Superbird-A2

Superbird-A2, known as Superbird-6 before launch, was a geostationary communications satellite ordered and operated by Space Communications Corporation (SCC) that was designed and manufactured by Hughes (now Boeing) on the HS-601 platform. It had a mixed K_u band and K_a band payload and was expected replace Superbird-A at the position at 158°East longitude. It was expected to provided television signals and business communications services throughout Japan, southern and eastern Asia, and Hawaii.^[5][6][4]

While the launch was within the margins specified by the satellite manufacturer, the trajectory analysis had been inexact and the satellite suffered sever life and power degradation. It tried to use a supersynchronous transfer strategy, but Boeing had failed to take into consideration the effect of the Moon. Thus, the lowest part of the orbit dropped too fast and much propellant had to be spent on a fast transit to geosynchronous orbit. Additionally, the solar panels suffered damage from the extreme contact with the atmosphere. Given the damage to the spacecraft, it was never put into service.^[5][7]

Satellite description

The spacecraft was designed and manufactured by Boeing on the BSS-601 satellite bus. It had a launch mass of 3,100 kg (6,800 lb), a begging of life mass of 1,528 kg (3,369 lb) and an end of life mass of 1,477 kg (3,256 lb). It was designed for a 13 year life. When stowed for launch, it measured 4.5 m × 3.5 m × 3.5 m (15 ft × 11 ft × 11 ft). It had two wings with four solar panels each, that generated 4378 W at the end of its design life. When fully deployed, the solar panels spanned 26.2 m (86 ft), with its antennas in fully extended configuration it was 7.5 m (25 ft) wide.^[5][6] It had a 29-cell NiH₂ battery with a power charge of 200Ah.^[6]

Its propulsion system was composed of a LAE with a thrust of 445 N (100 lb_f). It also used had 12 22 N (4.9 lb_f) bipropellant thrusters for station keeping and attitude control. It included enough propellant for orbit circularization and 13 years of operation.^[6]

It had a dual K_u band and K_a band payload. The K_u band section had its 85 in (2.2 m) dual gridded shaped antenna on the West side. It had twenty three transponders powered by TWTA with and output power of 85 Watts. It had a wide beam footprint that covered Japan, southern and eastern Asia, and Hawaii.^[6][4][5]

It's K_a band section had a 85 in (2.2 m) single gridded shaped antenna on the East side for the wide beam, and a Nadir 47 in (1.2 m) shaped surface antenna for the steerable beam. It had four 100 MHz transponders powered by TWTA with and output power of 70 Watts. The wide beam covered Japan, southern and eastern Asia, and Hawaii, while the steerable beam could be focus on any zone that had line-of-sight to the satellite.^[6][4][5]

History

Space Communications Corporation (SCC) was founded in 1985, the same year as the original companies that later formed JSAT.^[8] On September 2001 SCC ordered its third BSS-601 based spacecraft, Superbird-6. It was to use the 158° East position and offer a Japan wide beam service in K_u band and K_a band, plus steerable K_a band spot beams. It was expected for a Fall of 2003 launch aboard an Atlas IIAS.^[5][7]

It was decided to launch Superbird-6 into a 2,895 minutes period supersynchronous orbit with an apogee of 120,679 km, a perigee of 1,138 km and a 25.5° inclination. This extreme perigee and a six-maneuvers circularization program would reduce the propellant expenditure to its final position in geosynchronous orbit.^[5][7]

It was launched on April 16, 2004 by an Atlas IIAS that injected in the supersynchronous orbit specified by the satellite manufacturer, at which point it was named Superbird-A2. But the orbit analysis had failed to take into consideration the influence of the Moon at such high apogees and the perigee started to drop dangerously fast. Most of its propellant had to be spent and the solar panels suffered damage that reduced the power production. It was never commissioned into service.^[5][7]

References