SpaceX says the splashdown occurred at approximately 3:38 p.m. EDT (1938 GMT).
There are no updates from SpaceX yet confirming a good parachute deployment.
At this time, the unpressurized trunk of the Dragon spacecraft should have separated from the ship's entry capsule. The trunk will burn up in the atmosphere.
Dragon is carrying more than 1.6 tons of cargo from the space station in its pressurized cabin. The capsule is the only robotic cargo freighter able to retrieve equipment from the space station and return it to Earth for analysis or repairs.
About a dozen SpaceX engineers and technicians are at the splashdown site, which lies about 265 miles west of Baja California southwest of San Diego.
The SpaceX crew includes a four-person dive team to help retrieve the capsule after splashdown.
Ignition of the capsule's thrusters is set for 2:43:07 p.m. EDT (1843:07 GMT) for an appoximately 10-minute deorbit burn. Splashdown 265 miles west of Baja California is scheduled for 3:39:38 p.m. EDT (1939:38 GMT).
NASA Television coverage of the Dragon resupply flight has ended. No live video is expected of the Dragon's splashdown, but you can check back here for updates on the status of the mission as we receive information.
You can also follow us on Twitter to get periodic updates.
Ignition of the capsule's thrusters is set for 2:43:07 p.m. EDT (1843:07 GMT) for an appoximately 10-minute deorbit burn. Splashdown 265 miles west of Baja California is scheduled for 3:39:38 p.m. EDT (1939:38 GMT).
NASA Television coverage of the Dragon resupply flight has ended. No live video is expected of the Dragon's splashdown, but you can check back here for updates on the status of the mission as we receive information.
You can also follow us on Twitter to get periodic updates.
The spacecraft are flying over the southern Gulf of Thailand right now.
The Dragon's laser rendezvous sensor is reported to be operating as planned.
Astronaut Reid Wiseman will command the arm to release the capsule at 9:57 a.m. EDT (1357 GMT), while Russian cosmonaut Barry "Butch" Wilmore will assist. The duo will man a communications panel to issue commands to Dragon if necessary.
The crew will monitor the spacecraft until it exits the so-called keep-out sphere 200 meters around the space station.
Astronaut Reid Wiseman will command the arm to release the capsule at 9:57 a.m. EDT (1357 GMT), while Russian cosmonaut Barry "Butch" Wilmore will assist. The duo will man a communications panel to issue commands to Dragon if necessary.
The crew will monitor the spacecraft until it exits the so-called keep-out sphere 200 meters around the space station.
Closing out a five-week mission, a SpaceX Dragon cargo craft will depart the International Space Station on Saturday and dive back into Earth's atmosphere, deploy parachutes and splash down in the Pacific Ocean.
The spaceship is packed with nearly 3,300 pounds of gear, including research specimens housed inside refrigerators, 10 mice launched to study muscle atrophy in microgravity, spacewalk hardware, computer components, cameras and other equipment.
Astronauts living on the space station loaded the return cargo into the Dragon spacecraft's pressurized cabin over the last few weeks.
The Dragon cargo craft launched Sept. 21 aboard a Falcon 9 rocket from Cape Canaveral. It reached the space station Sept. 23, delivering nearly 5,000 pounds of supplies and experiments, including a 3D printer, spacesuit batteries, a small satellite deployer, and a $26 million NASA instrument to help meteorologists study the intensification of hurricanes.
The gumdrop-shaped re-entry capsule, measuring 12 feet diameter and 14 feet tall, will streak through the atmosphere flying southwest-to-northeast over the Pacific Ocean, heading for a splashdown zone a few hundred miles west of Baja California.
SpaceX's resupply freighter is the only spacecraft capable of returning significant amounts of cargo to Earth. Russia's Soyuz crew capsule can land with limited cargo, and the space station's other supply ships from Orbital Sciences Corp., Russia, Europe and Japan are designed to burn up during re-entry to dispose of trash.
Operating on commands from mission control, the space station's robotic arm grappled the Dragon cargo capsule and removed it from the Harmony module's Earth-facing docking port early Saturday.
