NASA confirms TESS temporarily felled by command error

"NASA has confirmed that its planet hunter, TESS (Transiting Exoplanet Survey Satellite), entered safe mode due to a command error that inadvertently left the spacecraft's solar arrays angled away from the Sun. TESS was recovered days after entering safe mode due to discharged batteries. This was caused by the vehicle's solar panels being pointed away from the Sun, which meant the batteries could not charge sufficiently. The incident was the result of a command transmitted from the ground."

"A NASA spokesperson told The Register that there were no guardrails in place to prevent this scenario, although there were protections to prevent the spacecraft's batteries from draining completely. It is likely these kicked in and sent the spacecraft into safe mode, from which it could be recovered. A spacecraft's safe mode shuts down all but the most essential systems, usually maintains attitude control, and awaits instructions from controllers. It is designed to protect the vehicle."

"A spokesperson at the space agency added: "The mission is reviewing and updating procedures to prevent this command error from happening in the future." In many ways, TESS was lucky. There are plenty of examples of spacecraft being left borked after a command from Earth had unintended consequences. The Viking 1 Mars lander, for example, ended its mission in 1982 after a faulty command from Earth terminated communications, and attempts to regain contact proved unsuccessful."

NASA confirmed that TESS entered safe mode when a ground command left the spacecraft's solar arrays angled away from the Sun, leading to discharged batteries. The vehicle was recovered days later after battery protections and safe mode preserved essential systems during a week-long observation of comet 3I/ATLAS. There were no guardrails to prevent the commanded attitude, though battery safeguards likely triggered safe mode and enabled recovery. Safe mode shuts down nonessential systems, maintains attitude control, and awaits instructions to protect the spacecraft. The mission will review and update procedures to prevent similar command errors. Historical cases such as Viking 1 and SOHO show command mistakes can be mission-ending.

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