After nearly a week of frustrating technical and then weather delays, a United Launch Alliance Delta IV rocket finally got off the ground today and successfully deployed the Air Forces AFSPC-4 mission to geosynchronous orbit. Once again waiting out the typically fickle summertime Florida weather, the launch vehicle thundered off the pad at Space Launch Complex 37 at 7:28 pm EDT to mark the 8th launch for ULA in 2014. Confirmation was received a few hours after launch of the successful deployment of the two primary Geosynchronous Space Situational Awareness Program (GSSAP) spacecraft and ANGELS microsatellite that comprise the AFSPC-4 mission.

“The ULA team is proud to have delivered the twin Geosynchronous Space Situational Awareness Program (GSSAP) spacecraft to orbit today,” said Jim Sponnick, ULA vice president, Atlas and Delta Programs. “We are privileged to work with a top notch U.S. government and contractor mission team that is committed to mission success.”

Blasting off from Space Launch complex 37, AFSPC-4 was launched aboard a Delta IV Medium-plus (4,2) configuration EELV with a single ULA common booster core powered by an Aerojet Rocketdyne RS-68 main engine and 4-meter payload fairing. Two ATK GEM-60 solid rocket motors provided additional thrust for the first one and a half minutes of flight. The strap-on boosters are 5 ft in diameter and 53 ft long and constructed of a graphite-epoxy composite.

The Delta IV booster is structurally rigid and constructed of isogrid aluminum barrels, spun-formed aluminum domes and machined aluminum tank skirts. Delta IV booster propulsion is provided by the RS-68 engine system which burns cryogenic liquid hydrogen and liquid oxygen which delivers 663,000 lb of thrust at sea level.

The booster’s cryogenic tanks are insulated with a combination of spray-on and bond-on insulation and helium-purged insulation blankets. The booster is controlled by the DCSS avionics system, which provides guidance, flight control.

Four minutes after liftoff, the first stage engine shutdown, followed by stage two separation 15 seconds later and ignition of the upper Delta Cryogenic Second Stage (DCSS) RL10B-2 engine manufactured by Aeroject Rocketdyne.

The DCSS is a cryogenic liquid hydrogen/liquid oxygenfueled vehicle, and uses a single engine that produces 24,750 lb of thrust. The DCSS cryogenic tanks are insulated with a combination of spray-on and bond-on insulation, and helium-purged insulation blankets. An equipment shelf attached to the aft dome of the DCSS liquid oxygen tank provides the structural mountings for vehicle electronics.


The twin GSSAP spacecraft, built by Orbital Sciences Corporation, will support U.S. Strategic Command space surveillance operations as a dedicated Space Surveillance Network (SSN) sensor. The GSSAP will also support Joint Functional Component Command for Space (JFCC SPACE) tasking to collect space situational awareness data, allowing for more accurate tracking and characterization of man-made orbiting objects. The satellites will have unobstructed and distinct vantage points for viewing resident space objects orbiting earth without the disruption of weather or atmosphere that can limit ground-based systems.

Data from the GSSAP will uniquely contribute to timely and accurate orbital predictions, enhancing our knowledge of the geosynchronous orbit environment and further enabling space flight safety to include satellite collision avoidance.

The GSSAP will communicate information through the world-wide Air Force Satellite Control Network (AFSCN) ground stations, then to Schriever Air Force Base, CO where 50th Space Wing satellite operations will oversee day-to-day command and control operations.

ANGELS examines techniques for providing a clearer picture of the environment surrounding our nation’s vital space assets. Launch integration and flight operations of the ANGELS spacecraft are performed in partnership with the Department of Defense (DoD) Space Test Program (STP).

“This launch marks the first EELV secondary payload adapter (ESPA) to launch on a Delta rocket,” said Sponnick. “This mission represents an excellent utilization of rideshare capabilities that has enabled a low-cost way for the AFRL ANGELS team to flight demonstrate future spacecraft technologies.”

During the planned one-year mission life, ANGELS will test several new spacecraft technologies and operations methodologies. The spacecraft hosts an SSA sensor payload to evaluate techniques for detection, tracking, and characterization of space objects, as well as, attribution of actions in space. ANGELS will evaluate these SSA techniques in a limited region around the second stage of the Delta IV rocket, testing maneuvering concepts above geosynchronous earth orbit (GEO).


Additional payloads that aid spacecraft operations include a GPS system for GEO and high-performance accelerometers. The GPS system uses advanced algorithms from NASA to receive GPS side lobe signals and generate near-continuous navigation solutions. The high-performance ac celerometers precisely measure small spacecraft accelerations for enhanced guidance and navigation while the experimental on-board vehicle safety system explores methods for dramatically reducing the probability of collision with other space objects in an increasingly congested space environment.


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