Release from the robot arm is set for 9:56 a.m. EDT (1356 GMT).
The Dragon's Draco maneuvering thrusters will conduct three burns to depart the vicinity of the space station, then the craft will close and latch the door to its navigation bay before setting up for a de-orbit burn at 2:43 p.m. EDT (1843 GMT).
The spaceship will jettison its unpressurized trunk section and solar panels a few minutes later to burn up in the atmosphere, while the main module re-enters cocooned inside a specialized ablative heat shield developed by NASA and SpaceX to withstand temperatures reaching up to 3,000 degrees Fahrenheit on its hypersonic approach to a landing zone off the coast of Baja California.
Dual drogue parachutes will deploy when the capsule passes an altitude of about 45,000 feet, then three 116-foot-diameter main chutes will open to slow down the craft's descent to a gentle 10 mph for splashdown at 3:39 p.m. EDT (1939 GMT).
A maritime recovery team will be on standby to recover the capsule from the Pacific Ocean and ferry it back to port in Long Beach, Calif., where SpaceX will hand over time-sensitive samples to NASA for delivery to science teams around the world.
The Dragon's splashdown will end SpaceX's fourth commercial resupply flight to the space station, which began with a middle-of-the-night launch Sept. 21 aboard a Falcon 9 rocket from Cape Canaveral.
SpaceX's next cargo mission to the orbiting research lab is set for launch around Dec. 9.
Orbital Sciences, NASA's other cargo transportation provider, is preparing its third operational mission to the space station for liftoff Oct. 27.
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While Gerst is at the controls of the Canadian-built robotic arm, astronaut Reid Wiseman is overseeing the Dragon spacecraft's position and status from the space station's windowed cupola module. Wiseman has a command panel to order Dragon to retreat or abort if a problem develops.
Astronaut Reid Wiseman says the Dragon appears to be in the correct position for this point in the rendezvous. The crew has a control panel linked with Dragon via UHF radio to issue simple commands in case of any problem. For example, the astronauts could tell the spacecraft to hold, abort or retreat.
Wiseman and ESA astronaut Alexander Gerst, who will operate the station's robot arm to grapple Dragon, are inside the space station's cupola module for this morning's arrival.
The rendezvous will culminate with grapple by the outpost's robotic arm around 7:04 a.m. EDT (1104 GMT).
The SpaceX-owned spaceship is carrying more than 5,100 pounds of cargo to reinforce the space station's stocks of research experiments, crew provisions and spare parts.
The Dragon capsule has fired its Draco thrusters multiple times since it launched aboard a Falcon 9 rocket Sunday at 1:52 a.m. EDT (0552 GMT), raising its altitude to match the orbit of the space station and set up for today's final rendezvous sequence.
By about 2:25 a.m. EDT (0625 GMT), the Dragon spacecraft was about 28 kilometers, or 17 miles, below and behind the space station. At that distance, the Dragon was within range of a UHF communications panel the space station's crew can use to issue simple commands to the supply ship in the event of a problem.
Several height-adjustment and midcourse correction rocket burns fine-tuned Dragon's rendezvous, guiding the ship into position 350 meters, or about 1,150 feet, directly beneath the space station at 5:10 a.m. EDT (0910 GMT).
The Dragon initially relied on relative GPS navigation data to guide its approach to the space station. Once directly beneath the complex, its computers were to switch to laser and thermal sensors.
Dragon carries a laser guidance sensor package and and a pair of thermal cameras to aid its final rendezvous with the space station.
Before leaving the initial hold point 1,150 feet beneath the space station, the cargo craft conducted a 180-degree yaw maneuver to align its grapple fixture with the position of the space station's robot arm.
Soon after beginning its final approach sequence, the Dragon spacecraft halted again at a hold position 250 meters, or 820 feet, below the space station. This brief hold allowed ground controllers to assess the status of the rendezvous and issue a "go" for the Dragon to enter the so-called keep-out sphere, an imaginary circle around the space station in which traffic is tightly controlled for safety reasons.
