Sunday, December 4, 2016

Vega Rocket to Send Turkish Earth-Observing Satellite into Orbit

Encapsulated in its protective payload fairing, GÖKTÜRK-1 is hoisted to the upper level of the Vega launch site’s mobile gantry, readying it for installation atop the launcher. Photo Credits: ESA / CNES / Arianespace

Arianespace is gearing up for its tenth mission of the year that will launch the Göktürk-1 Earth-observing spacecraft for the Turkish Armed Forces. The satellite will be launched by the company’s light-lift Vega booster on Dec. 5 at 13:51 GMT (8:51 a.m. EST) from the Vega Launch Complex (SLV) in Kourou, French Guiana.

The mission is designated VV08 in Arianespace’s numbering system as it is the eighth Vega launch to date. VV08 is tasked with delivering Göktürk-1 into a Sun-synchronous orbit at an altitude of 435 miles (700 kilometers) with a semi-major axis of 4,387 miles (7,060 kilometers), inclined 98.11 degrees.

The planned launch is a result of a contract inked in July 2009 between the Turkish Ministry of National Defense and Telespazio, an Italian satellite services provider. Under this agreement, Telespazio serves as the prime contractor for the mission, also developing the ground segment for the Göktürk program. Thales Alenia Space, a subsidiary of Thales which is a minority owner of Telespazio, was responsible for building the satellite. In June 2014, Telespazio chose the Vega booster to launch the mission.

The mission campaign started in late October with the arrival of Göktürk-1 at French Guiana and integration of Vega’s first two stages. The third stage and upper stage of the rocket were integrated on Oct. 27 and Oct. 31, respectively.

After arrival at the Guiana Space Center, the satellite was transported to the S1B hall for fit-checks and initial checkouts. On Nov. 4, the spacecraft was transferred to the S5B hall in order to carry out fueling operations. With the fueling finished in mid-November, the satellite was ready for its integration with the payload adapter which took place on Nov. 17.

Göktürk-1 was encapsulated in the payload fairing on Nov. 18, forming an upper composite which was delivered to the launch site on Nov. 22 and installed on the launch vehicle one day later. The fully assembled rocket was then ready for the start of fueling operation of its upper stage on Nov. 25.

With this stage loaded with propellant and pressurized, the engineers conducted final preparations of the launcher and final inspection of the payload fairing. The launch readiness review took place on Dec. 2, clearing the way for the final countdown scheduled to begin nine hours before liftoff.

After launch on Monday, the rocket will fly for about one hour to release the satellite at 57 minutes into the mission. However, the separation of the spacecraft will not end the VV08 mission as the upper stage will be in-flight tested while conducting a one-minute engine burn at T+1 hour and 46 minutes, and the whole flight will conclude about two hours after the launch.

Göktürk-1 is based on the Proteus satellite bus provided by Thales Alenia Space. The spacecraft’s dimensions are 13.78 ft × 8.2 ft × 5.25 ft (4.2 m × 2.5 m × 1.6 m) and its mass at launch is 1.06 metric tons. The satellite features two deployable solar arrays and is expected to be operational for seven years and three months.

Göktürk-1 is a very high-resolution optical Earth observation satellite for civilian and military applications. It carries a high-resolution (0.8 meters) optical instrument and an onboard X-band digital imaging system to handle data compression, storage, and downloading. The spacecraft’s imaging capabilities will be used mainly in such areas as forest control, illegal construction, crop management, and casualty assessment after natural disasters.

“Göktürk-1 Program is a very important milestone for Turkish space and satellite road map. So far, RASAT and Göktürk-2 satellites were manufactured indigenously, launched [into space] and operating perfectly,” İsmail Demir, Turkey’s Undersecretary for Defence Industries, said in May 2015.

Göktürk-2 was launched into space in December 2012. It is also an Earth-observing satellite; however, it acquires lower resolution images than Göktürk-1. Turkey also plans to launch Göktürk-3 by the end of 2019 and could, additionally, send into orbit the Göktürk-1B in case of Göktürk-1’s failure.

The Vega rocket that will be employed for Monday’s flight is a single-body launcher with three solid-propellant stages and a liquid-propellant upper module for attitude and orbit control as well as satellite release.

With a height of 98 feet (30 meters) and a diameter of 9.8 feet (3 meters), the launcher is described as being capable of placing satellites with a mass of 660–3,300 pounds (300–1,500 kilograms) into polar or low-Earth orbits that are used for many scientific and Earth observation missions. The first flight of this booster was conducted in February 2012.

The rocket’s first stage is a one-piece solid-fuel rocket engine named P80. This stage is 38 feet (11.7 meters) tall with a diameter of 9.8 feet (3 meters). After liftoff, P80 burns for one minute and 50 seconds. Zefiro 23 is Vega’s second stage with a height of 27.5 feet (8.39 meters) and a diameter of 6.2 feet (1.9 meters). The engine of this stage burns for one minute and 17 seconds. The rocket’s third stage – Zefiro 9 – is 13.5 feet (4.12 meters) in length and 6.2 feet (1.9 meters) in diameter. This stage powers the launch vehicle for about two minutes during the flight.

Vega’s upper stage, named Attitude Vernier Upper Module (AVUM), has dimensions of 5.6 ft × 6.2 ft (1.7 m × 1.9 m). It consists of two modules: APM (AVUM Propulsion Module) and AAM (AVUM Avionics Module). The first one uses an RD-843 rocket engine to boost the payload into a targeted orbit, while the second contains the main components of the avionics subsystem of the vehicle. The burn time of this stage is 11 minutes and seven seconds.

Monday’s launch will be Arianespace’s tenth mission of the year as well as Vega’s second flight in 2016. Göktürk-1 will be the sixth Turkish satellite launched by this company. Arianespace’s next orbital mission is currently planned for Dec. 20 when an Ariane 5 launcher is slated to loft two communications satellites into space – Star One D1 for Brazil and JCSAT-15 for Japan.

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