Under the New Frontiers program, NASA has launched a pair of inspiring missions to explore the unknown within our solar system. New Horizons revealed Pluto to the world. The frozen world towards the end of our solar system proved to be more spectacular than anyone could imagine. Juno is set to do the same with Jupiter.

On September 8th, the third New Frontiers spacecraft will take to the skies. OSIRIS-REx (Origins, Spectral Integration, Resource Identification, Security – Regolith Explorer asteroid sample return mission) will begin its journey to the asteroid Bennu. Its mission? To gather a sample of its surface material and return it to Earth.

New Frontiers is all about pushing the limit, and OSIRIS-REx is one of the most ambitious missions yet. It marks the first U.S. mission to collect a sample of an asteroid and bring it back to Earth.

If all goes according to plan, the spacecraft will reach the asteroid in 2018 and be back home in 2023.

The OVIRS instrument

OSIRIS-REx isn’t just going to land on the asteroid as soon as it gets there. The spacecraft will conduct an extensive survey of Bennu over the course of about a year. During this time, scientists back on Earth will closely study the best potential sample sites before selecting one.

One instrument is vital in this process. It’s called OVIRS (OSIRIS-REx Visible and Infrared Spectrometer). OVIRS sees the visible and near-infrared light reflected and emitted from the asteroid and can measure the spectral signatures of the Bennu’s minerals.

The OSIRIS-REx team is particularly interested in a sample with organics in it. And that’s where OVIRS comes in says Dante Lauretta, the principal investigator for the mission. “In particular, we rely on it to find the areas of Bennu rich in organic molecules to identify possible sample sites of high science value, as well as the asteroid’s general composition.”

During the approach to Bennu, OVIRS will be busy covering one entire hemisphere at a time. It will be looking to see how the asteroid’s spectrum changes as the asteroid rotates.

All of this data will be compiled into detailed maps of the surface. Armed with these maps, scientists back on Earth will be able to find the perfect sample site.

Did You Know: Once the site is selected, the spacecraft has three chances to collect the sample it needs. The sampling arm will touch Bennu for about five seconds. Bursts of nitrogen gas will stir up rock and dirt on the surface into the sampler head. There’s only enough nitrogen for three sampling attempts. The goal is to collect anywhere between 60 and 2000 grams of surface material.

OSIRIS-REx spacecraft

The OSIRIS-REx spacecraft.

OVIRS will do much more than help scientists find a sample site. One thing scientists will be keeping a close eye is on the Yarkovsky Effect. This is the changes in Bennu’s orbit caused by surface heating and cooling as its surface enters and exits sunlight. As the surface is warmed by the sun, thermal radiation is tossed in different directions. It causes a small push, but a push all the same. The more we understand this effect, the better we can predict the slight changes in the orbits of other asteroids.

OVIRS uses just 10 watts

Dennis Reuter, OVIRS instrument scientists at NASA’s Goddard Space Flight Center, said, “I can’t think of a spectral payload that has been quite this comprehensive before.”

Comprehensive and also efficient. Everything has to be at NASA. You only have so much power to play with. The compact OVIRS instrument uses just 10 watts of power. That’s less power than the light bulb I change way too often in my kitchen.

“We’ve put a big job in a compact instrument,” said Amy Simon, deputy instrument scientist for OVIRS.

And it’s not just power. OVIRS doesn’t have any moving parts. Reuter likened it to a computer. There’s no “is it plugged in” in space. Each mission team has one chance to get it right. Building OVIRS without moving parts lowers the risk of malfunction big time.

The OSIRIS-REx team is trying to prepare themselves for every challenge. That includes the weather on Earth. September in Florida? Yep, it’s still humid. Since OVIRS will also be looking for trace amounts of water on the asteroid’s surface, the team can’t afford for any water inside the instrument to skew the results.

Right after launch, several heaters will kick in to evaporate any water that built up while sitting on the hot, humid launch pad.

“There are always challenges that we don’t know about until we get there, but we try to plan for the ones that we know about ahead of time,” said Simon.

If everything goes smoothly, OSIRIS-REx’s sample return capsule will softly touch down at the Utah Test and Training Range in September 2023. The science team will study the sample for two years. After that, NASA plans to preserve 75% of the sample at the Johnson Space Flight Center in Houston for further research.


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