On its eighth mission of a marathon 15 planned flights in 2014, United Launch Alliance (ULA) is ready to deliver a pair of Geosynchronous Space Situational Awareness Program (GSSAP) satellites and a single Automated Navigation and Guidance Experiment for Local Space (ANGELS) satellite into a near-geosynchronous orbit of about 22,300 miles (35,900 km), fulfilling the requirements of the Air Force Space Command (AFSPC)-4 mission. Liftoff of the Delta IV Medium+ (4,2) vehicle—numerically designated to identify a 13-foot-diameter (4-meter) Payload Attach Fitting (PAF) and the presence of two solid-fueled Graphite Epoxy Motors (GEM)-60—is scheduled to occur from Space Launch Complex (SLC)-37B at Cape Canaveral Air Force Station, Fla., at 7:03 p.m. EDT on Wednesday, 23 July. According to the 45th Space Wing’s Weekly Planning Forecast, issued Sunday, skies are expected to be partly cloudy throughout Wednesday, with a 60-percent likelihood of rain showers and lightning later in the day.
This launch comes hard on the heels of a highly successful year for ULA, which has seen the return to flight of the Delta II on 2 July, as well as four Atlas V missions—which delivered NASA’s latest Tracking and Data Relay Satellite (TDRS) on 24 January, followed by a Defense Meteorological Satelllite Program (DMSP) on 3 April and the classified NROL-67 and NROL-33 payloads for the National Reconnaissance Office (NRO) on 10 April and 22 May respectively—together with a pair of Delta IV Medium+ (4,2) missions to deliver two Global Positioning System (GPS) Block IIF satellites on 21 February and 17 May. Launched from both Cape Canaveral Air Force Station, Fla., and Vandenberg Air Force Base, Calif., these missions have further bolstered ULA’s reliability credentials. On two occasions in 2014 the company has succeeded in launching two missions within a week of each other.
The Delta IV Medium+ (4,2) is one of the key workhorses of ULA’s fleet, having been utilized for the maiden voyage of the Delta IV, back in November 2002, which launched the commercial Eutelsat W5 communications satellite into geosynchronous orbit. As a rocket, it has the capacity to deliver payloads weighing up to 26,280 pounds (11,920 kg) into low-Earth orbit and up to 14,800 pounds (6,720 kg) into geosynchronous orbit. Since its maiden voyage, it has also boosted the classified NROL-22 and NROL-27 reconnaissance satellites in June 2006 and March 2011 respectively, as well as a pair of Geostationary Operational Environmental Satellites (GOES) for meteorological research in June 2009 and March 2010. More recently, between May 2010 and May 2014, it also placed five members of the current six-strong constellation of GPS Block IIF satellites into medium-Earth orbit. Despite an upper-stage thrust shortfall during the GPS IIF-3 ascent in October 2012, the Delta IV Medium+ (4,2) has never failed to deliver a primary payload into orbit. Wednesday’s flight will be the 12th mission by this particular configuration, as well as the 27th overall launch by a Delta IV and the 85th launch under the auspices of ULA.
The central component of the Medium+ (4,2) is a single Common Booster Core (CBC), which stands 134 feet (41 meters) tall and is equipped with a single RS-68 engine. Fueled with cryogenic oxygen and hydrogen, this powerplant generates 663,000 pounds (300,000 kg) of propulsive yield at the instant of liftoff. It will roar to life at T-5 seconds and undergo a brief period of computer-controlled health checks, ahead of the command to fire the twin GEM-60 strap-on boosters at T-0.01 seconds and the release of the hold-down clamps for launch at T-0.
Following the liftoff command, the vehicle—which stands 206 feet (62 meters) tall, when topped off with its Delta Cryogenic Second Stage (DCSS) and Payload Attach Fitting (PAF)—will be released from the pad surface and commence a fast climb away from SLC-37B. Eight seconds after liftoff, the Delta IV Medium+ (4,2) will execute a combined pitch, yaw, and roll program maneuver to establish itself onto the proper azimuth to deliver the payloads of the AFSPC-4 mission into near-geosynchronous orbit. Powered by its RS-68 engine and twin boosters, it will burst through the sound barrier at T+47 seconds, and, at one minute after launch, it will encounter a period of maximum aerodynamic turbulence on its airframe, known colloquially as “Max Q.”
The GEM-60 boosters—each of which measures 53 feet (16.1 meters) in length—will exhaust their solid fuel at T+94 seconds and will be jettisoned about 100 seconds into the flight, after which the RS-68 will continue to propel the stack toward orbit for a further three minutes. It will be shut down at T+245 seconds and discarded six seconds later, preparatory to the ignition of the DCSS. Equipped by Pratt & Whitney Rocketdyne’s RL-10B2 engine, capable of 24,750 pounds (11,220 kg) of thrust, the DCSS will fire at T+265 seconds. Eleven seconds later, the two-piece (“bisector”) shell of the PAF will be jettisoned. Measuring 38.5 feet (11.7 meters) long, the bullet-like PAF provides the AFSPC-4 payloads with aerodynamic, acoustic, and thermal protection during ascent through the lower atmosphere. Its departure will expose the payloads to the space environment for the first time. How long the RL-10B2 will continue burning after PAF separation remains unknown, for the mission will enter a “media blackout” after this time.
