In the next few days a ‘space tug’ satellite will be launched into orbit from the Baikonur cosmodrome in Kazakhstan. The satellite, MEV-1 built by Northrop Grumman, will drift for about 3 months in a geostationary transfer orbit and rendezvous with a satellite which will have deliberately been raised out of its conventional orbit by 300 kms.
With the old satellite in its safe ‘graveyard’ orbit, MEV-1 will then attach itself to the satellite and if all goes well dramatically extend the life of the old satellite.
That old satellite is Intelsat 901, an important communications mid-Atlantic craft (operating at 29.5 degrees West) and launched in June 2001. It carries 72 C-band transponders and also providing Ku-band spot beam coverage for Europe, as well as C-band coverage for much of North America, all of South America, Europe and almost all of Africa.
I-901 was the first of an improved, more powerful fleet of satellites and built by Space Systems/Loral (now part of Maxar Technologies). Its anticipated lifetime was a perfectly normal 13 years, so it is praiseworthy that Intelsat’s ground technicians have managed to keep it working so well some 18 years after launch.
But fuel is now extremely low, which is why it is the perfect candidate for an orbital visit from a rescue mission. MEV-1 brings with it a full tank of fuel. This will not be injected into the old satellite but MEV-1 will act as a ‘space buddy’ (officially a “Combined Vehicle Stack:), linking itself to I-901 and then taking over the normal station-keeping duties of the old satellite.
Intelsat’s I-901 clients are now served by an even more powerful craft (I-37e) so all is well in terms of customers, and the ‘graveyard’ orbit means should anything go wrong with the meet-up no harmful debris will affect other satellites in their correct geostationary orbits.
Naturally, Intelsat and Northrop’s engineers are planning for a successful rendezvous between the two. But the relationship will only be for about 5 years. Intelsat 901 will – with the help of MEV-1 – move to a new orbital slot and stay in position for those 5 years, after which MEV-1 will detach itself and move onto another failing satellite.
Intelsat has already ordered up a second MEV for future use. Intelsat has assets in its fleet that are still working some 25 years after launch, and this is the target for I-901 once MEV-1 is in place.
Over time, other elements of a satellite will degrade and fail, not least the solar panels, batteries or other key components.
There’s also the ‘functionality’ thinking behind a satellite’s design. Today’s modern satellites are significantly more flexible in terms of adaptability, with on-board data processing and switching of beams and frequencies. Satellite operators have to consider whether to keep an old craft in orbit and sweat the asset, and perhaps adding a Space Tug if it makes commercial sense, or replacing an old model with an up-to-date design.
But first Intelsat wants to see this valuable experiment work.