# Where is Lucy going? (asteroid mission)

On Halloween (31-Oct-2018) NASA Goddard announced that Lucy has a green light:

NASA’s Mission to Jupiter’s Trojans Given the Green Light for Development

All I have are these links which are now getting a little old

and the images below. Note it's drawn in Jupiter's rotating (synodic) frame.

While the JWST has had a planning orbit solution in Horizons for quite a while now (still no launch in sight) for Lucy there is nothing. And the difference is that Lucy is a clockwork-like rendezvous with seven different asteroids moving within Jupiter's Trojan asteroid groups in funky orbits.

Is a more detailed trajectory available anywhere?

I could try to link them up myself, in a non-rotating frame the orbit is probably a more conventional-looking heliocentric ellipse, and it's the two asteroid groups that pass through Lucy's aphelion one after another.

But if there's more orbital-mechanical details out there, that would be great to see.

Source

Fifty years ago today (June 1), The Beatles released their album 'Sgt. Pepper's Lonely Hearts Club Band,' which included the iconic song "Lucy In The Sky With Diamonds." The popular song was critically acclaimed for evoking a surreal dreamscape, along the lines of Lewis Carroll’s classic "Alice's Adventures in Wonderland" fantasy. John Lennon said it was inspired by a drawing his son Julian — then age 3 — had made of a nursery school classmate named Lucy.

Photo from the 'Sgt. Pepper's Lonely Hearts Club Band' album. Credits: ©Apple Corps Ltd.

The Lucy fossil, photographed in 2009. Credits: Jason Kuffer (via Creative Commons) CC BY-NC-ND 2.0

A more detailed trajectory is available in the usual place for the sort of detail you're looking for: the NTRS.

LUCY: NAVIGATING A JUPITER TROJAN TOUR

A unique trajectory was discovered which visits this diverse sample of Jupiter Trojans of scien- tific interest with only one visit to each of the L4 and L5 swarms. These targets have a variety of ecliptic inclinations, so the timing of the encounters has to coincide with the arrival of the spacecraft and the targets at the intersection (nodes) of the spacecraft and Trojan orbital planes. This means that the arrival times are not flexible and any delays will be accompanied by a large delta-v penalty.

Lucy is a very high delta-v mission, with total delta-v for the required deep space maneuvers coming in at 1.678 km/s. There is also a resonance in the six year orbital period of the spacecraft with Jupiter’s 12 year period, allowing for the possibility of an extended mission.

Lucy’s L4 encounter trajectory is highly elliptical, with an eccentricity of 0.7, an ecliptic inclination of between 4-5 degrees, and a period of six years. Two Earth flybys and two deep space maneuvers (DSMs) alter the trajectory to encounter the first target, main belt asteroid Donaldjohanson, while a third DSM puts the spacecraft on course to the Jupiter L4 swarm.

All maneuvers are described in the paper.

One month after launch is the mission’s first deep space maneuver, a relatively small 14 m/s which is largely a timing maneuver to position the trajectory properly for the first Earth gravity assist (EGA-1) one year after launch. This flyby serves primarily to increase the semi-major axis, increasing the period to just over two years and providing a small, 0.19 degree, inclination change.

along with details on spacecraft navigation, etc.

• That paper is gold, exactly what I needed. Thank you very much!
– uhoh
Jan 30, 2019 at 23:36
• Anyone know what propulsion system is going to be used for these maneuvers. Jan 31, 2019 at 15:20
• @SteveLinton that sounds like a really good question, please ask it! There's not much here for example. You might ask about both Lucy and Psyche and compare their engines and total mission delta-v. planetary.org/blogs/guest-blogs/van-kane/…
– uhoh
Jan 31, 2019 at 16:15

I haven't found much except the videos on the mission tour page at lucy.swri.edu.

On the PI's space page, Dr. Hal Levison of the Southwest Research Institute in Boulder, Colorado is interviewed:

How did you come up with the trajectory for this mission?

We started out with a simple goal, come up with a trajectory to fly by the asteroid Eurybates, and the rest of the targets were really just lucky accidents. Eurybates is special because it is the largest member of the only known collisional family’’, the remnants of a broken up Trojan Asteroid, in either of the Trojan swarms. So by flying by that target we hope to learn a lot about what the Trojans are really made of. And fortunately we found a path to fly by it where we could also fly by a number of other targets in the L4 swarm along the way.

Originally we thought the mission would be over after we flew through the L4 swarm, but when a flight dynamicist integrated the orbit forward to make sure it wasn’t going to cause any planetary protection problems (since the orbit is crossing Mars and going out to the orbit of Jupiter we needed to make sure that the spacecraft won’t hit any astrobiologically important world like Mars or Europa), they saw that the spacecraft would fly near what are now the final pair of targets for the Lucy mission (and my personal favorites), Patroclus and Menoetious...

However watching the video in the non-rotating frame (left) you can notice that after the tour of the L4 group of Trojan asteroids, Lucy passes Earth and returns to Jupiter's orbital distance to intercept (at least one) L5 asteroid. If you look closely you can see that aphelion has rotated substantially from the previous one, indicating that Lucy must has swung past Earth fairly close. I don't think that this third flyby of Earth is just a coincidence. Rather than "...they saw that the spacecraft would fly near what are now the final pair of targets for the Lucy mission..." this really looks like it was thought through carefully ahead of time.

This is really beautiful trajectorizing!

below: screen shot of one of two videos at http://lucy.swri.edu//mission/Tour.html The other is in an frame rotating with Jupiter, and in that frame the trajectory has the same butterfly pattern as seen in the still image in the question.