Bookended by yesterday’s launch of NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) mission and the impending departure of India’s Mars Orbiter Mission (MOM) from Earth orbit, both bound for the Red Planet, a quieter mission will actually set off from MARS—or, to be more specific, Pad 0B at the Mid-Atlantic Regional Spaceport (MARS), on Wallops Island, Va.—on Tuesday, 19 November. The U.S. Air Force’s Operationally Responsive Space (ORS)-3 mission is scheduled to roar into low-Earth orbit atop Orbital Sciences’ four-stage Minotaur-1 vehicle, during a 105-minute “window” from 7:30-9:15 p.m. EST. It consists of a Space Test Program payload, known as “STPSat-3,” and 28 small CubeSats, making this the largest number of satellites ever despatched into orbit on a single rocket launch. One of these CubeSats, provided by Thomas Jefferson High School for Science and Technology in Alexandria, Va., is the first satellite to be built by high school students.
According to Orbital Sciences, Tuesday’s flight will be the 25th mission by a member of the Minotaur rocket family, which traces its heritage back to the Peacekeeper and Minuteman-II intercontinental ballistic missiles. Standing 63 feet (19.2 meters) tall, the Minotaur-1 variant has flown 10 successful missions since January 2000 and has the capability to insert payloads weighing up to 1,280 pounds (580 kg) into low-Earth orbit and up to 730 pounds (331 kg) into Sun-synchronous orbit. Six flights have been staged from Space Launch Complex (SLC)-8 at Vandenberg Air Force Base, Calif., and four others from Pad 0B at MARS. The vehicle has delivered a variety of small military payloads into orbit for purposes ranging from reconnaissance and infrared missile-plume observations to automated rendezvous and proximity operations and from evaluations of advanced imaging and communications technologies to meteorology, climatology, “space weather” monitoring, and bacterial research. Significantly, it has a proven track record in providing near-term solutions to military requirements, successfully launching the TacSat-2 mission less than seven months after the contract award, and demonstrating an ability to progress from payload mating to launch in less than six days.
All four stages for tonight’s launch are solid-fueled, with the lower two stages consisting of hardware from decommissioned Minuteman-II missiles and the upper two stages utilizing hardware from Orbital’s Pegasus air-launched booster. Tonight’s launch will get underway with the ignition of the Minotaur-1’s first-stage engine, which produces a total yield of about 210,000 pounds (95,250 kg). Two and a half seconds after leaving Pad 0B, the rocket will commence a computer-commanded pitch and roll program maneuver to establish itself onto the proper flight azimuth for its ascent to orbit. At T+37.2 seconds, it will encounter a period of maximum aerodynamic turbulence—known as “Max Q”—on its flight surfaces. The first stage engine will shut down at 61.3 seconds into the flight and the SR-19 second-stage engine will pick up the baton, pushing the vehicle uphill with a thrust of 60,000 pounds (27,200 kg) for 72 seconds and separating a little over two minutes after liftoff. Next will come the Pegasus-derived Orion-50XL of the third stage, which will fire for 74 seconds with an impulse of 26,600 pounds (12,000 kg). During this period, at T+145 seconds, the Minotaur-1’s payload fairing will be jettisoned, exposing the ORS-3 payload to near-vacuum.
Judging from the ascent profile of the most recent Minotaur-1 mission, back in June 2011, the completion of third-stage flight will lead to an extended phase of “coasting,” lasting approximately 327 seconds, ahead of the separation of the third stage and ignition of the fourth stage’s Orion-38 engine at T+547.9 seconds. Burning for 66 seconds, this powerplant will contribute about 7,800 pounds (3,530 kg) of thrust and should establish ORS-3 and its companion payloads into a circular low-Earth orbit of about 310 miles (500 km), inclined 40.5 degrees relative to the equator. “The launch, from ignition to the delivery of the satellites in orbit,” explained Orbital Sciences, “will take a little less than 12.5 minutes.” According to Orbital’s press kit, “Payload Sep” is scheduled for T+734.05 seconds, or 12 minutes and 14.05 seconds after launch.
Known as “The Enabler Mission,” ORS-3 has been in development for some time and is intended to evaluate space-based tracking technologies and an autonomous flight-termination system. At present, radar tracking instruments and optical sensors are employed to track ascending rockets and, if necessary, destroy them in the event that they should substantially depart from the planned trajectory. “We’re working really hard on what we call space-based range systems,” said Peter Wegner, until February 2013 the director of the ORS Office at Kirtland Air Force Base, N.M., quoted by Spaceflight Now. “The idea behind space-based range is you literally take all that range infrastructure, which is time-consuming and costly, try to streamline it and put it on the rocket.”
Aboard the Minotaur-1, the largest payload will be the Space Test Program’s 360-pound (165 kg) STPSat-3 satellite, built by Ball Aerospace and Technologies Corp. of Boulder, Colo. It carries five experiments to study plasma energies and densities, characterize Earth’s ionosphere and thermosphere, and monitor changes in solar irradiance in the upper atmosphere. The satellite also carries the capability to de-orbit itself within 25 years. According to Ball Aerospace, STPSat-3 was built in less than seven weeks and was actually completed ahead of the final selection of its five payloads, thereby demonstrating the flexibility of the hardware. “With a full initial payload manifest, Ball proceeded to build the STPSat-3 bus in only 47 days,” the company noted, “completing the spacecraft in January 2011. In May 2012, the Air Force selected a different payload manifest for STPSat-3. Only 11 months later, the Ball team had integrated and tested the new payloads and STPSat-3 was ready to ship.”
The Minotaur-1 will also carry 28 small CubeSat military and civilian passengers and “two non-separating tertiary payloads.” STPSat-3 and the CubeSats will ride an Integrated Payload Stack aboard the Minotaur-1. “These enablers,” noted Orbital, “not only focus on the ability to execute a rapid call-up mission, they also automate engineering tasks that once took months and reduce those timelines to day or hours, resulting in decreased mission costs.”
Of particular note is TJ3Sat, developed by students from Thomas Jefferson High School for Science and Technology in Alexandria, Va., which Orbital describes as “the first satellite built by high school students to orbit the Earth.” Inaugurated in December 2006, the TJ3Sat project carries as its primary mission a drive to “provide educational resources to other K-12 educational institutions and foster interest in aerospace through the successful design and flight of a CubeSat.” Orbital funded the purchase of the satellite hardware, and its staff mentored the students with engineering support. Once in orbit, students and other users from around the world will be able to submit text strings to be uploaded to the TJ3Sat website. Approved text strings will be transmitted to the satellite and its Text Speak module will convert them into voice signals for relay back to Earth via amateur radio, using an on-board Stensat radio.
“Since the beginning of the TJ³Sat program, Orbital has purchased flight hardware and contributed mentors and advice throughout the process, as well as assistance with final testing prior to launch,” said Mr David W. Thompson, Orbital’s President and Chief Executive Officer. “We are thrilled to see the hard work and dedicated efforts of the students at Thomas Jefferson High School come to fruition and look forward to the educational benefits this satellite will bring to other students around the world.”
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