It doesn’t have a nickname like old faithful, old goat or crusty the satellite. The controllers and those involved with it on a daily basis call it plain old Marisat F-2.
Maybe that’s because Comsat’s Marisat F-2 doesn’t act its age or that the optimism of its prolonged youth keeps it trekking around the planet.
Either way, Marisat F-2, the oldest commercial communications satellite in service at 24-years-old, continues to serve a purpose even today. The U.S. Navy Space and Naval Warfare Systems Center has signed an agreement with Comsat to use Marisat F-2 on behalf of U.S.-based National Science Foundation (NSF), keeping the satellite functional for at least another year.
The satellite, which was initially launched into geosynchronous orbit in 1976 from Cape Canaveral, Fla., will be used to transfer research data gathered by scientists at the Amundsen-Scott Station in the South Pole back to the United States. The NSF is installing a large, 9-meter antenna in the South Pole to transfer the data to the satellite. The antenna will replace the existing 3-meter antenna.
Comsat will receive data via its gateway facilities located at its teleport in Clarksburg, Md., with the use of a new, very powerful antenna of its own.
Old man satellite
The agreement seems odd considering the age of Marisat F-2. Jimmy Carter was elected president of the United States, Apple Computers was founded, Chinese Premier Zhou Enlai died of cancer and North and South Vietnam were united in 1976, the year Marisat F-2 was first launched.
Since, Marisat F-2 has been estimated to have made 8,500 trips around the world, which is more than 2.2 billion kilometers.
The contract between NSF and Comsat is for just one year with options to continue through 2005, but that has nothing to do with the mileage of Marisat F-2, according to Dan Swearingen. Swearingen has been with Comsat for the entire life of Marisat F-2 and is now the vice president for advanced engineering and planning.
“It’s to minimize hassle with government contracting,” Swearingen says. “Multiyear contracts create a lot of hassle on their part.”
Marisat F-2 has a few age-induced blemishes and has already outlived the expected five-year design life, but the people at Comsat aren’t worried about failure.
“It’s had all of its capacity operational throughout the lifetime,” says Swearingen. “It’s lost a little redundancy and being so old its lost its solar cells and its station keeping fuel are a bit depleted. But it’s still got plenty of life left.”
And there’s plenty of reason for Comsat’ s confidence in the satellite, as it has encountered few technical problems in its 20-plus years of existence. The most major situation it has suffered involved the uninstructed use of fuel, according to Swearingen. In the end, the problem turned out to be beneficial to Inmarsat (Comsat is a signatory of Inmarsat) by reducing the inclination of the satellite. Otherwise, the history of Marisat F-2 is virtually untarnished with inadequacies or failures.
That doesn’t mean NSF hasn’t taken notice of its age. The foundation is very experienced in using older satellites and didn’t overlook that Marisat F-2 is nearly 20 years older than its expected lifespan.
“Yes, we are,” says Patrick Smith, technology development manager in the NSF’s Office of Polar Programs, when asked if NSF is at least a little worried about the satellite’s age. “So, we have a kind of orbit sparing philosophy. We have more than one, all with similar capability. If you lose one you can still provide the same kind of service with the same kind of quality levels but what happens is you lose a little contact time per day.”
But NSF had few choices that could provide the kind of service necessary and Marisat F-2 proved to be the best option.
“When you’re into this business right now and you know how you can get this kind of capability, the realization is, based on some surveys that we have done, the only way we can get an inclined satellite like this is one that is beyond its published lifetime,” says Smith. “That’s because most operators will not disable north-south station keeping until sometime into the space craft mission with the motivation to preserve life, if you were to start at year zero following the launch and let it drift, it would probably take around nine to 10 years to drift to the inclination.
“The geosynchronous Comsat folks have always been good about debris management, meaning when you hit a certain state in spacecraft life, it’s disposed. When they dispose them, we can’t use them.”
In the name of science
The NSF’s purpose in the South Pole is to gather scientific data in various subjects and transfer it to the United States.
“The data that’s flowing would come mainly from our Astronomy and Astrophysics programs,” says Smith. “They have a 1k by 1k for an infrared telescope for sky imaging. We have a group that’s using the ice cap as a neutrino detector. They have basically a prototype for a large cubic kilometer size array that they would like to build to form a telescope that would detect neutrinos.”
