Launch weather office Mike McAleenan says very few thunderstorms have developed so far with the afternoon sea breeze, and upper level winds are looking good. All weather rules are currently observed "go" for launch.
The launcher's on-board power systems will be activated around 2:40 p.m. EDT (1840 GMT).
Cargo items packed inside the capsule's pressurized module include a habitat housing 20 mice, which will be euthanized and dissected by astronauts aboard the space station to examine how spaceflight affects muscle and bone loss, vision and immune systems.
The space station will also receive an espresso machine made by the Italian company Lavazza to make tea, coffee, broth or other hot beverages.
Dan Hartman, NASA's deputy space station program manager, said the coffee maker was a commercial experiment and could help boost the spirits of the crew.
"The psychological support is very, very important," Hartman said.
All told, the SpaceX cargo capsule will deliver equipment to support 40 scientific investigations on the space station, according to NASA.
Today's launch marks SpaceX's sixth operational resupply run to the space station under a 15-mission contract with NASA covering cargo services through 2017.
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 17th launch of a Falcon 9 rocket since debuting in June 2010. It's the 12th mission of the improved Falcon 9 v1.1 version, which made its inaugural launch in September 2013 from Vandenberg Air Force Base.
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 forecast for today's instantaneous launch window has improved slightly, with U.S. Air Force meteorologists now predicting a 60 percent chance of favorable weather.
"The low level flow is expected to be southerly today," the weather team wrote in this morning's forecast. "This will neither help, nor hinder the westward migration of the sea breeze. Expect some storms over the northwest portions of the spaceport during the countdown. The storms and the sea breeze should migrate to I-95 by launch time. Maximum upper-level winds will be from the west at 40 knots at 45,000 feet."
The outlook calls for isolated rain showers and thunderstorms, scattered clouds at 3,000 feet and 15,000 feet, plus a broken high-level deck of clouds at 26,000 feet.
Winds should be from the southeast at 12 to 17 mph, with a temperature at launch time of 80 degrees Fahrenheit.
Like yesterday, the prime concerns are with the anvil cloud and cumulus cloud rules.
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The post-scrub operations include draining propellant from the Falcon 9 rocket.
There is a 50 percent chance weather will prohibit liftoff Tuesday, with scattered thunderstorms expected along Florida's Space Coast. The primary weather worries Tuesday will be with cumulus and anvil clouds, along with lightning in the area.
Scattered clouds are expected at 3,000 feet, broken clouds at 15,000 feet and an overcast deck at 26,000 feet. Winds will be out of the south at 10 to 15 mph, and the temperature is forecast to be 80 degrees Fahrenheit.
The instantaneous launch window means this is an automatic scrub for today.
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.
The launch vehicle is reported ready to proceed with the terminal countdown.
Linkup with the complex is scheduled at 7 a.m. EDT (1100 GMT) Wednesday, when astronaut Samantha Cristoforetti will grapple the Dragon spacecraft with the space station's robotic arm.
Partly cloudy skies will greet the Falcon 9 rocket when it blasts off at 4:33:16 p.m. EDT (2033:16 GMT).
Radio checks between the rocket and the Air Force's Eastern Range, along with first motion checks, have been completed as planned. The launch team also just completed a test of the Falcon 9 rocket's destruct mechanisms.
The launcher's on-board power systems will be activated around 3:03 p.m. EDT (1903 GMT).
Cargo items packed inside the capsule's pressurized module include a habitat housing 20 mice, which will be euthanized and dissected by astronauts aboard the space station to examine how spaceflight affects muscle and bone loss, vision and immune systems.
The space station will also receive an espresso machine made by the Italian company Lavazza to make tea, coffee, broth or other hot beverages.
Dan Hartman, NASA's deputy space station program manager, said the coffee maker was a commercial experiment and could help boost the spirits of the crew.
"The psychological support is very, very important," Hartman said.
All told, the SpaceX cargo capsule will deliver equipment to support 40 scientific investigations on the space station, according to NASA.
Today's launch marks SpaceX's sixth operational resupply run to the space station under a 15-mission contract with NASA covering cargo services through 2017.
At this time, weather conditions are "no go" for launch due to a violation of the attached anvil rule.
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 17th launch of a Falcon 9 rocket since debuting in June 2010. It's the 12th mission of the improved Falcon 9 v1.1 version, which made its inaugural launch in September 2013 from Vandenberg Air Force Base.
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.
Read our full story.
The main chance of violating weather rules will be with anvil clouds and cumulus clouds over the launch site, raising concerns the rocket could trigger lightning when it climbs into the sky.
"Summer-like weather continues across Central Florida," the forecast team from the Air Force's 45th Weather Squadron wrote in a weather summary. "Warm temperatures and afternoon thunderstorms are expected to continue for the next several days. Most thunderstorm activity will be inland today as low level winds are easterly along the Space Coast, helping to push the sea breeze inland quickly.
"However, with upper level westerly winds, thunderstorms will tend to drift back toward the Spaceport late this afternoon, soon after T-0. The primary launch weather concerns are anvils from inland thunderstorms. Maximum upper-level winds will be northwest at 50 knots near 45,000 feet."
Scattered clouds at 3,000 feet, broken clouds at 14,000 feet and an overcast deck at 28,000 feet are predicted in the official launch forecast. Winds will be from the southeast at 12 to 17 mph, and the temperature will be 80 degrees Fahrenheit.
If launch does not occur Monday, the forecast worsens slightly for Tuesday's launch opportunity at 4:10 p.m. EDT (2010 GMT), with a 50 percent chance of weather prohibiting liftoff.
The privately-owned spacecraft will deliver nearly 2.2 tons of supplies and experiments to the International Space Station.
Time-sensitive cargo installed hours before Monday's scheduled launch included 20 mice housed in a special habitat. The mice will be euthanized and dissected by astronauts in orbit to help scientists study how their immune systems respond to infection in space.
Researchers will also use the mice to examine intracranial pressure build-up in microgravity as they seek to find the cause of vision impairment experienced by some astronauts after long-duration space missions.
Other cargo added to the Dragon's internal cabin included fresh food for the six astronauts living on the space station.
The primary concern is with thick clouds and anvil clouds over Florida's Space Coast at the Falcon 9 rocket's launch time of 4:33 p.m. EDT (2033 GMT).
Forecasters say a summer-like weather pattern over Central Florida will generate sea breeze boundaries and thunderstorms Monday, primarily focused over inland areas. But there is a chance some of the activity could encroach near the Falcon 9's launch pad at Cape Canaveral Air Force Station.
The outlook issued Sunday calls for isolated rain showers, scattered clouds at 3,000 feet, broken clouds at 14,000 feet and an overcast cloud deck at 28,000 feet. Winds will be from the southeast at 12 to 17 mph, and the temperature is expected to be near 80 degrees Fahrenheit.
The mission will delivery nearly 4,400 pounds of supplies to the International Space Station, and SpaceX will use the launch to experiment with the recovery of the Falcon 9's booster stage on a platform 200 miles northeast of Cape Canaveral in the Atlantic Ocean.
Conditions at the landing site are expected to be favorable, but there is a chance of rain showers with 70 percent cloud coverage predicted. Waves will be between 4 and 6 feet in height, and surface winds will be out of the south at 15 knots.
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