2357 GMT (6:57 p.m. EST)
NASA says the two solar arrays on DSCOVR have been extended and the spacecraft is power positive following tonight's launch. It is communicating with ground controllers.
2344 GMT (6:44 p.m. EST)
It will take 110 days for DSCOVR to enter a halo orbit around the L1 point. A mid-course correction maneuver is timed for 31 hours after launch to fine-tune the spacecraft's journey toward the insertion point at L1.

DSCOVR's solar arrays should be deploying now, and the craft's magnetometer boom is to be extended on the fourth day after launch.

Then instrument calibrations are planned over the next few months. Once DSCOVR arrives at L1, the door to the EPIC camera -- which will take the full disk images of Earth -- is to be opened.

after the spacecraft is released, we have a mid-course burns that comes up after that. you have a mid-course correction, or MCC, burn that happens at about launch plus 31 hours.

2339 GMT (6:39 p.m. EST)
DSCOVR separation! The Deep Space Climate Observatory is free of the Falcon 9 rocket, heading for the L1 Lagrange point.
2336 GMT (6:36 p.m. EST)
SpaceX confirms a good second burn of the Falcon 9's upper stage. Separation of DSCOVR coming up at 6:38 p.m. EST (2338 GMT).

The rocket achieved an orbit toward the L1 Lagrange point with an apogee of 1,371,156 kilometers, a perigee of 187 kilometers and an inclination of 37 degrees.

2333 GMT (6:33 p.m. EST)
Coming up on restart of the Falcon 9's second stage engine. NASA reports its network of TDRS satellites is receiving signals from DSCOVR now.
2325 GMT (6:25 p.m. EST)
The Falcon 9 rocket achieved an on-target parking orbit following the first second stage burn in today's launch. The launcher is circling Earth in an orbit with a low point of 184 kilometers, a high point of 186 kilometers, and an inclination of 36.99 degrees.
2314 GMT (6:14 p.m. EST)
Restart of the Falcon 9's Merlin upper stage engine expected around 2333 GMT (6:33 p.m. EST) for about 58 seconds.
2312 GMT (6:12 p.m. EST)
T+plus 9 minutes. The Falcon 9's upper stage has shut down after completing the first of two burns required to boost DSCOVR on a million mile journey to the L1 Lagrange point.
2311 GMT (6:11 p.m. EST)
T+plus 8 minutes. The vehicle remains in a nominal trajectory. The terminal guidance phase of the launch will start soon.
2310 GMT (6:10 p.m. EST)
T+plus 7 minutes. The kerosene-fueled Merlin 1D upper stage engine generates about 161,000 pounds of thrust in vacuum.
2308 GMT (6:08 p.m. EST)
T+plus 5 minutes. Everything reported to be going well with this second stage engine firing. The Merlin vacuum engine uses an ultra-thin niobium nozzle extension for greater efficiency in the upper atmosphere.
2307 GMT (6:07 p.m. EST)
T+plus 4 minutes. The Falcon 9's payload fairing has been jettisoned.
2306 GMT (6:06 p.m. EST)
T+plus 3 minutes. The Falcon 9 first stage engines have cut off, the stages have separated, and the rocket's second stage Merlin vacuum engine has ignited for its nearly seven-minute firing to reach orbital velocity.

The first stage is now beginning its turnaround and flyback maneuver, targeting a soft landing in the ocean.

2305 GMT (6:05 p.m. EST)
T+plus 2 minutes. Now soaring at an altitude of more than 20 miles, the Falcon 9 rocket's first stage will shut down and jettison in about one minute.

And chilldown of the second stage's vacuum-rated Merlin 1D engine has started in preparation for its ignition.

2304 GMT (6:04 p.m. EST)
T+plus 1 minute. The Falcon 9 rocket is approaching the speed of sound and the phase of maximum aerodynamic pressure.
2303 GMT (6:03 p.m. EST)
T+plus 20 seconds. The Falcon 9 rocket's pitch program has initiated to put the 224-foot-tall rocket on an east-northeast trajectory from Cape Canaveral.
2303 GMT (6:03 p.m. EST)
LIFTOFF of the Falcon 9 with DSCOVR, launching the world's most distant weather satellite to an operating post a million miles from Earth.
2302 GMT (6:02 p.m. EST)
T-minus 60 seconds. In the final minute of the countdown, the flight computer will command checks of the first stage Merlin engine steering system and the Falcon 9 propellant tanks will be pressurized for flight. Thousands of gallons of water from the 53 water nozzles on ground facility's Niagara system will also be dumped onto the launch pad deck to suppress the sound and acoustics of liftoff.

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.

2302 GMT (6:02 p.m. EST)
T-minus 90 seconds and counting. The SpaceX launch director and the Air Force Eastern Range have given their final approvals for liftoff of the Falcon 9 rocket at 6:03 p.m. EST (2303 GMT).
2301 GMT (6:01 p.m. EST)
T-minus 2 minutes and counting. The rocket's Merlin 1D engines have been chilled down for ignition.
2301 GMT (6:01 p.m. EST)
T-minus 2 minutes, 30 seconds. The strongback has been locked in to launch position.
2300 GMT (6:00 p.m. EST)
T-minus 3 minutes and counting. The rocket's destruct system is on internal power and being armed, and liquid oxygen topping is being terminated.

