Spaceflight Insider

Dawn will enter lowest ever orbit around Ceres

This picture is one of the first images returned by Dawn in more than a year, as Dawn moves to its lowest-ever and final orbit around Ceres. Dawn captured this view on May 16, 2018 from an altitude of about 270 miles (440 kilometers). Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

This picture is one of the first images returned by Dawn in more than a year, as Dawn moves to its lowest-ever and final orbit around Ceres. Dawn captured this view on May 16, 2018 from an altitude of about 270 miles (440 kilometers). Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

NASA’s Dawn spacecraft has begun maneuvers that should bring it to its lowest and final orbit around the dwarf planet Ceres.

The probe’s destination is less than 30 miles (50 km) above Ceres’s surface, which is ten times closer than its previous closest orbit. From there, it is planned to have Dawn gather gamma ray and neutron spectra that should help scientists better understand chemical changes in the surface’s uppermost layer as well as obtain detailed, high-resolution images.

From this vantage point, scientists will have the opportunity to closely study specific sites of interest, such as Occator Crater, home to highly reflective salt deposits similar to those seen on Earth.

By studying the crater and the area surrounding it, which together are known as a “geological unit,” researchers hope to better understand the site’s complex geology.

Mission engineers hope to fly low over Occator Crater in each orbit.

Accomplishing this requires difficult maneuvers because Dawn’s Gamma Ray and Neutron Detector (GRaND) will need to fly over the region 20 times to record enough of the site’s faint nuclear radiation.

The new orbit, which Dawn will begin on June 7, is designated extended mission orbit seven or XMO7. Because the spacecraft was not designed to operate at such close orbits and because the reaction wheels that control its orientation are no longer functioning, Dawn will have to take an elliptical orbit to study Ceres’s surface.

“The team is eagerly awaiting the detailed composition and high-resolution imaging from the new, up-close examination. These new high-resolution data allow us to test theories formulated from the previous data sets and discover new features of this fascinating dwarf planet,”said mission Principal Investigator Carol Raymond of NASA’s Jet Propulsion Laboratory (JPL).

Engineers have spent the last several months plotting the descent to the low orbit to come up with a plan that will provide the best opportunity for science observations. To accomplish this, they mapped out more than 45,000 possible paths to the close orbit before settling on the current one.

The orbit transfer is difficult because the spacecraft, which has been circling Ceres since March of 2015, uses ion engines for propulsion.

In his Dawn Journal blog, mission director and chief engineer Mark Rayman discussed the challenges of bringing the spacecraft into its final orbit in detail.

During XMO7, Dawn should orbit Ceres once every 27 hours and 13 minutes, which equals exactly three times the dwarf planet’s rotational period.  In what is known as a three-to-one resonant orbit, the probe should complete one orbit around Ceres for every three rotations the dwarf planet makes.

The blue curve is Dawn’s flight path from XMO5, the outer green ellipse, to XMO6, the inner one. Image credit: NASA/JPL-Caltech

 

 

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Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.

Reader Comments

Are they Ceres? Seriously, though, I’m very interested in this latest fact foray. Why the final orbit? Any new adventures for Dawn after Ceres?

Daniel Suggs

What do they mean by “final orbit”? Is it leaving Ceres, crashing into it, or going to be parked in this orbit forever?

June 3, 2018

Mr. Suggs,
If you read the article you’ll see which of the three the headline refers to.
Jason Rhian – Editor, SpaceFlight Insider

It’s incredible that we can see up close to Ceres and study its topography; before machine learning and AI, it would have taken much longer to map 45,000 possible paths to the close orbit before settling on the current one. Excellent information.

James Lunar Miner

Ceres is wonderful!

Why?

Consider a simple but useful idea:

“So, if you can mine Ceres, there is enough material for space habitats large enough to replicate the tropical rain forests, deserts, Antarctica, Siberia, Himalayas etc etc. as well as all our cities teaming with humans, and do all of that over four hundred times over”

From:
“Asteroid Resources Could Create Space Habs For Trillions; Land Area Of A Thousand Earths”
By Robert Walker July 17th 2013
At:
http://www.science20.com/robert_inventor/blog/asteroid_resources_could_create_space_habs_trillions_land_area_thousand_earths-116541

James Lunar Miner

The Dawn spacecraft has clearly demonstrated the critical importance of high Isp electric space propulsion systems for efficient high delta-v missions to two asteroids.
Note:
Low Earth Orbit as well as low orbits around Mars could now be quite important for future high Isp electric space propulsion powered spacecraft headed to explore and mine Ceres and other asteroids.
Why?
“The European Space Agency (ESA) has successfully tested a prototype ion engine powered by air that could provide propulsion for orbiting satellites almost indefinitely, and could even help power future missions to Mars.”
From:
‘Air-fueled ion thruster could provide unlimited power for space missions’ By Mark Austin 3/25/2018
At:
https://www.digitaltrends.com/cool-tech/esa-tests-air-fueled-ion-engine/
A high Isp “Air-fueled” ion thruster means propellants for various high Isp electric space propulsion systems can be efficiently and affordably ‘mined’ from the very tenuous upper atmospheres of Earth and Mars.
See:
‘Propulsive fluid accumulator’ at Wikipedia.
At:
https://en.wikipedia.org/wiki/Propulsive_fluid_accumulator

I wasn’t trying to be rude, I just don’t see where in the article it says what is meant by ‘final’.
I had read it previously and reread it several times, but can’t find the answer.
Is it final, because it will crash eventually, or leave Ceres eventually, or be left in a stable orbit?
If I have somehow still missed the answer, I apologize.

June 12, 2018

Mr. Suggs, per the article: “The probe’s destination is less than 30 miles (50 km) above Ceres’s surface, which is ten times closer than its previous closest orbit. From there, it is planned to have Dawn gather gamma ray and neutron spectra that should help scientists better understand chemical changes in the surface’s uppermost layer as well as obtain detailed, high-resolution images.” It is not known how long the Dawn mission will last.
Sincerely, Jason Rhian – Editor, SpaceFlight Insider

James Lunar Miner

Upcoming options for greatly extending the life of large and valuable spacecraft in orbit of the Earth, Mars, and Ceres will begin initial testing soon.

Significantly extending Dawn’s mission of orbiting Ceres, or possibly even moving it to orbit another asteroid and then into a high Earth orbit, could become doable and affordable with eventual advanced Electric Propulsion powered mission extension spacecraft that will have a 9,000+ Isp.

Note:

“The next event to watch is the launch of Orbital ATK’s first mission extension vehicle known as MEV-1. The company in December got approval from the U.S. Federal Communications Commission to conduct ‘rendezvous, proximity operations and docking’ with Intelsat-901 in a graveyard orbit.”

From:
‘In-orbit services poised to become big business’
By Sandra Erwin June 10, 2018′
At:
http://spacenews.com/in-orbit-services-poised-to-become-big-business/

See also:
‘MEV-1 working to expand spaceflight revolution, extend on-orbit operations’ By Jason Rhian September 19, 2017
At:
http://www.spaceflightinsider.com/organizations/orbital-sciences-corp/mev-1-working-expand-spaceflight-revolution-extend-on-orbit-operations/

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