On 4/12/23 13:07, a425couple wrote:
> A little bit ago, this would have been considered far off
> impossible science fiction.  Now we just keep doing it!
> Flying on another planet!
>
> rom
> https://spectrum.ieee.org/mars-helicopter-ingenuity-50
>
> What Flight 50 Means for the Ingenuity Mars Helicopter

back at start--

How NASA Designed a Helicopter That Could Fly Autonomously on Mars The
Perseverance rover's Mars Helicopter (Ingenuity) will take off,
navigate, and land on Mars without human interventionEVAN ACKERMAN17 FEB
20218 MIN READ
NASA engineers modifying the flight model of the Mars Helicopter inside
the Space Simulator at NASA JPL.
NASA engineers modifying the flight model of the Mars Helicopter inside
the Space Simulator at NASA JPL. PHOTO: NASA/JPL-CALTECH
ROBOTIC EXPLORATIONSPACE FLIGHTMARSINGENUITYDRONESHELICOPTERNASAMARS
ROVERSPERSEVERANCE
Tucked under the belly of the Perseverance rover that will be landing on
Mars in just a few days is a little helicopter called Ingenuity. Its
body is the size of a box of tissues, slung underneath a pair of 1.2m
carbon fiber rotors on top of four spindly legs. It weighs just 1.8kg,
but the importance of its mission is massive. If everything goes
according to plan, Ingenuity will become the first aircraft to fly on Mars.

In order for this to work, Ingenuity has to survive frigid temperatures,
manage merciless power constraints, and attempt a series of 90 second
flights while separated from Earth by 10 light minutes. Which means that
real-time communication or control is impossible. To understand how NASA
is making this happen, below is our conversation with Tim Canham, Mars
Helicopter Operations Lead at NASA’s Jet Propulsion Laboratory (JPL).

It’s important to keep the Mars Helicopter mission in context, because
this is a technology demonstration. The primary goal here is to fly on
Mars, full stop. Ingenuity won’t be doing any of the same sort of
science that the Perseverance rover is designed to do. If we’re lucky,
the helicopter will take a couple of in-flight pictures, but that’s
about it. The importance and the value of the mission is to show that
flight on Mars is possible, and to collect data that will enable the
next generation of Martian rotorcraft, which will be able to do more
ambitious and exciting things.

Here’s an animation from JPL showing the most complex mission that’s
planned right now:

Ingenuity isn’t intended to do anything complicated because everything
about the Mars helicopter itself is inherently complicated already.
Flying a helicopter on Mars is incredibly challenging for a bunch of
reasons, including the very thin atmosphere (just 1% the density of
Earth’s), the power requirements, and the communications limitations.

With all this in mind, getting Ingenuity to Mars in one piece and having
it take off and land even once is a definite victory for NASA, JPL’s Tim
Canham tells us. Canham helped develop the software architecture that
runs Ingenuity. As the Ingenuity operations lead, he’s now focused on
flight planning and coordinating with the Perseverance rover team. We
spoke with Canham to get a better understanding of how Ingenuity will be
relying on autonomy for its upcoming flights on Mars.

IEEE Spectrum: What can you tell us about Ingenuity’s hardware?

Tim Canham: Since Ingenuity is classified as a technology demo, JPL is
willing to accept more risk. The main unmanned projects like rovers and
deep space explorers are what’s called Class B missions, in which there
are many people working on ruggedized hardware and software over many
years. With a technology demo, JPL is willing to try new ways of doing
things. So we essentially went out and used a lot of off-the-shelf
consumer hardware.

There are some avionics components that are very tough and radiation
resistant, but much of the technology is commercial grade. The processor
board that we used, for instance, is a Snapdragon 801, which is
manufactured by Qualcomm. It’s essentially a cell phone class processor,
and the board is very small. But ironically, because it’s relatively
modern technology, it’s vastly more powerful than the processors that
are flying on the rover. We actually have a couple of orders of
magnitude more computing power than the rover does, because we need it.
Our guidance loops are running at 500 Hz in order to maintain control in
the atmosphere that we're flying in. And on top of that, we’re capturing
images and analyzing features and tracking them from frame to frame at
30 Hz, and so there's some pretty serious computing power needed for
that. And none of the avionics that NASA is currently flying are
anywhere near powerful enough. In some cases we literally ordered parts
from SparkFun [Electronics]. Our philosophy was, “this is commercial
hardware, but we’ll test it, and if it works well, we’ll use it.”

Can you describe what sensors Ingenuity uses for navigation?

We use a cellphone-grade IMU, a laser altimeter (from SparkFun), and a
downward-pointing VGA camera for monocular feature tracking. A few dozen
features are compared frame to frame to track relative position to
figure out direction and speed, which is how the helicopter navigates.
It’s all done by estimates of position, as opposed to memorizing
features or creating a map.

Ingenuity viewed from below showing its laser altimeter and navigation
camera.NASA’s Ingenuity Mars helicopter viewed from below, showing its
laser altimeter and navigation camera.PHOTO: NASA/JPL-CALTECH
We also have an inclinometer that we use to establish the tilt of the
ground just during takeoff, and we have a cellphone-grade 13 megapixel
color camera that isn’t used for navigation, but we’re going to try to
take some nice pictures while we’re flying. It’s called the RTE, because
everything has to have an acronym. There was an idea of putting hazard
detection in the system early on, but we didn’t have the schedule to do
that.

In what sense is the helicopter operating autonomously?