Other projects in the South Pole that need data to be transferred involve biology and medicine, geology and geophysics, ocean and climate and glaciology.
The hope is that Marisat F-2 will help improve the quality of communications and life for the scientists and staff working in the South Pole with a hefty transfer rate of 2 Mbps or more from the South Pole and 1.5 or more from the U.S.
Marisat F-2 is one in a very small handful of satellites capable of serving the NSF’s needs.
“The National Science Foundation would like it to have eternal life,” says Swearingen. “They value these inclined orbit satellites. The mission they’re trying to take care of is the South Pole. Ordinary geostationary satellites can’t be seen from the South Pole. They had their eyes open for inclined orbit geosynchronous satellites and non-geostationary, but they were looking for satellites that had enough bandwidth to carry at least a megabit per second.”
Marisat F-2 is smaller than most of today’s satellites with a weight of 680.389 kilograms, a height of 3.81 meters and a diameter of 2.03 meters. It is one of three Marisat satellites, but Marisat F-2 is the only one still serving some purpose.
Marisat F-2 will be visible to scientists for five to six hours per day and has the equivalent of 48 telephone circuits, which is capable of 28 million bits per second. It will deliver NSF’s data on an L-band. NSF is using four other military satellites – TDRS F-1, Goes 3, Les 9 and ATS 3 — along with Marisat F-2 to provide numerous services to the South Pole Station on a more continuous basis.
“We have a sort of junk box collection of spacecraft we’re using,” says Smith. “All were launched a very long time ago. Another satellite we’re using for a capability similar to Marisat is the old weather satellite, Goes 3. You put the two together and we’ll get about 11 hours a day of continuous satellite coverage.”
The ATS 3 is the oldest noncommercial communications satellite in use. It was launched in 1967. nine years prior to Marisat F-2.
At the moment, TDRS F-1 is enabling the majority of data transfers as it can provide an astounding transfer rate of 5 Mbps. The problem is that TDRS F-1 is nearing the end of its life. This means NSF needs another satellite with decent transfer rates to replace it. Enter Marisat F-2.
“What we’re going to use Marisat for in addition to general Internet service is we’ll also be using it as a backup, high-speed data relay,” says Smith. “I think it will meet our current need, but it doesn’t have a lot of long-term growth capacity.
“But it does an important thing for us in that it provides backup for the NASA [TDRS] satellite. The NASA satellite is in very bad condition and NASA is worried about losing control of it. Marisat will give us basically a backup and depending on how NASA feels about the health of the satellite a replacement for TDRS F-1.”
Still, there are plenty of valuable uses for Marisat F-2 while TDRS F-1 is still functional. Marisat F-2 will offer Internet service and services that will improve the quality of life for the scientists.
The link will be asymetric with the outbound direction from the South Pole having a bigger pipe than the inbound direction from the U.S. to the Pole.
“For Marisat in particular, the big service we are trying to provide is Internet for all intents and purposes,” says Smith. “This convergence helps us out because we’ve already made a commitment to have Internet to begin with and collapse all of the skills into it.
“We’re going to be using it for a lot of things, including sending science data, but also people will be using it for morale purposes. The people out at the South Pole Station, it’s not like they can go off to another phone company and get their own private Internet or phone service. We have to do it all and with a reasonable amount of quality. So, we have to have enough head room to support that.”
The satellite still has to be tested by the government once it reaches a station in August.
Finding of the Holy Grail
The reason for Marisat F-2’s nearly immortal life span isn’t an unpublished Comsat secret. It’s a matter of basic janitorial-like work.
“The satellite has been well taken care of for one thing,” says Swearingen. “The other is that it’s been parked in front of the orbit, which is where the East-West station keeping fuel requirements are not so large. Twice a year you have an eclipse season, and the batteries where you carry the electric load are reconditioned shortly before the season.”
Dennis Boiter, Comsat’s manager of orbital dynamics, adds, “We’re very conservative in what we do with the satellite and we never spend fuel that we don’t have to.”