Timeline of Minotaur-C launch with SkySats and Doves

Credit: Orbital ATK

Orbital ATK’s Minotaur-C rocket will deliver 10 commercial Earth observations satellites into a 310-mile-high (500-kilometer) orbit for Planet during a 20-minute flight sequence.

The four-stage rocket, formerly known as the Taurus, is standing on a launch pad overlooking the rugged Pacific coastline, ready for its trip into orbit set to begin at 2:37 p.m. PDT (5:37 p.m. EDT; 2137 GMT) Tuesday, the opening of a 30-minute window.

The 104-foot-tall (32-meter) Minotaur-C is carrying six 242-pound (110-kilogram) SkySat satellites and four Dove CubeSats, each weighing about 10 pounds (3 kilograms). The commercial satellites are owned by Planet, a San Francisco company established to collect imagery with a globe-spanning network of surveillance craft for users that include Google, the U.S. and foreign governments, scientists, businesses and private citizens.

It will take around 10 minutes for the Minotaur-C rocket to deliver the six SkySats and four Doves to orbit.

The first stage Castor 120 rocket motor will propel the 104-foot-tall (32-meter) vehicle off the pad at Vandenberg and guide it to the south, generating more than 400,000 pounds of thrust during a burn lasting nearly one-and-a-half minutes.

After burnout of the first stage, an Orion 50S XLT second stage motor will ignite at T+plus 1 minute, 25 seconds, to continue climbing into space. Ignition of the third stage Orion 50 XLT is programmed for T+plus 2 minutes, 51 seconds, followed by separation of the Minotaur-C’s payload fairing about seven seconds later at an altitude of 99 miles (160 kilometers)

The rocket will coast more than four minutes after burnout of the third stage motor. The Minotaur-C’s Orion 38 fourth stage is scheduled to fire at T+plus 9 minutes, 16 seconds, and complete its burn a little more than a minute later, completing the powered phase of the mission.

The first four SkySats will release from their dispenser at 20-second intervals beginning at T+plus 13 minutes, 22 seconds, followed by separation of a bulkhead at T+plus 15 minutes, 22 seconds, to reveal the other two SkySats for deployment.

All six SkySats should be away from the rocket by T+plus 17 minutes, and the Dove CubeSats will separate in pairs before the 20-minute mark of the mission.

The Minotaur-C launch team will lose contact with the rocket when it passes out of range of a tracking station shortly before beginning the satellite separation sequence. Officials will confirm the final success of the launch when the SkySats pass over another ground antenna soon after deployment in orbit.

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