Although " data-gt-translate-attributes="[{" attribute="">NasaThe ingenuity of " data-gt-translate-attributes="[{" attribute="">March The helicopter defied expectations, proved that powered and controlled aircraft flight was possible on Mars, and was an incredible success all around, the approach of the Martian winter brings additional challenges. Every sol (day of Mars) could be Ingenuity’s last.

With less daylight reaching the Ingenuity Mars Helicopter’s solar array during winter on Mars, it will likely be deficient in keeping its batteries charged. It is believed to already be suffering from battery brownouts at night, where the low voltage caused the electronics to reset. It is also likely that the heatsink power is insufficient to keep the electronic components within their safe temperature range. This cold cycle every night could cause the electronics to fail.

As detailed in a recent post, for the first time in our year-long extended mission, we had a loss of communication with Ingenuity starting downlink on May 3 (Sol 427) and May 4 (Sol 428) . After a week of anomaly investigation, two floors dedicated to data collection, and the heroic efforts of the Perseverance and Ingenuity operations teams, I am very pleased to report that we have restored reliable communications with Ingenuity. Based on all available telemetry, the helicopter appears healthy and we have resumed a modified form of operations. Assuming winter recommissioning activities nominally end, Ingenuity’s 29th flight could take place in the next few soils.

Ingenuity telemetry confirmed that the loss of communication was due to low battery state of charge (SOC) overnight, which caused our mission clock to reset. This daily SOC deficit is likely to persist for the duration of the Martian winter (until September/October).

NASA’s Ingenuity Mars helicopter is seen here in a close-up taken by Mastcam-Z, a pair of zoomable cameras aboard the Perseverance rover. This image was taken on April 5, the 45th Martian day, or sol, of the mission. Credit: NASA/JPL-Caltech/ASU

Challenges like these are to be expected: After hundreds of sols and dozens of flights beyond the originally planned five flights, the solar-powered helicopter is in uncharted territory. We are now operating well beyond our original design limits. Historically, Mars is very difficult for spacecraft (especially solar-powered spacecraft). Every floor could be Ingenuity’s last.

Below is a summary of our anomaly investigation over the past two weeks, our high winter risk posture, and possible pathways for Ingenuity through the winter and beyond.

Sol 427 and 428 Loss of communication

We have reached the point in late fall/early Martian winter at which Ingenuity can no longer meet the energy demands of nominal operations. Beginning on the evening of Sol 426, we believe that Ingenuity began experiencing overnight battery brownouts (battery brownouts), which reset the electronics. Due to the seasonal decrease in available solar power, increased airborne dust density, and lower temperatures, the demand for energy to keep electronics powered up and warm throughout the night exceeded Ingenuity’s available energy budget.

Below is a graph of the environmental conditions at Jezero Crater. The black line is a climatological model of airborne dust density (called “tau”) over a Martian year, and the expected daily insolation (amount of solar radiation reaching the solar array) is shown by the green dotted line. We are now in the part of the Martian year with a peak in tau, combined with a drop in insolation. This graph does not show the additional trend of lower average daily temperatures, which also adds to Ingenuity’s energy demand. We expect to be in this harsh winter energy paradigm until around Sol 600, at which time we expect to become positive in power from ground to ground again.

Environmental plot in Jezero: This graph depicts the environmental conditions at Jezero Crater since the day NASA’s Perseverance Mars rover landed through Sol 600. The black line shows a climatological model of the airborne dust load, while the green dotted line shows daily insolation. Credit: NASA/JPL-Caltech

In the winter, each night we expect our battery SOC to drop low enough to:

1. Cold cycle components: Our heating thermostat can no longer maintain the battery (and surrounding electronics) at their programmed set point (eg minus 13°F / minus 25°C). As a result, we expect Ingenuity electronics to reach nighttime ambient temperatures of approximately minus 80°C (minus 112°F).Impact 1: This cold cycle every night presents a lifelong risk to our electronic components.and
2. Mission Complete Clock: The battery can no longer support our voltage regulators and our mission clock. This nightly brownout resets (or clears) our mission clock.Impact 2: Every morning when Ingenuity warms up, charges its dead battery, and attempts to turn on its computer, it boots to a misaligned alarm schedule, which is out of sync with Perseverance.

