Engineers up the torque to get Lucy's solar array latched

Nobody wants flappy bits during an engine burn of Trojan asteroid explorer

Engineers are to double down on efforts to get Lucy's solar array fully deployed amid worries regarding potential damage during a main engine burn of the Trojan asteroid explorer.

Problems were noted shortly after launch last year, when one of the probe's 7.3 meter (23.9 feet) solar arrays failed to latch into place after deployment. Enough of the fan-like array had opened to generate plenty of power for the spacecraft, but not enough to latch securely into place. Engineers reckon that the array got to approximately 345 out of 360 degrees before stalling.

The issue did not present an immediate threat to the mission. Engineers pondered if they might simply leave things as is; after all, the array was generating ample power. However, as investigations have proceeded, particularly with regard to what might happen during an engine firing, a decision has been taken to try and latch the array in place.

As of now, Lucy is approximately 105.1 million km (65.33 million miles) from Earth. It will have its first Earth flyby and gravity assist in October this year, another in December 2024 and reach the Trojan asteroid Eurybates and its satellite Queta in 2027. The Trojan asteroids orbit the sun "in front of" and "behind" Jupiter, and scientists reckon they represent leftovers of the material that formed the outer planets.

To deal with the array issue, engineers plan to use both primary and backup motors to give the lanyard attached to the end of the solar array a hefty tug (or, in NASA-speak, use "both motors simultaneously to generate higher torque.") There is only 20 to 40 inches of lanyard left (out of approximately 290 inches in total) to retract to latch the array in place.

The primary motor reeled in the lanyard after launch to open the array. A backup motor was included for purposes of redundancy.

Engineers plan a two step process. The first, expected to occur next month, will pull in most of the remaining lanyard and check that what happens in flight matches ground testing. The array is unlikely to latch at that point – that will come a month later, if all goes well, when engineers will have enough data to give the snarled lanyard a final pull and latch the array in place ahead of October's Earth flyby. ®

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