A satellite mission built to rescue a space telescope from fiery reentry (the uncontrolled fall back through Earth's atmosphere that destroys aging spacecraft) is instead spinning out of control. NASA announced Tuesday that Link, built by Katalyst Space Technologies to extend the life of its Swift gamma-ray telescope, ran into attitude control problems over the weekend, less than a month after launch. Sporadic contact with the spacecraft has followed.
What attitude control means and what it means to lose it
Attitude control is a spacecraft's ability to point itself in a specific direction. The word sounds like altitude, but it is about orientation, not height. A satellite without it cannot aim its antenna at the ground or hold a steady course. That is where Link stands.
The primary tools for attitude control on most small satellites are reaction wheels: small motorized gyroscopes housed inside the spacecraft that spin at varying speeds to rotate the vehicle without burning propellant. Link carries three of them. NASA's preliminary investigation found that two of those three reaction wheels are no longer operable.
The backup system has problems as well. NASA reported some loss of functionality in Link's cold gas thruster, a secondary pointing mechanism that fires short bursts of pressurized gas to fine-tune orientation. With both systems degraded, Link cannot reliably face the ground, which explains the intermittent communications.
What Link was built to do
Swift is a NASA gamma-ray telescope that has been watching the sky since 2004. As a spacecraft ages in low orbit, atmospheric drag gradually pulls it lower. Without propulsion to compensate, it eventually falls back through the atmosphere and burns up. That is the fate NASA was trying to prevent.
Link was designed as a commercial fix. Katalyst Space Technologies built it specifically to dock with Swift, provide new propulsion, and push the telescope into a higher, safer orbit. NASA described the spacecraft as a first of its kind for a commercial mission of this nature.
What NASA said and what remains unanswered
NASA's Tuesday statement attributed the spinning and the loss of steady contact directly to the attitude control failures. The agency said engineers are continuing the preliminary investigation.
What has not been addressed: whether either of the two failed reaction wheels can be recovered, whether the partial thruster loss can be worked around, or what happens to Swift if Link cannot regain enough stability to resume the rescue attempt.
Swift's fate is now tied to a spacecraft that is itself waiting to be stabilized.