Bad astronomy | The Lucy mission to Jupiter’s asteroids is testing its cameras

A space mission that I follow avidly is Lucy, launched last October. It is heading into Jupiter’s orbit – not Jupiter itself, but its orbit — to go through quite a few asteroids that share their path with the giant planet. In a sense, this is the most ambitious asteroid mission ever created: it will take close-up images of at least Seven asteroids!

These are called Trojan asteroids, and they may have orbited the Sun with Jupiter since the dawn of the solar system. They congregate in two places, one 60° ahead and the other 60° behind Jupiter in its orbit, and having so many together makes it much easier to approach and study such a large number of them in a single mission.

Shortly before launch, I wrote an overview of the mission and its extremely wild trajectory through the inner solar system. You don’t normally hear much about missions like this until they get closer to their goal, but it just so happens that footage obtained on February 14, 2022 has just been released. They were taken by engineers to Earth to test Lucy’s camerasand they are pretty cool.

This photo, taken on Earth in New Mexico, shows the familiar sight of Orion as well as part of Gemini and Monoceros (the unicorn). The image is an unguided long exposure, so the stars are a bit streaky due to Earth’s rotation, but it’s enough to show where Lucy’s cameras were pointed when they took their test observations of ‘engineering.

The red rectangle shows the field of view of Lucy’s endpoint tracking cameras, also known as T2C. These are a pair of cameras – one for main operations and the other as a backup in case something goes wrong with the first – with a wide field of view that will be used when Lucy gets close to each of its asteroid targets. Stars on the ground will be analyzed on board to aid in autonomous asteroid tracking. It takes about half an hour at least for light to reach Earth from Jupiter’s orbit, which is too long to control imaging sequences from the ground, so the spacecraft has to do it itself. same.

The T2C can also take scientific data; the wide field of view means that even at a close approach they can get the whole asteroid at once, and as the spacecraft moves these images can be used to create 3D stereo pairs to determine a surface topography on asteroids, which is extremely cool.

The engineering test image is a bit off – there is some background noise, for example, but that can be dealt with – but you can still see a million stars. This fuzzy spot in the lower right is real: it’s the fantastic Rosetta Nebula, a star-forming cloud of gas about 5,000 light-years away, containing thousands of newborn stars. The fact that it can be seen at all in that 10 second exposure says a lot about the sensitivity of the camera.

The blue band in the first image shows the field of view of the Multicolor Visible Imaging Camera, or MVIC, one of the detectors on a camera called The Ralph. The name is…interesting; the first camera Ralph flew on the New Horizon Pluto mission, and was named so because a different camera on that spacecraft was named Alice, after the husband and wife characters from the old sitcom The Honeymooners. The Ralph camera on Lucy is the same setup, so they called it L’Ralph to show it’s part of Lucy.

Anyway, MVIC has five filters that pick out the colors associated with the different minerals you would expect to see on the surfaces of asteroids. It can also take a clear image without a filter, called a panchromatic image, and here is the result of its test:

Although the exposure time was less than a second, many stars can be seen (it may help to look at the original image). Note that this field overlaps that of T2C so they can see the same thing at the same time, which will help with scientific analysis.

The small yellow square in the center of the first image shows the field of view of ORRI – the Lucy LOng Range Reconnaissance Imager – the highest resolution camera on Lucy, which means she will see the most detail on the asteroids.

In the 10 second test image, the stars 1/25,000and as faint as the human eye can see are visible. They are stretched slightly due to the long exposure, but this can be compensated for in science exposures to create usable images. Clearly the LORRI will be able to see faint detail on asteroids, and is one of the most capable cameras on Lucy that will provide a large amount of scientific data.

While none of these images win an award for beauty, they are all indeed stunning: they show us a working spacecraft 6 months into a mission that will span many, many years. We are just now T-3 years before it passes its first asteroid – (52246) Donald Johansona main rocky belt about 4 kilometers wide – so it won’t be long before the first scientific images are sent to Earth, and we visit yet another asteroid up close and personal. What will we see?

If we knew that, we wouldn’t have to send missions there. With each spacecraft closely investigating new objects, the only thing we can expect is the unexpected, and it’s never surprising that we’re surprised.

I can not wait.


Addendum: There is a bug in the mission at the moment: Lucy has two circular solar panels that have extended like a fan, but one has not fully extended and is about 345° from its fully extended 360° state. It can provide enough power, but if not locked in position, burning out the main motor could damage it. So engineers will try to use a spare engine – redundancy is everything in space missions – to finish the job, and should start that around May 9.

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