Auto-acquire VSAT terminals are marvels of technology, allowing someone who has little or no training in satellite technology to commission a satellite link simply by pushing a button. Developed for the satellite newsgathering (SNG) and military markets, auto-acquire terminals originally were operated by satellite technicians and engineers, but over the years the telecommunications market kept pushing for terminals which were fully autonomous, thereby eliminating costly manpower.

Over the last several years a new generation of auto-acquire terminals have been introduced with dramatically lower price points and enhanced features, including the capability to track satellites in inclined orbits.

Inclined Orbit Satellites

In an ideal world, once a satellite is maneuvered into its orbital slot it could simply be left alone, free to drift through space relaying signals to and from ground stations. Unfortunately, a number of factors prevent this celestial utopia, including: the gravitational pull of the Earth, Sun, and Moon as well as solar radiation. Since the Earth’s axis cants it to one side roughly 23.5 degrees from vertical, the Earth’s equatorial plane is different than the plane in which our planet revolves around the Sun. Our Moon orbits the Earth in yet another plane, setting up an interesting dynamic of gravities, each exerting its own pull on the orbiting satellite.

If left alone, a geosynchronous satellite’s east-west orientation would remain fairly close to its assigned position, but its north-south orientation would begin to drift much more rapidly. Mathematical calculations reveal that a satellite starting in the equatorial plane would reach 0.8 degrees of inclination in just a year. To counter this movement, satellites are equipped with either rocket motors or ion drives to gently nudge the satellite back into its desired location. Stationkeeping maneuvers cause the satellite to travel in a figure-8 path and care is taken to make sure the satellite is kept within +/- 0.15 degrees of its assigned orbital location. The periodic adjustment of the satellite’s directional path is known in the industry as keeping the satellite in the box. When the amount of rocket fuel or xenon gas for the ion drives on board the satellite diminishes to a certain level, satellite operators typically will make the decision to put the satellite into an inclined orbit. The satellite’s east-west coordinates are maintained easily with a minimum of fuel consumption, while the north-south stationkeeping maneuvers are halted. This action prolongs the satellite’s life in orbit but reduces its capabilities as it drifts outside the station keeping box, causing the signal strength to vary.

Euroconsult studies supply and demand in the satellite market as well as utilization and leasing rates for transponders in different frequency bands and regions. Alexandre Duflos, analyst at Euroconsult, is responsible for assessing the supply in orbit. “There are roughly 230 operational communication satellites in geostationary orbit today, without counting military proprietary systems or satellites dedicated to government usage. Of those, about 40 are reported today in inclined orbits. Half of those will be retired soon, leaving about 20 satellites which are still operational and able to carry traffic,” he said. The percentage of transponders available varies by region but there are satellites in inclined orbits serving every region of the world. “Moreover, there are a significant amount of satellites that will be retired in the next few years, those satellites were launched at the end of the 1990s to address the boom in the DTH market. This is a well understood cycle in the industry. As an operator’s fleet of satellites gets older, some satellites have to be replaced and are placed into inclined orbit to free an orbital slot. Those satellites can then enter a new service life while being inclined or eventually be retired by desorbitation.”

Euroconsult does not include inclined satellites in its models when calculating overall commercial capacity because they behave differently than geostaionary satellites, Duflos says. “First, older satellites are not as productive as new ones. They use old coding and modulation techniques, and the natural degradation of their solar panels is also an issue. This decreases beam strength, which in turn decreases the spectral efficiency and, thus, the maximum data rate available. Moreover, there are additional signal losses due to imperfect tracking since the satellite moves outside the traditional station keeping box. In all, inclined satellites are not very commercially efficient and require an investment in a tracking system.” As with new satellites, Duflos notes that demand drives the market price for capacity on satellites in inclined orbits. Pricing per megahertz ranges from one-fourth to one-third of the prevailing monthly commercial rate, but can be as high as one-half the commercial rate in rare “hot” areas. Indeed, despite its drawbacks, inclined capacity could be useful to answer specific demand. “Militaries often use capacity on inclined satellites because there simply isn’t any other capacity, and this one can be found worldwide, moreover, military trucks are already fitted with tracking antennas and don’t need additional investment,” Duflos says. 

Auto-Acquire

Auto-acquire VSAT antennas eliminate the need to send a trained technician to the remote site to set up the equipment and commission the terminal. This saves both time and labor expense. Because the process is automated, many auto-acquire terminals can find the assigned satellite and frequency quicker than a human can. The cost to send a trained technician to install a VSAT can be significant. Airline travel, lodging and food as well as the technicians’ time needs to be factored in. Multiply those costs by three times, or more, for international installations. When you compare the cumulative costs to manually install a VSAT compared to the capital required for an auto-acquire system you quickly see why the automated systems are gaining in popularity.

