Hughes plans to build a new body-stabilized satellite that will fill a new market in high-power space communications. The announcement was made at Telecom ’87, an eight-day conference in Geneva, Switzerland.
Hughes representatives invited to speak at the conference were Chairman of the Board Albert Wheelon, Vice President Harold Rosen, and chief scientist Bruno Miglio.
Development of the HS-601 body-stabilized satellite marks the seventh and largest investment in satellite design since the company began building spacecraft 28 years ago.
The HS-601’s high-power capabilities will enable satellite services, such as direct broadcast, mobile communications, and private business networks, through antenna dishes known as VSAT, or very small aperture terminals. VSATs mounted on homes, cars, planes, or at business sites will be used to gain direct satellite access.
Designed by Space and Communications Group to fill this market, the HS-601 signals a new direction in the Group’s tradition of building satellites. It will complement services provided by the Group’s long line of spinning spacecraft.
“We have found it necessary, because of changing launch vehicle capacities and customer requirements, to make major investments in new designs on six occasions,” said Dr. Rosen.
“This is the seventh such investment, and is the biggest and most important since the original Syncom.”
Syncom’s first-of-its-kind spinning configuration was conceived by Dr. Rosen, who, along with Senior Scientist Tom Hudspeth and the late Don Williams, invented the pioneering satellite.
Syncom was launched in 1963 and was the first satellite whose orbit was synchronized to that of Earth’s, making it appear stationary over a specific area of the globe. The result was continuous communications, which led to 24-hour worldwide coverage.
Since then, Hughes has built 66 commercial communications satellites, 34 of which account for more than half of those in operation today. All have relied on the operational simplicity of spin-stabilization.
“In the area of orbit and attitude control, the spinners win hands down,” said Dr. Rosen.
Only four thrusters are used to periodically tweak a “spinner’s” orbit and orientation to Earth compared to at least 12 thrusters required to perform the same functions on a body-stabilized satellite.
Dr. Rosen explained that stability produced by the spin also keeps propellant from sloshing about, controls temperature by exposing all sides of the satellite evenly to sun and shade, and make spacecraft nearly impervious to external influences in space.
Because of their operational simplicity spinners are better suited for low and medium-power applications, such as domestic telephone and television services, than body-stabilized satellites, said Dr. Rosen.
“A body-stabilized satellite is much more sensitive to external influences, and its attitude control is more complex and subtle,” he explained.
“But, in the area of power generation,” Dr. Rosen continued, “the body-stabilized configuration has the big advantage.”
Elongated solar panel “wings” capture the sun’s energy three times as effectively as the cylindrical panels on spin-stabilized satellites.
The HS-601 can handle up to 6000 watts of power. The spinner’s practical limit is considerably lower. Although no applications at this time require as much energy as the HS 601 is capable of accommodating, the satellite will be able to meet any future needs, said Dr. Rosen.
Despite power generation shortcomings, Hughes’ spin-stabilized satellites kept up with increasing power demands through improvement in solar cell efficiency. When solar cell technology began to level off in the late 1970s, it became increasingly difficult for the company to meet higher power demands, said Dr. Rosen.
The disadvantage, however, was offset by having satellites that could be launched from the Space Shuttle and whose launch costs were low.
With shuttle flights cancelled after the Challenger exploded in January 1986, the cost-savings factor disappeared. Other launch vehicle failures underscored the importance of having a spacecraft compatible with a variety of launch services.
The HS-601 can be launched from the U.S. rockets Titan and Atlas Centaur, the European Ariane, and Long March built by the People’s Republic of China, as well as the Space Shuttle.
Stowed for launch, the satellite folds into an eight-foot cube. Depending upon the number of solar panels used, it can unfold to more than 100 feet in the highest power configuration.
Subsidiary first to order new high-power satellites
The first bid for two of the company’s HS-601 body-stabilized satellites has been placed by a Hughes subsidiary.
Hughes Communications, Inc. has requested authorization from the Federal Communications Commission to construct, launch, and operate one spin-stabilized C-band satellite and two body-stabilized Ka-band satellites.
Both satellite designs are products of Space and Communications Group.
The spin-stabilized satellite, to be known as Galaxy V, will be the fifth in HCI’s fleet of HS-376 satellites that is used to transmit cable and other TV programming, radio, and business communications.
The proposed HS-601 body-stabilized satellites, to be known as Galaxy C and D, will kick off HCI’s planned Ka-band system. The new system is expected to open markets in direct broadcast, mobile communications and private business networks through the use of small Earth terminals.
Very small aperture terminals are produced by Hughes Network Systems (HNS), a new subsidiary whose purchase gave HCI the capability of offering a full range of satellite services.
The Galaxy Ka-band system is expected to support as many as several hundred thousand very small aperture terminals for private business networks by the year 2000, said Bruce Elbert, Galaxy program director. If authorized it will be in operation of the early 1990s.
Although the Galaxy satellites are owned and operated by HCI, their transponders are sold or leased to private companies. All of the major cable carriers, including HBO, Showtime, MTV, cable News Network, and the Discovery Cannel use the Galaxy C-band network.
Comment by Steve Dorfman
A very challenging business decision which exceeded our expectations but at the time was quite risky. The mindset going in was if it doesn’t spin we won’t win but we read the future correctly, the importantance of high power. Not only did we sell lots of HS 601s but we opened up the opportunity for new applications the most important of which was DirecTV.