With its NROL-67 mission currently grounded at Cape Canaveral Air Force Station, due to ongoing problems in the aftermath of a radar tracking system fire, United Launch Alliance (ULA) is continuing its preparations for another Atlas V mission from the West Coast. The company will launch the 19th Defense Meteorological Satellite Program (DMSP) spacecraft, atop an Atlas V 401 vehicle, from Space Launch Complex (SLC)-3E at Vandenberg Air Force Base, Calif., within a 10-minute “window” which opens at 7:46 a.m. PDT Thursday, 3 April. When operational in a Sun-synchronous, near-polar orbit of about 450 nautical miles (830 km), the so-called “DMSP Block 5D3 Flight 19” will join a network of satellites whose heritage extends back over five decades to provide strategic and tactical weather prediction in order to aid the U.S. military in planning operations at sea, on land, and in the air.
The DMSP Block 5D3 Flight 19 spacecraft arrived at Vandenberg in early August 2013, having been transported aboard an Air Force C-17 Globemaster III aircraft from Sunnyvale, Calif. Since then, it has undergone exhaustive inspections and tests, ahead of integration with the Atlas V 401 launch vehicle. This is the second DMSP launch atop an Atlas V 401, following the 5D3 Flight 18 mission in October 2009. The 401 boasts a 13-foot (four-meter) payload fairing, no strap-on solid-fueled boosters, and a single-engine Centaur upper stage. It can transport up to 21,600 pounds (9,800 kg) of payload into low-Earth orbit and up to 10,470 pounds (4,750 kg) into geostationary transfer orbit.
The 401 was first flown on the Atlas V’s maiden voyage, back in August 2002, which delivered the Hotbird-6 communications satellite into geostationary transfer orbit. Since then, its record has been near-flawless, with 20 missions completed, the most recent of which was the delivery of NASA’s latest Tracking and Data Relay Satellite (TDRS-L) in January 2014. Of those 20 missions, only one—back in June 2007—was classified as a “partial failure,” when its Centaur upper stage shut down prematurely and left two ocean surveillance satellites stranded in a lower-than-planned orbit.
In addition to supporting commercial customers, the 401 has lofted military communications satellites, meteorological satellites, navigation satellites, missile early-warning satellites, National Reconnaissance Office (NRO) classified payloads, and two TDRS geosynchronous platforms for NASA. It has also launched several key exploration missions: the Mars Reconnaissance Orbiter (MRO) in August 2005, the Lunar Reconnaissance Orbiter (LRO) and Lunar Crater Observation and Sensing Satellite (LCROSS) in June 2009, the Solar Dynamics Observatory (SDO) in February 2010, the Van Allen Probes (formerly the Radiation Belt Storm Probes) in August 2012, and the Mars Atmosphere and Volatile Evolution (MAVEN) in November 2013.
Judging from earlier Atlas V processing campaigns, the final preparations to move the 196-foot-tall (60-meter) vehicle out to SLC-3E at Vandenberg should commence about 11 hours ahead of launch, punctuated by detailed weather and payload status checks. The Mobile Launch Platform (MLP) will depart the giant Vertical Integration Facility (VIF) at T-8 hours and should be “hard-down” on the SLC-3E pad surface within the next hour or so. This will be followed by a flurry of activity to establish pad connections, perform pneumatic and other checks, and verify the performance of the Atlas V’s flight control systems. Status checks will be conducted until relatively late in the count. Two minutes before the scheduled 7:46 a.m. PDT liftoff time, the vehicle will transition to internal power.
In readiness for Thursday’s launch, the booster and payload hardware have arrived from all over the United States and from around the world. From ULA’s own headquarters in Decatur, Ala., to the launch site at Vandenberg Air Force Base, Calif., and from the fabrication of the Centaur upper stage fuel tank in San Diego to the manufacturing of the RD-180 first stage engine in Khimki, Russia, and from the construction of the Atlas V payload fairing in Zurich, Switzerland, to the final assembly of the vehicle in Alabama, this vehicle boasts the distinctive flavor of many states and nations. All of those have now converged on Vandenberg to be launched toward space.
Early Thursday morning, at T-2 hours, a 30-minute built-in hold will begin, ahead of the loading of propellants aboard the Atlas V. At this stage, all stations will be polled for their readiness to support the launch. Assuming a unanimous “Go for Launch,” the process of pumping liquid oxygen into the Centaur upper stage will get underway and should reach flight levels and enter a topping-off mode to replenish the effects of cryogenic boil-off by T-64 minutes. Meanwhile, the three-stage operation of fueling the Atlas’s Common Core Booster (CCB) with liquid oxygen and a highly refined form of rocket-grade kerosene (known as “RP-1”) will also get underway, proceeding through its Slow Fill, Fast Fill, and Topping modes. The last propellant to be loaded will be liquid hydrogen into the Centaur, which will be at Topping level by T-39 minutes.
