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Mars Ingenuity helicopter and Perseverance are talking again

NASA drops heater temp to boost batteries as dust hits solar supply

The long-lived Ingenuity helicopter has made contact with NASA's Perseverance rover on Mars after an unexpected communications blackout.

Ingenuity just passed the milestone of a year of operations on the Red Planet, after being designed for five experimental test flights over 30 Martian days during 2021. Thus far, the helicopter has managed to fly more than 4.2 miles in 28 sorties, proving NASA's reputation for over-engineering its space kit.

Ingenuity uses Perseverance as a base station to send data to and receive commands from Earth. Well, up until May 3, when communications between rover and helicopter dropped out. The problem? Dust, it turns out, which was stopping the helicopter from charging properly from its solar panels.

In the hope of hearing a call from the helicopter, engineers commanded the rover to spend much of May 5 listening for a signal. Thankfully, one was received at 1145 local Mars time. While the data was limited in order to preserve battery power, there was enough to indicate the helicopter was OK and its power source was being charged.

Perseverance rover runs on a radioisotope thermoelectric generator (RTG), however, Ingenuity uses batteries charged by a solar array. A seasonal increase of dust in the Martian atmosphere means there is less sunlight hitting the array, meaning less charging and available power, and the temperature is dropping as winter approaches, which means more battery-sucking heating to keep the electronics operational.

Although more telemetry is required, engineers reckon, given these circumstances, Ingenuity's power levels dropped below a lower limit resulting in the shutdown of the field-programmable gate array (FPGA) that manages the helicopter's electronics. As well as controlling the heaters and turning bits of the helicopter's avionics on and off, the FPGA also maintains time and controls when Ingenuity wakes up for a communications session with Perseverance.

When the solar array began to recharge the batteries, the FPGA came back up. However, its clock was reset, and so when Ingenuity tried to communicate, Perseverance was not listening.

Communications issue aside, it is the heaters that will cause engineers the greatest headache. The heaters keep the temperature of critical components onboard the helicopter from dropping too low during the Martian night and use battery power to do so. However, there may be some leeway – in order to accumulate as much of a battery charge as possible, the team has uplinked commands to lower the point at which the heaters kick in. The previous position was 5°F (-15°C) and the latest one is -40°F (-40°C).

A few nights of this should result in enough charge for normal operations to resume, if one assumes the mostly commercial off-the-shelf components from which Ingenuity is constructed can survive.

Ingenuity team lead Teddy Tzanetos of NASA's Jet Propulsion Laboratory said: "Our top priority is to maintain communications with Ingenuity in the next few sols, but even then, we know that there will be significant challenges ahead."

Challenges there may be. The helicopter is, after all, over a year into a month-long mission and the technology demonstrator has surpassed all reasonable expectations for its performance. Its most recent flight resulted in Ingenuity travelling approximately 1,371 feet horizontally at a maximum altitude of around 33 feet.

We would not bet against the boffins extracting just a bit more science from the little gizmo just yet. ®

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