The strongback has retracted into the launch position about 20 degrees from the rocket.

The second stage thrust vector steering system has checked out and is ready for flight.

2258 GMT (5:58 p.m. EST)
T-minus 5 minutes and counting. The cradles connecting the strongback to the Falcon 9 rocket have opened.

The DSCOVR spacecraft should be operating on internal power at this time.

2257 GMT (5:57 p.m. EST)
T-minus 6 minutes and counting. The Falcon 9 rocket is now operating on internal power.

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.

2257 GMT (5:57 p.m. EST)
T-minus 6 minutes, 30 seconds. The Falcon 9's heaters are being deactivated, and the rocket will be transitioned to internal power in a few seconds.
2256 GMT (5:56 p.m. EST)
T-minus 7 minutes and counting. Within the next minute, the Falcon 9's flight computer will be commanded to its alignment state. The Merlin engine pumps are continuing to chill down.
2255 GMT (5:55 p.m. EST)
T-minus 8 minutes and counting. Good chilldown continues on the first stage engines, and closeouts of the upper stage's gaseous nitrogen attitude control system are underway.
2254 GMT (5:54 p.m. EST)
T-minus 9 minutes, 30 seconds. Prevalves leading to the Falcon 9's Merlin 1D first stage engines are opening, permitting super-cold liquid oxygen to flow into the engines to condition the turbopumps for ignition.
2253 GMT (5:53 p.m. EST)
T-minus 10 minutes and counting. The terminal countdown autosequence has started. Any hold after this point will result in an automatic abort and recycle to T-minus 13 minutes.
2251 GMT (5:51 p.m. EST)
T-minus 12 minutes. The launch team has verified all consoles are go for liftoff at 6:03:32 p.m. EST (2303:32 GMT).

The countdown is expected to progress down to T-minus 2 minutes in hopes an issue with a first stage telemetry link can be resolved.

The terminal countdown autosequence is about to begin at the T-minus 10 minute mark.

2248 GMT (5:48 p.m. EST)
T-minus 15 minutes and counting. Here are some statistics on today's launch:
2246 GMT (5:46 p.m. EST)
T-minus 17 minutes and counting. The Falcon 9 rocket stands 224 feet tall and measures 12 feet in diameter. At liftoff, its nine Merlin 1D first stage engines will generate about 1.3 million pounds of thrust.

Fully fueled for launch, the Falcon 9 contains about 1.05 million pounds of kerosene and liquid oxygen propellants.

2243 GMT (5:43 p.m. EST)
T-minus 20 minutes and counting. The final poll of SpaceX's 14-person launch team will begin at T-minus 13 minutes before the countdown enters the final phase.
2241 GMT (5:41 p.m. EST)
The DSCOVR spacecraft will be switched to internal battery power in a few minutes.
2237 GMT (5:37 p.m. EST)
See our Facebook page for images of today's countdown and launch!
2233 GMT (5:33 p.m. EST)
T-minus 30 minutes and counting. Today's launch is timed for exactly 6:03:32 p.m. EST (2303:42 GMT).

The first stage liquid oxygen tank is now being topped off to flight level.

2231 GMT (5:31 p.m. EST)
Liquid oxygen topping continues on the Falcon 9 rocket's first and second stages.
2223 GMT (5:23 p.m. EST)
T-minus 40 minutes. The Falcon 9 countdown is in a quiet phase now, with the two-stage rocket filled with kerosene and super-cold liquid oxygen.
2207 GMT (5:07 p.m. EST)
Weather conditions are nearly perfect for a rocket launch at Cape Canaveral this evening. Air Force weather office Mike McAleenan says the conditions are favorable for a "spectacular sunset launch" at 6:03 p.m. EST (2303 GMT).

2140 GMT (4:40 p.m. EST)
The SpaceX launch team reports the Falcon 9 rocket has been fueled with kerosene and topping is underway on the liquid oxygen tanks. The cryogenic liquid oxygen tanks on the first and second stages will continue to be slowly replenished until the final minutes before launch to replace propellant that gradually boils off due to the warm ambient temperatures in Florida.
2130 GMT (4:30 p.m. EST)
Testing of the Falcon 9 rocket's flight termination system has finished at this point in the countdown, as fueling of the two-stage launcher is wrapping up.

A final weather briefing is planned at the T-minus 1 hour point in the countdown, but no problems with weather are expected this evening.

It will take about 35 minutes for the Falcon 9 rocket deliver the Deep Space Climate Observatory to its targeted escape trajectory away from Earth. DSCOVR will take 110 days to reach its operating post around the L1 Lagrange point a million miles from Earth.

2020 GMT (3:20 p.m. EST)
Fueling of the 224-foot-tall Falcon 9 rocket is underway at Cape Canaveral's Complex 40 launch pad. The two-stage rocket burns RP-1 fuel -- a high-refined kerosene -- and liquid oxygen during today's nine-minute launch sequence.

Radio checks between the rocket and the Air Force's Eastern Range were scheduled for 3:18 p.m. EST (2018 GMT), followed by first motion checks at 3:33 p.m. EST (2033 GMT).

Testing of the Falcon 9 rocket's destruct mechanisms are scheduled for 4:18 p.m. EST (2118 GMT), and the launcher's on-board power systems will be activated at 4:33 p.m. EST (2133 GMT).

Earlier updates