A mission to save a falling spacecraft is now in need of its own rescue
For over two decades, the Neil Gehrels Swift Observatory, known as Swift, has been studying gamma ray bursts from space. It was launched back in 2004, with a planned life expectancy of only two years.
Now after an additional 20 years of science and observations, Swift is falling out of its orbit. NASA contracted commercial company Katalyst Space to rescue Swift. Using its LINK satellite, the plan is to grab onto the observatory and give it a boost back up into orbit.
After what appeared to be a successful launch of LINK, the satellite now seems to have run into a problem -- it unexpectedly began spinning out of control. Ars Technica’s space reporter Stephen Clark has been covering the launch and technical issues with the mission. Clark said the issue began when LINK was passing outside of the range of one of Katalyst’s ground stations the company has positioned around the world to communicate with the spacecraft.
“They lost contact as expected with the Link spacecraft as it moved out of range of one ground station,” Clark said. “When it came back in range of the next ground station as it made its way around the Earth, they noticed it was in this tumble, in this spin, a three-axis spin. So complete attitude control loss.”
Clark said an investigation is underway to try and determine what exactly caused the loss of control, but for now, the LINK team is using other technology on the spacecraft to try and regain control.
“They have electric propulsion, which are these very low thrust engines on the spacecraft that are actually supposed to be used to raise the orbit of the of the spacecraft, of Swift,” Clark said. “When it gets to Swift, there is a low impulse that comes out of those engines, and they can actually gimbal or pivot or vector those engines to use them in another mode they were really never designed to, which is control the attitude or orientation of the spacecraft, and that's what they've been focusing on.”
Clark reports the company said LINK’s spinning rate had been cut in half. While the spinning is a major issue, Clark said the team had been preparing for mishaps and that the mission itself is risky.
“They're burning propellant that they would have used if they successfully captured Swift to actually boost its orbit,” Clark said. “So, they're burning fuel unexpectedly right now. But as for the underlying risk of approaching Swift, from NASA's perspective, if they take no action Swift is going to re-enter the atmosphere. The mission will be over… There's very little risk of losing anything by doing this mission, but there's tremendous upside if this mission is actually able to grab on to Swift for these robotic arms and then pulse its engines and actually raise its orbit.”
NASA said with the fixes in place, LINK is now expected to reach Swift at the end of August.
When things go wrong in space, how do you fix them?
When missions have technical issues or mishaps, engineers can’t always send a crew into orbit to fix it. Most of the troubleshooting is carried out on Earth by looking at data.
In the case of the LINK mission, engineers used data to find out the spacecraft was spinning. Florida Tech’s director of Spaceport Education Center in Titusville, Don Platt said when it comes to fixing problems with a spacecraft, it starts with predicting potential issues before the mission even takes off.
“You got to look at all of the kinds of the typical things that could go wrong and kind of go down a list of troubleshooting steps,” Platt said. “So, they'll create essentially a flowchart of steps before the mission even happens, identifying what are the most likely causes of a problem and how would they sort of manifest themselves then. And so, you've got to go through all of that, identify the problem first before you even have a chance to figure out how to fix it.
Platt said having backup plans is crucial so teams can adapt to any abnormalities a spacecraft may have. It’s important to predict or even recreate a potential problem on Earth before a mission launches.
“The key is designing into the spacecraft resiliency, and so that part of that is oftentimes redundancy,” Platt said. “You have backup systems. If one battery doesn't work, then there's another one that has been fully charged and ready to go, and so then you can switch the power system over to that backup battery and recover the problem. That gives you more time than to try to figure out why the primary battery went dead.”
Platt said companies can always learn from mistakes. For instance, he referenced Blue Origin’s New Glenn static fire test that ended in and explosion at the launch pad at Cape Canaveral. Now, Platt said the company is uncovering why the explosion happened and rebuilding the rocket – all while improving any engineering issues that might be to blame.
“You want to look at it from the point of view of collecting data,” Platt said. “That's why they're always collecting and sending radio signals back to the ground to make sure they have as much information as possible to, in fact, learn if there is an issue and the mission is lost. We definitely don't want that same thing to happen again in the future. So, how do we redesign the system? How do we make it more fail safe? How do we add a level of redundancy to the next spacecraft that comes down the line.”