You can almost think of the helicopter like a traditional JPL spacecraft
in some ways. It has a sequencing engine on board, and we write a set of
sequences, a series of commands, and we upload that file to the
helicopter and it executes those commands. We plan the guidance part of
the flights on the ground in simulation as a series of waypoints, and
those waypoints are the sequence of commands that we send to the
guidance software. When we want the helicopter to fly, we tell it to go,
and the guidance software takes over and executes taking off, traversing
to the different waypoints, and then landing.

This means the flights are pre-planned very specifically. It’s not true
autonomy, in the sense that we don’t give it goals and rules and it’s
not doing any on-board high-level reasoning. It’s sort of half-way
autonomy. The brute force way would be a human sitting there and flying
it around with joysticks, and obviously we can’t do that on Mars. But
there wasn’t time in the project to develop really detailed autonomy on
the helicopter, so we tell it the flight plan ahead of time, and it
executes a trajectory that’s been pre-planned for it. As it’s flying,
it’s autonomously trying to make sure it stays on that trajectory in the
presence of wind gusts or other things that may happen in that
environment. But it’s really designed to follow a trajectory that we
plan on the ground before it flies.

This isn’t necessarily an advanced autonomy proof of concept—something
like telling it to “go take a picture of that rock” would be more
advanced autonomy, in my view. Whereas, this is really a scripted
flight, the primary goal is to prove that we can fly around on Mars
successfully. There are future mission concepts that we’re working
through now that would involve a bigger helicopter with much more
autonomy on board that may be able to [achieve] that kind of advanced
autonomy. But if you remember Mars Pathfinder, the very first rover that
drove on Mars, it had a very basic mission: Drive in a circle around the
base station and try to take some pictures and samples of some rocks.
So, as a technology demo, we’re trying to be modest about what we try to
do the first time with the helicopter, too.

Is there any situation where something might cause the helicopter to
decide to deviate from its pre-planned trajectory?

The guidance software is always making sure that all the sensors are
healthy and producing good data. If a sensor goes wonky, the helicopter
really has one response, which is to take the last propagated state and
just try to land and then tell us what happened and wait for us to deal
with it. The helicopter won’t try to continue its flight if a sensor
fails. All three sensors that we use during flight are necessary to
complete the flight because of how their data is fused together.

This illustration depicts Mars Helicopter Ingenuity during a test flight
on Mars.An artist’s illustration of Ingenuity flying on
Mars.ILLUSTRATION: NASA/JPL-CALTECH
How will you decide where to fly?

We’ll be doing what we’re calling a site selection process, and that’s
even starting now from orbital images of where we anticipate the rover
is going to land. Orbital images are the coarse way of identifying
potential sites, and then the rover will go to one of those sites and do
a very extensive survey of the area. Based on the rockiness, the slope,
and even how textured the area is for feature tracking, we’ll select a
site for the helicopter to operate in. There are some tradeoffs, because
the safest surface is one that’s featureless, with no rocks, but that’s
also the worst surface to do feature tracking on, so we have to find a
balance that might include a bunch of little rocks that make good
features to track but no big rocks that might make it more difficult to
land.

What kind of flights are you hoping the robot will make?

Because we’re trying this out for the first time, we have three main
flights planned, and all three of them have the helicopter landing in
the same spot that it took off from, because we know we’ll have a
surveyed safe area. We have a limited 30 day window, and if we have the
time, then we might try to land it in a different area that looks safe
from a distance. But the first three canonical flights are all going to
be takeoff, fly, and then come back and land in the same spot.

JPL has a history of building robots that are able to remain functional
long after their primary mission is over. With only a 30 day mission,
does that mean that barring some kind of accident, the rover will end up
just driving away from a perfectly functional Mars helicopter?

Yeah, that’s the plan, because the rover has to get on with its primary
mission. And it does consume resources to support us. And so they gave
us this 30 day window, which we’re very grateful for of course, and then
they’re moving on, whether we’re still working or not. Whatever wild and
crazy stuff we want to do, we’ll have to do within our 30 days. We don’t
actually have the final two flights planned yet. Depending on how
quickly the first three go, we may have a week or so to try some more
exotic things. But we’re really concentrating on those first three flights.

Our ultimate success criterion is a single flight, so if we get that
first flight, we’re going to be doing high fives. The next two flights
are going to be stretching that envelope a little bit. And then the
final two flights are, hey, let’s see how adventurous we can get. We
might fly off a hundred meters, or do a big circle or something like
that. But the whole point is understanding how it flies, and that means
doing our first flight and seeing how well it performs.

Let’s say everything goes great on your first four flights and you have
one flight left. Would you rather try something really adventurous that
might not work, or something a little safer that’s more likely to work
but that wouldn’t teach you quite as much?

That’s a good question, and we’ll have to figure that out. If we have
one flight left and they’re going to leave us behind anyway, maybe we
could try something bold. But we haven’t really gotten that far yet.
We’re really concentrating on those first three flights, and everything
after that is a bonus.

Anything else you can share with us that engineers might find
particularly interesting?

This the first time we’ll be flying Linux on Mars. We’re actually
running on a Linux operating system. The software framework that we’re
using is one that we developed at JPL for cubesats and instruments, and
we open-sourced it a few years ago. So, you can get the software
framework that’s flying on the Mars helicopter, and use it on your own
project. It’s kind of an open-source victory, because we’re flying an
open-source operating system and an open-source flight software
framework and flying commercial parts that you can buy off the shelf if
you wanted to do this yourself someday. This is a new thing for JPL
because they tend to like what’s very safe and proven, but a lot of
people are very excited about it, and we’re really looking forward to
doing it.

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