A robot rescue craft launched to save NASA's space telescope lost its balance and fell into crisis before regaining its attitude. With the problem of uncontrolled spinning resolved, hope has grown that it will dock with the space telescope as planned and complete its mission to extend the telescope's life.
NASA said on the 11th that "Catalyst Space has successfully achieved a flight software update for the LINK spacecraft, which is scheduled to dock with the Neil Gehrels Swift Observatory space telescope and raise its orbit."
The newly updated attitude control algorithm is designed to use the craft's own thrusters to maintain LINK's stability. That day, Catalyst said, "By updating the flight software, we were able to regain control of the LINK spacecraft," adding, "We are proceeding carefully and calmly, assessing LINK's performance at each stage."
◇The space telescope cuts orbital decay in 'Superman mode'
LINK was launched on a Pegasus XL rocket dropped by Northrop Grumman's large Stargazer aircraft from an altitude of 12 kilometers on the 3rd. LINK's mission was to grab the space telescope with three robotic arms and fire its engine to raise it to its nominal orbit over three months.
Swift was launched in Nov. 2004 and has observed gamma-ray bursts, the final moments of stars. But recently, its altitude dropped sharply after being pushed by high-energy particles ejected from the sun. When it was first launched, its mission orbit was 600 kilometers above Earth, but over the past two years it fell to 360 kilometers.
In late July, LINK began rotating once every 40 seconds for no clear reason. Communications with the ground were also temporarily cut. Two of the three reaction wheels that LINK uses to hold its attitude were not working, and some of the small thrusters for fine movements were also reported to have failed. Catalyst engineers then spent two weeks firing the spacecraft's thrusters to control the spin.
NASA signed a $30 million (about 42.5 billion won) contract with Catalyst in Sept. last year to extend Swift's mission. At the time, less than a year remained before Swift would fall below 300 kilometers, an altitude at which rescue would be impossible. Catalyst developed and launched LINK in eight months. Given the tight schedule, there was a possibility of contingencies.
NASA said the Swift operations team, using an innovative approach, succeeded in reducing the telescope's drag and slowing its orbital decay. Swift is currently at an altitude of 347 kilometers. To cut atmospheric drag, since Feb., Swift has aligned its telescope and solar panels in a straight line with the direction of travel.
Experts said Swift's current posture is akin to the so-called "Superman mode," like Superman flying with his cape streamlined. Phil Evans of the University of Leicester said, "By switching to Superman mode, we were unable to carry out observations, but we were able to save at least 17 kilometers of altitude loss."
A specific timetable for when LINK will dock with Swift and raise its altitude has not yet been announced. NASA said that while Catalyst fires thrusters and performs maneuvers over several days to match LINK's orbit with Swift's, the two sides will work closely together, assessing performance at each stage.