The Dragon spacecraft departed the 250-meter hold point around 5:34 a.m. EDT (0934 GMT), heading for a 30-meter hold position before pressing on to a final point about 10 meters, or 33 feet, beneath the space station.
Arrival at the final hold point is scheduled around 6:46 a.m. EDT (1046 GMT).
Astronauts Alexander Gerst and Reid Wiseman will monitor the final phase of the Dragon's approach, including manning the space station's robotic arm to grapple the free-flying cargo craft. Gerst will grapple Dragon with the robot arm around 7:04 a.m. EDT (1104 GMT).
Once the Dragon is firmly snared by the robotic arm, the 58-foot Canadarm will move the capsule into position for berthing with the Earth-facing port on the space station's Harmony module around 9:30 a.m. EDT (1330 GMT).
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The rocket is now traveling more than 6,000 mph.
And chilldown of the second stage's vacuum-rated Merlin 1D engine has started in preparation for its ignition.
The command to start the ignition sequence for the first stage will be issued at T-minus 3 seconds, triggering the Merlin engines' ignitor moments before the powerplants actually ramp up to full power.
The strongback has retracted into the launch position more than 20 degrees from the rocket.
The second stage thrust vector steering system has checked out and is ready for flight.
The strongback umbilical tower will soon be lowered a few degrees to clear the rocket for launch. The procedure begins with opening of cradles gripping the rocket at attach points, then hydraulics lower the tower into launch position.
The terminal countdown autosequence is about to begin at the T-minus 10 minute mark.
Fully fueled for launch, the Falcon 9 contains about 1.05 million pounds of kerosene and liquid oxygen propellants.
Linkup with the complex is scheduled at 7:04 a.m. EDT (1104 GMT) Tuesday, when astronauts Alexander Gerst will grapple the Dragon spacecraft with the space station's robotic arm.
We will also be tweeting countdown updates. U.S. readers can also sign up from their phone by texting "follow spaceflightnow" to 40404. (Standard text messaging charges apply.)
And if you are need tips on picking a good viewing spot, check out this authoritative guide on where to go.
Among the supplies packed inside are the first 3D printer to be launched into space, 20 mice riding in a specially-made habitat, an instrument to monitor ocean winds, and a commercial experiment that could improve the design of golf clubs.
The Dragon's total internal payload includes 1,644 pounds of science and research gear, 1,380 pounds of crew provisions, 403 pounds of vehicle hardware, 101 pounds of computer tools and 55 pounds of spacesuit equipment.
A $26 million NASA instrument is mounted inside the Dragon capsule's external trunk section. Named RapidScat, the instrument will be placed outside the space station to measure ocean winds and aid in hurricane forecasting.
Today's launch marks SpaceX's fourth operational resupply run to the space station under a 12-mission, $1.6 billion contract with NASA covering cargo services through 2016.
The two-stage rocket burns RP-1 fuel -- a high-refined kerosene -- and liquid oxygen during today's nine-minute launch sequence.
Today's flight marks the 13th launch of a Falcon 9 rocket since debuting in June 2010. It's the 8th mission of the improved Falcon 9 v1.1 version, which made its inaugural launch in September 2013 from Vandenberg Air Force Base.
Launch time is set for 1:52:03 a.m. EDT (0552:03 GMT), roughly the moment Earth's rotation carries the Cape Canaveral launch base into the path of the International Space Station's orbit.
The main weather concerns are with the cumulus cloud rule and the flight through precipitation rule.
The outlook at launch time calls for isolated rain showers, scattered clouds at 3,000 feet, and broken clouds at 20,000 feet, with northwest winds at 10 to 15 mph and a temperature of 73 degrees Fahrenheit.
SpaceX is preparing to begin fueling operations, in which kerosene and liquid oxygen propellants, along with helium pressurant, will be pumped aboard the two-stage Falcon 9 rocket.
