IN THE early evening of 19 May 1998 the US was suddenly plunged into communications darkness. About 40 million pagers-90 per cent of the nation鈥檚 total-went down, and there was trouble on TV network audio feeds and with wireless Internet access. Some automated teller machines refused to fork out cash, and a few automatic gas pumps ignored customers鈥� credit cards.
The culprit? Orbiting high above Earth, a communications satellite named Galaxy 4 had shut down. The chaos lasted until the next morning, when Galaxy 4鈥檚 operator, PanAmSat, was finally able to redirect services to other satellites. Of course, there was a bright side: the general public was granted a merciful, if brief, respite from pager buzzers on trains and buses.
All the same, the breakdown underscored the fragility of our modern communications system. What if it had been a defence satellite that malfunctioned during a period of international tension? That鈥檚 scary enough, but what鈥檚 worse is that PanAmSat didn鈥檛 have a clue what was wrong with Galaxy 4-it could have been a blown fuse, inclement space weather, computer hackers or an asteroid collision. And they had no way of finding out, as the malfunction, whatever it was, had taken the craft鈥檚 on-board diagnostics with it.
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Flying doctor
What PanAmSat needed was a satellite doctor that made house calls. Such a doctor could have inspected its orbiting patient for external wounds, listened to its internal 鈥渙rgans鈥� for unhealthy noises, and imaged its interior to reveal any telltale signs of damage. Then it could have relayed its diagnosis to engineers on the ground. To make it happen, all you need is cheap, throwaway satellites with diagnostic gear to escort big, expensive ones in orbit. And according to a team formed by microsatellite manufacturer AeroAstro of Herndon, Virginia, and space insurance broker Space Machine Advisors in Greenwich, Connecticut, that should be a cinch.
These satellites don鈥檛 exist yet. But AeroAstro and Space Machine Advisors are working on it. Their proposed craft, called Escort, measures a diminutive 10 脳 20 脳 25 centimetres-about the size of your average shoebox-and has a mass of no more than 20 kilograms. Its mission: to manoeuvre to within a few metres of an ailing or dead satellite, fly around it while photographing it and running diagnostic tests with a dozen or so sensors, then to beam the data back to Earth.
But there鈥檚 more to Escort than a friendly bedside manner. It could also be a useful research tool, helping satellite manufacturers improve their designs. And you don鈥檛 even have to own a satellite to call the doctor in. Escort would also make a great private eye. Insurance brokers, for example, would be able to hire an Escort to monitor the health of satellites they cover, or check out claims they believe are excessive or fraudulent.
The need for Escorts or their ilk is clear. As long as satellites have been going up, their on-board equipment has been going down. Back in October 1957, Sputnik 1鈥檚 transmitter went on the blink after only 21 days in orbit. Despite nearly half a century of experience in sending satellites into space, everything can and will go wrong on a satellite. Antennas won鈥檛 deploy, solar arrays won鈥檛 extend, reflectors get stuck. A thermal leak can develop from a rip in the craft鈥檚 insulation.
Often these problems can be diagnosed by the satellite鈥檚 on-board systems. Sometimes they can鈥檛. 鈥淭here are certain things you can鈥檛 do from the perspective of the satellite itself,鈥� says Rick Fleeter, president of AeroAstro, veteran of the Jet Propulsion Laboratory in Pasadena, California, and a microsatellite engineer since 1988. 鈥淭here are no diagnostics that would tell you that the solar panels are not functioning. You would know you were not getting the power, but you wouldn鈥檛 know what component was giving you the trouble.鈥�
Then too, on-board diagnostic systems themselves can go down. Unfortunately, this usually happens at the moment they are needed most-when there鈥檚 a widespread malfunction. Galaxy 4 is a perfect example. The hardware in charge of its housekeeping functions-its brain, in effect-failed. Without its operators鈥� knowledge, the backup unit was already kaput. There was no way to get any information from it.
鈥淓scort doesn鈥檛 seek to replace the on-board sensing components,鈥� says Alden Richards, president of Space Machine Advisors. 鈥淚t鈥檚 just trying to supplement those sensors with others.鈥� Its cameras, for instance, could be invaluable for pinpointing problems. One satellite, Fleeter recalls, developed a problem after the deployment of its solar panels, which were designed to pivot back and forth as they tracked the Sun. On this particular satellite the panels moved in one direction, then refused to reverse for no apparent reason. 鈥淭he operators had no idea why that was, or what the fix was, and whether it would affect other satellites in this series,鈥� Fleeter explains. 鈥淭hey spent tens of millions of dollars in six months trying to find out what was wrong, and they could have fixed it with one picture.鈥�
Then there was the case of a Canadian radar imaging satellite that just stopped functioning one day in 1997. To this day, no one has a clue what happened up there-only that a few hundred million dollars鈥� worth of extraterrestrial hardware refuses to phone home.
In all of these cases, Escort could have helped. The craft鈥檚 sensors include infrared mappers that can detect hot and cold spots inside an ailing satellite, indicating short circuits or thermal leaks. It also has a broadband radio receiver that listens in to the sounds the satellite emits. By running these alongside a healthy signal recorded during pre-launch testing, engineers can work out which device is malfunctioning, as well as detect any intentional or unintentional radio interference from outside sources.
The craft has other uses as well. 鈥淪ome customers would also like to have a picture of their satellite in orbit,鈥� says Fleeter. The reason: engineers could then analyse videos of accessories such as solar panels working in the weightless conditions of space, learning how they function in that environment and how to improve them. 鈥淭hey can learn a lot by seeing how it works in orbit,鈥� Fleeter says. In fact, video footage of a geosynchronous satellite unfurling its solar panels was captured for the first time only last February, from a camera mounted on the satellite itself.