“There are three essential design features that every auto-acquire terminal needs to have or else it can cause interference,” says Jim Oliver, founder of AvL Technologies. “Your initial pointing accuracy must be dead on. In addition, backlash in the pointing mechanism needs to essentially be reduced to zero. If the mechanical linkage that points the antenna has even a half a degree of backlash, the antenna will move back and forth when the wind blows and spray adjacent satellites with illegal energy. The antenna also needs to be stiff enough to resist deflecting when the wind blows,” he says.

Brent Guffey, director of sales, Winegard special products division, agrees with Oliver regarding initial, pointing accuracy, backlash and antenna stiffness, adding ruggedness of design to the list of key design elements. “A large number of our systems are used in the energy industry and they are always exposed to harsh conditions. Reliability and repeatability are essential in any satellite aiming system. As such, all of our drive systems are sealed to prevent the intrusion of dust, grit, and saltwater. Likewise, all of our motors are sealed against the elements. You can’t have an accurate system if grit and corrosion are eating away the pointing mechanism. Pointing mechanisms which use aluminum gears cost less than stainless ones do, and aluminum gears may work fine in a fresh-from-the factory system, but aluminum gears wear quickly, creating a significant amount of backlash. For this reason, we use stainless hardware exclusively.”

While many auto-acquire terminals are designed as transportables, with major components shipped in cases or to be mounted on vehicles, two new entries are designed to be mounted either permanently or semi-permanently. The Winegard SPA (semi-permanent auto-acquire) series of antennas and MotoSat’s MESA (motorized Earth station antenna) are an entirely new genre of auto-acquire antennas and use a pole mount, thereby minimizing complexity and cost.

Most auto-acquire terminals now have integrated tracking capabilities, allowing them to communicate via inclined orbit satellites. Antenna tracking systems for large antennas have been available for several decades but only recently have cost effective VSAT antennas with tracking capabilities become available. “Acquiring space segment on an inclined orbit satellite is much cheaper,” says Leslie Klein, president of C-Com. “The services on the satellite can no longer be guaranteed, so the rates drop. It is like renting an abandoned house, but the service may stop working at any moment. The auto-acquire capability allows you to store another satellite in the controller and repoint quickly if you need to change satellites. The news media and military users are great candidates to use inclined satellite capacity.” 

The Need for Regulation

The use of auto-acquire systems has been increasing worldwide. Unfortunately, the number of cases of satellite interference caused by the new terminals has also been increasing. In an effort to help the industry come to grips with this problem, the Global VSAT Forum (GVF) recently launched the Auto-Acquire Initiative. “Step-track or similar tracking antenna controllers require continual readings of the downlink level from the antenna. In the old days, you would use a dedicated beacon receiver which was tuned to the satellite’s beacon signal,” says Ralph Brooker, president of SatProf and contributor to the Auto-Acquire subgroup of the Global VSAT Forum’s Type Approval Working Group. “To lower the overall cost of an auto-acquire terminal, manufacturers often rely on the communications modem as the tracking receiver. There are lots of subtle issues about doing this. For instance, how fast does the demod respond?  Does it uniquely measure the desired carrier, or can it be misled by a strong signal on an adjacent satellite?  How stable is the reading, and what happens during scintillation and rain fade? How much random fluctuation is there?  Most likely, the modem manufacturer did not design the demod to serve as a tracking receiver, so the terminal designer must carefully characterize its response as a critical element in the servo control loop which must keep the antenna pointed accurately enough to minimize ASI,” he says.

“There has been an interesting dynamic which has driven the volume of new auto-acquire terminals being deployed,” says David Hartshorn, secretary general of GVF. “There was a daisy chain of natural and man-made disasters over several years which drove budgets to solutions. On the heels of this sudden surge in demand for auto-acquire systems came the invasions of Afghanistan and Iraq, which added even more demand. Existing manufacturers ramped up production and new manufacturers sprang up. The presence of adequate engineering and manufacturing expertise to support that trend has, increasingly, fallen short of the mark. Quality issues have arisen. As an industry, we need to get our arms around this problem and move toward more exacting production and type approval processes. ” 

Conclusion

The functionality of auto-acquire terminals has increased while prices have come down, significantly improving the price-performance ratio. In the past, organizations would buy small numbers of these terminals due to their expense, but now it is common to see satellite service providers equipping entire fleets of vehicles or trailers with auto-acquire terminals. Not only does the automation eliminate the labor expense associated with set up and commissioning a VSAT, the tracking capabilities allow service providers, news media and militaries to utilize cost-effective space segment on satellites in inclined orbits. The combination of auto-acquire technology and inclined orbit satellites looks to be a good match for a long time to come.

Greg Berlocher has been active in the satellite industry for twenty five years and is the President of Transcendent Global Networks LLC.