The weather has improved over Florida's Space Coast on Saturday, but meteorologists will be closely watching scattered rain showers and thick clouds that have a 60 percent chance of prohibiting liftoff during Sunday's instantaneous early morning launch opportunity.
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Among the supplies packed inside are the first 3D printer to be launched into space, 20 mice riding in a specially-made habitat, an instrument to monitor ocean winds, and a commercial experiment that could improve the design of golf clubs.
The Dragon's total internal payload includes 1,644 pounds of science and research gear, 1,380 pounds of crew provisions, 403 pounds of vehicle hardware, 101 pounds of computer tools and 55 pounds of spacesuit equipment.
A $26 million NASA instrument is mounted inside the Dragon capsule's external trunk section. Named RapidScat, the instrument will be placed outside the space station to measure ocean winds and aid in hurricane forecasting.
Today's launch marks SpaceX's fourth operational resupply run to the space station under a 12-mission, $1.6 billion contract with NASA covering cargo services through 2016.
Two launch weather rules are currently observed "no go" for liftoff -- the thick cloud rule and the disturbed weather rule.
The Air Force weather officer sees little chance conditions will improve in time for launch.
We will also be tweeting countdown updates. U.S. readers can also sign up from their phone by texting "follow spaceflightnow" to 40404. (Standard text messaging charges apply.)
And if you are need tips on picking a good viewing spot, check out this authoritative guide on where to go.
The main concerns are with thick clouds and precipitation over Cape Canaveral as a weather system traverses Central Florida. Two weather rules -- the thick cloud and disturbed weather rules -- are currently "no go" at the launch site.
Liftoff time has been adjusted by one second to 2:14:38 a.m. EDT (0614:38 GMT) based on the latest orbit data for the International Space Station.
The two-stage rocket burns RP-1 fuel -- a high-refined kerosene -- and liquid oxygen during today's nine-minute launch sequence.
Today's flight marks the 13th launch of a Falcon 9 rocket since debuting in June 2010. It's the 8th mission of the improved Falcon 9 v1.1 version, which made its inaugural launch in September 2013 from Vandenberg Air Force Base.
For details on the Falcon 9 v1.1, here is part of our story on the rocket stemming from an interview with SpaceX boss Elon Musk last year:
Musk said the redesigned Falcon 9 is the prototype for a reusable rocket SpaceX envisions could drastically reduce launch costs, decreasing the price of a Falcon 9 flight even lower than SpaceX's advertised rate, which undercuts competing rockets, such as the Russian Proton and Europe's Ariane 5 launcher.
It is this version of the Falcon 9 that SpaceX hopes will safely deliver astronauts to orbit on the way to the space station, beginning as soon as 2017.
Reliability is paramount in the launch business, and cost and schedule are right behind in a matrix of concerns for rocket buyers.
Musk said SpaceX answered these appeals, and added power and efficiency to the Falcon 9's Merlin engines to loft heftier payloads into higher orbits.
SpaceX engineers installed a triple-redundant flight computer in the Falcon 9 rocket, adding another level of confidence in the launcher's avionics. They also wrote new software for the computer, which is based on a flight-proven unit from SpaceX's Dragon cargo-carrying space station freighter.
"You could put a bullet hole in any one of the avionics boxes and it would just keep flying," Musk said.
Designers adjusted the connection points between the Falcon 9's first and second stages, replacing nine hardware interfaces and three spring-like pusher elements - pneumatic devices which ensure stage separation occurs - with three connectors with integrated pushers.
"We go from 12 things that can go wrong to three at the point of staging," Musk said.
The Falcon 9 v1.1 is powered by 10 Merlin 1D engines - nine on the first stage and one on the second stage - each generating 147,000 pounds of sea level thrust. The vacuum-rated upper stage engine, sporting a niobium nozzle to radiate engine heat, produces 161,000 pounds of thrust once out of the atmosphere.
The Merlin 1C engine, used on all five of the Falcon 9's previous missions, was capable of firing with 95,000 pounds of thrust at sea level.
