After almost two months of delays, caused by raging wildland fires which swept across vast areas of Vandenberg’s North and South Base, a United Launch Alliance (ULA) Atlas V rocket successfully roared away from Space Launch Complex (SLC)-3E at 10:30 a.m. PST (1:30 p.m. EST) on Friday, 11 November. Liftoff came precisely on the opening of today’s 15-minute “window.” The workhorse Atlas—flying in its “barebones” 401 configuration, equipped with a 13-foot-diameter (4-meter) Large Payload Fairing (LPF), no strap-on boosters, and a single-engine Centaur upper stage—delivered DigitalGlobe’s WorldView-4 imaging satellite into orbit. The satellite will join its four siblings in providing unrivaled commercial views of Earth at resolutions as fine as 10 inches (25 cm) for panchromatic and 3.3 feet (1 meter) for multispectral. This offers an imaging capability previously unobtainable outside the military.
As detailed in AmericaSpace’s WorldView-4 preview article, this mission was originally scheduled to fly from Vandenberg on 16 September. Routinely postponed by 24 hours, due to a ground-side liquid hydrogen leak, the launch teams were working toward a resolution when the first of five wildland fires hit Vandenberg. These continued to rage for much of the second half of September, and although SLC-3E and the Atlas V themselves were undamaged, teams were stood down until a new launch date could be determined. Early November was targeted, but additional “minor problems” with the Atlas V forced that date to slip to the right, eventually settling on the morning of the 11th.
Yesterday (Thursday), ULA completed a standard L-1 Launch Readiness Review (LRR), which cleared a significant remaining milestone, ahead of Friday morning’s rollback of the Mobile Service Tower (MST) from SLC-3E, which exposed the 194-foot-tall (59-meter) Atlas V to the elements. Launch personnel stepped smartly through Flight Control and Communications checks and, at length, the Launch Director polled the team for a “Go” to begin loading cryogenic oxygen and hydrogen.
The Common Core Booster (CCB)—the Atlas V’s first stage, powered by a Russian-heritage RD-180 engine—utilizes rocket-grade kerosene (“RP-1”) and liquid oxygen, whilst the Centaur upper stage is fed by liquid oxygen and hydrogen. After loading, these were continuously topped-up until close to T-0, thereby ensuring that boiled-off cryogens were replenished and propellant tanks kept at Flight Ready levels. About 30 minutes before the 10:30 a.m. PST opening of the 15-minute launch window, liquid oxygen tanking aboard the Centaur attained Flight Level and entered Replenishment Mode. This was followed by the liquid hydrogen loading protocol.
Although this has been the first ULA launch from Vandenberg in 2016, the site characteristically played ball in terms of a near-perfect weather outlook. With a 90-percent probability of acceptable conditions at T-0, the main issues centered upon launch visibility, primarily due to thick cloud cover, although these conditions were expected to worsen to only 70-percent-favorable in the event of a 24-hour scrub to Saturday morning. In fact, the weather improved yet further. Thirty minutes ahead of the opening of Friday’s launch window, conditions were officially classified as 100-percent-favorable, with light winds of 5-8 knots and temperatures hovering around 22 degrees Celsius (72 degrees Fahrenheit).
In the final minutes before launch, WorldView-4—encapsulated within its two-piece (or “bisector”) Large Payload Fairing (LPF)—was transitioned to internal power, running off its on-board batteries until such time as it reached orbit, and was able to deploy its five electricity-generating solar arrays. A final “Go/No-Go” poll of all flight control stations, led by the ULA Launch Conductor, was greeted by an encouraging string of “Go” calls, across the board. The final station, that of the Launch Director, issued authorization for the Launch Conductor to launch the Atlas V. ULA’s ninth mission of 2016 was ready to fly.
