbital's fourth Cygnus spacecraft to orbit on its third operational mission.

The unmanned cargo hauler is comprised of two modules - a service and propulsion module built by Orbital Sciences and a pressurized logistics module built by Thales Alenia Space in Italy. It measures nearly 17 feet long and 10 feet in diameter.

The spacecraft features 32 thrusters built by Aerojet Rocketdyne and solar panels provided by Dutch Space, a subsidiary of EADS Astrium based in the Netherlands.

Cygnus will extend its solar panels moments after deploying from the Antares second stage about 10 minutes after liftoff. Engineers expect to get a signal from the spacecraft a moments after separation confirming that the panels have deployed.

T-minus 60 minutes and counting.

Fueling operations continue for today's liftoff at 6:45:04 p.m. EDT (2245:04 GMT). The launch window extends for 10 minutes.

Wallops regularly launches suborbital sounding rockets for scientific and engineering research purposes, and the facility has occasionally launched small satellites with Orbital Sciences Minotaur rockets.

The Virginia Commercial Space Flight Authority owns the Mid-Atlantic Regional Spaceport, which oversaw development of the launch pad used by Antares. The Commonwealth of Virginia paid for about $80 million of the $120 million cost of the launch pad, with most of the rest of the funding coming from the federal government.

Combined with the cost of the Antares hangar and a Minotaur rocket launch pad just south of the Antares facility, the MARS complex cost about $150 million.

Kerosene fueling began a few minutes ago, and low-flow loading of liquid oxygen into the first stage has begun.

The Wallops range is now red due to a sailboat in the restricted waters offshore the launch site.

Propellant is now being pumped into the Antares rocket's first stage. About 21,000 gallons of RP-1, a high-refined rocket-grade kerosene, and about 41,000 gallons of liquid oxygen will be loaded into the first stage over the next half-hour.

The kerosene is stored at roughly room temperature and the liquid oxygen is chilled to minus 383 degrees Fahrenheit. The oxygen will slowly boil off during the countdown, and liquid oxygen continue flowing into the rocket until shortly before liftoff.

The first stage tanks are designed by Yuzhnoye and built by Yuzhmash in Ukraine based on heritage from the Zenit rocket. The liquid oxygen tank is positioned in the upper part of the 12.8-foot-diameter stage and the RP-1 tank is in the lower part of the stage.

The first stage's two AJ26 engines will consume the liquid propellant during a 3-minute, 55-second burn.

The Antares second stage, a Castor 30B motor built by ATK, is propelled by solid fuel already loaded into the rocket.

Two hours until liftoff. Chilldown of the Antares rocket's liquid oxygen loading system continues to condition ground plumbing for loading of the super-cold propellant aboard the launcher's first stage later in the countdown.

With excellent conditions and a sun-splashed sky over NASA's Wallops Flight Facility, the launch weather officer predicts a 100 percent chance of acceptable weather for liftoff of the Antares rocket at 6:45:04 p.m. EDT (2245:04 GMT).

A few high cirrus clouds could approach the launch site from the west, but otherwise clear skies are expected with west-southwest winds at the surface and favorable upper level winds.

All systems with the Antares rocket, the Cygnus spacecraft, the Wallops range, and weather are currently green.

Here's the launch timeline the Antares rocket will follow during launch.

If you will be away from your computer but would like to receive occasional launch updates, sign up for our Twitter feed to get text message updates sent to your cellphone. U.S. readers can also sign up from their phone by texting "follow spaceflightnow" to 40404. (Standard text messaging charges apply.)

The launch team has completed testing of the rocket's flight termination system, and the countdown is now moving into activating the vehicle's pyrotechnic ordnance systems in a few minutes.

The subcooler at launch pad 0A has been filled with liquid nitrogen for chilldown of the liquid oxygen loading system. This procedure conditions the launch facility's pipes for the flow of liquid oxygen, which is chilled to approximately minus 298 degrees Fahrenheit.

Testing of the rocket's telemetry links is complete, and next comes testing of the flight termination system, which would be used to destroy the launcher if it flew off course.

The launch team is holding off on flight termination system testing until the red team dispatched to the launch pad earlier to adjust a valve is clear of the facility.

A poll of the launch team indicates all stations are go for chilldown of launch pad 0A's liquid oxygen loading system.

The launch countdown has resumed after officials extended a pre-planned hold by five minutes. A second planned hold later in the countdown will be shortened to 10 minutes to keep launch targeted for 6:45:04 p.m. EDT (1845:04 GMT) .

The launch team is powering up telemetry transmitters at this point in the countdown ahead of testing of the rocket's communications and flight termination systems.

Four hours until launch of the Antares rocket on its fifth flight in 18 months.

Cygnus time synchronization has been completed, and the launch management team has arrived on console to begin the final countdown procedures.

The launch team will soon begin the process of priming the plumbing on the launch facility for loading of super-cold liquid oxygen, which begins at about 5:15 p.m. EDT (2115 GMT).

The next step in the countdown is testing of the Antares rocket's radio transmitters.

An alignment of the rocket's guidance and navigation system has been completed.

The Antares rocket has been powered up and the launch team is receiving telemetry from the launcher and the Cygnus cargo craft.

The rocket's first stage thrust vector control system is being activated and checked out for flight. The steering system gimbals the first stage's two AJ26 engines to guide the rocket during the first 3 minutes, 54 seconds of flight.

A poll of the launch team indicates all consoles are ready for prelaunch processing.

The Antares rocket has been powered up and the launch team is receiving telemetry from the launcher and the Cygnus cargo craft.

The rocket's first stage thrust vector control system is being activated and checked out for flight. The steering system gimbals the first stage's two AJ26 engines to guide the rocket during the first 3 minutes, 54 seconds of flight.

