In the upcoming months and years, several events in space have the potential to threaten the existing array of satellites orbiting the planet. Any one of these events has the ingredients to do as little as weaken satellite strength to as much as knock out a satellite.
While these cycles have come and gone in the past, with more satellites orbiting than ever before, more critical communications functions are vulnerable. The rash of low-earth-orbit satellites systems alone is unprecedented, as Iridium L.L.C. plans to begin service in September and others continue launching the birds.
The first astronomical event is the upcoming Leonid meteoroid showers expected in November. The Aerospace Corp.’s Center for Orbital and Re-entry Debris Studies teamed with the American Institute of Aeronautics and Astronautics to host a conference in April titled “Leonid Meteoroid Storm and Satellite Threat Conference.”
While the earth experiences Leonid meteoroid showers every year as it passes through the tail of the comet Tempel-Tuttle, the earth will pass through the thickest section of the tail in the next two years, resulting in the most intense meteorite bombardment of the earth’s atmosphere in 33 years. A normal Leonid storm sees about 15 meteoroids an hour. Scientists expect some 200 to 5,000 meteoroids an hour this year.
“It’s a dramatic difference,” said Dr. Russ Patera, senior engineering specialist at CORDS. “This is to my knowledge the biggest one.” The last bombardment was in 1966, which saw 150,000 meteoroids an hour.
The meteoroids are very small, smaller than a strand of human hair, but they travel at speeds of about 160,000 miles per hour and carry the kinetic energy of a .22 caliber bullet.
“The chances are that you’re not going to get hit by a piece large enough to blow a hole in the satellite,” Patera said. The tiny particles haven’t the mass required to punch a hole in the bird, but instead vaporize on impact. At those speeds, that vapor-or plasma-becomes an ionized gas, which can affect the electrical system of a satellite.
“Most likely, they’ll just cause an electrical glitch,” Patera said. “They can short something out or cause a high voltage spike.”
A less intense meteoroid shower was responsible for knocking out a European Space Agency Olympus communications satellite in 1993.
Overall, the conference determined that no catastrophic events are expected from the next few storms, but caution is always prudent. There are several precautions a satellite provider can take. Since scientists know the exact direction from which the storm is coming, companies can rotate their satellites edge-wise to the onslaught and even turn more sensitive equipment to the lee side. Satellite providers even may be able to adjust a bird’s orbit to place it on the lee side of the planet, avoiding all contact during the peak period of the storm, which scientists have narrowed down to within a few hours.
Satellite providers also may opt to shut down satellites during the worst of the storm, so no current is flowing on the bird that might react with the ionized collisions.
Finally, CORDS recommends all personnel be ready to react to anything.
“They should keep their best team at the consoles controlling the satellite in case you have to take immediate action to save the satellite if something happens,” Patera cautioned.
Iridium officials said several precautionary measures are being put in place. First, the most critical components of its satellites already face earth and therefore are protected from the direction of the meteoroid. Its crosslink antennas are parallel to the storm as well, so less surface area is exposed.
Iridium plans to position its satellites’ solar arrays edge-wise during the storm and will upload operational software to better protected areas of the satellites.
Another potential problem is the peaking solar activity expected in the next two years. Just as sailboat traffic is affected by changes in the weather, so is satellite traffic by the weather in space.
Scientists at the Space Environment Center, a division of the National Oceanic and Atmospheric Administration in Boulder, Colo., say the sun is reaching the zenith of its 11-year solar flare activity cycle. Major and severe solar storms are expected to increase from nine this year to about 24 next year.
These solar storms give off waves of radiation and charged protons that can create atmospheric disruptions sufficient to delay satellite launches, shorten satellites’ lifetimes and disturb their performance.
The radiation may temporarily or permanently erase data from satellite instruments, physically damage the craft, disrupt the satellites radio signals by actually bending the Earth’s magnetic field, heat up the atmosphere so that it expands and slows the satellites down, create static electricity that can affect satellite electronics and affect navigational control.
Larry Combs, space weather forecaster for the SEC, said of most concern to satellites are the geomagnetic field disturbances, or a warming and expanding of the earth’s atmosphere, which creates a drag on orbiting satellites and can change their orbit pattern.
Also at issue is radiation causing differential charging or bulk charging, where a proton deposits charges in the satellite that can affect any of a number of onboard electrical systems.
“We’re dealing with a pretty harsh environment out there,” Combs said. “Things can happen and things have happened.”
While the issue has received more attention lately, no one really knows what kind of affect these storms may have.
“There’s always a chance of a significant effect,” Combs said. “Satellite companies keep the cards close to the chest on this. We don’t even know the total effects that can happen. This is still new to all of us.”
While mobile satellite providers have expressed little concern over these upcoming events, Combs said whatever the SEC knows, the satellite industry knows.
SoundView Financial Group’s Timothy O’Neil said the industry is putting on an ambivalent face because there’s really nothing it can do about the problem. The only thing to do is hope for the best and prepare for the worst.
Iridium and Orbital Communications Corp. are in the best condition, he said. Iridium has three launch standbys reserved and Motorola Inc. can build it a new satellite in a week.
Orbcomm also has a rapid satellite building time, he said, but its main strength is that satellites are launched from the Pegasus rocket, which takes off from a plane and therefore does not require waiting for a launch provider.
Since there are many LEO satellites in a given system, the chances increase that one may be affected. Going by odds alone, it is less likely that a geostationary system-which uses far fewer satellites-would be affected. However, it is more time consuming and costly to replace those satellites.