When Perseverance attempted to contact Ingenuity on the morning of floors 427 and 428, Ingenuity did not respond because he was waking up at the wrong time. The team responded by uplinking a full search activity to the helicopter base station (HBS) aboard Perseverance in an attempt to communicate with Ingenuity during one of its misaligned alarm widows, which has succeeded.

From Sol 429 and all floors since (with the exception of Sols 444 and 445, which contained no helicopter activity), we have been in daily contact with Ingenuity using similar morning search activities while we believe to be the most likely times when Ingenuity would be sufficiently charged to attempt to start its electronics. These morning search activities reprogram the helicopter’s mission clock on each sol, which for the duration of that sol allows additional scheduled activities to use the energy we have. Currently we are hitting sunset with ~68% SOC, with an estimated need of at least 70% for everything to be powered overnight. Our 2% SOC deficit is expected to reach a 7% deficit once we reach the winter solstice (Sol 500 in July), at which time conditions will begin to improve.

All telemetry transmitted so far suggests that Ingenuity is in good health, with no signs of damage from overnight cold cycles. This morning search followed by evening activities is our new normal for the immediate future.

Winter risk posture

Our latest models suggest that regardless of changes to our nighttime thermostat strategy, it will be extremely difficult, if not impossible, to keep our Central Electronic Module (ECM) components warm and at their rated temperature overnight. Although component failure has always been a risk we have carried since the deployment of the rover, that risk is now magnified. The ECM components were normally kept warm overnight by our battery heater (usually set to 5°, minus 4°, or minus 13°F, or minus 15°, minus 20°, or minus 25°C). We expect the ECM components to now thermally cycle to ambient nighttime temperatures of minus 112°F (minus 80°C). We have limited ECM component testing to suggest some components can survive the winter, but we cannot predict how the entire ECM will perform throughout the winter. Cold-soaking electronics are believed to have caused the Opportunity and Spirit Mars rovers’ missions to end.

Winter Operations and Beyond

Given our elevated risk position, our focus over the past few months has been to prioritize data top-down from Ingenuity to the HBS. We have a handful of Heli-to-HBS transfer activity left before all unique data is copied from Ingenuity to HBS. Specifically, we copy flight performance logs, electronic logs and high-resolution color images of the last eight flights that are still on board Ingenuity.

Once all critical logs have been transferred, the team will proceed with a recommissioning phase during which we will restore Ingenuity to flight readiness given our ongoing overnight cold cycle. As during the technology demonstration phase, we will perform a high-speed spin before flying. Should Ingenuity receive a good health check, we would be ready to execute a short southwest sortie in Flight 29. This flight will improve our radio link for approximately the next four to six months while Perseverance samples in the river delta. .

In the meantime, the Ingenuity flight software team will prepare a series of upgrades to enable advanced navigation features. These new abilities will help Ingenuity move up the river delta and continue forward scouting missions for Perseverance over the past winter.

Next steps

The Perseverance and Ingenuity operations teams have done an extraordinary job of restoring reliable communications with Ingenuity. From Sol 446, the team transferred approximately 3,500 megabits (Mb) of data from Ingenuity to the HBS on Perseverance. Approximately 400MB of data remains on Ingenuity of non-critical logs and images that will be opportunistically transferred as the team continues its recommissioning efforts this week. If the telecom link between Perseverance and Ingenuity remains stable and Ingenuity receives a good track record, we hope to run flight 29 in the next few sols.

Written by Teddy Tzanetos, Ingenuity Team Leader at NASA’s Jet Propulsion Laboratory.