For the first time, one commercial satellite has grabbed hold of another one in orbit around Earth, demonstrating a technology that could help reduce the proliferation of space debris around our planet by enabling the repair and refueling of dying spacecraft.
“This is the first time in history a docking has been performed with a satellite that was not pre-designed with docking in mind,” Joe Anderson, a vice president at SpaceLogistics, a subsidiary of Northrop Grumman, said during a telephone news conference on Wednesday.
The company built the robotic Mission Extension Vehicle-1, or MEV-1, which was launched in October on top of a Russian Proton rocket. Over the past few months, it has made its way to more than 22,000 miles above Earth’s surface, just above what is known as geosynchronous orbit. Its target was Intelsat 901, an 18-year-old communications satellite that is working fine but running low on fuel.
Intelsat removed the communications satellite from service in December and raised it to the same altitude as MEV-1 for this demonstration. Sky watchers like Jonathan McDowell, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics, noted that MEV-1 approached within a few miles of the Intelsat satellite about a week ago.
MEV-1 docked with Intelsat 901 on Tuesday at 2:15 a.m. Eastern time, Northrop Grumman announced. MEV-1 will remain connected, providing propulsion for the Intelsat with its electric thrusters. After tests of its systems, MEV-1 will push the Intelsat satellite to a new operational orbit in late March or early April.
Without MEV-1, Intelsat 901 would need to be retired within months. Under the contract, MEV-1 is to extend the lifetime of Intelsat 901 by five years. MEV-1 will then push it to a higher orbit known as the graveyard, where it will be decommissioned and not in danger of colliding with other satellites. Designed to last 15 years, MEV-1 will then undock and can be sent to help another satellite.
The two companies declined to talk about pricing, but Stephen Spengler, the chief executive of Intelsat, said, “The economics work for us.”
Northrop Grumman is scheduled to launch a second MEV satellite this year, aiming it for another Intelsat satellite. With this week’s success, that docking would occur at the Intelsat satellite’s current location, without taking it out of service.
Since the Soviet Union’s launch of Sputnik, the first artificial satellite, in 1957, the space around Earth has become increasingly cluttered. Today, there are more than 2,200 operational satellites, and it is estimated that there are 34,000 pieces of debris at least four inches wide, from used rocket bodies to fragments of satellites, speeding in orbit.
Most of the congestion is in lower orbits, a few hundred miles above the surface. But space in geosynchronous orbits is limited, and one collision there could damage several satellites. (Batteries on a DirecTV satellite operated by Intelsat malfunctioned in December, leading to a hasty decommissioning and move to a graveyard orbit because of fears it would explode.)
Companies like SpaceX and OneWeb are now planning to launch constellations of thousands of new satellites in lower Earth orbits, which would further increase the chances of collisions. In January, two dead satellites with no ability to maneuver barely missed a head-on collision at 32,800 miles per hour above Pittsburgh.
Satellite crashes have occurred. In February 2009, an Iridium satellite was destroyed when it was hit by a defunct Russian military satellite at 26,000 m.p.h.
Makers of orbital machinery now more often include plans to dispose of their spacecraft before they become uncontrollable hunks of metal speeding at thousands of miles per hour, and there are other efforts to develop methods to pull defunct objects out of orbit. A Japanese company, for example, wants to use a glue-armed satellite to collect space debris.
Satellite servicing is another approach. In addition to MEV-1, NASA is financing RESTORE-L, a spacecraft that is to launch in a few years and latch onto an aging Landsat observation satellite in low-Earth orbit.
Northrop Grumman officials said that at present their focus is on satellites in geosynchronous orbits, which are typically bigger, more complex and more expensive. But similar technology could be used to drag derelict satellites out of low-Earth orbit or to move satellites between orbits. It could even be used for a space tug to transfer spacecraft to high-Earth orbit where they could be captured around the moon.
Earlier satellite servicing in orbit was completed by human hands. The most prominent examples were five space shuttle missions where NASA astronauts performed repairs and upgrades to the Hubble Space Telescope.
In the aftermath of the destruction of the Columbia shuttle during re-entry in 2003 and the deaths of the seven astronauts aboard, NASA investigated whether a robotic mission could perform additional repairs on Hubble. However, the agency concluded that the technology was not yet ready, and a final shuttle mission to repair Hubble occurred in 2009.