Author: Steven Siceloff

The United Launch Alliance Atlas V that carries an Orbital ATK spacecraft to the station will be the 60th Atlas V mission for the workhorse rocket. Although it has flown numerous missions including sending probes to deep space, the Atlas V has not sent a spacecraft to the station until this mission.

If the Cygnus spacecraft lifts off on-time today, the six people living on the International Space Station will be able to watch it as the orbiting laboratory passes over Bermuda. The station is flying at 252 miles above Earth.

Orbital ATK reports the Cygnus spacecraft is on internal power and is go for launch at 4:44 p.m.

The enhanced Cygnus spacecraft being launched today carries 25 percent more mass than previous version. Here is a look at the upcoming flight.

The Orbital ATK Cygnus cargo spacecraft is switching to its on-board batteries for electrical power through the rest of the countdown. Once in space, Cygnus’ systems will be powered by a pair of twin, circular solar arrays.

4:22 p.m.                  Cygnus begins transfer to internal power
4:29 p.m.                  Cygnus verified configured for launch
4:37 p.m.                  Status check to continue countdown
4:44:54 p.m.           T-4 Minutes and counting
4:44:54 p.m.           RD-180 engine ignition
4:44:57 p.m.           Launch
4:45:15 p.m.           Begin pitch/yaw/roll maneuver
4:46:19 p.m.           Mach 1
4:46:30 p.m.           Maximum Dynamic Pressure
4:49:12 p.m.           Atlas booster engine cutoff (BECO)
4:49:18 p.m.           Atlas booster/Centaur separation
4:49:28 p.m.           Centaur first main engine start (MES1)
4:49:36 p.m.           Payload Fairing jettison
5:03:13 p.m.           Centaur first main engine cutoff (MECO1)
5:06:02 p.m.           Cygnus spacecraft separation
~5:45 p.m.              Cygnus solar array deploy

Orbital ATK’s Cygnus spacecraft will move into the vicinity of the International Space Station on Wednesday with a launch today from Space Launch Complex-41 at Cape Canaveral Air Force Station. Astronaut Kjell Lindgren would use the station’s robotic arm to grapple the Cygnus, which carries a fixture designed to work with the arm, and then pull the uncrewed spacecraft toward the Unity module, also known as Node 1. The Cygnus will be connected to the Earth-facing port on Unity where astronauts will unpack its 7,380 pounds of equipment and supplies.

Today’s countdown entered a planned hold at T-4 minutes. There are no technical issues in work and the weather remains green, with the forecast offering a 70 percent chance of acceptable conditions. Liftoff remains on schedule for 4:44 p.m. EST.