At 10:26 a.m. PST, the countdown clock was released from its final hold at T-4 minutes, inaugurating the Terminal Countdown. During this period, the rocket’s propellant tanks were pressurized and secured for flight and the Flight Termination System (FTS) was placed onto internal power and armed. With a minute remaining on the clock, the words “Range Green” came from the Range Operations Co-ordinator (ROC), signifying the Western Range’s approval to proceed with the launch.
Launch occurred on-time at 10:30 a.m. PST, marking the first ULA mission out of Vandenberg since October 2015. Despite this hiatus, the SLC-3E complex has seen more than a half-century of activity, with dozens of Atlas-Agena and Atlas IIAS launches recorded between July 1961 and December 2003, ahead of a $200 million facelift to prepare it for Atlas V operations. Between March 2008 and October 2015, SLC-3E saw a total of 11 Atlas Vs transport seven classified payloads, a pair of Defense Meteorological Satellite Program (DMSP) satellites, DigitalGlobe’s WorldView-3, and NASA’s Landsat-8 to orbit.
At T-2.7 seconds, the RD-180 engine roared to life, generating 860,000 pounds (390,000 kg) of propulsive yield from its twin nozzles. The Atlas V departed SLC-3E at T+1.1 seconds and ascended vertically, before the Centaur avionics commanded a pitch, roll, and yaw program maneuver to establish it onto the correct azimuth of 185.6 degrees. Passing Mach 1 about 80 seconds into the flight, the CCB continued to burn hot and hard, eventually shutting down a little over four minutes after launch. The Centaur then picked up the baton, with its RL-10-4-2 engine—capable of 22,300 pounds (10,100 kg) of thrust—igniting for 11 minutes to deliver WorldView-4 into orbit. The Centaur finally shut down at 10:46 a.m. PST, some 15 minutes and 37 seconds after departing Vandenberg. Targeted for an apogee of 423 miles (681 km) and a perigee of 383 miles (617 km), the 4,600-pound (2,100 kg) WorldView-4 will spend up to seven years enhancing DigitalGlobe’s unrivaled Earth-imaging portfolio. The satellite was successfully deployed from the Centaur some 19 minutes after launch.
Today’s mission was the 33rd flight of an Atlas V in its workhorse 401 configuration; an insignificant number at first glance, but notable in view of the fact that 66 Atlas Vs have now flown since August 2002. Thus, the 401—which can transport up to 21,600 pounds (9,800 kg) into low-Earth orbit and up to 10,470 pounds (4,750 kg) into Geostationary Transfer Orbit (GTO)—has now completed a full 50 percent of all Atlas V launches. This is more than four times as many missions as its next-most-flown variant, the more powerful 551.
And those launches have proceeded with an almost 100-percent success rate, tempered only by a premature Centaur shutdown in June 2007, which left two ocean surveillance satellites in a lower than intended orbit. A string of 401 vehicles have transported a range of communications, reconnaissance, early-warning, weather-monitoring, navigational, and military research satellites into orbit, as well as several planetary and deep-space-exploration missions and a pair of Orbital ATK Cygnus cargo ships toward the International Space Station (ISS).
Launching WorldView-4 thus completes ULA’s ninth mission of 2016 and its first since the early September flight of the Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer (OSIRIS-REx). In spite of the close proximity to year’s end, no fewer than three more missions are scheduled, all launching out of Cape Canaveral Air Force Station, Fla. ULA has confirmed that it will fly the Geostationary Operational Environmental Satellite (GOES-R) from the Cape’s SLC-41 on 19 November for weather forecasting, storm tracking, space-weather monitoring, and meteorological research. Two weeks later, the latest Wideband Global Satcom (WGS-8) high-capacity communications satellite will launch atop a Delta IV booster from the Cape’s SLC-37B, with the multi-spot Ka-band EchoStar XIX communications satellite (also known as “Jupiter-2”) slated for a mid-December Atlas V launch from SLC-41. With 12 missions completed in a single calendar year, this will tie with ULA’s accomplishment from 2015, although the Centennial, Colo.-based organization’s personal best remains the 16 launches it conducted back in 2009.