Along with greater performance, the Merlin 1D is easier to manufacture thanks to high-efficiency processes, increased robotic construction and a reduced parts count, according to SpaceX's press kit.
SpaceX upgraded the propellant injection system inside the Merlin 1D, replacing two valves dedicated to fuel and oxidizer with a single unit to improve reliability and save weight.
Musk said the Merlin 1D engine weighs in at less than 1,000 pounds.
"If we don't have the world record for thrust-to-weight ratio, we're very close," Musk said.
Musk's rocket team modified the engine arrangement on the first stage, an effort he said allows engineers to remove aerodynamic manifolds around the perimeter of the rocket.
Earlier Falcon 9s featured a square "tic-tac-toe" layout of the nine first stage engines arrayed in a three-by-three pattern. The Falcon 9 v1.1 uses what SpaceX calls an "octaweb" design, with eight engines surrounding a center engine in a circular pattern.
According to Musk, engineers installed ablative bumpers between the engines to prevent a mishap with one engine from damaging another.
The first stage upgrades also include a heat shield and stretched propellant tanks for the Merlin engines' supply of kerosene and liquid oxygen.
"We put a stronger heat shield at the base of the rocket to better enable the first stage to survive the high dynamic pressure on re-entry," Musk said.
The new Falcon 9 first stage is 60 percent longer but has the same diameter as the Falcon 9's previous version, permitting the rocket to be fabricated with the same tooling already inside SpaceX's rocket factory in Hawthorne, Calif.
Seven weather criteria -- the surface electric field mill rule, the lightning rule, the cumulus cloud rule, the attached anvil cloud rule, the disturbed weather rule, the thick cloud rule and the flight through precipitation rule -- are currently in a "red" status.
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The main worries are with the thick cloud rule and the flight through precipitation rule in the rocket's launch commit criteria.
Liftoff is set for 2:14:37 a.m. EDT (0614:37 GMT) Saturday.
An approaching upper level trough will bring moisture to Florida's Space Coast on Friday, creating thick clouds, rain showers and developing a low pressure area north of the Bahamas, according to a forecast issued by the U.S. Air Force's 45th Weather Squadron.
The official outlook predicts rain showers and overcast clouds at 25,000 feet, with scattered and broken cloud levels at 3,000 feet and 13,000 feet.
Winds will be from the northeast at 12 to 17 mph, the launch time temperature will be 74 degrees Fahrenheit, and relative humidity will be 85 percent, according to the forecast.
Clouds and rain will diminish over Central Florida later Saturday, so forecasters say there is a 70 percent chance of good weather for Sunday morning's launch opportunity at about 1:53 a.m. EDT (0553 GMT).
Wednesday night's practice countdown was punctuated by ignition of the Falcon 9 rocket's nine Merlin 1D first stage engines for several seconds while the launcher was restrained on the ground.
Engineers planned an exhaustive data review before clearing the rocket for launch.
Saturday's liftoff, planned for 2:14 a.m. EDT (0614 GMT) from Cape Canaveral's Complex 41 launch pad, will kick off SpaceX's fourth resupply run to the space station under a $1.6 billion contract with NASA.
The Falcon 9 rocket's ascent into orbit will take less than 10 minutes, when the launcher's single-engine upper stage will release a SpaceX-owned Dragon cargo capsule to start a two-day pursuit of the space station.
After a laser-guided rendezvous, the Dragon spacecraft will hold its approach 30 feet beneath the complex for grapple by the space station's Canadian-built robotic arm.
It is carrying more than 5,000 pounds of experiments, provisions for the station's crew, spacesuit batteries, electronics and a research package for mounting on the outpost's exterior to track winds over the world's oceans.
The Dragon freighter will be mated to the space station's Harmony module, where astronauts can enter the craft's pressurized cabin to unload cargo and pack equipment tagged for return to Earth.
In mid-October, after nearly a month attached to the space station, the Dragon capsule will depart and descend back to Earth for a parachute-assisted splashdown in the Pacific Ocean, returning home with 3,800 pounds of cargo and research samples.
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