With all tanks confirmed at flight levels, the final checkout of the Flight Termination System (FTS)—tasked with destroying the vehicle in the event of a major, off-nominal event during the climb to orbit—will be performed and ascent software, based upon the real-time weather situation, will be updated. Four minutes before launch, the terminal countdown will get underway. The Atlas V will transition to internal power, and, 60 seconds ahead of liftoff, the Launch Control System will be enabled and the Atlas’ computers will assume primary command of all critical functions.
Two and a half seconds ahead of liftoff, the first stage’s Russian RD-180 engine—with a propulsive yield of 860,000 pounds (390,000 kg)—will roar to life, and climb-out from SLC-3E will occur at T+1.1 seconds. Shortly after clearing the tower, the Atlas will execute a combined pitch, roll, and yaw program maneuver, which will position it onto the proper 186.4-degree flight azimuth for the insertion of the DMSP 5D3 Flight 19 payload into orbit. According to ULA’s mission brochure, the mission will follow a near-south trajectory, for emplacement into a near-polar, Sun-synchronous orbit. Ascent and mission telemetry will be gathered by stations at Vandenberg (the Western Range), Diego Garcia in the Indian Ocean, Thule in Greenland, and RAF Oakhanger in the United Kingdom.
Eighty-three seconds into the flight, with the RD-180 still burning hot and hard, the vehicle will burst through the sound barrier. At around this time, the maximum aerodynamic stresses (known as “Max Q”) will be felt through the Atlas’ airframe. In response to this aerodynamic situation, the RD-180 will be temporarily throttled back to 95 percent of its rated performance. “Guidance steering is enabled approximately 120 seconds into flight,” noted ULA in its brochure for the TDRS-L mission, also flown aboard an Atlas V 401. “At 212 seconds, the vehicle throttles up to a constant 5.0 G-level. Approximately 10 seconds prior to Booster Engine Cutoff (BECO), the Atlas V throttles down to a constant 4.6 Gs.” This final throttling-down of the RD-180 occurred at T+4 minutes and 22 seconds and, after separation, the turn came for the Centaur upper stage, which carried the key responsibility for delivering TDRS-L into geostationary transfer orbit.
At T+4 minutes and 30 seconds, the Centaur/DMSP combo will separate from the Atlas and its Pratt & Whitney Rocketdyne-built RL-10A engine will roar to life for Main Engine Start (MES)-1. Eight seconds after the ignition of the engine, the huge, two-piece payload fairing encapsulating DMSP 5D3 Flight 19 will be jettisoned, exposing it to the near-vacuum of space for the first time. The RL-10A engine will then provide 25,000 pounds (11,340 kg) of thrust in a vacuum to complete the climb into orbit. The engine has the capacity for multiple restarts, although Thursday’s mission will require just a single “burn” to inject its payload into the orbital location.
“Approximately 16 minutes into the mission,” noted ULA’s mission brochure, “the first Centaur main engine cut-off (MECO-1) occurs, followed by the release of the DMSP-19 satellite at approximately 18 minutes and 28 seconds after liftoff.” At the point of payload separation, the DMSP satellite will reside in a near-circular orbit, at an altitude of 460.5 nautical miles (852.8 km), inclined 98.87 degrees to the equator.
At the time of writing, weather conditions remain about 90 percent favorable for an on-time launch on Thursday. According to ULA’s Facebook page, the Launch Readiness Review was completed Tuesday, 1 April, producing a unanimous “Go for Launch.” This will be the first Atlas V 401 mission from Vandenberg since the NROL-39 classified payload was lofted on behalf of the National Reconnaissance Office on 6 December 2013.
Operated by the Air Force Space and Missile Systems Center (SMC) on behalf of the Department of Defense, the DMSP program is focused upon the meteorological, oceanographic, and solar-terrestrial physics environments. Each of its satellites operates from a 101-minute-period, Sun-synchronous, near-polar orbit and carries a battery of visible and infrared sensors to collect images across a 1,860-mile (3,000 km) swath. This enables the system to provide global coverage twice daily, and its combination of three “day/night” satellites and one “dawn/dusk” satellite allows for the monitoring of global patterns, such as clouds, every six hours. The DMSPs can also observe environmental features such as bodies of water, snow, fires, and areas of pollution at visual and infrared wavelengths. Their data can be used to determine cloud type and height, land and surface water temperatures, sea currents, ocean surface features, ice, and snow.
Missions » DMSP-19 »