Sunday, November 13, 2016

WorldView-4 Successfully Launches atop Atlas V

A United Launch Alliance (ULA) Atlas V rocket carrying the WorldView-4 satellite for DigitalGlobe lifts off from Space Launch Complex-3 at Vandenberg Air Force Base, CA. Credit: United Launch Alliance/Lockheed Martin

WorldView-4, the newest member of commercial satellite company DigitalGlobe’s constellation of high-resolution satellites, was successfully launched into orbit atop a United Launch Alliance (ULA) Atlas V 401 booster. The rocket lifted off from Space Launch Complex (SLC)-3 at Vandenberg Air Force Base in California at 10:30 a.m. PST (18:30 GMT) on Friday. The launch was ULA’s ninth for the year and the 112th overall since the company was founded in 2006. ULA also launched WorldView-3 atop an Atlas V in 2014. 
“Congratulations to the entire mission team. ULA is honored to celebrate the successful launch of the WorldView-4 satellite for DigitalGlobe and Lockheed Martin,” said Gary Wentz, ULA vice president of Human and Commercial Services. “This morning’s Atlas V launch delivered the WorldView-4 satellite into [a] near Sun-synchronous orbit during a flawless flight. ULA is proud to have launched the entire constellation of DigitalGobe’s satellites and served in an essential role to get this revolutionary capability to orbit.”

Worldview-4 was originally scheduled to launch on September 16, but a leaking hydrogen line forced a scrub. A wildfire that began burning on September 17 resulted in further delays. More recently, an issue discovered by ULA during final preparations for launch resulted in the launch being pushed back to no earlier than November 11.

“Thank you to the men and women at the 30th Space Wing who worked tirelessly to combat and contain the fires that delayed a launch attempt in mid-September,” Wentz said.

The ULA Launch Readiness Review was completed on Thursday morning and the L-1 forecast showed a 90 percent chance of favorable weather conditions for the launch. Favorable weather conditions held and Friday’s countdown began under partially clouded skies.

At 10:24 a.m. PST (18:24 GMT), near the end of a 20-minute hold in the countdown, the readiness poll was conducted, during which managers and engineers were polled for the system readiness poll. The readiness poll includes everything from hydraulics to electrical systems, and “Go!” was declared for each item. About a minute-and-a-half after the launch team gave the “go for launch”, the countdown resumed from T–4 minutes.

At T–3 seconds, the RD-180 engine built by Russian company NPO Energomash roared to life, lifting the rocket from the launch pad a few seconds later. Shortly thereafter, pitch, yaw, and roll maneuvers were performed to put the rocket on the correct path.

The rocket made it through maximum dynamic pressure, or Max-Q – the point of the flight where the most stress is applied to the airframe. This is the riskiest part of the flight after liftoff.

About four minutes into the flight, the RD-180 engine shutdown and stage separation occurred. At this point, the Centaur upper stage’s Aerojet Rocketdyne RL-10A took over. At around T+5 minutes, the payload fairing was jettisoned, and the Centaur continued carrying the satellite into orbit.

At T–16 minutes, main engine cutoff for the Centaur stage occurred. The vehicle coasted for just over 3 minutes before stage separation occurred and Worldview-4 was released. The satellite will orbit the Earth at an altitude of approximately 383 miles (617 kilometers).

Worldview-4, a multispectral, high-resolution commercial imaging satellite, owned and operated by DigitalGlobe, will hope customers around the world see more of our changing planet. The satellite was built by Lockheed Martin Space Systems Company and will provide 31-centimeter panchromatic resolution and 1.24-meter multispectral resolution. This is the same resolution as DigitalGlobe’s Worldview-3 satellite.

As the fifth satellite in the DigitalGlobe constellation, Worldview-4 joins Worldview-1, -2, -3, and GeoEye-1. With the addition of Worldview-4, the constellation can image a location on average of 4.5 times per day at 1-meter ground sample distance or less.

“High-resolution commercial satellite imagery plays a critical role in modern society, from helping to keep nations safe, to supporting disaster response efforts, to powering a wide range of location-enabled applications and services. We are proud to support the launch of WorldView-4 and its sophisticated technology, which millions of commercial users throughout the world will rely upon for years to come,” said Eileen Drake, president and CEO of Aerojet Rocketdyne, the company that provided the RL10C-1 upper-stage engine, six helium pressurization tanks, and 12 Centaur upper-stage Reaction Control System thrusters.

Aerojet Rocketdyne also provided the 12 MR-106L 5-lbf (22.24 N) hydrazine rocket engines which provide WorldView-4 with all of its maneuvering and attitude control propulsion requirements.

ULA’s next launch is the GOES-R satellite for NASA. The launch is scheduled for Nov. 19 from Space Launch Complex-41 at Cape Canaveral Air Force Station, Florida.

Written by: Jim Sharkey
Original source: spaceflightinsider.com

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