Build-up begins for first Minotaur rocket launch from Cape Canaveral

File photo of a Minotaur 4 rocket before a launch from Kodiak Island, Alaska. Credit: Stephen Clark/Spaceflight Now

Ground crews at a long-dormant launch pad at Cape Canaveral are stacking surplus military missile motors for the Aug. 25 launch of a Minotaur 4 rocket with a satellite designed to track orbital traffic thousands of miles above Earth.

The process to construct the Minotaur 4 rocket began with the hoisting of the launcher’s first stage at pad 46 at Cape Canaveral Air Force Station. The lower three solid-fueled stages of the Minotaur 4 come from the Air Force’s stockpile of decommissioned Peacekeeper missiles deployed in the 1980s to hurl nuclear weapons to targets around the world.

A spokesperson for Orbital ATK, which operates the Minotaur family in agreement with the U.S. Air Force, confirmed stacking of the Minotaur 4 booster recently started at Cape Canaveral.

Liftoff is set for Aug. 25 at 11:15 p.m. EDT (0315 GMT on Aug. 26), the opening of a four-hour launch window.

The Minotaur 4 is typically made of four stages — the three Peacekeeper motors and an additional commercial Orion 38 solid rocket on top — to send military satellites into orbit. Minotaur 4 variants have launched payloads into orbit on three occasions from Kodiak Island, Alaska, and Vandenberg Air Force Base, California, and a shortened three-stage version has launched two times on suborbital missions.

The build-up of the next Minotaur 4 rocket at launch pad 46 should be complete by mid-August, along with the attachment of SensorSat, a microsatellite designed to locate and monitor movements of spacecraft and debris in geosynchronous orbit, a belt more than 22,000 miles (nearly 36,000 kilometers) over the equator.

SensorSat will go into a unique equatorial orbit at an altitude of around 372 miles (600 kilometers). The mission’s unusual equator-hugging orbit required engineers to add an additional Orion 38 upper stage, making the Minotaur 4 set to launch later this month a five-stage booster.

The final Orion 38 motor burn will reduce the angle of the ORS-5 satellite’s orbit, redirecting the spacecraft to fly over the equator.

This illustration of SensorSat is the only one released by the Air Force. Many details about the mission remain secret. Credit: U.S. Air Force

Some details of SensorSat’s mission remain secret, but the satellite will be a gap-filler to provide geosynchronous tracking data to the military after the retirement of the Space Based Space Surveillance, or SBSS, satellite launched in 2010, which is nearing the end of its design life.

A follow-on space surveillance satellite is scheduled for launch in the early 2020s.

SensorSat is funded by the Air Force’s Operationally Responsive Space office, a division established in 2007 to seek less expensive ways to field satellites and launch opportunities for the military. The Air Force also calls the space surveillance mission ORS-5, and the spacecraft was developed by the Massachusetts Institute of Technology’s Lincoln Laboratory.

With a mass between 175 and 250 pounds (approximately 80 to 110 kilograms), SensorSat will collect “unresolved visible imagery of resident space objects in geosynchronous orbit from a novel low Earth orbit,” according to information posted on Lincoln Laboratory’s website.

Pad 46 last hosted a space launch in 1999, when a Lockheed Martin Athena rocket took off with an experimental Taiwanese satellite. Located on the easternmost tip of Cape Canaveral, the launch pad was dormant until Space Florida, a state government agency set up to lure commercial aerospace business to the Sunshine State, took over the facility and brokered the deal to bring Orbital ATK’s Minotaur rocket to the Space Coast.

Technicians partially assembled an inert Minotaur 4 rocket at pad 46 earlier this year to rehearse stacking procedures.

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Follow Stephen Clark on Twitter: @StephenClark1.