The spacecraft successfully cleared some dust off its solar panels, helping
to raise its energy and delay when it will need to switch off its science
instruments.
The team behind NASA’s InSight Mars lander has come up with an innovative
way to boost the spacecraft’s energy at a time when its power levels have
been falling. The lander’s robotic arm trickled sand near one solar panel,
helping the wind to carry off some of the panel’s dust. The result was a
gain of about 30 watt-hours of energy per sol, or Martian day.
Mars is approaching aphelion, its farthest point from the Sun. That means
less sunlight reaches the spacecraft’s dust-covered solar panels, reducing
their energy output. The team had planned for this before InSight’s two-year
mission extension. They’ve designed the mission to operate without science
instruments for the next few months before resuming science operations later
this year. During this period, InSight will reserve power for its heaters,
computer, and other key components.
The power boost should delay the instruments being switched off by a few
weeks, gaining precious time to collect additional science data. The team
will try to clear a bit more dust from the same solar panel this Saturday,
June 5, 2021.
Dust in the Wind
InSight’s team has been thinking up ways to try to clear dust from its solar
panels for almost a year. For example, they tried pulsing the solar panel
deployment motors (last used when InSight opened its solar panels after
landing) to shake the dust off but didn’t succeed.
More recently, several members of the science team started pursuing the
counterintuitive technique of trickling sand near – but not directly on top
of – the panels. Matt Golombek, a member of the InSight science team at
NASA’s Jet Propulsion Laboratory in Southern California, which manages the
mission, noted that it might be possible to strike dust on the panels with
sand grains that would “saltate,” or hop off the solar panel surface and
skip through the air in the wind. The larger grains might then carry off the
smaller dust particles in the wind.
To try the technique, the team used the scoop on InSight’s robotic arm to
trickle sand next to InSight’s solar panels on May 22, 2021, the 884th sol
of the mission, at around noon Mars time – the windiest time of day. It was
easiest for InSight’s arm to be positioned over the lander’s deck, high
enough for the winds to blow sand over the panels. Sure enough, with winds
blowing northwest at a maximum of 20 feet (6 meters) per second, the
trickling of sand coincided with an instantaneous bump in the spacecraft’s
overall power.
“We weren’t sure this would work, but we’re delighted that it did,” Golombek
said.
While it’s no guarantee that the spacecraft has all the power it needs, the
recent cleaning will add some helpful margin to InSight’s power reserves.
Surviving on Mars
InSight’s panels have outlasted the two-year prime mission they were
designed for and are now powering the spacecraft through the two-year
extension. Relying on solar panels for power enables such missions to be as
light as possible for launch and requires fewer moving parts – thus, fewer
potential failure points – than other systems. Equipping the spacecraft with
brushes or fans to clear off dust would add weight and failure points. (Some
members of the public have suggested using the Ingenuity Mars Helicopter’s
whirring blades to clear off InSight’s panels, but that’s not an option,
either: The operation would be too risky, and the helicopter is roughly
2,145 miles, or 3,452 kilometers, away.)
However, as the Spirit and Opportunity Mars rovers showed, gusts and
whirlwinds can clear solar panels over time. In the case of InSight, the
spacecraft’s weather sensors have detected many passing whirlwinds, but none
have cleared any dust.
By August, as Mars moves in its orbit closer to the Sun, InSight’s solar
panels should be able to gather more energy, allowing the team to turn the
science instruments back on. Depending on the available power, they might
begin by turning some on for short periods at key times during the day, as
they’ve been doing to save energy.
Whether the instruments are on or off, InSight operations will pause again
around October 7, when Mars and the Earth will be on opposite sides of the
Sun. Known as Mars Solar Conjunction, this period happens every two years.
Because plasma from the Sun can interrupt radio signals sent to spacecraft
at that time, all of NASA’s Mars missions will become more passive,
continuing to record data and send updates to engineers on Earth, though no
new commands will be sent back to them. The moratorium on Mars commands will
last several weeks until late October.
Reference:
NASA
Tags:
Space & Astrophysics