The two GSSAP spacecraft, built by Orbital Sciences Corp., will support U.S. Strategic Command space surveillance operations as a dedicated Space Surveillance Network (SSN) sensor, as well as providing assistance for the Joint Functional Component Command for Space (JFCC-Space) in its task of more accurately tracking and characterizing man-made objects in orbit. When operational, the highly maneuverable satellites will “drift” above and below the geosynchronous Earth orbit “belt” and will employ advanced electro-optical sensors to observe other objects in space. This data is expected to enhance the Air Force’s knowledge of the geosynchronous environment and enable the development of new safety systems, including collision-avoidance mechanisms. The GSSAP satellites will communicate through worldwide Air Force Satellite Control Network (AFSCN) ground stations and from thence to Schriever Air Force Base, near Colorado Springs, Colo.
In March 2014, Gen. William Shelton, head of Air Force Space Command, described the mission as nothing less than a “neighborhood watch” system for U.S. satellites. “GSSAP will produce a significant improvement in space object surveillance, not only for better collision avoidance, but also for detecting threats,” Gen. Shelton told the Air Warfare Symposium in Orlando, Fla., quoted in an article by Space.com. “GSSAP will bolster our ability to discern when adversaries attempt to avoid detection and to discover capabilities they may have which might be harmful to our critical assets at these higher altitudes.” Two of those assets include the Advanced Extremely High Frequency (AEHF) satellites, the most recent of which was launched in September 2013, and the Space-Based Infrared System (SBIRS), whose second “Geosynchronous” element was boosted into orbit in March 2013. “One cheap shot against the AEHF constellation would be devastating,” explained Gen. Shelton. “Similarly, with our Space Based Infrared System, one cheap shot creates a hole in our environment.” Two more GSSAP satellites will ride an Atlas V into orbit in 2016.
Meanwhile, the ANGELS satellite is managed by the Air Force Research Laboratory (AFRL) Space Vehicles Directorate at Kirtland Air Force Base in Albuquerque, N.M., and is designed to examine techniques for providing a clearer picture of the geosynchronous environment surrounding the United States’ critical military satellites. Originally conceived a decade ago, the satellite was developed by Orbital Sciences Corp., under a $29.5 million contract with the AFRL, signed in November 2007. Targeting a one-year operational mission, ANGELS will demonstrate several new technologies, including a Space Situational Awareness (SSA) sensor, which will be evaluated in a limited region close to the DCSS of the Delta IV. “The vehicle will begin experiments approximately 30 miles (50 km) away from the upper stage and cautiously progress over several months to tests within several kilometers,” a Kirtland Air Force Base fact sheet explained. “As part of the research effort, ANGELS will explore increased levels of automation in mission planning and execution to enable more timely, safe and complex operations with a reduced operations footprint. AFRL engineers will maintain positive control of the spacecraft throughout the automation experiments, with ground-commanded authorization to proceed points, ensuring a ‘man-in-the-loop’ throughout the experiment.”
ANGELS is also equipped with a GPS system for geosynchronous and high-performance accelerometers. The latter will employ advanced, NASA-provided algorithms to generate near-continuous navigation solutions and will precisely measure tiny satellite accelerations for enhanced guidance and navigation. An experimental on-board vehicle safety system will also explore methods to reduce the likelihood of collision with other space objects. “The ANGELS program will develop key technologies and capabilities for a broad spectrum of defense and civilian space missions,” explained Dr. Antonio Elias, then serving as Orbital’s Executive Vice-President and General Manager of the Advanced Programs Group, in the November 2007 news release. “Under AFRL’s leadership, this effort will help maintain the United States’ continuing technological and industrial superiority in space.”
Wednesday’s mission also marks the first use of the Evolved Expendable Launch Vehicle (EELV) Secondary Payload Adapter (ESPA) on a Delta IV vehicle. The adapter, which provides an inter-stage “ring” for launching secondary payloads aboard Department of Defense Delta IV and Atlas V flights, is part of an effort to reduce launch costs and achieve minimal impact to the mission. Developed in the 1990s by the AFRL, together with the DoD’s Space Test Program (STP), the adapter ring was designed to accommodate a primary payload weighing up to 15,000 pounds (6,800 kg) and as many as six radially mounted secondary payloads, each weighing up to 400 pounds (180 kg). First trialed on the STP-1 mission in March 2007, launched via an Atlas V, the ESPA housed six military research satellites. More recently, it was employed to support NASA’s Lunar Crater Observation and Sensing Satellite (LCROSS) as a secondary payload alongside the Lunar Reconnaissance Orbiter (LRO), lofted by another Atlas V in June 2009.
Missions » Air Force OTV » AFSPC-4 »