The Link satellite developed by Katalyst Space Technologies "experienced issues with attitude control" over the weekend, NASA said, causing the spacecraft to spin and resulting in sporadic communications.
Reaction wheels work by discharging momentum to control the pointing, or attitude, of a spacecraft in orbit. They are standard components on many satellites. The Link servicing satellite's cold gas thruster system is used for finer control, particularly as it nears the mission's target: NASA's Swift observatory.
The Link mission began July 3 with a ride to orbit aboard an air-launched Northrop Grumman Pegasus XL rocket. NASA and Katalyst reported good progress in the first weeks of the mission, with successful deployment of the satellite's power-generating solar arrays and stable contact with ground controllers at Katalyst's operations center. The spacecraft's xenon-fueled electric thrusters also completed their first firings in orbit.
The electric thrusters are one of the most critical elements of the rescue mission. They are used for orbit raising to allow Link to rendezvous with the Swift satellite some 200 miles above Earth. Once Link attaches itself to Swift with a set of three robotic arms, the electric thrusters will turn on again to raise Swift's orbit and save it from destruction. Katalyst is now calling upon the electric thrusters to stabilize the Link spacecraft's attitude, something they were not intended to do.
Without a rescue, Swift is on track to reenter the atmosphere and burn up in the next few months. The Neil Gehrels Swift Observatory is nearly 22 years old and is operating well beyond its originally intended lifetime. The spacecraft cannot save itself because it lacks its own propulsion system. NASA officials want to keep Swift going because it is one of the only missions in the agency's fleet tuned to detect gamma-ray bursts, the most powerful explosions in the known Universe. NASA is paying Katalyst $30 million for the rescue service.
Extending Swift's scientific mission was not the only consideration when NASA officials selected Katalyst to build and launch a satellite to boost Swift's orbit. The space agency is using the rescue mission as a technology demonstration and as a way to test the mettle of the commercial satellite servicing industry.
With Swift's orbit rapidly decaying, NASA gave Katalyst nine months to build and launch the Link satellite, an unusually fast timeline for such a complex mission. Katalyst answered the call and delivered the Link satellite for integration with the Pegasus rocket in early June. Poor weather and a technical glitch with the rocket delayed the launch until July 3.
No matter the outcome of the Swift rescue attempt, NASA officials said last month they were already pleased with the results. "From a programmatics standpoint, I consider this a success already, just from the fact that we're even going to try this," said Shawn Domagal-Goldman, director of NASA's astrophysics division.
Katalyst's Link spacecraft is still generating sufficient electrical power in communication with ground teams, NASA said. That gives engineers time to develop a plan to address the reaction wheel problems.
Kieran Wilson, Link's principal investigator at Katalyst, talked about a scenario like this before the launch.
"Our previous programs had issues with power systems and communications," Wilson said. "Those are a lot of the basic things that most of the engineering team gets very concerned about because we're confident that as long as we have spacecraft that can function at a fundamental level, that gives us the freedom and flexibility to work through any issues we find during rendezvous and more challenging dynamical operations."
(Score: 2) by VLM on Tuesday August 04, @04:00PM
Standard in the sense of the technology typically used, not standard in the sense there's a performance or design standard from ISO or a popular standardized COTS supplier.
There should be a COTS supplier but its that rocket scientist moth to a flame thing where its better to have an optimized mission fail, than to have a successful mission thats 1 gram heavier than a hyper optimized design.
I read some stuff about this mission and its wheels, for a few minutes at least, and the supply chain is not public, they may have made it themselves, and there's extensive trash talking that most designs use 4 or more wheels so if 1 fails they still have some 3-d control but supposedly these guys cowboy'd it and launched with only 3 wheels, at least one of which isn't working, so they're pretty much SOL at least WRT 3-d control.
Its interesting sometimes just how little information is available. LINK was launched ito a 244/225 mile orbit. Swift was launched into a 375/364 orbit twenty years ago and is in a 235/232 orbit now, and they're hoping to get another ten years out of it if the mission is successful, so I guess if the electric thrusters work for the planned 3 months it'll go up more than halfway to the original 375 mile orbit. To give some context, lifespan in orbit below 200 miles is really short.
Something to keep in mind about trying to boost it on the cheap is the entire Swift mission, from construction to launch to operating it for over 20 years was $500M, so spending $30M seems a good deal... unless it fails. If it would cost say $100M for a successful mission or even worse $250M, it would be better to spend the rescue money to launch a newer cooler replacement.
Its a fun rabbit hole to study. Apparently they're not out of the woods yet, even if they get altitude control they need some good luck to grab onto swift which was never designed for this kind of stuff.