Escort鈥檚 mission won鈥檛 just be all about helping controllers on the ground diagnose why equipment has broken. In some situations, the craft could be sent up to snoop. For instance, disgruntled operators could use them to check manufacturer鈥檚 claims of a satellite鈥檚 operational capabilities-say, its power output, or the specifications of its antennas. And they could be used by insurance companies to verify claims. That鈥檚 obviously appealing to an industry that paid out $1.9 billion in 1998. 鈥淎n insurance company might want to use Escort to see what their options are,鈥� Fleeter explains. 鈥淏efore they pay off a claim they may want to see if it can be fixed.鈥� Or they could use it to probe satellites once thought lost for good.
Peace of mind
Each Escort microsatellite would cost around $5 million, which, according to Fleeter and Richards is a small price to pay for peace of mind, or useful information. Especially considering that communications satellites these days can cost upwards of half a billion dollars. And ultimately, it could save money. 鈥淲ith a satellite costing in the $500 million range, having it up there doing nothing is a pretty expensive wait,鈥� says Fleeter.
Escort can be launched in one of two ways: it can be sent up on a special mission to inspect a particular damaged or dead satellite, or it can be launched piggyback on a healthy new one. Once in orbit, Escort would have a lifespan of roughly three years while dormant, and the ability to stay in operation for up to 30 days once it鈥檚 activated. If it鈥檚 placed in a geosynchronous orbit, it has enough fuel to do the rounds among several satellites-say, all those owned by a particular operator, or insured by a particular agency-and provide diagnostic services should any one of them fail.
Chaperone satellites like Escort are an emerging genre of spacecraft. In October, the US is due to launch the Earth Observing-1 satellite, which will join NASA鈥檚 Landsat 7 in orbit as it collects and beams back images of Earth. EO-1 will match Landsat image for image, and these will be processed by scientists at Goddard Space Flight Center in Greenbelt, Maryland, for later comparison with the Landsat photos. EO-1鈥檚 job is not to diagnose problems with Landsat鈥檚 hardware. Rather, it鈥檚 meant to act as a sort of grader, testing the craft鈥檚 accuracy.
NASA also plans to build a companion satellite of its own-a kind of robotic assistant for spacewalking astronauts working on the International Space Station and the shuttle. The spherical unit is a mere 35 centimetres in diameter and based on the light-sabre training droid from Star Wars. It comes equipped with two colour TV cameras, 12 nitrogen-gas thrusters and a padded exterior: no one wants to see it flying out of control and punching holes in fragile spacecraft exteriors.
In the private sector, there鈥檚 the restoration satellite proposed by AssureSat of El Segundo, California. This will be placed in geostationary position where it will patiently wait for a communications satellite to go down. When one does, AssureSat will move the restoration satellite into position and take over the ailing satellite鈥檚 functions until it鈥檚 fixed or replaced. All for a tidy fee, naturally. But AssureSat says it鈥檚 worth it, given that financial losses from a sick or dead satellite can run up to five times the satellite鈥檚 value.
鈥淩emember a couple of years ago, the incident with all the cell phones going out?鈥� says Bill Krenn of AssureSat. 鈥淭hings like that can happen. Some of these satellite television companies, if their service gets interrupted, it鈥檚 a huge loss-it could sink some companies.鈥� Last May AssureSat contracted the Palo Alto-based manufacturer Space Systems/Loral to build two satellites, which are due to be launched in 2002 from the new mid-Pacific Sea Launch platform.
One reason for the sudden surge of interest in chaperones is that the satellite industry is changing: it鈥檚 now big business. Until the 1980s, satellite operators were rarely private concerns with finite budgets, a profit motive, and stockholders to answer to. Instead they were civil entities like NASA or the European Space Agency, or military operators like the US Air Force and the Soviet army. These operators might have purchased only two or three identical satellites from a manufacturer. Today, operators tend be commercial bodies that routinely buy five, six or even seven copies of a satellite. When one malfunctions in space, operators want to troubleshoot the problem for the sake of its sister craft. That also goes for satellites that aren鈥檛 related. A satellite built by, say, the aerospace company Lockheed Martin often uses the same subsystem as one built by, say, Hughes. 鈥淜nowing what subsystems fail can be pretty valuable,鈥� says Fleeter. 鈥淲hen you know what went wrong in one it can lower the overall risk.鈥�
There鈥檚 also the competition to think about. 鈥淚t鈥檚 clear some satellite applications are getting a run for their money from fibre-optic cable,鈥� Richards says. 鈥淭hat has made satellite operators increasingly concerned with reliability, and Escort plays into that philosophy. It doesn鈥檛 create reliability for damaged spacecraft, but it can create reliability for subsequent spacecraft.鈥�
For that very reason, Escort could have made a big difference in the aftermath of the Galaxy 4 failure. Ground controllers suspected that the problem was with the switch that controlled Galaxy鈥檚 back-up brain, and Richards says that Escort鈥檚 on-board diagnostics would have been able to confirm this. As it was, PanAmSat never found out what was wrong and had to declare Galaxy 4 a total loss. Though the satellite was insured for $150 million, building a replacement could run as high as $250 million.
It鈥檚 figures like these that convince Fleeter his Escort project is a winner. 鈥淢y theory is that ten years from now if a programme manager for a $200 million satellite proposed a mission and did not have an escorting miniature satellite, he would be considered some kind of yahoo,鈥� he says. 鈥淚t鈥檚 going to be what you do when you fly a satellite. Saying `it鈥檚 not talking to us any more鈥� is not going to be good enough.鈥