A poll of the launch team indicates all consoles are ready for prelaunch processing.

The updated weather forecast now shows a 99 percent chance of favorable conditions for this evening's launch, which is set for 6:45:04 p.m. EDT (2245:04 GMT).

The weather officer just briefed the Antares launch team, reporting he expects mostly clear skies with a few clouds at 24,000 feet, southwest winds at 3 knots, and a temperature of 61 degrees Fahrenheit at launch time.

With optimal weather expected this evening, the launch should be visible along a swath of the East Coast from the Carolinas to New England.

The countdown began on time to begin final preps for today's 6:45 p.m. EDT (2245 GMT). blastoff of the 14-story Antares rocket from the Mid-Atlantic Regional Spaceport at NASA's Wallops Flight Facility in Virginia.

The Antares rocket will be powered up shortly before 1 p.m. EDT (1700 GMT), and the launch team is going through a checklist of testing to ensure all systems are in good shape. The launch pad is also scheduled to be evacuated of all personnel around 12:15 p.m. EDT (1615 GMT).

The call-to-stations for the engineers on the launch team occurred at 10:45 a.m. EDT (1445 GMT), with voice checks and opening of the prelaunch checklist at 11 a.m. EDT (1500 GMT).

Chilldown of the Antares liquid oxygen loading system begins at 3:30 p.m. EDT (1930 GMT) in preparation for propellant loading at 5:15 p.m. EDT (2115 GMT).

A commercial Cygnus supply freighter set for launch Monday will transport a motley mix of experiments to the International Space Station, helping scientists engaged in a range of research disciplines from studying the birth of the solar system to helping astronauts survive marathon missions in space.

Read our full story.

Skywatchers along the U.S. East Coast have a chance of getting a unique light show from Monday evening’s launch of an Antares rocket from Virginia's Eastern Shore.

Read our full story.

With ideal weather predicted on Virginia's Eastern Shore for Monday's launch window, Orbital Sciences and NASA officials gave the green light this morning to continue preparations for liftoff of an Antares rocket with nearly 5,000 pounds of experiments and hardware to sustain the International Space Station.

Liftoff from NASA's Wallops Flight Facility is set for 6:45 p.m. EDT (2245 GMT) at the opening of a 10-minute window.

The 139-foot-tall rocket is standing on launch pad 0A at the Mid-Atlantic Regional Spaceport, a facility owned by the government of Virginia on NASA property.

The two-stage launcher rolled out from a horizontal integration facility Friday evening, riding a self-propelled transporter for the one-mile trip to the launch pad, where it was lifted vertical on top of the launch mount.

Workers connected the rocket and its transporter-erector-launcher system to the pad's fluid and electrical systems after it arrived.

Mike Pinkston, Orbital's program director for the Antarse rocket, said pad crews are on pace to complete preparatory work on the rocket and ground systems ahead of schedule.

Pinkston said technicians completed a combined systems test Saturday night, and workers are conducting closeouts of the launch pad Sunday, including the removal of barriers and handrails and the closure of access doors on the launch vehicle and ground facilities.

The Wallops weather team expects clear skies, light southwest winds and a temperature between 59 degrees and 63 degrees Fahrenheit for Monday's launch opportunity, which comes about a half-hour after sunset at Wallops Island, Va.

There is a 98 percent chance weather conditions will be acceptable for launch Monday, officials said.

The launch countdown will begin less than eight hours before liftoff Monday, with the opening of the Antares launch checklist at 11 a.m. EDT (1500 GMT).

The launch team will pump RP-1 and liquid oxygen propellants into the Antares rocket Ukrainian-built first stage Monday afternoon. The propellants will be consumed by the first stage's twin AJ26 main engines, which were built in Russia in the 1970s, imported to the United States and upgraded with modern systems by Aerojet Rocketdyne.

The rocket's computer-controlled terminal countdown sequence will begin three-and-a-half minutes before liftoff.

The Antares rocket's AJ26 engines will power up to more than 700,000 pounds of thrust to propel the booster away from the launch site. Breaking the speed of sound as it arcs over the Atlantic Ocean, the Antares rocket will fire its AJ26 engines for nearly four minutes before letting go of the first stage to fall back into the sea.

The launcher's payload fairing will jettison at an altitude of 81 miles -- above the dense layers of the atmosphere -- and the Antares will ignite a solid-fueled Castor 30XL upper stage motor made by ATK to send it into orbit.

The Cygnus spacecraft will deploy from the rocket about nine-and-a-half minutes into the mission, unfurl its Dutch-made solar panels, and begin its pursuit of the space station.

Officials opted to schedule the Antares launch earlier than necessary for the Cygnus spacecraft's Nov. 2 docking opportunity, choosing to give the launch team multiple launch attempts and still preserve an on-time arrival at the space station.

Orbital spokesperson Barry Beneski said the company has reserved launch opportunities with NASA's Wallops Flight Facility for Oct. 27, 28, 29 and 30.

The Cygnus spacecraft will approach the football field-sized station Nov. 2, carefully flying within 30 feet of the complex as astronauts take control of the lab’s robotic arm to reach out and capture the cargo capsule.

The spaceship will remain at the space station until around Dec. 3, when it will be released for a destructive re-entry in Earth's atmosphere with trash and other unneeded items from the space station.

Ground crews transferred an Antares rocket out of an assembly building to a launch pad on Virginia's Eastern Shore on Friday in a major step before liftoff Monday to resupply the International Space Station.

Read our full story.

Orbital Sciences Corp. is set to launch its next commercial resupply flight to the International Space Station on Monday after inspections revealed a rocket tracking station in Bermuda weathered a direct hit from Hurricane Gonzalo last week.

Read our full story.